ALBERT

Description: The Molucca Sea Collision Zone in eastern Indonesia is the site of an orthogonal collision between two active subduction systems. Both the Halmahera subduction zone, to the east, and the Sangihe subduction zone, to the west, have subducted oceanic lithosphere of the Molucca Sea Plate, which has now been completely consumed. Both volcanic arcs were active since the Neogene and provide a means of probing the element fluxes through the two systems. The geochemistry of Neogene and Quaternary lavas from each volcanic arc is compared to constrain changes in the mass fluxes through the systems and the processes controlling these fluxes at different times during their history. Both arcs show increased evidence for sediment recycling as the collision progressed, but for contrasting reasons. In Halmahera this may represent an increased sediment flux through the arc front, while in Sangihe it may simply reflect a greater opportunity for melting of sediment-fluxed portions of the mantle wedge. In both cases the change in arc geochemistry can be related to the evolving architecture of the particular subduction zone. The Halmahera lavas also record a temporal change in the chemistry of the mantle component that resulted from induced convection above the falling Molucca Sea Plate drawing compositionally distinct peridotite into the mantle wege.

Description: Recycling of oceanic plate back into the Earth's interior at subduction zones is one of the key processes in Earth evolution. Volcanic arcs, which form above subduction zones, are the most visible manifestations of plate tectonics, the convection mechanism by which the Earth loses excess heat They are probably also the main location where new continental crust is formed, the so-called subduction factoiy' About 400f modern subduction zones on Earth are intra-oceanic. These subduction systems are generally simpler than those at continental margins as they commonly have a shorter history of subduction and their magmas are not contaminated by ancient sialic crust. They are therefore the optimum locations for studies of mantle processes and magmatic addition to the crust in subduction zones. This volume contains a collection of papers that exploit the relative simplicity of intra-oceanic subduction systems to provide insights into the tectonic, magmatic and hydrothermal processes associated with subduction.

Description: Periodicity is a common component of many sedimentological processes, but seldom is it considered across all scales of fluvial processes in order to understand the complete impact on sediment supply to basins. Temporal changes in sediment supply within drainage systems and sedimentary basins are a consequence of the inherent instability in transport processes. The causes of fluctuations are of 2 main types: (i) changes in factors endemic to the supply of sediment but which are at least partly independent of erosive forces and (ii) changes in the magnitude of forces available to transport sediment. Fluctuations at spatial scales from grain -- through reach -- to basin -- scales and at temporal scales from minutes to millennia are discussed and evaluated. All fluctuations are reflected in sedimentary deposits in some way. For example, irregular patterns of bed break-up during erosion can generate bedforms that are recorded in deposits, the passage of waves of sediment can cause cycles of incision and aggradation in a reach; large flood events will flush sediment into coastal regions and will be recorded as an identifiable package' in the deposits. Many models of basin processes and products assume a consistent supply of sediment which is far from the case in nature. One of the challenges in the coming decade is to move away from using long-term averages of sediment supply and to link models directly into geomorphic processes.

Description: The Mediterranean drainage basin incorporates more than 160 rivers with a catchment 〉200 km2, of which only a few are larger than 50 x 103 km2: this observation emphasizes the role of the smaller rivers. The present investigation, incorporating the analysis of data sets from 69 rivers, has estimated a total sediment flux of some 1 x 109 tonnes (t) year-1; of this, suspended sediment contributes some two-thirds of the load, with the remaining third supplied by the combined dissolved and bed-load components. The magnitude of the sediment supply is best demonstrated by various observations: (i) some 46% of the total length of the Mediterranean coastline (46 133 km) has been formed by sediment deposition; (ii) many Mediterranean deltas have prograded in recent times by, at least, several metres per year; and (iii) Holocene coastal (inner shelf) deposits are some tens of metres in thickness. The construction of hundreds of dams around the Mediterranean Sea, especially over the last 50 years, has led to a dramatic reduction in the sediment supply- to approximately 50% of the potential (natural) sediment supply. Such a reduction is considered to be the primary factor responsible for the loss of coastal (mainly deltaic) land, with annual rates of erosion ranging from tens (Ebro, Po) to hundreds of metres (Nile).

Description: The suggestion of the concept of scientific revolution' by Thomas Kuhn in 1962 was, in itself, a significant event in the history of science, and crucial' episodes or paradigm shifts' have come to be of special interest in the history of geology (as in other sciences). The appearance of a new paradigm is commonly associated with attempts by the most talented and well-established practitioners to consolidate or sustain the position of the previously prevailing paradigm. For almost 40 years, global theories in geology have been developing under the influence of mobilist ideas. It is no secret that in Russia the mobilist school initially met with serious opposition, and that even up to the present it has had numerous opponents. However, Western, and especially popular, scientific literature usually exaggerates the intensity of the situation and underestimates the contribution of Russian geologists and geophysicists to the development of mobilism and plate tectonics. The present paper describes some of the debates in Russia concerning mobilist doctrines, the work done in that country in the last three decades of the twentieth century from a mobilist perspective, and various theories that had currency in Russia at the end of that century.

Description: Between 1890 and the 1920s petrologists and mineralogists began to apply concepts of theoretical chemistry -- in particular, the concept of chemical equilibrium -- to the study of metamorphic rocks. The majority of the petrological community, however, hesitated to apply the new method on a large scale to metamorphism. Focusing on the works of Becke, Goldschmidt and Eskola, some early approaches to a linkage of metamorphic petrology and theoretical chemistry are reviewed. The controversial discussion, particularly of Goldschmidt's classical study of the Christiania area, led Miyashiro to distinguish two paradigms of early twentieth-century metamorphic petrology. With regard to the contemporary discussion, as well as to Miyashiro's interpretation, this paper is concluded by an epilogue on image and logic', which is intended to relate the paradigms of early modern metamorphism to different cultures, and national styles' of Earth sciences in the nineteenth and early twentieth centuries.

Description: Before 1900, Henry Clifton Sorby, the founder of sedimentary petrography', covered many aspects of the study of sedimentary rocks. During the first half of the twentieth century, there followed numerous detailed descriptions of such rocks and actualistic ideas were increasingly introduced. Specialization began between the two World Wars. The use of single grains and their statistical evaluation, especially of heavy minerals, and the investigation of clay minerals, were stimulated by the needs of the oil industry, together with regional descriptions, including facies studies on land and on the sea bottom. Specialization further increased between 1945 and 1968, with an explosion of publications. Ongoing field and laboratory studies, and new concepts such as the origin of turbidites, or diagenesis -- especially in carbonate rocks -- were treated in much greater detail. Again the oil industry was one of the major driving forces. Since 1968, global aspects gained greater attention, as for example with the Deep-sea Drilling Project. Geophysics contributed to facies and basin analysis. Extraterrestrial factors such as variation in Earth's orbit or bolide impacts, and their indications in sediments, came to be considered important for understanding world climates, and also evolution. Cross-disciplinary and international approaches have become, and continue to be, of growing importance.

Description: The main determinants of the interaction between surface water and groundwater are the distribution of areas with different infiltration rates, the thickness of sediment layers and the hydraulic head gradient. These conditions determine the volume and velocity of infiltrating water which, together with the direction of water flow, are required to model the interaction processes. Due to difficulties with measurement, only the direction of water flow is usually determined and boundary conditions are estimated from simplified assumptions. Field techniques have now been developed that help characterize surface water-groundwater interaction. Results from field experiments using a percussion probe and a large-scale laboratory column experiment set up to simulate infiltration processes are presented. Measurements of the 222Rn distribution in the column are used to determine infiltration velocities.

Description: The management of groundwater resources in England and Wales was initially based only on measures of the renewable resource. This has been extended to include the need to preserve the springs, river flows and surface water levels dependent on groundwater discharges as a key objective of a sustainable management of groundwater resources. The impacts of all new groundwater abstraction proposals on the surface water environment are now evaluated using a number of techniques, some of which are under further development. The sustainable management of groundwater catchments also includes the control of pumping from existing groundwater sources to meet agreed environmental targets. This approach is illustrated by examples of groundwater catchments managed to augment surface flows, to prevent saline intrusion and to preserve the integrity of wetland conservation sites.

Description: Arsenic is widespread in groundwater of the Holocene alluvial aquifers in southern Bangladesh, yet its concentration is highly variable spatially and with depth. A conceptual model of arsenic in the aquifer is proposed, as a basis for addressing questions concerning sustainability of groundwater development. Patterns and profiles of arsenic distribution in the aquifer have been determined at Meherpur in western Bangladesh, over an area of 15 km2 and a depth range of 15-225 m. The hydrochemical and hydraulic environments of arsenic occurrence have been established. The conceptual model incorporates the conditions of arsenic release to groundwater, the depth distribution of the arsenic source, likely sedimentological controls on the lateral discontinuity of the arsenic source, and the hydraulic regime imposed by pumping from the hydrogeologically leaky, multi-layered aquifer. Reducing conditions, conducive to arsenic release from sedimentary iron oxyhydroxides, are widespread. The arsenic source occurs at a distinct horizon at a depth of about 20m, but is laterally discontinuous. The catchments of shallow, hand-pumped tubewells (HTWs) are limited in extent by vertical leakage. Arsenic concentration in water pumped from tubewells depends on the depth separation between the HTW screen and the arsenic source, the overlap between the HTW catchment and the arsenic source layer, and the duration of pumping. Implications are drawn for treatment, tubewell location and design, monitoring, and predictive modelling.

Description: Groundwater abstractions affect the water balance in catchments of rivers in hydraulic continuity with groundwater and may lead to reductions in river baseflow. The Environment Agency issues licences for groundwater abstractions and takes into account the risk of such adverse impacts when deciding whether to grant licences and what conditions to associate with each licence. Assessing the impact of a particular licence is a difficult task, but analytical solutions to idealizations of the complex river-aquifer interaction can help guide such judgements. This paper presents a brief review of available analytical solutions and discusses their applicability to real groundwater systems. The most useful analytical solutions (developed by Theis, Hantush and Stang) have been incorporated into a spreadsheet and a new methodology has been made available to support Environment Agency hydrogeologists working in abstraction licensing. This offers a consistent approach to making an initial evaluation of the impact of groundwater abstraction on river flow that may be applied across the diverse hydrogeological systems found throughout the Environment Agency Regions of England and Wales. The use of analytical solutions in this methodology inevitably represents a significant simplification of what is generally a very complex issue, and the limitations of the new methodology are emphasized.

Description: In the Arabian Peninsula, hydrogeological and engineering solutions have failed to solve the severe and worsening problem of unsustainable groundwater abstraction, which threatens rural environments and livelihoods. Conventional western fiscal and regulatory measures to reduce abstractions seem to be impracticable in the present institutional and social contexts. In the region, groundwater rights without volume limitations are distributed mostly among numerous private well owners, and individual interests predominate over a communal imperative for aquifer sustainability. The solution may lie more in modifying the institutional context than in attempting to introduce official controls. This would involve the decentralization of water resources management to a basin or aquifer level and the development of local users associations. Water users associations could improve users' understanding of local hydrological limitations, promote conservation among irrigators, and cooperatively develop sustainable strategies and rules, which might ultimately include tradable rights and quotas. Government subsidies and incentives are necessary. Essential components of this participatory approach are strong leadership at national and local levels, the active engagement and leadership of Islamic institutions, and the use of modern communication methods.

Description: Cretaceous radiation of angiosperms from low to high palaeolatitudes, coupled with the break-up of Gondwana, played a major role in establishing and maintaining biogeographic patterns across the southern hemisphere. Uncertainties in details of plate reconstructions provide conflicting hypotheses about area relationships of Gondwana fragments. This has led to a number of competing proposals concerning angiosperm migration across Gondwana. Central to this debate is the role of the Antarctic Peninsula, a region that is often envisaged as providing the main connection between east and west Gondwana. The initial radiation of angiosperms into the Antarctic Peninsula region, however, postdates appearances elsewhere in east Gondwana (e.g. Australia), strongly suggesting that the Antarctic Peninsula was not the main gateway, at least in the early stages of Gondwana radiation. A steep climatic gradient in this part of the world probably acted as an effective barrier to angiosperm radiation. The peak of floristic replacement coincides with the peak of Cretaceous warmth (Turonian) which in turn suggests that climatic warming acted as a forcing mechanism by pushing latitudinal belts of vegetation southwards. Once into the southern high latitudes angiosperms diversified, and as climates cooled during the Late Cretaceous a number of important groups seem to have their origins here. Recent investigations of Antarctic macro- and microfloras indicate progressive floristic replacement through the Cretaceous. Bryophytes, hepatophytes, bennettites and other seed plants all show a rapid decline in diversity. In contrast, ferns initially decline then recover, while conifers remain relatively stable. The ecological preferences of the replaced groups imply that angiosperms initially occupied areas of disturbance and were understorey colonizers, only later replacing fern thickets and becoming important in the overstorey. This pattern is consistent with those observed elsewhere through the Cretaceous.

Description: Over long periods of time the tectonic evolution of the solid Earth has been recognized as the major control on the development of the global climate system. Tectonic activity acts in one of two different ways to influence regional and global climate: (i) through the opening and closing of oceanic gateways and its effect on the circulation patterns in the global ocean; (ii) through the growth and erosion of orogenic belts, resulting in changes in oceanic chemistry and disruption of atmospheric circulation. The Arabian Sea region has several features that make it the best area for studies of climate and palaeoceanographic responses to tectonic activity, most notably in the context of the South Asian monsoon and its relationship to the growth of high topography in the adjacent Himalayas and Tibet. The Tectonic and Climatic Evolution of the Arabian Sea Region brings together a collection of recent studies on the area from a wide group of international contributors. The paper range from high resolution, Holocene palaeoceanographic studies of the Pakistan margin to regional tectonic reconstructions of the ocean basin and surrounding margins throughout the Cenozoic. Marine geophysics, stratigraphy, isotope chemistry and neotectonics come together in a multidisciplinary approach to the study of interactions of land and sea. while much work remains to be done to understand fully the tectonic and climatic evolution of the Arabian Sea, a great deal has been achieved since the last major review, as detailed in the 26 contributions. This volume is essential reading for palaeoceanographers, sedimentologists and geophysicists. It will also be interest to structural geologists and those working in the petroleum industry.

Description: We present a revised magnetic isochron map of the conjugate Arabian a and Eastern Somali basins based on an up-to-date compilation of Indian, French, and other available seasurface magnetic data. We have used the magnetic anomaly and the modulus of the analytical signal computed from the magnetic anomaly to identify and precisely locate the young and old edges of magnetic chrons in both basins. In addition to the major, well-defined anomalies, we have also used correlatable second-order features of the magnetic anomalies, the tiny wiggles', to strengthen the interpretation. The resulting isochrons and tectonic elements have been validated using the stochastic method of palaeogeographical reconstruction. The magnetic anomaly pattern in both basins depicts clear oblique offsets, characteristics of pseudofaults associated with propagating ridge segments. Our tectonic interpretation of the area revealed: (1) a complex pattern of ridge propagation between Chrons 28n (c. 63 Ma) and 25n (c. 56 Ma), with dominant eastward propagation between Chrons 26n (c. 58 Ma) and 25n; (2) numerous, systematic westward propagations between Chrons 24n (c. 53 Ma) and 20n (c. 43 Ma); (3) asymmetric crustal accretion (caused by ridge propagation and asymmetric sea-floor spreading) in the conjugate basins during the whole period; (4) a slowing of India-Somalia motion after c. 52 Ma.

Description: The Iranian Makran has been entirely mapped geologically on a scale of 1:250 000, except for a narrow coastal strip, which exposes the very youngest Cenozoic sediments of the main Makran accretionary prism. The geology of the Makran is less widely known than the geology of Oman, because it has been published in detail only in reports of the Geological Survey of Iran. There is no extension of the geological formations of Oman into the Makran, the only extension of Oman ophiolitic formations into Iran being at Neyriz and Kermanshahr, hundreds of kilometres to the NW. This summary is based on field mapping, photo-interpretation being used only to connect traverse lines. The oldest rocks are metamorphic rocks, which form the basement to the Bajgan-Dur-kan microcontinental sliver', a narrow block that extends hundreds of kilometres from the Bitlis Massif in Turkey, through the Sanandaj-Sirjan Block of the Zagros, to north of Nikshahr in the east of the Makran. Other metamorphic rocks form the Deyader Complex near Fannuj on the southern margin of the Jaz Murian Depression. These include blueschists, and are thought to form the tip of the Tabas Microcontinental Block, largely exposed north of the depression. There is also a small microcontinental block to the east, the Birk Block, which exposes only Cretaceous platform limestones and Permian sediments. The Bajgan Metamorphic Series are overlain, with a tectonized unconformable contact, by highly deformed and disrupted platform carbonates of Early Cretaceous to Early Paleocene age (Dur-kan Complex), containing tectonic inliers of Carboniferous, Permian and, rarely, Jurassic age. Ophiolites occur in two structural positions. South of the Bajgan-Dur-kan Block, the tectonic Coloured Melange of the Zagros continues eastwards inland of the Bashakerd Fault; this includes two layered ultramafic complexes, one with chromities. The blocks forming the melange include radiolarites and deep-water limestones of Jurassic to Early Paleocene age. Ophiolites developed north of the microcontinental block form three distinct igneous complexes, two layered and one with intermediate sheeted dykes. Intercalated in the volcanic rocks of these ophiolites are radiolarites and deep-water limestones ranging in age from Jurassic to Paleocene time. There are small developments of Cretaceous sediments carrying rudists in the extreme NW of the inner ophiolite tract. In the NE, ophiolites are developed in the Talkhab Melange. All these ophiolites represent former, largely Cretaceous, tracts of deep ocean. The Cenozoic rocks form two immense accretionary prisms. The main Makran prism includes Eocene-Oligocene and Oligocene-Miocene flysch turbidite sequences, estimated as individually 〉10 000 m thick. Above these sequences, there is an abrupt passage up without any apparent unconformity, through reefal Burdigalian limestones, and locally a harzburgite conglomerate development, into neritic sequences with minor turbidites, extending into the Pliocene units. The Saravan accretionary prism to the east repeats tectonically three thick flysch turbidite sequences of Eocene-Oligocene age, but younger sediments are restricted here to minor Oligocene-Miocene conglomerates, unconformable on the above sequences. There is a line of Oligocene(?) granodiorite bodies within the Saravan accretionary prism. Intense folding and development of schuppen structure, dislocation and melanging of the sediments affected the entire region in Late Miocene-Early Pliocene time. Post-tectonic uplift was followed by scattered developments of fanglomerates beneath the fault scarps. The Neogene deformation has obscured earlier deformational events. There is unconformity beneath Eocene sediments representing a mid-Paleocene disturbance. There is also evidence of a discontinuity in mid-Oligocene time. Pliocene-Pleistocene fanglomerates are unconformable on folded rocks. There are discontinuous developments of Eocene-Oligocene neritic sediments unconformably above the older rocks (ophiolites, platform limestones, metamoprhic rocks), and to the north of the southern edge of the Jaz Murian Depression, the northern limit of the Makran, there is evidence of the survival here of a very shallow sea through Neogene time and the formation of small patches of reefal Oligocene-Miocene limestones, and Eocene to Pliocene shallow-water clastic sediments. A 150 km wide tract separates the coast from the trench, the total Cenozoic accretionary prism being 500 km wide. Extension from the Murray Ridge affects the extreme east of the region. The Saravan accretionary prism, it is suggested, faced a gulf, comparable with the Gulf of Oman, and this Saravan Gulf filled up and closed up by Early Oligocene time. Seismological evidence suggests that there is now active continental collision continuing along this suture.

Description: Settling nitrogen fluxes intercepted by sediment traps on the mid-slope and in the deep basin off Somalia show a consistent annual range of 3.4 {+/-} 0.2{per thousand} in their stable isotope composition. Seasonal minima in {delta}15N of 3.7{per thousand} are associated with the moderate N fluxes derived from coastally upwelled water, which is rapidly carried offshore along eddy margins passing over the mooring sites during the SW monsoon (June-September). Coastal upwelling, offshore transport and deep wind mixing cease at the end of the SW monsoon, leading to enhanced utilization of the up to 20 {micro}M of NO3- in the photic layer, maxima in the N export flux, and an increasing {delta}15N by Rayleigh distillation. Yet as stratification develops, nutrient exhaustion follows and export production collapses as the {delta}15N increases to over 7{per thousand}. Cyanobacterial N2 fixation probably diminishes the {delta}15N by 0.4-1.6{per thousand} during the autumn intermonsoon (November-December) when settling N fluxes are lowest. Nutrient utilization remains high during the NE monsoon (January-March), when nutrient entrainment by deep wind mixing results in enhanced N export with maxima in {delta}15N of up to 7.4{per thousand}. Annual N fluxes have virtually the same {delta}15N of 6.0{per thousand} in all traps despite considerable differences in both N flux and {delta}15N between the traps during the year and at different depths. In comparison with the annual {delta}15N of 6.0{per thousand} arriving on the sea floor, core-top sediments are enriched by +0.6{per thousand} on the upper slope (at 487 m) increasing to +2.9{per thousand} in the deep basin (at 4040 m), whereas the N sediment burial efficiency declines from about 17% to 3%. It appears that the extent of oxic decomposition at the sediment-water interface is the most likely cause of such isotope enrichment. Similar positive gradients in {delta}15N with bottom depth have been reported from other continental margin transects and are generally attributed to increased nutrient utilization in the photic ocean with distance offshore. As for Somalia, nitrogen isotope fractionation as a result of oxic decomposition on the bottom rather than nutrient utilization at the ocean surface may account for the observed increase of sedimentary {delta}15N down continental margins in general.

Description: We review previous models for the Paleogene tectonic evolution of the Arabian and Eastern Somali basins and present a model based on a new compilation of magnetic and gravity data. Using plate reconstructions, we derive a self-consistent set of isochrons for Chron 27 to Chron 21 (61-46 Ma). The new isochrons account for the development of successive ridge propagation events along the Carlsberg Ridge, leading to an important spreading asymmetry between the conjugate basins. Our model predicts the growth of the outer and inner pseudofaults associated with the ridge propagation events. The location of outer pseudo-faults appears to remain very stable despite a drastic change in the direction of ridge propagation before Chron 24 (c. 54 Ma). The motion of the Indian plate relative to the Somalian plate is stable in direction through Paleogene time; spreading velocities decrease from 6 to 3 cm a-1. Our reconstructions also confirm that the Arabia-India plate boundary was located west of the Owen Ridge along the Oman margin during Paleogene time; some compression is predicted at about Chron 21 (47 Ma) between the Indian and Arabian plates.

Description: Petrographic and geochemical data for new basalt and peridotite samples recovered from sampling sites at the Southern Murray Ridge help to constrain models for the evolution of the Owen-Murray Ridge system, which forms the northwestern boundary of the Indian plate. Trace elements immobile during alteration (Ti, Zr, Nb, Y and rare earth elements) suggest that the altered microphyric metabasalt has affinities to magmatism of active margins (island-arc tholeiite sensu lato). It is distinctly different from mid-ocean ridge basalt, back-arc-basin basalt, or intra-plate Deccan Trap basalt. The sampled serpentinized harzburgite or clinopyroxene-poor lherzolite was deformed under mantle conditions and is similar to the mantle section of nearby ophiolite sequences. This association of rocks suggests that an ophiolite melange was sampled. However, results from sampling station 462 NIOP indicate that the Murray Ridge complex also contains igneous rocks with Deccan Trap affinity. For the emplacement of the island-arc tholeiite we assume an origin in a convergent supra-subduction setting, related to the closing of a Late Cretaceous Neo-Tethyan ocean basin between the Arabian and Indian plates to the south and the Eurasian plate to the north. Since Neogene time, the Murray Ridge-Dalrymple Trough has been underlain by attenuated (?)continental crust and characterized by extensional rift tectonics.

Description: The northern Arabian Sea is at present characterized by a pronounced oxygen minimum zone (OMZ) with oxygen concentrations reaching values as low as 2 {micro}M between 150 and 1250 m. This intense mid-water OMZ results from high annual organic particle fluxes and a moderate rate of thermocline ventilation. Sediment studies have shown that the intensity of the northern Arabian Sea OMZ has fluctuated on Milankovitch and sub-Milankovitch time scales, in conjunction with changes in either surface water productivity or thermocline ventilation. Here we evaluate the role of convective mixing in the periodical breakdown of the OMZ by reconstructing the density gradient for periods showing a well-ventilated water column. For this reason we reconstructed sea surface temperatures and salinities for the last 70 ka based on alkenone thermometry and {delta}18O analyses on planktic and benthic foraminifers. For the studied time span thermocline ventilation by intermediate water formation in the northern Arabian Sea is a viable mechanism to explain observed fluctuations in the intensity of the OMZ. We postulate that the necessary decrease in the vertical density gradient during well-ventilated periods resulted from intensified winter monsoonal winds in combination with effects caused by glacio-eustacy.

Description: Absolute and relative abundances of calcareous dinoflagellate cyst species in surface sediment samples from the Arabian Sea are compared with environmental parameters of the upper 100 m of the water column to gain information on their largely unknown autecology. Ten species or morphotypes were encountered of which four occurred only as accessories. On the basis of the distribution patterns of the six more abundant species or morphotypes, the studied area is subdivided into three provinces, demonstrating a clear relationship to monsoon-controlled upper-ocean conditions. The two dominant species, Thoracosphaera heimii and Orthopithonella granifera, show opposite trends in distribution of both their absolute and relative abundances. In the NE Arabian Sea, low absolute and relative abundances of T. heimii are mainly attributed to enhanced dissolution of the small tests in this region, whereas elevated concentrations of O. granifera seem to be related to higher water temperatures and the influence of the Indus River. Sphaerodinella albatrosiana and Calciodinellum operosum are most abundant in the open ocean, associated with lower nutrient levels, relatively high temperatures and low seasonality. Spiny cysts (mainly represented by Scrippsiella trochoidea), in contrast, exhibit a more shelf-ward distribution and are most abundant in regions that are influenced by coastal upwelling, characterized by eutrophic and rather unstable conditions with seasonally lower temperatures and a shallow thermocline. A generally negative correlation of calcareous dinoflagellate cysts with primary productivity or high nutrient concentrations, as proposed by other workers, cannot be confirmed. Cyst accumulation rates off Somalia show that strong turbulence and high current speeds are unfavourable for calcareous dinoflagellates, suggesting that these organisms are more successful under rather stratified conditions.

Description: The hot springs at Bath are the largest natural thermal source in Britain. Sustainable use of the waters for a spa requires maintenance of their temperature and flow rate. Together with smaller springs at Hotwells, Bristol, they form the outflow from a regional thermal aquifer that occurs where the Carboniferous Limestone is buried at depths 〉 2.7 km in the Bristol-Bath structural basin. The aquifer is recharged via limestone outcrops forming the south and west portions of the basin rim. Current knowledge of the basin's structure is reviewed, and important uncertainties identified concerning the hydrogeological role of thrust faults which may cut the limestone at depth. A simple numerical model is used to determine the possible influence of thrusts upon groundwater flow within the thermal aquifer. Comparison of the modelled flow patterns with geochemical data and structure contours eliminates the hypothesis that thrusts completely disrupt the continuity of the aquifer. The most successful model is used to simulate the possible impact of dewatering by large quarries at the limestone outcrops north and south of Bath. Substantial reductions in modelled flow at Bath result from proposed dewatering in the eastern Mendips, although the steady-state approach adopted has severe limitations in that it does not take account of the incremental staging of actual dewatering, nor allow for partial restitution of groundwater levels. The geological uncertainties highlighted by the modelling could be addressed by future research into the effect of thrusts on the continuity of the Carboniferous Limestone. More refined modelling to predict the timing of possible impacts of quarry dewatering will require measurements of the storativity of the thermal aquifer.

Description: The High Plains Aquifer, located in the United States, is one of the largest freshwater aquifers in the world and is threatened by continued decline in water levels and deteriorating water quality. Understanding the physical and cultural features of this area is essential to assessing the factors that affect this groundwater resource. About 270f the irrigated land in the United States overlies this aquifer, which yields about 300f the nation's groundwater used for irrigation of crops including wheat, corn, sorghum, cotton and alfalfa. In addition, the aquifer provides drinking water to 820f the 2.3 million people who live within the aquifer boundary. The High Plains Aquifer has been significantly impacted by human activities. Groundwater withdrawals from the aquifer exceed recharge in many areas, resulting in substantial declines in groundwater level. Residents once believed that the aquifer was an unlimited resource of high-quality water, but they now face the prospect that much of the water may be gone in the near future. Also, agricultural chemicals are affecting the groundwater quality. Increasing concentrations of nitrate and salinity can first impair the use of the water for public supply and then affect its suitability for irrigation. A variety of technical and institutional measures are currently being planned and implemented across the aquifer area in an attempt to sustain this groundwater resource for future generations. However, because groundwater withdrawals remain high and water quality impairments are becoming more commonplace, the sustainability of the High Plains Aquifer is uncertain.

Description: Numerical models of groundwater flow and arsenic transport to tubewells in southern Bangladesh have been developed, based on a conceptual model derived from field observations. The catchment of a single hand-pumped tubewell (HTW) is incorporated within a model domain 8110m2 in area and 60m thick. Three tubewell specifications represent typical Bangladesh HTW designs. Constant-concentration cells act as a single-layered arsenic source, arranged to represent the observed depth distribution of arsenic in the aquifer and the range of possible patterns of overlap between HTW catchments and discontinuous zones of arsenic release from sediment to groundwater. A variety of sorption regimes is simulated, and sensitivity to sorption is illustrated. Boundary conditions are modified to simulate the effects of deep production wells. The models reproduce the observed scale and range of arsenic concentration in groundwater pumped from HTWs, and demonstrate likely long-term trends. Breakthrough of arsenic to HTWs may occur a few years after the start of pumping, but at many tubewells the concentration of arsenic could continue to rise significantly over tens to hundreds of years. Spatial distributions and depth profiles of arsenic in groundwater from tubewells should be viewed as transient in the long term. These preliminary models allow implications for the sustainability of the shallow alluvial aquifer to be quantified provisionally. The mechanisms and scale of sorption of arsenic by the aquifer sediments remain as significant uncertainties.

Description: Mining is an important part of the economy of Chile. A high proportion of mines are located in remote, high altitude, extremely arid environments in northern Chile. The demands of the mining industry for potable and ore-processing water, along with existing longer term demands, mean that water has a high commercial value in this region. Set against this is the desire to conserve the unique flora and fauna, highlighted by the existence of a number of conservation sites of international importance. A typical case study charting the investigation of an aquifer in this region [the Monturaqui-Negrillar-Tilopozo (MNT) aquifer] and the development of a plan for groundwater use observing the requirement for sustainability is presented. The important aspects of the geology and hydrogeology of the aquifer are presented, and a description is given of the techniques used to arrive at a sustainable groundwater development strategy. The unusual characteristics of the aquifer meant that the use of spatially distributed time-variant numerical models to identify a sustainable groundwater abstraction strategy was necessary. The abstraction strategy will enable sustainable abstraction of a significant volume of groundwater from the MNT basin, taking advantage of the high storage to recharge/discharge ratio of the aquifer.

Description: The thermal and denudational history of Ireland is evaluated using an extensive new apatite fission-track (AFT) dataset derived from surface samples. Modelled thermal histories are used to construct maps of denudation for a number of time slices from Triassic time to 10 Ma using a time-dependent palaeogeotherm. The maps illustrate the spatial variability of denudation and subsidence within each time slice. The patterns of denudation are complex, showing considerable variability at the length scale of 101-102 km, with especially high denudation rates found over known igneous centres such as the Mournes of County Down. Based on the onshore AFT data alone, there is no definitive signature of an Irish Sea Dome extending significantly across Ireland in Early Tertiary time. The cumulative amount of denudation during Tertiary time varies depending on the AFT annealing model used, but is generally in the region between 1 and 2 km and without clear spatial trends. High amounts of denudation have been mapped over the Tertiary intrusions in County Down, reflecting their unroofing since emplacement in Paleocene time. The cumulative denudation from Triassic time to 10 Ma shows relatively low amounts of denudation (〈2 km) in the Irish Midlands and the extreme NE of the island, consistent with the observation that Mesozoic-Tertiary sediments and igneous products are preserved in the Ulster Basin. The western flank of Ireland and the region between Dublin and County Down show high cumulative amounts of denudation (〈4 km), the latter being consistent with the high amounts of denudation interpreted for the Irish Sea region. This denudation pattern explains in part the outcrop of Precambrian and Lower Palaeozoic rocks in these areas. The spatial integration of the denudation over the entire landmass gives the average denudation rate and the sediment discharge from Ireland as a function of time. Average denudation rates are moderately high in Triassic time, falling to low values in Cretaceous time, and increasing substantially in Tertiary time. However, the total volumetric discharge of sediment in Tertiary time is an order of magnitude smaller than the preserved solid volume of Tertiary sediment in the basins offshore western Ireland.

Description: Based upon dinoflagellate cyst and nannofossil data, a detailed zonation of the Lower Paleocene succession in the Nuussuaq Basin, onshore West Greenland has been established. The succession is divided into the five dinoflagellate cyst zones: Trithyrodinium evittii, Cerodinium pannuceum, Senegalinium iterlaaense, Palaeocystodinium bulliforme and Alisocysta margarita. The dinoflagellate cyst zones are correlated with nannoplankton zones. The stratigraphically most important nannofossils recorded include Chiasmolithus cf. bidens, Neochiastozygus modestus, N. perfectus, N. saepes, Prinsius martinii and Zeugrhabdotus sigmoides. A new zonal scheme has been erected and resolves previous problems relating biostratigraphic and 40Ar/39Ar data in the region. The Upper Maastrichtian-Lower Paleocene succession records faulting and valley/submarine canyon incision resulting from pre-volcanic rifting and regional uplift of the basin. Two Early Paleocene tectonic phases have been recognized during NP1-NP3. These uplift phases were followed by rapid subsidence during NP4. Initiation of volcanism onshore West Greenland is broadly concurrent with the Alisocysta margarita Zone indicating that volcanism began during late NP4, in accordance with recent palaeomagnetic results and 40Ar/39Ar dating of the volcanics. On the basis of the first occurrence datum of the dinoflagellate cyst species Cerodinium kangiliense and Alisocysta margarita, it is possible to correlate the lowermost volcanic Anaanaa Member hyaloclastites from the southwestern part of Nuussuaq with sediments of the Eqalulik Formation from the northern coast of Nuussuaq.

Description: The papers in this volume represent a step forward in our knowledge of the geological evolution of the North Atlantic from the Cretaceous-Palaeogene boundary through to the early Eocene. With the increase in hydrocarbon exploration activities in the Faroe-Shetland Basin (Fig. 1), new interpretations of the regional geology have become increasingly important, and the accuracy of the time frame for this work is vital to our understanding of the sequence of volcanic and sedimentary events. The synthesis of data relating to Palaeogene volcanism and sedimentation along the Norwegian Margin by Eldholm et al. emphasizes the importance of transfer zones, possibly inherited from the Proterozoic basement, in the distribution of sediments and volcanic products during rifting (Fig. 2). Furthermore, subsequent uplift and the development of marginal highs are invoked as factors which affected water circulation within the basins, leading to a deterioration in the Eocene climate. This work identifies the relevance of the North Atlantic Igneous Province (NAIP) as an influence on environmental systems on a global scale. Ar-Ar and Pb-U isotopic age data show that the main period of continental flood basalt volcanism in the NAIP extended from c. 60.5 Ma through to c. 54.5 Ma (Table 1). Biostratigraphical analysis of these volcanic-sedimentary sections (Jolley et al. 2002) shows that the onset of this interval equates to the Late Paleocene Thermal Maximum (LPTM). New isotopic dating of the oldest part of the volcanic sequence on the Faroe Islands, the Lower Formation, by Waagstein et al. has further confirmed the age ... This 250-word extract was created in the absence of an abstract.

Description: Palaeogene volcanism on the NW margin of the Faroe-Shetland Basin is represented by the Faroes Lava Group, within an age range of 57.5-60.56 Ma. The volcanic sequence comprises 〉1000 m of basaltic volcaniclastic rocks deposited in estuarine or marginal lagoons, overlain by three laterally-extensive formations of subaerial facies basaltic lavas: Lower, c. 3250 m; Middle, c. 1400 m; Upper, at least 900 m (top not preserved). The Lower and Upper formations comprise high-volume sheet flows, commonly with ferrallitized tops, interbedded with reddened, thin, fluvial claystone and basaltic siltstone deposits. Laterally-impersistent coals occur within the Lower Lava Formation. The Coal-bearing Formation (c. 20 m) was deposited in an overbank floodplain environment during an hiatus in the volcanism between the Lower and Middle formations. The Volcaniclastic Sandstone Sequence comprises hydroclastic and pyroclastic deposits which post-date the Coal-bearing Formation and represent a return to volcanism, prior to the eruption of the Middle Lava Formation which is mainly characterized by inflated pahoehoe flows. The onshore sequence of the Faroes Lava Group can be correlated with basaltic flows within the Faroe-Shetland Basin, where lavas in Well 205/9-1 are interpreted to be of Lower Lava Formation affinity, possibly erupted from a local vent system. Seismic and gravity mapping and modelling suggest that the offshore extension of the Lower Lava Formation, together with the oldest part of the Middle Lava Formation, comprise subaqueous hyaloclastites deposited in a prograding Gilbert-type lava delta system. The youngest part of the Middle Lava Formation and all of the Upper Lava Formation occur as subaerial facies lavas within the basin.

Description: An extensive suite of igneous sills, collectively known as the Faroe-Shetland Sill Complex, has been intruded into the Cretaceous and Tertiary sedimentary section of the Faroe-Shetland Channel area. These sills have been imaged offshore by three-dimensional (3D) reflection seismic surveys and penetrated by several exploration boreholes. Data from wireline log measurements in these boreholes allow us to characterize the physical properties of the sills and their thermal aureoles. The borehole data has been compiled to produce new empirical relationships between sonic velocity and density, and between compressional and shear sonic velocities within the sills. These relationships are used to assist in calculation of synthetic seismic traces for sills intruded into sedimentary section, in order to calibrate the seismic response of the sills as observed in field data. This paper describes how the seismic amplitude response of the sills can be used to predict sill thickness where there is some nearby well control, and use this technique to estimate the volume of one well-imaged sill penetrated by Well 205/10-2b. Since the sills have a high impedance contrast with their host rocks, they return strong seismic reflections. 3D seismic survey data allow mapping of the morphology of the sills with a high level of confidence, although in some instances disruption of the downgoing seismic wavefield causes the seismic imaging of deeper sills and other structures to be very poor. Examples of sub-circular and dish-shapes sills, and also semi-conical and sheet-like intrusions, which are highly discordant are shown. The introduction of intrusive rocks can play an important role in the subsequent development of the sedimentary system. An example is shown in which differential compaction or soft sediment deformation around and above the sills appears to have controlled deposition of a reservoir quality sand body. The positioning of the sills within sedimentary basins is discussed, by constructing a simple model in which pressure support of magma from a crustal magma chamber provides the hydrostatic head of magma required for intrusion at shallow levels. This model is made semi-quantitative using a simple equation relating rock densities to intrusion depth, calibrated to observations from the Faroe-Shetland area. The model predicts that sills can be intruded at shallower levels in the sedimentary section above basement highs, which agrees with observations detailed in this paper.

Description: The North Faroe-Shetland Basin (NFSB) Sill Complex is of late Paleocene/earliest Eocene age and was emplaced within Cretaceous and Paleocene sedimentary rocks, in places to depths as shallow as a few hundred metres below the contemporaneous basin floor. Intersections of the Complex occur in exploration wells drilled by the oil industry and indicate tholeiitic basaltic compositions. High quality 3D seismic data, obtained during hydrocarbon exploration along the NE Atlantic Margin, provide a unique view of an uneroded suite of these sheet-like intrusions in UK Quadrants 218 and 219 and indicate the multi-centred nature of the NFSB Sill Complex, with upward-fingering terminations from broad bowlshaped foci of intrusion. Where the intrusion depth is very shallow, depending upon the host lithology, sill emplacement has lead to the development of structures on the contemporaneous basin floor interpreted as submarine hyaloclastite-dominated vents, up to c. 2 km across and with heights of up to c. 100 m. Where intrusion depth is greater, seismic chimney' structures are interpreted as the fluidescape feeders of sedimentary-hydrothermal mounds. Subsequent differential compaction of sedimentary sections, with and without shallow-emplaced sills, has given rise to distinctive eye' structures, as seen in seismic sections.

Description: The NW Arabian Sea is characterized by a strong seasonal contrast in surface water hydrography. During the SW monsoon of 1992, we encountered strong coastal upwelling characterized by low sea surface temperatures (SST), high nutrient concentrations, a shallow thermocline and a near-surface chlorophyll maximum. By contrast, the hydrography during the NE monsoon of 1993 was characterized by a relatively warm nutrient-depleted surface mixed layer and a deep chlorophyll maximum. We show that the faunal composition, depth habitat and abundance of living planktic foraminifera respond to the hydrographic changes controlled by the seasonally reversing monsoon system. Total shell concentrations (〉 125 {micro}m) ranged from 4 to 332 individuals (ind.) m-3 during upwelling and from 3 to 85 ind. m-3 during the non-upwelling season. During upwelling, the fauna was dominated by Globigerina bulloides. During non-upwelling the fauna was characterized by relatively high concentrations of tropical symbiont-bearing species such as Globigerinoides ruber, Globigerinoides sacculifer and Globigerinella siphonifera, whereas concentrations of Globigerina bulloides were an order of magnitude lower. Factor analysis on 15 species yields an upwelling assemblage (UA), a tropical assemblage (TA) and a subsurface assemblage (SA). A fourth factor represents the distribution of the species Globigerina falconensis, which is mainly found in subsurface waters during the non-upwelling period (NE monsoon). A model is presented to calculate the base of the productive zone from the vertical shell concentration profile of a given species. The model is validated by comparing the range in calcification temperatures of G. bulloides, derived from its {delta}18O, with the in situ sea-water temperature range of the productive zone as predicted from the model. It appears that shell growth (calcite precipitation) is restricted to the productive zone as defined by this method. The average calcification temperature of G. bulloides corresponds to the point of maximum change in the shell concentration profile (i.e. the inflection point). For most shallow-dwelling species, the inflection point is found at or below the depth of the chlorophyll maximum, although above the main thermocline. This study indicates that the depth habitat and abundance of different species varies seasonally. Consequently, the abundance and stable isotope composition of specimens in the fossil record reflects a mixture of specimens that were produced at various depths during the different seasons.

Description: Interaction between uplift related to the Cretaceous--Paleocene opening of the North Atlantic, Neogene shortening (basin inversion) and Pleistocene glacio-isostasy is illustrated by the complex denudation pattern of Britain; such denudation is greatest over the submergent East Irish Sea basin, some 500 km from the Atlantic margin. This paper reports on analysis of sedimentary porosities using sonic velocity logs from 42 wells in the East Irish Sea basin. We present a new map showing the variation in exhumation magnitude at the uppermost Mesozoic unconformity (i.e. thickness of denuded Mesozoic and Cenozoic sedimentary rocks), today buried beneath a thin veneer of Pleistocene sediment. It indicates that exhumation is mostly 〈 1500 m (632-2132 m; mean standard deviation 407 m), less than denudation results obtained from vitrinite reflectance and apatite fission-track data. The map also reveals substantial variation in exhumation over short distances, often between adjacent wells sited on opposing walls of individual faults. This is interpreted in terms of the influence of Neogene basin inversion on the exhumation of the EISB. The role of late Tertiary tectonics in western UK exhumation is therefore discussed.

Description: Denudational history is commonly reconstructed from basin sediments derived from the denuded source area, and less frequently from the source area itself. Northern Britain is an important source area for the surrounding sedimentary basins and this paper reviews the erosional history of Scotland from Devonian time to the present using evidence both from onshore geology and geomorphology and from patterns of sedimentation in surrounding basins. Cover rocks were extensive in Scotland during late Palaeozoic time but the persistence of sediment source areas within the upland areas of Scotland makes it unlikely that basement highs were ever completely buried, and depths of post-Devonian erosion of basement have been correspondingly modest (〈 1-2 km). During Mesozoic time, Scotland experienced several major erosional cycles, beginning with uplift, reactivation of relief and stripping of cover rocks, followed by progressive reduction of relief through etchplanation and culminating in extensive marine transgressions in Late Triassic, Late Jurassic and Late Cretaceous time. Mid-Paleocene pulses of coarse sediment to the Moray Firth Basin coincided with major uplift. This uplift was associated with major differential tectonics within the Highlands, with warping and faulting along the margins of the Minch and the inner Moray Firth Basins. Tectonic activity was renewed on a lesser scale in late Oligocene time and continued into Late Neogene time. Differential weathering and erosion under the warm to temperature humid climates of Neogene time created the major elements of the preglacial relief, with formation of valleys, basins, scarps and inselbergs, features often closely adjusted to lithostructural controls and, in some cases, with precursors that can be traced back to Devonian time. The history that can be read' from the onshore region complements the source area history interpreted from sedimentary basins derived from these areas.

Description: We use the flux of bulk sediment (CaCO3, biogenic opal, organic carbon, lithogenic material), and of planktic foraminifera (PF) and other shell-bearing plankton from sediment trap EPT-2 off Pakistan to (1) constrain the seasonal pattern of regional productivity and (2) search for indications of the NE monsoon winter situation that may serve as a modern analogue to better reveal the seasonal climatic signals preserved in the sedimentary record of the Arabian Sea. Our trap data show a clear seasonality of fluxes that can also be traced in the composition of non-bioturbated (varved) summer and winter sediment laminae preserved within the oxygen minimum zone. In EPT-2, the flux of PF is low during summer, but during winter and late spring it is higher, as at trap station WAST, in the upwelling area of the western Arabian Sea. Globigerina bulloides, a PF species linked to summer upwelling and high productivity, is of minor importance off Pakistan. In contrast, Globigerina falconensis dominates in flux and relative abundance, and is indicative of winter mixing, when NE monsoonal winds cool the highly saline surface waters and break up stratification. An enhanced horizontal flux of suspended sediments stirred up on the shelf and upper slope is clearly shown by the peak in occurrence of small benthic foraminifera during winter. Altogether, our data suggest that the particle flux in the northeastern Arabian Sea is determined by local sediment resuspension and winter productivity rather than by summer monsoonal upwelling, representing a non-upwelling' environment, in contrast to the summer upwelling' regime off Oman, Somalia and southern India. We used this evidence to reconstruct the seasonal intensity of both monsoons for the past 25 ka: the SW and NE monsoon both were weak during the last glacial period. The NE monsoon peaked during the cool phases of the glacial to interglacial climatic transition (i.e. during the Younger Dryas (YD) and Heinrich Event H1). The SW monsoon was reinforced after the YD. Both monsoons were enhanced during early Holocene time, when summer insolation and hence atmospheric forcing was at a maximum.

Description: The tectonic evolution of Archaean granite-greenstone terranes remains controversial. Here this subject is reviewed and illustrated with new data from the Slave craton. These data show that a thick, c. 2.7Ga, pillow basalt sequences extruded across extended sialic basement of the Slave craton at a scale comparable with that of modern large igneous provinces. The pillow basalts do not represent obducted oceanic allochthons. Basement-cover relationships argue for autochthonous to parautochthonous development of the basaltic greenstone belts of the west-central Slave craton, an interpretation that is further supported by geochemical and geochronological data. Similar data exist for several other cratons and granite-greenstone terrains, including the Abitibi greenstone belt of the Superior craton, where stratigraphic and subtle zircon inheritance data are equally incompatible with accretion of oceanic allochthons. Many classical granite-greenstone terrains, including most well-documented komatiite occurrences, thus appear to have formed in extensional environments within or on the margins of older continental crust. Closest modern analogues for such basalt-komatiite-rhyolite-dominated greenstone successions are rifts, marginal basins and volcanic rifted margins. Indeed, these environments have high preservation potential compared with fully oceanic settings. Collapse and structural telescoping of these highly extended volcano-sedimentary basins would allow for the complex structural development seen in granite-greenstone terrains while maintaining broadly autochthonous to parautochthonous tectonostratigraphic relationships. Seismic reflection profiles cannot discriminate between these telescoped autochthonous to parautochthonous settings and truly allochthonous accretionary complexes. Only carefully constructed structural-stratigraphic cross-sections, allowing some degree of palinspastic reconstruction, and underpinned by sufficient U-Pb zircon dating, can address the degree of allochthoneity of greenstone packages. Furthermore, seismic reflection profiles are essentially blind for the steep structures produced by multiple phases of upright folding and buoyant rise of mid- to lower-crustal, composite, granitoid and gneiss domes. Such structures are ubiquitous in granite-greenstone terrains and, indeed, most of these terrains appear to have experienced at least one phase of convective overturn to re-establish a stable density configuration, irrespective of the complexities of the pre-doming structural history. Buoyant rise of mid- to lower-crustal granitoid and gneiss domes can explain the typical size and spacing characteristics of such domes in granite-greenstone terranes, and the coeval deposition of late-kinematic, Timiskaming-type' conglomerate-sandstone successions in flanking basins. The extensional and subsequent contractional evolution of granite-greenstone terrains may have occurred in the overall context of a plate tectonic regime (e.g. volcanic rifted margins, back-arc basins) but highly extended, intraplate, rift-like settings seem equally plausible. Explaining the evolution of the latter in terms of Wilson cycles is misguided. Periods of intense rifting and flood volcanism (e.g. 2.73-2.70 Ga) may have been related to increased mantle plume activity or perhaps catastrophic mantle overturn events. Although there is evidence for plate-like lateral movement in late Archaean time (e.g. lateral heterogeneity of cratons, arc-like volcanism, cratonscale deformation patterns, strike-slip faults, etc.), the details of how these plate-like crustal blocks interacted and how they responded to rifting and collision appear to have differed significantly from those in Phanerozoic time. The most productive approach for Archaean research is probably to more fully understand and quantify these differences rather than the common emphasis on the superficial similarities with modern plate tectonics.

Description: The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle is linked to the mantle via subduction of carbonatized basalts and degassing of CO2 at the mid-ocean ridges. Feedback is provided by the dependence of carbonatization on the amount of dissolved carbonate in sea water. Unlike the continental cycle, the oceanic cycle has no thermostat. Hence surface temperatures can become very low if CO2 is the only greenhouse gas apart from water. Currently the continental cycle is more important, but early in Earth's history the oceanic cycle was probably dominant. We argue that CO2 greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of Proterozoic and Archaean time. We echo current fashion and favour biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in Hadean time. Despite its name, the Hadean Eon might have been the coldest era in the history of the Earth.

Description: Lithosphere that formed in Archaean and possibly early Proterozoic time is thicker, more buoyant, and geochemically distinct from lithosphere that formed after about 2.3 Ga. Mantle xenolith and seismic data indicate that some cratonic roots, or keels', extend to depths of c. 250 km, compared with normal continental lithosphere of thickness 150 km or less; yet many cratons have experienced uplift, dyking and kimberlite emplacement, suggesting interactions with hot, rising asthenosphere referred to as mantle plumes. Plumes supply additional heat to the base of the lithospheric plates, whose base can be heated and entrained in the flow (thermal erosion). How have these cratonic keels persisted despite their interactions with mantle plumes? The geometry of cratonic keels during their interactions with mantle plumes is a critical factor controlling keel preservation. To a laterally spreading plume head, cratonic keels appear as major obstacles, and the hot, buoyant plume material ponds beneath thinner lithosphere. Our model simulations show that deep keels deflect mantle plume material and that steep gradients at the lithosphere-asthenosphere boundary between Archaean keels and normal' lithosphere will focus flow, leading to localized adiabatic decompression melting. Plume processes can lead to a reduction in the breadth of a cratonic root where the plume rises beneath the craton, regardless of the initial breadth of the craton. Where the plume rises beneath a craton the hot plume material will spread laterally beneath the keel and attain thicknesses of tens of kilometres. This transfers heat to the base of the lithosphere and could generate small volumes of melt at considerable depth, depending on the composition of the lower lithosphere. We have used model simulations of plumes beneath Africa to predict the magnitude and direction of seismic anisotropy caused by lateral flow of hot plume material beneath and around a cratonic keel. The shear-wave splitting in our models is greatest at the edge of the cratonic keel, and its azimuth is parallel to the plume flow direction.

Description: Depressurization of reservoirs in petroliferous basins commonly occurs through cap-rocks at structural crests where pore pressures are locally elevated because of either the presence of a hydrocarbon column or the redistribution of overpressures by water flow along laterally extensive inclined permeable aquifers. In exhumed petroliferous basins this deflation of excess pore pressures is enhanced by the denudation process, which results in the large-scale removal of overburden during regional uplift. Evidence from the exhumed basins of the Atlantic margin indicates that hydrocarbon accumulations in these basins are commonly characterized by underfilled traps and hydrostatically pressured or modestly overpressured reservoirs. These observations are reviewed in the context of the generic mechanisms by which top-seals leak, the properties of cap-rocks and the physical processes that occur during exhumation. Water-wet shaly cap-rocks can form a capillary seal to a hydrocarbon column while simultaneously accommodating brine flow and equilibration of pressures between the reservoir and the top-seal. In contrast, thick, low-permeability shale or evaporite sequences may form pressure seals that restrict vertical brine and hydrocarbon flow and prevent the equilibration of aquifer pressures above and below the seal. In any sedimentary basin, the presence of regional pressure seals can result in a layered hydrogeological regime with hydrostatically pressured strata decoupled from over- or underpressured cells. Recently exhumed basins typically show limited overpressuring and in a number of these basins underpressured reservoirs have been described. Post-exhumation overpressure generation is primarily driven by tectonic compression, aquathermal pressuring and hydraulic head. The fluid retention capacity of any cap-rock lithology during exhumation is dependent upon the physical and mechanical characteristics of the cap-rock at the time of exhumation and the timing and conditions of the associated deformation relative to the timing of hydrocarbon emplacement. The permeability and deformational characteristics of halite render it an excellent cap-rock with a high retention capacity, even under conditions of exhumation. However, mudrocks may also form effective cap-rocks in exhumed basins when the deformation associated with exhumation occurs before embrittlement and the shale cap-rock exhibits ductile behaviour. Shale and evaporite cap-rocks form the main regional seals to hydrocarbon accumulations in exhumed basins of the Atlantic margin and borderlands. Syn-exhumation top-seal efficiency (fluid retention capacity) is a major exploration risk in these basins, although post-exhumation top-seal integrity in these basins may be relatively high under certain conditions. Consequently, a major exploration risk factor in exhumed basin settings pertains to the limited hydrocarbon budget available post-regional uplift and the efficiency of the remigration process.

Description: The volcanic succession in the inland Prinsen af Wales Bjerge contains the oldest known onshore lava flows (61 Ma) of the Palaeogene East Greenland flood basalt province. These flows and interbedded sediments define the Urbjerget Formation and are found in the southernmost part of Prinsen af Wales Bjerge. Flows of the Urbjerget Formation are chemically similar to the coastal Vandfaldsdalen Formation flows and the two formations may be chronostratigraphical equivalents. The Urbjerget Formation is overlain by the 〈 57 Ma tholeiitic basalts of the Milne Land Formation. Four regional volcanic formations are found along the Blosseville Kyst, but the Milne Land Formation is the only one present in the southern Prinsen af Wales Bjerge. Flows of the absent formations (Geikie Plateau, Romer Fjord and Skraenterne formations) may not have been able to enter the area due to local uplift, more distal located eruption sites or possibly topographic features. A high-Si (SiO2 〉 52 wt%) lave flow succession in the Milne Land Formation consists of crustally contaminated magmas which were arrested in crustal chambers as the magma supply rate from the mantle decreased, either due to a general lowering of potential mantle temperatures or a decrease in the rate of continental rifting. Tholeiitic high-Ti flows (MgO: 10-15 wt%, TiO2: 5-6 wt%) within the Milne Land Formation are unique to the Prinsen af Wales Bjerge region, and equivalents have not been reported from other flood basalt provinces. Local flow composition variations in the Milne Land Formation can be explained as the result of melting under lithosphere of variable thickness, small-scale variations in mantle composition and mixing in small magma chambers. Unconformably overlying the Milne Land Formation is a succession of c. 53 Ma alkaline flows, known as the Prinsen af Wales Bjerge Formation. Several crater sites are known from this flow succession and this suggests that the Prinsen af Wales Formation was only covered locally by later volcanic or sedimentary units. The duration of alkaline volcanic activity in the Prinsen af Wales Bjerge is not well constrained but may have been less than 2.5 Ma. The hiatus between the Urbjerget and Milne Land formations is a regional feature in the North Atlantic as it occurs at a similar stratigraphic level at Nansen Fjord, the Faroe Islands and in the ODP Leg 152 volcanic succession off SE Greenland at c. 63{degrees}N. It represents a 3-4 Ma long cessation of, or very low frequency of activity in East Greenland/Faroese volcanism and may be explained as the time interval between two pulses in the palaeo-Icelandic plume.

Description: Quartz veins in the Eastern Tonale mylonite zone (Italian Alps) were deformed in strike-slip shear. Due to the synkinematic emplacement of the Adamello Pluton, a temperature gradient between 280{degrees}C and 700{degrees}C was effected across this fault zone. The resulting dynamic recrystallization microstructures are characteristic of bulging recrystallization, subgrain rotation recrystallization and grain boundary migration recrystallization. The transitions in recrystallization mechanisms are marked by discrete changes of grain size dependence on temperature. Differential stresses are calculated from the recrystallized grain size data using paleopiezometric relationships. Deformation temperatures are obtained from metamorphic reactions in the deformed host rock. Flow stresses and deformation temperatures are used to determine the strain rate of the Tonale mylonites through integration with several published flow laws yielding an average rate of approximately 10-14s-1 to 10-12s-1. The deformation conditions of the natural fault rocks are compared and correlated with three experimental dislocation creep regimes of quartz of Hirth & Tullis. Linking the microstructures of the naturally and experimentally deformed quartz rocks, a recrystallization mechanism map is presented. This map permits the derivation of temperature and strain rate for mylonitic fault rocks once the recrystallization mechanism is known.

Description: Sulphide-rich sediments, stromatolitic limestones and tidal-flat deposits in the late Archaean (2.7 Ga) Manjeri and Cheshire Formations, Belingwe greenstone belt, Zimbabwe show evidence for complex and extensive prokaryotic mat communities, including (1) shallow-water coastal sulphur mats; (2) mats, probably in somewhat deeper water; (3) nearby stromatolites that lived by oxygenic photosynthesis in shallow coastal settings. Petrological and geochemical (rare earth element; REE) evidence, coupled with high-resolution stable isotope results, identifies several complex interdependent metabolic consortia of bacteria and archaea. These microbial consortia would have exchanged nutrients and products both locally within prokaryotic mats and more widely via the waters of the Belingwe basin. This isotopic, sedimentological and REE evidence for a complex ecology of bacteria and archaea is consistent with metabolic inferences from rRNA phylogeny and is direct evidence that a diverse prokaryotic community, managing carbon on a global scale, had evolved by the late Archaean.

Description: High pressure (HP) and ultrahigh (UHP) metamorphic rocks are exhumed from subduction zones at high rates on the order of plate velocity (cm/year). Their structural and microstructural record provides insight into conditions and physical state along the plate interface in subduction zones to depths of 〉100 km. Amazingly, many identified (U)HP metamorphic rocks appear not to be significantly deformed at (U)HP conditions, despite their history within a high strain rate mega-shearzone. Other (U)HP metamorphic rocks seem to be deformed exclusively by dissolution-precipitation creep. Indications of deformation by dislocation creep are lacking, apart from omphacite in some eclogites. Available flow laws for dislocation creep (extrapolated to low natural strain rates, which is equivalent to no deformation on the time scales of subduction and exhumation, i.e., 1 to 10 Ma) pose an upper bound to the magnitude of stress as a function of temperature along the trajectory followed by the rock. Although the record of exhumed (U)HP metamorphic rocks may only be representative of specific types or evolutionary stages of subduction zones, for such cases it implies: (1) strongly localized deformation; (2) predominance of dissolution-precipitation creep and fluid-assisted granular flow in the shear zones, suggesting Newtonian behaviour; (3) low magnitude of differential stress; which (4) is on the order of the stress drop inferred for earthquakes; and (5) negligible shear heating. These findings are easily reconciled with exhumation by forced flow in a low viscosity subduction channel prior to collision, implying effective decoupling between the plates.

Description: To investigate the influence of stress on permeability anisotropy during mechanical compaction, a series of triaxial compression experiments with a new loading configuration called hybrid compression were conducted on three porous sandstones. The effective mean and differential stresses in hybrid compression tests were identical to those in conventional triaxial extension tests. Permeability was measured along the axial direction in both hybrid compression and conventional extension tests, which corresponds to flow along the maximum principal stress direction in the former case and the minimum principal stress direction in the latter case. Since their loading paths coincide, the comparison of permeability values from the two types of tests provides quantitative estimates of the development of permeability anisotropy as a function of effective mean and differential stresses. Our data show that the permeability evolution is primarily controlled by stress. Before the onset of shear-enhanced compaction C*, permeability and porosity reduction are solely controlled by the effective mean stress, with negligible stress-induced anisotropy. With the onset of shear-enhanced compaction and initiation of cataclastic flow, the deviatoric stress induces enhanced permeability and porosity reduction. The permeability tensor may show significant anisotropy. Our data indicate that the maximum principal component of permeability tensor k1 is parallel to the maximum principal stress {sigma}1, and the minimum principal component k3 is parallel to the minimum principal stress {sigma}3. During the initiation and development of shear-enhanced compaction, k1 can exceed k3 by as much as two orders of magnitude. With the progressive development of cataclastic flow, changes of permeability and porosity become gradual again, and the stress-induced permeability anisotropy diminishes as k1 and k3 gradually converge. Our data imply that permeability can be highly anisotropic in tectonic settings undergoing cataclastic flow, inducing the fluid to flow preferentially along conduits subparallel to the maximum compression direction. However, this development of permeability anisotropy is transient in nature, becoming negligible with an accumulation of strain of about 10%. The anisotropic development of permeability in a lithified rock is dominantly controlled by microcracking and pore collapse. This is fundamentally different from the mechanisms active in unconsolidated materials such as sediments and fault gouges, in which the permeability evolution is primarily controlled by the development of fabric and shear localization via the accumulation of shear strain.

Description: Several recent studies have suggested that antitaxial fibrous veins may form without fracturing, and not by the commonly invoked crack-seal mechanism. It has also been suggested that such veins would derive their nutrients locally by diffusional transport. This hypothesis was tested on carbonaceous shale-hosted antitaxial fibrous calcite veins from Oppaminda Creek in the northern Flinders Ranges, South Australia. Apart from their fibrous texture, these veins lack the classical features of crack-seal veins, such as wallrock-parallel inclusion bands. Diffusional transport of locally derived calcite cannot explain all major and trace element data of the veins and their adjacent wallrock and indicate that part of the calcite was transported over distances of at least 〉decimetres, probably 〉〉100m. Sr isotopic fingerprinting shows that an external fluid that carried radiogenic Sr must have percolated through the system. Fluid flow was pervasive as there is no evidence that this fluid preferentially percolated through the veins. Our data support the view that antitaxial fibrous veins of the type found at Oppaminda Creek grew in the absence of fractures, but show that such veins do not necessarily indicate local diffusional transport. Our data confirm a recently postulated basin-wide fluid flow event around 586 Ma that is probably related to copper mineralization in the area.

Description: Multidisciplinary studies undertaken within the EU-funded PACE Network have permitted a new 3-D reassessment of the relationships between the principal crustal blocks abutting Baltica along the Trans-European Suture Zone (TESZ). The simplest model indicates that accretion was in three stages: end-Cambrian accretion of the Bruno-Silesian, [L]ysogory and Ma[l]opolska terranes; late Ordovician accretion of Avalonia, and early Carboniferous accretion of the Armorican Terrane Assemblage (ATA), which had coalesced during Late Devonian -- Early Carboniferous time. All these accreted blocks contain similar Neoproterozoic basement indicating a peri-Gondwanan origin: Palaeozoic plume-influenced metabasite geochemistry in the Bohemian Massif in turn may explain their progressive separation from Gondwana before their accretion to Baltica, although separation of the Bruno-Silesian and related blocks from Baltica during the Cambrian is contentious. Inherited ages from both the Bruno-Silesian crustal block and Avalonia contain a 1.5 Ga Rondonian' component arguing for proximity to the Amazonian craton at the end of the Neoproterozoic: such a component is absent from Armorican terranes, which suggests that they have closer affinities with the West African craton. Models showing the former locations of these terranes and the larger continents from which they rifted, or to which they became attached, must conform to the above constraints, as well as those provided by palaeomagnetic data. Hence, at the end of the Proterozoic and in the early Palaeozoic, these smaller terranes, some of which contain Neoproterozoic ophiolitic marginal basin and magmatic arc remnants, probably occurred within the end-Proterozoic supercontinent as part of a Pacific-type' margin, which became dismembered and relocated as the supercontinent fragmented.

Description: The Superior Province, which forms the nucleus of North America, is the largest preserved Archaean crustal block in the world and may have originated as the result of a widespread crustal accretion event (c. 2.7 Ga) manifested in Archaean cratons worldwide. An understanding of the accretionary evolution of this craton is the objective of the continuing Lithoprobe transect in the Western Superior Province, Canada. The geophysical components of the transect include seismic reflection and refraction, magnetotellurics and teleseismic experiments. The Teleseismic Western Superior Transect (TWiST) was designed to explore the structural and physical properties of the subcrustal lithosphere and their implications for proposed accretionary models. A north-south-trending array of 17 broadband three-component seismometers was deployed between May and November 1997. Surface-wave analyses, SKS-splitting studies and travel-time tomography show variations in the velocity structure and anisotropy between the southern end of the transect, a region affected by Keweenawan rifting, and the northern part, which lies in the Proterozoic Trans-Hudson shear zone. Surface waves reveal evidence for a thin high-velocity layer, 5-20 km thick, beneath a 37-43 km thick crust and above c. 250 km of high-velocity continental root. This thin layer is also visible in wide-angle refraction data from the southern end of the line and may be evidence of underplating during terrane accretion. Discrepancies in the Love and Rayleigh waves and surface-wave particle motions show evidence for an anisotropic mantle. SKS analysis shows large amounts (up to 2 s) of shear-wave splitting with a roughly eastwest trend in the fast-shear-wave polarization direction for most stations. This conforms with crustal deformation trends. Stations in the younger Trans-Hudson orogen show much less splitting. Detailed analysis at a permanent station in the Western Superior shows evidence for two layers of anisotropy. A thinner upper layer is aligned with the surface geology, indicating crust-mantle coupling during craton formation, whereas a thicker lower layer is aligned with the direction of absolute plate motion. Tomographic results show a featureless mantle beneath the Sachigo proto-craton and more heterogeneity towards the south end of the line. A steeply dipping slab-like feature in the lithosphere correlates with wide-angle refraction and deep-reflection seismic profiles. A similar high-velocity feature continues well into the transition zone, but its origin remains to be understood. Towards the southern end of the line there is a deep-seated low-velocity anomaly, which may be associated with Keweenawan plume activity. As a whole, the seismic results show many features that support ideas of subduction-related accretion of a thick stable Archaean tectosphere. There are, however, interesting details that are to date unique to the Western Superior Province. These include thicker than normal Archaean crust, a slab-like velocity anomaly in the mantle transition zone, and large SKS splitting in the Archaean Superior Province but little splitting in the surrounding Trans-Hudson Proterozoic shear zone.

Description: This review discusses the attempts that have been made by geologists to numerically simulate the evolution of microstructures in rocks. The strengths and weaknesses of the differing techniques are compared and equivalent materials science results are included. In particular we focus on the application of techniques that have been used to predict texture development, grain boundary geometries, deformation in one and two-phase systems and crystal growth.

Description: Continued studies of xenolith suites found in kimberlites on and around the Kaapvaal Craton, together with those from newly discovered localities on other cratons, are providing new insights into the generation and evolution of the Earth's oldest continents. Comparison of modal abundance data with melt depletion models, together with trace element and isotope systematics in Kaapvaal low-temperature peridotites, suggest that much or all of the diopside and garnet in these rocks may have formed significantly after initial melt depletion. The Re-Os isotope system has been instrumental in providing an improved understanding of the timing of the formation of cratonic lithospheric keels. New studies that focus on carefully selected whole-rock peridotites and use combined platinum group element (PGE) and Re-Os isotope analysis provide better constraints on the significance of Re-Os model ages. The large database of Re-Os isotope analyses for peridotites for the Kaapvaal Craton indicate formation of significant amounts of lithospheric mantle in Neoarchaean time, associated with voluminous mafic magmatism. Formation of lithospheric mantle in Neoarchean time (3.0-2.5 Ga) follows the cessation of major crustal differentiation events at c. 3.1 Ga and marks the onset of craton stabilization. Some lithospheric mantle was produced in Palaeo- to Mesoarchaean time (3.8-3.0 Ga) in southern Africa, which preserved ancient crustal fragments. Large-scale preservation of Archaean continental masses was effective only after the formation of substantial, buoyant, rigid, deep lithospheric keels and their stabilization in Neoarchean time. Formation of lithospheric mantle beneath the surrounding Proterozoic crustal regions occurred in Mesoproterozoic time, with lower degrees of mantle melting than associated with the cratonic peridotites. This circum-cratonic mantle is of similar age to the oldest overlying crust and has been coupled to the margins of the craton since its formation. Major magmatic events, some coincident with the formation of circumcratonic mantle, added new lithosphere to the Kaapvaal mantle root but failed to destroy it. The mechanically strong, buoyant lithospheric keels beneath cratons protect their crust from subduction and recycling over 3 Ga time periods.

Description: We present fault analyses from the exhumed middle crustal slab of the High Himalaya in eastern Lunana in NW Bhutan. Fault planes from within two-mica, tourma-line-bearing leucogranites, leucogranitic rocks and migmatites indicate a complex brittle fault pattern with two distinct fault groups. A first group of faults (D1) characterized by chlorite, quartz and tourmaline slickenfibres is mainly defined by steeply SSE-dipping oblique-slip normal faults, and by shallowly NNW-dipping normal faults. A second, younger group of faults (D2) characterized by cataclasis products comprises strike-slip faults displaying conjugate patterns and E- and W-dipping conjugate normal faults, all which indicate E-W extension. Cross-cutting relationships amongst the D1 fault group demonstrate that progressively steeper members of the fault group become younger within the NNW-dipping faults and become older within the SSE-dipping faults. These are all post-dated by the D2 fault group. The D1 fault group indicates that the slab experienced ongoing NNW-SSE extension (i.e. flow) via brittle fault accommodation, contemporaneous with fault rotation. This may reflect rotation of the entire upper orogen due to movement over deeply located major ramp structures formed by out-of-sequence thrusting (Kakhtang Thrust) within the High Himalayan Slab of the Bhutan Himalaya.

Description: X-ray and neutron diffraction techniques have been applied to quantitative texture analysis of a glaucophanite from the Sesia-Lanzo Zone (Western Italian Alps), naturally deformed under eclogite facies conditions. The comparison has been carried out in order to reveal the limits and problems of texture analysis related to strongly deformed polymineralic. Different methods of measuring and computing the orientation distribution function from diffraction data have been tested, in particular X-rays, direct peak integration, and neutron diffraction using Rietveld-texture analysis. Due to grain-size problems and heterogeneity of individual amphibole minerals, neutron radiation is shown to be the best probe for characterizing the whole rock: being more penetrative than conventional X-rays, a larger volume of the mineral aggregate is sampled, giving better statistics. However, results obtained by summing the corresponding individual spectra of at least three X-ray diffraction experiments on parallel slabs of the same specimen also give statistically valid, semiquantitative results that reproduce the overall textures. The quantitative texture analysis shows the strong texture of the two generations of amphiboles (AmpI and AmpII), which are mainly characterized by [001]*-directions at an angle of about 10{degrees} to the mineral lineation and by (hk0) planes describing girdles around the lineation. The texture is comparable to those described in the literature for amphibole deformed under different temperature and pressure conditions, and the pronounced asymmetry of the [001]* directions with respect to the mineral lineation is consistent with a non-coaxial component that occurs during the deformation.

Description: The influence of the dominance of different processes on the microstructural development of a quartzite was investigated using the numerical model ELLE'. Dynamic recrystallization of a polycrystalline aggregate was simulated by the concurrent operation of viscous deformation, lattice rotation, subgrain formation, rotational recrystallization, nucleation of new grains from strongly strained grains and recovery. The different observed microstructural characteristics depend on the relative rates at which grain boundary migration, subgrain formation, recrystallization by rotation and nucleation affect the microstructure. Observed sizes of recrystallized grains are significantly influenced by these different relative rates of processes. These rates are determined by parameters that mainly depend on temperature, fluid absence or presence, shear stress and strain rate. Therefore, the specific conditions at which deformation took place have to be taken into account if recrystallized grain sizes are used for palaeopiezometry. Comparison and combination of our results with experimental data and observations in natural examples provide the possibility of interpreting microstructures quantitatively in terms of temperature and shear strain rate.

Description: 2D deformation experiments on multilayer models of a brittle-ductile lithosphere are reviewed. The experimental method consists of simulating simplified strength profiles which incorporate brittle (frictional) and ductile (viscous) rheologies with gravity forces. A selection of models built with sand and silicone putties to represent brittle and ductile lithosphere layers, respectively, is used to illustrate the effects of variations in strength profiles on deformation patterns. Models of extension first consider lithosphere necking and the development of narrow rifts, with application to continental rifts and passive margins, and, second, lithosphere spreading with application to the development of wide rifts and core complexes. Models of compression compare sandbox-type and brittle-ductile multilayer-type experiments. Results are applied to mountain belt formation and, in particular, to the Pyrenees and the western Alps. Both extensional and compressional experiments demonstrate that the presence/absence of a sub-Moho brittle mantle and the coupling/decoupling between brittle and ductile layers play a dominant role on localized versus distributed deformation, at lithosphere scale.

Description: Palaeozoic Amalgamation of Central Europe summarizes recent research designed to clarify the timing, geometry and processes by which discrete terranes of Central Europe became amalgamated during the Palaeozoic Era. The area studied extends from the southern North Sea to Central Poland along the Trans-European Suture Zone, covering much of Germany, Denmark, Belgium, the Czech Republic and Poland. The 16 papers within the volume are divided into five sections: biostratigraphic/provenance evidence; isotopic constraints; petrological and geochemical evidence; structural evolution; seismic traverses and deep crustal structure. The first section contains papers summarizing continent-specific micropalaeontological and sediment provenance information backing current debates about microcontinent derivation and timing of their accretions to the proto-European continent, Baltica. The section on isotopic constraints discusses the use of isotopic dating to constrain the timing of accretions of rock units exposed in the northern Bohemian Massif, while the following section has more detailed studies of metamorphosed ophiolitic complexes adjoining palaeosutures in the same area. The two papers on the structural evolution of the area contrast a detailed review of the structural evolution of the Sudetes, with a broader, more regionally based hypothesis for the structural evolution of all Central Europe. The final section discusses models based on extensive seismic traverses in contrasting parts of the area - Belgium, the southern North Sea and Poland. This wide-ranging study thus encapsulates the most up-to-date ideas on the Palaeozoic amalgamation of Central Europe from the leading international researchers in the field. The volume will be of interest to those earth scientists in industry and academia with a broad-based interest in the construction of the European continent, primarily biostratigraphers, geophysicists, structural geologists and geochemists.

Description: Following recognition of the Vendian to mid-Ordovician rotation of Baltica, with more than 55{degrees} of that rotation occurring in the Upper Cambrian and Lower Ordovician, the Tornquist Margin of Baltica must have faced northwards towards Laurentia and the Panthalassic Ocean, rather than, as now, southwestwards towards Gondwana (including Avalonia). Unequivocally Baltic endemic trilobite, brachiopod and other faunas are known from both the Cambrian and the Ordovician of the Holy Cross Mountains, Poland, and from both parts of them, i.e. the Ma[l]opolska Block and the [L]ysogory Block. Whether or not these two blocks were united into a single terrane or were separate as two terranes is equivocal from the faunal evidence, and there is no faunal evidence of substantial strikeslip faulting of the blocks in relation to the main Baltic craton: they are perceived as having made up part of the margin of Baltica itself. However, both Holy Cross Mountain blocks were different and palaeogeographically separate from the Bruno-Silesian Block, whose continental origins are yet to be finally determined. The Ordovician clastic sediments at both Rugen, north Germany, and Pomerania, NW Poland, have yielded no macrofossils other than graptolites, but microfossils (acritarchs and chitinozoa) are interpreted as having been deposited at relatively high palaeolatitudes, i.e. at a higher palaeolatitude than Baltica, and may have been deposited in an ocean basin within the Tornquist Ocean between Baltica and Avalonia.

Description: The West Sudetes (NE margin of the Bohemian Massif) consist of a complex mosaic of several tectonometamorphic units juxtaposed during the Variscan orogeny. The polyphase Variscan tectonothermal development of the West Sudetes was determined by 40Ar/39Ar ages of single grains and mineral concentrates. Late Famennian (359 Ma) mica ages from the high-grade Gory Sowie Block suggest continuous uplift after a Late Devonian high temperature-low pressure (HT-LP) event contemporaneous with the end of subduction-related high pressure-low temperature (HP-LT) metamorphism in the East Krkono[s]e Complex. Mid-Late Devonian high pressure events in the Krkono[s]e-Jizera Terrane and Orlica-[S]nie[z]nik Dome are followed by coeval high temperature events between 345 and 335 Ma (Visean). The latter are interpreted as consequence of uplift, and decompression during overthrusting of both complexes on their forelands. Subsequent small- to large-scale shear movements dated at around 325-320 Ma (early Namurian) affected the Orlica-[S]nie[z]nik Dome, Krkono[s]e-Jizera Terrane, including the Intra-Sudetic Fault, and also the eastern Lusatian Granitoid Complex. They were accompanied by contemporaneous emplacement of the Krkono[s]e-Jizera pluton. The upper limit of the tectonometamorphic and magmatic activity is dated at 314-312 Ma (Namurian/Westphalian boundary). The final juxtaposition of the diversified tectonometamorphic units, which constitute the West Sudetes, took place in early Namurian times.

Description: Tectonically disturbed Ordovician rocks penetrated by deep drillholes in Pomerania, NW Poland (Koszalin-Chojnice Zone) belong to the Heligoland-Pomerania Deformation Belt. Earlier data demonstrate that the Avalonia-Baltica collision occurred in Late Ordovician times, but in Pomerania, the timing of convergence has not been ascertained, and it is uncertain if the rocks underneath the Koszalin-Chojnice Zone belong to Avalonia or Baltica. Data from chitinozoans, organic-walled Palaeozoic microfossils with applications in biostratigraphy and palaeobiogeography, were assessed from ten boreholes (Brda 2; Brda 3; Chojnice 5; Karsina 1; Ko[s]ciernica 1; Nowa Wie[s] 1; Okunino 1; Sarbinowo 1; Skibno 1; Wyszeborz 1) to address these problems. The results improve the biostratigraphy of the cores and demonstrate that the youngest Ordovician rocks are of a Burrellian (early mid Caradoc) to Cheneyan (late mid Caradoc) age. Because these rocks are interpreted as forming part of the deformation belt, the obtained ages put a lower age limit on the initiation of foreland basin sedimentation on the foreland of the orogeny, i.e. the Baltic platform. Quantitative comparison of chitinozoan assemblages demonstrates a high level of similarity between Pomerania and Avalonia. Together, Pomerania and Avalonia show greater similarity to Baltoscandia than to North Gondwana, supporting the idea that the Tornquist Ocean had narrowed significantly in early Caradoc times.

Description: A review is given of recently published and new data on Avalonia east of the Midlands Microcraton. The three megasequences from Cambrian to mid Devonian described in Wales and Welsh Borderland are also present east of the Midlands Microcraton (Brabant Massif, Condroz, Ardennes, Remscheid and Ebbe inliers, Krefeld high). The three megasequences are caused by a tectonic driving mechanism and are explained by three different geodynamic contexts: an earlier phase with extensional basins or rifting and rather thick sequences, when Avalonia was still attached to Gondwana; a second phase with a shelf basin with moderately thin sequences when Avalonia was a separate continent and a later phase with a shelf or foreland basin development and thick sequences. Deformation of the megasequences 1 and 2 or 1 to 3 varies between areas. In Wales and the Lake District the Acadian phase is long-lived and active from early to mid Devonian. In the Ardennes inliers a deformation is active between the late Ordovician and the Silurian (Ardennian Phase), with a similar intensity as the core of the Brabant Massif, when present erosion levels are compared. The Brabant Massif is partly deformed by the long-lived Brabantian Phase from late Silurian till early mid Devonian. Both the Ardennes inliers and the Brabant Massif are not classic orogenic belts, only slate belts where no more than the epizone is reached at present erosion levels. Areas supposedly close to the microcraton or basement are nearly undeformed (SW Brabant Massif and central Condroz). A model of anticlockwise rotation of Avalonia of about 55{degrees} from Caradoc to Emsian is proposed to explain the deposition setting of megasequence 3 and the subsequent Acadian and Brabantian deformation. Immediately after the Avalonian microcontinent touched Baltica in Caradoc times it created a short-lived subduction magmatic event from The Wash to the Brabant Massif and soon after the magmatism ended a foreland basin developed. Possibly during and after that development a long-lived and slow compressional event occurred, leading to the deformation of the Anglo-Brabant Deformation Belt. In the early Devonian, contemporaneous with the shortening of the Anglo-Brabant Deformation Belt, extension occurred in the Rheno-Hercynian Zone, possibly caused by the same slow rotation of Avalonia. More evidence emerges that Avalonia east of the Midlands Microcraton comprises not one but probably two terranes: the remnant of the palaeocontinent Avalonia, and what is called the palaeocontinent Far Eastern Avalonia; the latter is only occasionally observed in the few deep boreholes into the Heligoland-Pomerania Deformation Belt, in southern Denmark, NE Germany and NW Poland, with scant available indirect data in between indicating only Proterozoic basement and no Caledonian deformation. For Far Eastern Avalonia a similar palaeogeographical history is postulated as Avalonia, with rifting from Gondwana in Arenig or earlier times, collision with Baltica before the mid-Ashgill and deformation between the late Ordovician and latest Silurian. The Avalonia concept might need to be expanded to an Avalonian Terrane Assemblage' with cratonic cores and small short-lived oceans as in the Armorican Terrane Assemblage.

Description: Strongly tectonized Ordovician rocks appear in the Ebbe Anticline (Rheinisches Schiefergebirge), West Germany. These fine-grained detrital rocks of the Herscheider Schichten are divided into the Plettenberger Banderschiefer. Unterer (Kiesberter) Tonschiefer, (Rahlenberger) Grauwackenschiefer, and the Oberer (Solinger) Tonschiefer. The scope of this investigation was to improve the dating of the entire Ordovician succession. but especially the Oberer (Solinger) Tonschiefer. We used chitinozoans. Palaeozoic microfossils of high biostratigraphic value, and Nd isotopes, which previously have been used for correlation and terrane affinity analysis. Chitinozoan preservation is poor, but some taxa could be confidentially identified to the species level. The {varepsilon}Nd(t) values obtained from the Ordovician succession range from -8.0 to -9.2. Joint evaluation of chitinozoan and Nd isotope data together with previously known age-ranges suggest the following ages for the Herscheider Schichten: Plettenberger Banderschiefer (early Abereiddian, earliest Llanvirn), Unterer (Kiesberter) Tonschiefer (early to mid Abereiddian, early Llanvirn). (Rahlenberger) Grauwackenschiefer (Aurelucian, earliest Caradoc), and Oberer (Solinger) Tonschiefer (late Caradoc). The Ebbe {varepsilon}Nd(t) values are most readily compared with {varepsilon}Nd(t) values from Avalonia. and we therefore support the inclusion of the Ordovician rocks of the Ebbe Anticline in that palaeocontinent.

Description: The West Sudetes, NE Bohemian Massif, comprises several suspect terranes accreted to the margins of Laurussia during Variscan orogenesis. Whole rock REE and Sm-Nd isotope data for seven separate provinces (Izera, Kaczawa, Rudawy Janowickie and K[l]odzko complexes; Fore-Sudetic and Gory Sowie Blocks; Sl[e][z]a Ophiolite) suggest involvement of a variety of crustal and mantle sources. Felsic metasedimentary rocks ({varepsilon}Nd(t) = -8.3 to -5.0) have two stage TDM ages of 1.9 to 1.5 Ga, whereas acidic metavolcanic rocks and granite gneisses ({varepsilon}Nd(t) = -5.4 to +0.8) have two stage TDM ages of 1.5 to 1.0 Ga. A range of sources is implicated: predominantly Archaean and Palaeoproterozoic sources for the metasedimentary rocks, and Archaean. Palaeoproterozoic and Neoproterozoic to early Palaeozoic sources for the meta-igneous felsic lithologies. LREE depleted tholeiitic metabasites ((Ce/Yb)N = 0.8 to 3.4) generally have {varepsilon}Nd(t) = +4.0 to +9.1, indicating derivation from depleted mantle asthenosphere. LREE enriched meta-alkali basalts ((Ce/Yb)N = 4.6 to 10.1) with {varepsilon}Nd(t) between +3.1 and +7.0 implicate utilization of enriched mantle asthenosphere. Analogous lithologies from elsewhere in the Sudetes, North Bohemian Massif and the Armorican Terrane Assemblage have similar REE abundances, {varepsilon}Nd values and TDM ages. Complexes previously considered to have had disparate Neoproterozoic to early Palaeozoic histories may be integrated into a unifying geodynamic model of derivation from the North Gondwanan (North African) margin during a widespread episode of continental margin break-up.

Description: Hoodoo Mountain volcano (HMV), a Quaternary composite volcano in northwestern British Columbia, is a well-exposed example of peralkaline, phonolitic icecontact and subglacial volcanism. Its distinctive morphology and unique volcanic deposits are indicative of subglacial, within-ice, and/or ice-contact volcanic eruptions. Distinct ice-contact deposits result from three different types of lava-ice interaction: (1) vertical cliffs of lava, featuring finely jointed flow fronts up to 200 m in height, resulted from lava flows being dammed and ponded against thick masses of ice; (2) pervasively-jointed, dense lava flows, lobate intrusions, and domes associated with mantling deposits of poorly-vesiculated breccia are derived from volcanic eruptions contained beneath relatively thick ice; and (3) an association of pervasively-jointed, highly-vesicular lava flows or dykes encased by vesicular hyaloclastite of identical composition formed by eruption under and/or through relatively thin ice. The distribution of these three deposit types largely explains the distinctive morphology of Hoodoo Mountain and can be used to reconstruct variations in ice thickness surrounding the volcano since c.85 ka. Our analysis suggests that at c.85 ka Hoodoo Mountain erupted underneath ice cover of at least several hundred metres. At c.80 ka eruptions were no longer subglacial, but the edifice was surrounded by ice at least 800 m high that dammed lava flows around the perimeters of the volcano. After a period of eruptions showing no apparent evidence for ice interaction, from 〈80 to 〉40 ka, subglacial eruptions began again, signalling the build-up of regional ice levels. Local ice thickness during these eruptions may well have been over 2 km thick.

Description: This paper presents the first modern volcanological study of a subglacial-to-emergent rhyolite tuya, at SE Rauthufossafjoll, Torfajokull, Iceland. A flat-topped edifice with a volume of c. 1 km3 was emplaced in Upper Pleistocene time beneath a glacier 〉350m thick. Although it shares morphological characteristics with basaltic tuyas, the lithofacies indicate a very different eruption mechanism. Field observations suggest that the eruption began with vigorous phreatomagmatic explosions within a well-drained ice vault, building a pile of unbedded ash up to 300m thick. This was followed by a subaerial effusive phase, in which compound lava flows were emplaced within ice cauldrons. Small-volume effusive eruptions on the volcano flanks created several lava bodies, with a variety of features (columnar-jointed sides, subaerial tops, peperitic bases) that are used to reconstruct spatially-heterogeneous patterns of volcano-ice interaction. Volcaniclastic sediments exposed in a stream section provide evidence for channelised meltwater drainage and fluctuating depositional processes during the eruption. Models are developed for the evolution of SE Rauthufossafjoll, and the differences between subglacial rhyolitic and basaltic eruption mechanisms, which are principally caused by contrasting hydrological patterns, are discussed.

Description: Palaeoenvironmental reconstructions and 40Ar/39Ar geochronology of volcanism at Mt. Murphy and the Crary Mountains in eastern Marie Byrd Land (MBL), West Antarctica, provide records of changing ice levels of the West Antarctic Ice Sheet (WAIS) since the late Miocene. Interpretations of eruptive and depositional environments are based on lithofacies studies and indicate whether the volcanoes erupted below, near or above the level of the ice sheet. Seventy-seven new 40Ar/39Ar dates offer a precise chronological frame-work for the ice volcanic history. Late Miocene (9-8 Ma) basal volcanic sequences at Mt. Murphy and the Crary Mountains (Mt. Rees and Mt. Steere) exhibit fluctuations between wet' ice-contact lithofacies and dry' subaerial lithofacies. The wet' lithofacies include pillow lava and hyaloclastite breccia; the dry' lithofacies include massive and deuterically oxidized lava and associated welded breccia deposits. The sequences at Mt. Murphy include several erosion surfaces and tillites, which are inferred to represent fluctuations in the WAIS. At Mt. Rees and Mt. Steere, the alternating lithofacies form the constructional slopes of the volcano and are inferred to represent interactions with local slope ice that occurred above the level of the regional ice sheet. The Miocene to Pleistocene volcanic history of the area provides a proxy record of ice-level changes in West Antarctica, with the following three major conclusions. First, the oldest evidence for a large-scale WAIS is from Late Miocene (c. 9 Ma) glaciovolcanic sequences at Mt. Murphy and several other sites in Marie Byrd Land. The combined Mt. Murphy and Crary Mountains records indicate that ice-level expansions of the WAIS were more extensive at coastal sites than at inland sites. Second, the present-day WAIS appears to be in a near maximum configuration that has existed at several times since 9 Ma but was rarely exceeded. Finally, a significant expansion of the WAIS above its present-day level occurred at 590 {+/-} 15 ka, when ice levels were 550 m higher at the coastal volcano, Mt. Murphy.

Description: A synthesis of published and new data is used to interpret the Sudetic segment of the Variscan belt as having formed by the accretion of four major and two or three minor terranes. From west to east the major terranes are (1) Lusatia-Izera Terrane, exposing Armorican continental basement reworked by Ordovician plutonism and Late Devonian-Carboniferous collision, showing Saxothuringian affinities; (2) composite Gory Sowie-K[l]odzko Terrane characterized by multistage evolution (Silurian subduction, mid- to late Devonian collision, exhumation and extension, Carboniferous deformational overprint), with analogues elsewhere in the Bohemian Massif, Massif Central and Armorica; (3) Moldanubian (Gfohl) Terrane comprising the Orlica-[S]nie[z]nik and Kamieniec massifs, affected by Early Carboniferous high-grade metamorphism and exhumation and (4) Brunovistulian Terrane in the East Sudetes, set up on Avalonian crust and affected by Devonian to late Carboniferous sedimentation, magmatism and tectonism. The main terranes are separated by two smaller ones squeezed along their boundaries: (1) Moravian Terrane, between the Moldanubian and Brunovistulian, deformed during Early Carboniferous collision, and (2) SE Karkonosze Terrane of affinities to the Saxothuringian oceanic realm, sandwiched betwen the Lusatia-Izera and Gory Sowie-K[l]odzko (together with Tepla-Barrandian) terranes, subjected to high pressure-metamorphism and tectonized during Late Devonian-Early Carboniferous convergence. The Kaczawa Terrane in the NW, of oceanic accretionary prism features, metamorphosed and deformed during latest Devonian-Early Carboniferous times, may either be a distinct unit unrelated to closure of the Saxothuringian Ocean or represent a continuation of the SE Karkonosze Terrane.

Description: The Garibaldi Volcanic Belt (GVB) in southwestern British Columbia is dominated by intermediate composition volcanoes in a setting that has been intermittently subjected to widespread glaciation. The glaciovolcanic features produced are distinctive, and include flow-dominated tuyas, subglacial domes, and ice-marginal flows. Flow-dominated tuyas, which are intermediate in composition, are unlike conventional basaltic tuyas; they consist of stacks of flat-lying lava flows, and lack pillows and hyaloclastite. They are inferred to represent subglacial eruptions that ultimately breached the ice surface. Subglacial domes occur as steep-sided masses of heavily-jointed, glassy lava, and represent eruptions that were entirely subglacial. Ice-marginal flows derive from subaerial flows that were impounded against ice. Two unique aspects of GVB glaciovolcanic products are the presence of flow-dominated tuyas and the apparent scarcity of primary fragmental deposits. These unique features result from lava composition, the minimization of direct lava-water contact during eruptions, and topography. Composition influences morphology because eruption temperature decreases, and viscosity and glass transition temperature both increase with silica content. The result of this is that silicic subglacial volcanoes melt less water and are less likely to trap it near the vent, leading to the formation of structures whose shapes are strongly influenced by the surrounding ice. Topography also enhances meltwater drainage, favours lava flow impoundment in ice-filled valleys, and may, through erosion, influence the observed distribution of fragmental glaciovolcanic deposits.

Description: Palagonitization is a common, but imperfectly defined process that greatly modifies the physical and chemical properties of glassy basaltic tephra deposited in subaquatic/subglacial environments on Earth and perhaps Mars. It also results in textures and mineralogies that are distinct from other forms of (mainly pedogenic) low temperature alteration. Specifically, the process of palagonitization (1) initially results in the formation of palagonitized glass', a quasi- or nano-crystalline, rind-like material that contains smectite, as well as lesser amounts of other clays (e.g. serpentine), and (2) eventually results in consolidation of tephra, mediated through the accretion of palagonitized glass and later-formed authigenic cements. Conversely, pedogenic weathering of glassy basaltic tephra is characterized by disaggregation of tephra, and formation of a wide range of pedogenic products, including layer silicates (although not primarily smectite), short-range-order aluminosilicates and oxyhydroxides, whose composition reflects the intensity of the weathering environment. These mineralogical and textural properties can be readily recognized through a variety of techniques including electron microscopy/microprobe analysis, reflectance spectroscopy, X-ray diffraction and soil chemistry. Analyses of samples collected from the summit regions of Kilauea and Mauna Kea volcanoes on the island of Hawaii are presented here in order to illustrate differences between palagonitization and pedogenic weathering of glassy basaltic tephra. In the young Hawaiian tephras studied, palagonitization has occurred in response to hydrothermal activity shortly after deposition. Although some, non-hydrothermally affected tephras may eventually become palagonitized, those that have been strongly desilicated by intense pedogenic weathering will probably never become palagonitized.

Description: This book examines the process and patterns of glacier-influenced sedimentation on high-latitude continental margins and the geophysical and geological signatures of the resulting sediments and landforms. It contains a range of papers concerning modern and glacially-influenced sedimentation in high-latitude areas from both hemispheres, many of which discuss the relationship between glacier dynamics and the sediments and landforms preserved in the glacimarine environment This volume will be of interest to those in academia and industry working in the broad fields of glacimarine environments, the development of high-latitude margins and marine geology and geophysics

Description: The Norwegian continental margin has been affected by several cycles of growth and decay of the Fennoscandinavian Ice Sheet. Evidence for this former ice-sheet activity is found in the seismic stratigraphy of the shelf and slope, and in the morphology of seafloor sediments. The regional bathymetry of the mid-Norwegian shelf (63{degrees}N to 68{degrees}N) comprises a series of cross-shelf troughs, separated by shallower banks. In Traenadjupet and Suladjupet, streamlined, elongate sedimentary bedforms (known as mega-scale lineations) are found, aligned along trough long-axes. Spacing between ridge-tops is 400-500 m, and ridge width and height are about 250 m and less than 10 m, respectively. Streamlined bedforms are not present on the intervening shallow banks, and terminate abruptly at the trough margins, marking the former boundary of fast glacier flow. On northwestern Traenabanken and on either side of Traenadjupet, lateral ridges are inferred to mark the shear margin of ice streams in Sklinnadjupet and Traenadjupet. The Skjoldryggen Moraine records the seaward limit of Late Weichselian ice-sheet growth, and ridges inshore result from deposition in still-stands during ice retreat. The streamlined bedforms in Traenadjupet and Suladjupet are similar in morphology and scale to streamlined Antarctic bedforms, linked to the former presence of fast-flowing ice streams on the continental shelves of Antarctica. Several geomorphological criteria, identified as diagnostic of past ice-stream flow, are observed in our geophysical studies of the mid-Norwegian shelf. Using these criteria, we identify several fast-flowing ice streams on the western margin of the former Fennoscandinavian Ice Sheet. Numerical ice-sheet model predictions of fast-flowing ice coincide closely with the inferred locations of past ice streams based on the distribution of such suites of diagnostic bedforms.

Description: Trough-mouth fans are the main marine depocentres for glacier-derived sediments in the Polar North Atlantic, but their growth through the Late Quaternary is complex. Glacigenic debris flows (GDFs) are sourced from a common and homogeneous part of the upper fan and only develop as coherent individual flows after downslope transport. Their genesis and mode of deposition mean that GDFs are confined to particular areas of trough-mouth fans; accumulation of these subglacial sediments is controlled by a combination of margin glaciology and fan morphology. Although most of the fan sediment is deposited as GDFs, during glacials considerable areas of trough-mouth fans are dominated by sedimentation of suspension deposits, associated with extensive meltwater release from a warm-based ice sheet and probable contour current activity. The depositional sequence of these two sediment types may be important in generating the long run-out distances of GDFs, which are initiated and sustained over low gradients. Furthermore, emplacement of GDFs is interpreted to be a relatively low-frequency event, and temporally, at least, fans are not dominated by this mode of sediment emplacement whilst ice sheets are at the shelf break. Large-scale trough-mouth fan development is therefore asynchronous and non-uniform, a result of the interaction between glaciology, morphology, and oceanography.

Description: The glacigenic sequence of the southwestern Barents Sea shelf has for the first time been studied using 3-D seismic data. The close spacing of 3-D lines and powerful computer workstation interpretation techniques have allowed detailed mapping of the observed features. Several generations of subglacial lineations observed on four different palaeo-surfaces are interpreted to reflect the flow patterns of palaeo-ice sheets. To our knowledge, this is the first time that multiple levels of subglacial lineations have been observed. The lineations are 2.5-8 m in relief, 50 to 180 m wide and 0.5 to 20 km long. All four surfaces show a main lineation pattern comprising lineations with a N-S trend, suggesting that the dominant ice flow was directed northwards across the Barents Sea shelf at least four times during the last 0.8 Ma. Two of the surfaces display semi-circular to oblong depressions trending mainly in the same direction as the sub-parallel lineations. These depressions are 9-53 m in relief, 1.25-3.2 km wide and 1.9-9 km long. In contrast to the buried surfaces, the sea floor is dominated by 2.5-25 m deep cross-cutting iceberg plough-marks from the deglaciation phase of the last Barents Sea ice sheet. The 3-D seismic data are conventional industry data. Despite relatively low seismic frequencies and, hence, limited vertical resolution of seismic profiles, time slices and sub-horizontal time maps are of high spatial resolution, providing detailed images of different stages of buried Quaternary glacial geomorphology.

Description: This paper addresses the issue of the characteristic grain-size spectra of glacial and glacial marine sediments, an important topic because of the increasing emphasis on the use of specific sand-size fractions as indicators of iceberg rafting. Different methods of IRD identification can lead to different palaeoclimatic interpretations. We use three methods of grain-size analyses, with examples from the Labrador Sea, East Greenland, North Iceland, and the Ross Sea, Antarctica. The first method illustrates the real' grain size of glacial marine sediments by an examination of X-radiographs by image analysis and the sizing of clasts larger than 2 mm. Typically, grain-size analyses only apply to the matrix fraction of the sediment (smaller than 2 mm), and ignore the larger size clasts. The mean grain size appears to be between 8 to 10 mm. The second method includes counting the number of clasts larger than 2 mm from X-radiographs, and counts of particles (106-1000 {micro}m). These latter counts show that diamictons from the North Iceland shelf indicate a dominance of glacially abraded basaltic grains, but they also contain a small, consistent proportion of angular volcanic glass shards of various compositions. The third method is to examine grain-size spectra of surface samples from East Greenland and the Ross Sea region of Antarctica and compare these data with down-core data from neoglacial-age glacial marine sediments from Nansen Fjord, East Greenland, and with late glacial diamictons from the North Iceland shelf. These sediments have a mode in the silt fraction, but they frequently have secondary peaks in the coarse sand and fine sand/coarse silt areas, and a trough in the range of 100 to 500 {micro}m (medium to coarse sand). Most of the sediment samples analysed in this study contain 20-50% in the below 1 {micro}m grain size, which reinforces the importance of examining this fraction in provenance studies in glacial marine sediments.

Description: During the late Wisconsin Fraser Glaciation on the Pacific Margin of Canada, ice moved offshore from the Coast Mountains of the Canadian Cordillera and south into the Strait of Georgia, reaching a maximum extent at about 14 000 14C BP. Most of the strait was ice-free by 11 300 14C BP. Deglaciation was very rapid with regional downwasting and widespread stagnation. This resulted in a stratigraphy of thick till (30-60 m), overlain by ice-proximal glacimarine sediments and a thin and discontinuous ice-distal glacimarine unit. Glaciation of Queen Charlotte Basin reached a maximum sometime after 21 000 14C BP. Deglaciation in this region began sometime after 16 000 to 15 000 14C BP and ice had retreated fully onto mainland British Columbia by 13 500 14C BP. Deglaciation was rapid, with the eastward retreat of an ice shelf. This resulted in a stratigraphy of a till up to 50 m in thickness, usually turbated by iceberg scour and overlain in some areas by thin, ice-proximal glacimarine sediments and much thicker (20 m) widespread ice-distal glacimarine sediments. A significant difference between these two regions is the deglacial relative sea-level history. Rapid regression of the outer Queen Charlotte Islands shelf occurred between approximately 14 600 and 12 500 14C BP, primarily due to rapid isostatic rebound and contemporaneous with deglaciation of the continental shelf. Sea-level reached a maximum lowstand of greater than 150 m and remained low until approximately 12 400 14C BP. In Georgia Basin, sea-level was at a relative high stand of 50 to 200 m during initial deglaciation, falling to between 0 to 50 m below present sometime after 10 000 14C BP. We suggest that rapid emergence on the northern margin of the outer shelf was due to forebulge effects. Further, the very limited extent of glacial ice on the Queen Charlotte Islands and the exposure to the open Pacific forced the retreat of the Cordilleran ice-sheet margin eastwards thereby resulting in dominantly ice-distal glacimarine sedimentation. In contrast, the initial relative sea-level highstand during deglaciation between the Vancouver Island and Cordilleran glaciers in the Strait of Georgia resulted in significant ice-proximal deposition and limited ice-distal glacimarine deposition.

Description: Geological evidence indicates that sediment reworking is common around the continental margins and abyssal depths of the Norwegian-Greenland Sea, a high-latitude setting with glacier-influenced margins. Detailed analysis of 22 cores up to 5 m long, placed in context by accompanying geophysical data including high resolution sub-bottom profiles, swath bathymetry and backscatter maps, indicates that reworking is variable and ranges from debris flows and turbidity currents, to bottom-current activity, as well as iceberg scouring. Reworking by debris flows appears to be restricted mainly to the main trough-mouth fans and sediment slides. Elsewhere, turbidity-current activity frequently dominates, although iceberg ploughing down to 600 m depth and current winnowing assume increasing significance on continental shelves. Reworking in the Norwegian-Greenland Sea reflects variations in ice-sheet dynamics that, in turn, influence the rate of sediment delivery and location of depocentres. Spatial variations in the style of reworking may also reflect the influence of continental slope gradient and bedrock geology on continental shelves. The widespread nature of sediment reworking has important implications for palaeoceanographic investigations in the region, as reworking can result in erosion and disturbance of the sediment column. It is estimated that less than 7% of material delivered to the Norwegian-Greenland Sea since the Late Weichselian is derived from hemipelagic and pelagic sedimentation. This problem is significant where continuous, high-resolution records of hemipelagic and pelagic sedimentation are required, and attempts are made to correlate with other high-resolution proxy records, such as ice cores, at sub-millennial scales. Bioturbation results in the smoothing of high-resolution records and imposes a maximum resolution for sediment-core time-slices of generally 400 years or more. In the Norwegian-Greenland Sea, areas of high sedimentation such as trough-mouth fans or contourite drifts are commonly associated with extensive reworking. Identification of reworking is particularly important where attempts are made to link records of iceberg-rafted debris to past ice-sheet dynamics, as bottom-current winnowing and mass-flow processes can increase the concentration of coarse-grained iceberg-rafted debris. Such localized accentuation of the iceberg-rafted debris signal may lead to erroneous palaeo-environmental interpretations. It is therefore critical that palaeoceanographic interpretations are firmly underpinned by an explicit sedimentological assessment of reworking.

Description: The presence of ice during the Late Cenozoic distinguishes the nature and rates of processes on high-latitude margins from those elsewhere. Ice sheets terminating in marine waters deliver icebergs, meltwater and debris to high-latitude seas. Sea ice influences ocean salinity structure and downslope water and sediment transfer, and also transports fine-grained sediments over long distances. These cryospheric processes have led to the development of a distinctive sedimentary architecture on modern high-latitude continental margins. Large submarine fans made up almost entirely of stacked debris flows are present around the Norwegian-Greenland Sea. Large slides are located in a variety of settings relative to rates of sediment delivery from Quaternary ice-sheet margins, but no large slides have been mapped on the East Greenland margin. However, extensive channel systems and sediment-wave fields are present in the Greenland Basin, probably related to intermittent downslope flow of dense water and turbidity currents. The extensive NE Greenland shelf was not innundated by ice-sheet advance during recent full-glacial conditions, allowing sea-ice and deep-water production during both interglacials and full-glacials. Changes in the nature and rate of sedimentation within the Greenland Basin should provide clues on the rate of dense-water production, with implications for thermohaline circulation in the North Atlantic. Other erosional and depositional features on the Norwegian-Greenland Sea margins include canyons and contourite drifts. High-relief tectonic features influence sediment reworking by turbidity currents at abyssal depths. A simple conceptual model for glacier-influenced marine sedimentation summarizes the role of cryospheric processes in high-latitude margin sedimentary environments.

Description: The marine sedimentary record in Kejser Franz Joseph Fjord and on the East Greenland continental margin contains a history of Late Quaternary glaciation and sedimentation. Evidence suggests that a middle-shelf moraine represents the maximum shelfward extent of the Greenland Ice Sheet during the last glacial maximum. On the upper slope, coarse-grained sediments are derived from the release of significant quantities of iceberg-rafted debris (IRD) and subsequent remobilization by subaqueous mass-flows. The middle-lower slope is characterized by hemipelagic sedimentation with lower quantities of IRD (dropstone mud and sandy mud), punctuated episodically by deposition of diamicton and graded sand/gravel facies by subaqueous debris flows and turbidity currents derived from the mass failure of upper slope sediments. The downslope decrease of IRD reflects either the action of the East Greenland Current (EGC) confining icebergs to the upper slope, or to the more ice-proximal setting of the upper slope relative to the LGM ice margin. Sediment gravity flows on the slope are likely to have fed into the East Greenland channel system, contributing to its formation in conjunction with the cascade of dense brines down the slope following sea-ice formation across the shelf. Deglaciation commenced after 15 300 14C years , as indicated by meltwater-derived light oxygen isotope ratios. An abrupt decrease in both IRD deposition and delivery of coarse-grained debris to the slope at this time supports ice recession, with icebergs confined to the shelf by the EGC. Glacier ice had abandoned the middle shelf before 13 000 14C years with ice loss through iceberg calving and deposition of diamicton. Continued retreat of glacier-ice from the inner shelf and through the fjord is marked by a transition from subglacial till/bedrock in acoustic records, to ice-proximal meltwater-derived laminated mud to ice-distal bioturbated mud. Ice abandoned the inner shelf before 9100 14C years and probably stabilized in Fosters Bugt at 10 000 14C years . Distinct oxygen isotope minima on the inner shelf indicate meltwater production during ice retreat. The outer fjord was free of ice before 7440 14C years . Glacier retreat through the mid-outer fjord was punctuated by topographically-controlled stillstands where ice-proximal sediment was fed into fjord basins. The dominance of fine-grained, commonly laminated facies during deglaciation supports ablation-controlled, ice-mass loss. Glacimarine sedimentation within the Holocene middle-outer fjord system is dominated by sediment gravity flow and suspension settling from meltwater plumes. Suspension sediments comprise mainly mud facies indicating significant meltwater-deposition that overwhelms debris release from icebergs in this East Greenland fjord system. The relatively widespread occurrence of fine-grained lithofacies in East Greenland fjords suggests that meltwater sedimentation can be significant in polar glacimarine environments. The ice-distal continental margin is characterized by meltwater sedimentation in the inner shelf deep, iceberg scouring over shallow shelf regions, winnowing and erosion by the East Greenland Current on the middle-outer shelf, and hemipelagic sedimentation on the continental slope.

Description: New 40Ar/39Ar dating performed on Rare Metal Granites and W {+/-} Sn deposits in the northern Limousin has provided evidence of two metallogenic episodes. An Early Namurian episode (c. 325 Ma) was contemporaneous with the emplacement of the large peraluminous leucogranite bodies, which are associated with small W {+/-} Sn deposits, but also with some larger deposits, at Puy-les-Vignes (323.4 {+/-} 0.9 Ma) and Moulin-Barret (323.7 {+/-} 0.8 Ma) formed at a shallower level above cryptic granite plutons. These new data indicate that the metallogenic potential of the Namurian leucogranites might have been underestimated. Most other W {+/-} Sn deposits in the northern Limousin area are attributed to a Mid-Westphalian episode (c. 310 Ma), and are contemporaneous with the emplacement of all the Rare Metal Granites. Both episodes were related to leucogranite emplacement and associated fluid circulations, but in two different geodynamic contexts. The Early Namurian episode may be related to syncollisional extension of the Variscan belt, whereas the Mid-Westphalian one occurs during generalized extension and rapid exhumation of the belt associated with the granulite-facies metamorphism of the lower lithosphere probably related to the delamination of the lower lithosphere. Thus, W {+/-} Sn and rare metals (Ta, Nb, Be, Li) deposits are clearly temporally and probably genetically related to leucogranitic magmatism.

Description: Polymetamorphic schists and marbles of the Austroalpine Kreuzeck-Goldeck Complex are the host to auriferous arsenopyrite-pyrite as well as stibnite mineralization. In the Siflitz-Guginock area both types of mineralization are closely related spatially, but restricted to different lithologies. The auriferous arsenopyrite-pyrite mineralization is either disseminated or bound to quartz veins and strongly silicified fault-zones hosted in phyllites to (garnet-) micaschists. Similar disseminations within marbles are of minor importance. A stockwork-like mineralization of stibnite-filled fractures with weak metasomatic replacement is limited to marbles. Both types of mineralization in the Kreuzeck-Goldeck Complex are intimately related to roughly east-west-trending semi-ductile to brittle strike-slip faults which formed during orogen-parallel wrenching. Semi-ductile to brittle kinematic indicators point to dextral, as well as sinistral, modes of fault movements, coeval with the formation of pyrite-arsenopyrite-bearing quartz veins, as well as the intrusion of Oligocene lamprophyre dykes. Mineralizing fluids are suggested to be derived from devolatilization of the subducted Penninic upper crust. Fluid ascent and ore precipitation is controlled by a transpressive strike-slip regime related to oblique terrane accretion during the Late Eocene to Oligocene. Subsequent development of a Late Oligocene-Early Miocene pure shear regime with contraction trending (N)NE-(S)SW led to the development of conjugate NW-SE dextral and NE-SW sinistral brittle strike-slip faults, and overprinting by ESE-WNW oriented extension. These later events are related to the formation of auriferous mineralization from within the metamorphic core complex of the Tauern Window to the north of the Kreuzeck-Goldeck Complex, hence implying a significant change in spatial, temporal and structural control of Tertiary auriferous mineralization in the Eastern Alps.

Description: The post-Variscan hydrothermal activity and mineralization in Sardinia (Italy) is reviewed in the framework of the geological and metallogenic evolution of Western Europe. The deposits can be grouped into (a) skarn, (b) high- to low-temperature veins and (c) low-temperature palaeokarst. The structural, stratigraphical and geochemical data are discussed. The results suggest three hydrologically, spatially, and possibly temporally, distinct fluid systems. System 1 (precipitating skarn and high-temperature veins) is characterized by magmatic and/or (?) magmatically heated, meteoric fluids of low-salinity. The source of metals was in the Variscan magmatites, or in the Palaeozoic/Precambrian basement. System 2 (low-temperature veins and palaeokarst) is represented by highly saline, Ca-rich (formation or modified meteoric) fluids. Sources of the metals were the pre-Variscan ores and carbonate rocks. System 3 is characterized by low-temperature, low-salinity fluids of meteoric origin. The hydrothermal deposits related to Systems 1 and 2 can be framed in a crustal-scale hydrothermal palaeofield', characterizing most of the post-orogenic mineralization in Variscan regions of Western and Southern Europe, allowing for local age differences of each single ore district and background effects. The suggested timing for the hydrothermal events in Sardinia is: (1) Mid-Permian (270 Ma), (2) Triassic-Jurassic. It is suggested that the Mesozoic events were related to the onset of Tethys spreading.

Description: Volcanogenic massive sulphide (VMS) deposits commonly occur within much larger fluorine (F)-bearing hydrothermal systems, where cordierite-orthoamphibole rocks are characteristic pathfinder assemblages. Here we report whole-rock and mineral F contents for orthoamphibole bearing rocks and associated rock types from Zn-Cu-Pb deposits in Finland (Orijarvi, Iilijarvi, Pyhasalmi, Mullikkorame) and central Australia (Oonagalabi). Textural and mineralogical data suggest that F influx predates peak metamorphism in these deposits. The Mullikkorame whole-rock data show positive correlations between F and XMg = molar Mg/(Mg + Fe) and between F and elements of relatively low mobility (Ti, Al, Mg) and negative correlations between Fe and these elements. This suggests that iron was leached from silicate rocks by F-bearing fluids and was transferred to the Fe-rich sulphide ore. When normalized to immobile elements, F correlates positively with total metal content (Cu + Pb + Zn + Fe), consistent with the commonly observed increase of F content towards ore bodies. Combining all microprobe data, hydrous minerals show the following order of decreasing F/(F + OH) ratio when coexisting: apatite 〉 chondrodite 〉 biotite 〉 gedrite 〉 (hornblende, muscovite, anthophyllite) 〉 chlorite. The low- to medium-grade Finnish samples (Mullikkorame: 500-560 {degrees}C at 1-3 kbar; Orijarvi: 550-650 {degrees}C at 3-5 kbar; Pyhasalmi: 600-700 {degrees}C at 5-7 kbar) contain mainly F-poor anthophyllite, whereas F-rich gedrite is dominant in the higher grade Oonagalabi deposit (750-800 {degrees}C, 8-9 kbar). Temperature seems to have a significant, but XMg a negligible influence on F partitioning between biotite and orthoamphiboles.

Description: The Baikalide-Altaid, Transbaikal-Mongolian and North Pacific orogenic collages consist of several oroclinally bent magmatic arcs separated by accretionary complexes and ophiolitic sutures located between the major cratons. The tectonic and metallogenic patterns of these collages are principally similar as they were formed as a result of rotation of the surrounding cratons and strike-slip translation along the former convergent margins.

Description: The use of gypsum based mortar can be traced back over 4500 years. In Germany, in the vicinity of natural gypsum outcrops, in addition to lime mortars, calcium sulphate based mortars were widely used for joints in exterior walls of sacred buildings. There are several medieval buildings with well-preserved calcium sulphate-based mortars. The high water solubility of gypsum (CaSO4*2H2O) is a disadvantage that makes it difficult in general to handle calcium sulphate based building materials in areas exposed to weathering. Physico-mechanical as well as mineralogical investigations of historic calcium sulphate based mortars have shown that long-term weathered mortars have a much denser microstructure, larger average grain sizes, and a higher compressive strength than laboratory prepared mortars. Porosity models of these mortars will be presented which are helpful to prepare calcium sulphate based mortars with a higher water resistance for restoration purposes. The reason for the change of crystal size and morphology as well as of porosity and strength can be explained by crystallization and recrystallization processes of these calcium sulphate based mortars, as a consequence of long-term weathering. Since it is obvious that crystal size and its distribution have an enormous effect on the weathering resistance, the development of mortars with comparable structural properties is of present interest. In current use are chemical additives which modify the morphology and size of gypsum crystals of set mortars. Another possibility to influence the weathering resistance is the addition of hydraulic and/or latent hydraulic admixtures.

Description: The current condition of many building claddings and historical monuments clearly reveals that they are not immune to weathering action due to daily or seasonal temperature changes. In this study, porosity changes by variation in temperature have been investigated for two marble types: one calcitic and one pure dolomitic. The samples were exposed to ascending temperatures from 40 to 200{degrees}C. The results indicate that intergranular decohesion starts between 40 and 50{degrees}C. Some significant differences in temperature response for these two marble types could be distinguished. The temperature range 40-60{degrees}C is easily reached on building surfaces in most European countries during the summer months. A better understanding of the effect that temperature has on the porosity of marble could be used to develop a methodology for assessing suitable conditioning of marble before testing as well as to suggest appropriate impregnation and/or surface treatments of buildings and outdoor sculptures.

Description: Marbles as ornamental stones as well as in their natural environments show complex weathering phenomena. The physical weathering of marbles due to thermal treatment is often discussed as the initial stage of deterioration. Eighteen different well-known marble types were selected to quantify experimentally the effect of heating and cooling within the temperature range of 20{degrees}C to 85{degrees}C while three different ramps at 40{degrees}C, 60{degrees}C and 85{degrees}C were performed. The marbles differ in composition from calcitic to dolomitic as well as in their fabrics. The average grain size varies from 50 {micro}m up to 3 mm, while the grain boundary geometry differs from a granoblastic foam structure to those with weakly inequigranular-amoeboid structure. The lattice preferred orientations are also highly different in c-axis and a-axis distributions. With respect to the heating and cooling cycles three distinct groups of marbles can be distinguished: Type I is characterized by an isotropic thermal expansion ({alpha}) and large isotropic residual strain (permanent length changes); Type II exhibits an anisotopic {alpha} and no or small isotropic residual strains; while Type III shows an anisotropic {alpha} and anisotropic residual strain. Most samples show deteriorations due to thermal treatment, which cannot be uniformly explained without taking into account the rock fabrics. The magnitude and directional dependence of the thermal expansion is mainly controlled by the lattice and shape preferred orientation. The composition, grain size, grain boundary geometry and pre-existing microcracks modify in a more complex way the progressive loss of cohesion due to dilatancy caused by the anisotropic thermal expansion.

Description: Almost all natural carbonate rock surfaces as well as carbonate building stones are ubiquitously colonized by micro-organisms such as cyanobacteria, chlorophyceae, fungi and lichens. This colonization occurs endolithically, mostly euendolithically, through active penetration into the rock. Freshly exposed surfaces, such as in glacial forelands of the Dachstein Mountains (Austria) show mature, fully differentiated endolithic colonization after only 15 years of atmospheric exposure. After a time period of 100 to 150 years, coverage of carbonate rock surfaces by endolithic biofilms is almost complete. Most endolithic biofilms (lichens) show similar internal architecture. Under a residual, protective carbonate rock layer are photobiontic micro-organisms. They occupay a well defined zone between 150 to 300 {micro}m beneath the rock surface. In this zone up to 60% of the rock substrate is replaced by microbial biomass. Within the photobiontic layer a constant recycling of cells takes place, where bacteria act as decomposers. Deeper beneath the substrate develops an initially dense, then progressively thinning hyphal network of the mycobiont (i.e. a fungus). Significant differences in amounts and distribution of biomass were observed and quantified which are regional and climatic, but also local and surface age-controlled. Temperature, irradiation and water availability are presumed to be the primary factors. Evidence for a biogenic mechanical surface destabilization (grain loss, desquamation, exfoliation) as observed on siliciclastic rocks, was not found on natural carbonate rock surfaces. The life strategy' of endolithic biofilms is adapted to conserve their substrates. It commences with quick emplacement within the rock, initially causing some material loss. However, as soon as the endolithic biofilm is established, approaching an equilibrium with the climatic and ecological conditions, it behaves essentially conservatively: it does not continue with growth increments or habitat enlargement. This adaptation of euendolithic biofilms has a generally more protective than destructive impact on their carbonate rock substrates. These observations are important for a better understanding of weathering and deterioration processes, applicable to protection policies and maintenance of cultural monuments.

Description: To optimize stone consolidation it is necessary to understand the mechanisms of weathering in marbles, and its control by the mineralogical composition and the rock fabric. A knowledge of how the stone consolidants affect the weathering mechanisms and if they are compatible with the stone is also an important consideration. The weathering of marble can begin with thermal stress whereby cracks are generated. To verify whether consolidation influences the thermal behaviour of marbles, we compared the behaviour of weathered and consolidated marbles. For the investigations four marbles were selected with various fabrics (e.g. texture, grain size, grain boundary geometry, etc.) and different weathering conditions. Three consolidation approaches were adopted: a solved polymethyl-methacrylate (PMMAsol) dissolved in xylenes, a polysilicic acid ester (PSAE) and a total impregnation with a monomer methyl-methacrylate (PMMApoly). Measurements of the porosity and effective pore size distribution evidenced a strong modification of the pore space by consolidation. Both PMMA approaches show a re-establishment of cohesion which can be determined by ultrasonic velocity measurements. By reaching the respective glass transition temperatures of PMMAsol and PMMApoly, a strong modification of thermal behaviour occurs. The PSAE consolidated marbles show only minor changes of dilatation, but due to its low bonding effect no significant cohesion between the crystals occurs.

Description: A production method has been developed that makes it possible to produce dimension stone tiles only 4 mm thick without high amounts of waste material. The tiles are impregnated with a mixture of potassium-based water-glass, water, colloidal silica, and Berol 048 (non-ionic surfactant), using a repeated cycling between vacuum and atmospheric pressure. Mineralogy, fabric, and porosity affect the mechanical properties of rock used as dimension stone in the building industry. Tests for bending strength have been performed on tiles of eight different untreated and impregnated samples of igneous, sedimentary, and metamorphic rocks. Samples of three different thicknesses (4, 7 and 10 mm) were used in the tests. The untreated rock samples that had a fine-grained texture, low crack density, high mafic mineral content or a distinct ductile metamorphic texture showed the highest bending strength values, whereas those that had high amounts of carbonate minerals, and high crack or void density exhibited the lowest values. The stone types that gained the most from impregnation, in general, were those with high crack or void density.

Description: The research carried out by LISA on the decay of stone and glass by atmospheric pollution is presented. On building facades, areas unsheltered from rain are clear and eroded, while those that are sheltered darken due to the development of black crusts containing anthropogenic particles (fly-ash, soot) cemented by a framework of gypsum crystals. On calcareous stones, in-depth sulphation of the stone substrate may also occur at the same time. On porous calcareous stones, the black crusts detach periodically forming black slabs, creating a white, grey and black jigsaw-like pattern on the remaining stone surface. By exposing stone test samples to field and/or laboratory controlled polluted atmospheric conditions, the formation of embryonic black crusts has been observed. Grey crusts developed during pre-industrial times have been found to contain unburnt wood debris as a record of past air pollution. Glass alters by leaching, corrosion, encrusting and soiling. The quantification of the effects of atmospheric pollution can be accomplished either directly on buildings of different ages, or through field and/or laboratory controlled experiments. Modelling of the alteration of materials by atmospheric pollution consists of the determination of dose-response functions, of acceptable levels and thresholds and in risk assessment mapping.

Description: Sandstones are widely used as building stones throughout NW Europe. Unlike limestone, sandstones tend to experience episodic and sometimes rapid surface retreat associated with the action of salts and often leading to the development of hollows/caverns in the stone. The unpredictability of these decay dynamics can present significant problems when planning conservation strategies. Consequently, successful conservation requires a better understanding of the factors that trigger decay and determine the subsequent decay pathway. An overview of results from previous studies provided the basis for simulation experiments aimed at identifying the factors that (a) initiate decay and (b) permit the continuance of salt weathering despite rapid loss of surface material. These simulation studies involve investigation of changes in micro-environmental conditions as surface hollows develop and examination of salt weathering dynamics within such hollows. These data combined with knowledge gained from previous work have allowed the refinement of a conceptual model of rapid sandstone retreat. In this model decay is linked to the establishment of positive feedback conditions through interactions between factors such as porosity, permeability, mineralogy and their effect on salt penetration.

Description: The margin between Cote d'Ivoire and the Niger Delta is a region with a common structural history, this being reflected in similarities in the stratigraphic response and play fairways identified across the region. There has been significant exploration on the narrow shelf characterizing the margin, resulting in a series of modest oil and gas discoveries. It is shown in this paper that many of the aspects of the plays in the unexplored deep-water regions of the margin are considerably more favourable to the development of giant fields than those on the shelf. This play-fairway review is based on the integration of existing publications with focused studies of multiclient 3-D seismic data over a number of areas. Play fairways are classified by seismic sequence and trap type, with an analysis of each undertaken. The most attractive deep-water play types are: (1) anticlinal traps involving late syn-transform (Apto-Albian) and early post-transform (Late Cretaceous) reservoirs, (2) combination traps involving ponded turbidites on the shoreward flanks of these highs, and (3) stratigraphic traps associated with large Late Cretaceous submarine fan complexes. The anticlinal play is associated with the terminations of the St Paul and Romanche fracture zones, with the more recent structuring generally associated with the latter. 3-D imaging and amplitude mapping is critical to prospect delineation, particularly for the combination and stratigraphic plays. Active kitchens are evidenced involving Early and Late Cretaceous source rocks in the Cote d'Ivoire and western Ghana to Nigeria segments of the region, which are consequently upgraded. Considerable volumetric potential is indicated that promises to make the region one of significant new exploration activity in coming years.

Description: Tectonic activity, on a range of scales, is a fundamental control on sedimentary activity. The range of structural deformation within a region extends from the plate tectonic scale, governing, for example, rift initiation, to the basin scale, with the formation of basinbounding faults. Internal basin configuration is also strongly influenced by tectonic activity. However, the relationship between tectonic activity and sedimentation is a complex one, given the many additional factors which can also influence sedimentary activity, including erosion, sediment transport, source area lithology, groundwater chemistry, range of depositional environments, climate, eustasy, and the relative location of an area and its distality to marine influences. In this paper we provide a selective overview of the issues associated with the interlinked themes of tectonics and sedimentation, examining the main basin types forming in both extensional and compressional plate settings. We then review the various models of sedimentation in the selected basins, both on a local and a basinal scale. Finally, we look to the future -- providing a series of possible research areas, almost exclusively multidisciplinary, which would help to improve existing models of interlinked sediment-tectonics systems.

Description: The Oligocene to Miocene Tertiary Piedmont Basin (TPB) is located in the NW part of Italy at the junction between the Apennine and the Alpine thrust belts. The position of the TPB on top of the Alpine/Apennine Orogen poses fundamental questions as to the tectonics of the basin subsidence. Having undergone little deformation, the TPB sediments provide an insight into the stress regime and rotations in the kinematically very complex area surrounding the basin itself. In this study we integrate subsidence and structural analysis with measurements of magnetic susceptibility anisotropy (AMS) and natural remanent magnetization (NRM) in order to better constrain the tectonic kinematics of the basin evolution. A major important period of subsidence occurred in the Middle Miocene involving the whole basin. During this period the TPB experienced NE-SW-directed compression and limited shortening. Some NW-SE-directed compressional features have been identified and they were probably active during post Tortonian times. Structures associated with north-south tension are quite common, but the amount of strain that they accommodate is minor. In addition this research provides new preliminary data suggesting counterclockwise rotation in the TPB by c. 20{degrees} which has taken place during Middle Miocene time.

Description: As frontier exploration in Africa moves into ever-deeper water and new basins, there is an increasing need to mitigate the high costs by reducing risk. One way of doing this is by drawing on knowledge from other areas. The book includes regional papers ranging from syntheses on a continental scale to details of the salt tectonics of the West African margin. It also addresses the need to continue using technologies to their limits by including papers on topics as diverse as gravity interpretation and fluid inclusion studies. The book provides essential reading for those requiring further insight into the origins of Africa's diverse petroleum systems, and will be key to geologists and geophysicists involved in the exploration for and exploitation of oil and gas throughout Africa. Of particular note is the supplementary CD-ROM containing maps of Africa's petroleum basins classified by age of target reservoir system.

Description: The study of sediments and sedimentary basins in terms of their tectonic environment requires a multidisciplinary approach and has increasingly drawn both techniques and objectives from fields outside sedimentology. The application of different theoretical, experimental and empirical resources provided by structural geology, geochemistry, geophysics, scale modelling, and field geology, complement sedimentological methods, with the combined aim of achieving a deeper understanding of the origins, evolution and significance of sedimentary sequences in terms of their tectonic history. Studies presented in this volume range across a wide spectrum from the analysis of sedimentary sequence architecture at basin scale down to the chemical properties of individual grains, and include studies from a range of tectonic settings. The volume will be of interest to those involved with, or contemplating, studies involving the linkages between tectonics and sedimentation, as well as a wider audience to whom the results of such studies may provide fresh insight.

Description: The deposition of the late Eocene to early Oligocene Pechelbronn Beds in the northern Upper Rhine Graben was controlled by changes in accommodation space, sediment supply and basin physiography, imposed by the syn-rift tectonic framework. Base-level cycles, defined by variations of the ratio of accommodation space to sediment supply (A/S ratio), allow untangling of the depositional history in this complex structural setting. A transfer zone divided the northern part of the Upper Rhine Graben into a southern and a northern sub-basin and created major depositional gradients. The low A/S ratio in the transfer zone led to sediment bypassing and cannibalisation. Only asymmetric cycles of fluvial and alluvial fan deposits developed, as the sediment was transported to the sub-basins. The higher A/S ratio on the major gradient of the southern sub-basin, which increased from the transfer zone to the south, allowed the formation of symmetric delta/shoreface and lacustrine cycles. At times starvation occurred in the transfer-zone-distal parts of the sub-basin. On subordinate scale, within the southern sub-basin, tilt-blocks bounded by growth faults created halfgrabens with inferior depositional gradients. On the footwall crest, due to low A/S ratio, bypassing and erosion occurred. Here asymmetric cycles of coarse-grained channel fill deposits were preserved. On the hangingwall, close to the normal fault, high A/S conditions were present and symmetric cycles developed. The creation of accommodation space kept pace and even outpaced the footwall-derived sediment supply, which created thick shallow water deposits.

Description: The Belluno syncline is a structure located in the Venetian fold-and-thrust belt in the Italian Southern Alps. This SSE-vergent chain mainly developed during the Neogene as a back-thrust belt of the Alps deforming the northern margin of the Adria plate. The syncline is asymmetric in shape, with a steep backlimb, as the forelimb of the paired Monte Coppolo Anticline; it is the result of fault-propagation folding during the development of the underlying Belluno thrust. In plan view the Belluno thrust shows a prominent curvature interpreted as reactivation of inherited Mesozoic extensional structures. The hinge of the Belluno syncline presents a similar curvature. Rocks cropping out in the syncline core are Upper Chattian to Langhian fine-grained molassic sediments, mainly siltstones and marls. Most fractures on the Belluno syncline have formed at high angles to bedding. The dominant fracture trends are subparallel and orthogonal to the fold hinge. Sometimes these fractures show plumose structures revealing extension (Mode I) fracture mechanism and therefore they are referred to as longitudinal (bc) joints and cross (ac) joints respectively. Other fracture trends oblique to the hinge line are found in measurement stations located on limbs distant from the fold hinge. They are referred to as oblique (shear) fractures. Throughout the western part of the Belluno syncline the fracture network maintains a roughly symmetrical distribution with respect to the fold hinge, suggesting a development in association with folding.

Description: Intraplate strike-slip deformation belts are typically steeply-dipping structures that develop in both oceanic and continental lithosphere where they form some of the largest and most spectacular discontinuities found on Earth. In both modern and ancient continental settings, intraplate strike slip deformation belts are of major importance in accommodating horizontal displacements where they additionally form very persistent zones of weakness that substantially influence the rheological behaviour of the lithosphere over very long time periods (up to 1 Ga or more). These deformation zones provide a fundamental geometric, kinematic and dynamic link between the more rigid plate-dominated tectonics of the oceans and the non-rigid, complex behaviour of the continents. During convergence, they help to transfer major displacements deep into the plate interiors. During divergence, they act as transfer zones that segment rifts, passive continental margins and, ultimately, oceanic spreading ridges. Such belts are also of great economic importance, controlling the location of many destructive earthquakes, offshore and onshore hydrocarbon deposits and metalliferous ore deposits. In the oceans, intraplate strike-slip movements are relatively minor along transform-related fracture zones, but there are an increasing number of documented examples that may reflect spatial and temporal variations in spreading rate along individual active ridge segments.

Description: The Mongolian Altai is a Late Cenozoic intraplate strike-slip deformation belt which formed as a distant strain response to the Indo-Eurasian collision over 2000 km to the south. We report results from 5 weeks of detailed fieldwork carried out during summer 2000 in northwestern Mongolia investigating the crustal architecture of the Altai at latitude 48{degrees}N. The region can be divided into discrete Cenozoic structural domains each dominated by a major dextral strike-slip fault system or range-bounding thrust fault. Gentle bends along the major strike-slip faults are marked by transpressional uplifts including asymmetric thrust ridges, restraining bends, and triangular thrust-bounded massifs. These transpressional uplifts (Tsambagarav Massif, Altun Huhey Uul, Sair Uul, Hoh Serhiyn Nuruu, Omno Hayrhan Uula, Mengildyk Nuruu) comprise the highest mountains in the Mongolian Altai and are structural and metamorphic culminations exposing polydeformed greenschist-amphibolite grade basement recording at least two phases of Palaeozoic ductile deformation overprinted by Cenozoic brittle structures. Cenozoic thrust faults with the greatest amounts of displacement bound the W and SW sides of ranges throughout the region and consistently verge WSW. Each major range is essentially a NE-tilted block and this is reflected by asymmetric internal drainage patterns. Many faults are considered active because they deform surficial deposits, form prominent scarps, and define range fronts with low sinuosity where active alluvial fan deposition takes place. Reactivation of the prevailing NW-striking, NE-dipping Palaeozoic basement anisotropy is a regionally important control on the orientation and kinematics of Cenozoic faults. At first order, the Altai is spatially partitioned into a low-angle thrust belt that overthrusts the Junggar Basin on the Chinese side and a high-angle SW-vergent dextral transpressional belt on the Mongolian side. The mechanically rigid Hangay craton and Junggar basement block which bound the Altai on either side have played a major role in focusing Late Cenozoic deformation along their boundaries and within the Altai. The geometric relationship between rigid block boundaries, Palaeozoic basement structural anisotropy, and the dominantly NE SHmax (derived from India's continued NE indentation) has dictated the kinematics of Late Cenozoic deformation in the Altai, Gobi Altai, and Sayan regions.

Description: Provenance analysis of siliciclastic sedimentary rocks gives indications of the tectonic evolution and setting of source regions and the rocks contained in them. The composition of sedimentary rocks ideally reflects the nature of these regions, and only indirectly the tectonic setting of the basin where the erosional debris is deposited. This makes it possible to interpret Late Devonian to Early Carboniferous metasedimentary basement rocks of the Andes in southernmost Chile as having been deposited at a passive margin, despite geochemical indications of an active margin setting for the source rocks, and the position of the metasediments in the backstop of an accretionary wedge. Major and trace elements point to felsic source rocks from an active margin environment. The Nd model ages of 1170-1490 Ma indicate that the source rocks were part of an old continental crust in the Late Palaeozoic. The {varepsilon}Nd(T) values range between -7 and -2. These characteristics, in combination with the regional geology, suggest that the geochemical signal is dominated by rocks formed at an active margin, which later acted as feeders for the sediments deposited in a passive-margin environment. If corroborated by research in progress this emphasizes the problem of deducing the tectonic setting of a depositional basin from provenance data.

Description: Three-dimensional fracture networks, combined from seismic scale to wellbore scale, can greatly enhance the knowledge of fracture contribution to hydrocarbon storage and flow inside the reservoir. This paper presents some techniques used at ENI-Agip for fracture network simulation at wellbore scale. First, new imaging techniques adopted for enhancing and facilitating the data acquisition from orientated cores will be shown. We will discuss how the fracture data, acquired from the combined analysis of orientated core and wellbore image logs, have to be processed in order to calculate the geometrical parameters of each feature (dip direction, dip, size, terminations) and to classify them according to their filling (oil, water, shale, calcite, etc.). Second, we will illustrate how these kind of data are processed in order to extract the fracture representative parameters needed for stochastic simulation of fracture network at the wellbore scale: spatial distribution along the cored/logged interval, number of fracture sets, representative orientation and statistical distribution of each set, distribution laws of the fracture length and relevant minimum radii and fracture aperture estimate. Fracture porosity evaluation, matrix block size, fracture network connectivity at wellbore scale constitute the outputs of such simulations: they are used to better characterize a fractured reservoir and to describe its behaviour. The synthetic results of the application of such a methodology on a real case (tight packstone/wackestone of carbonate platform from a southern Apennine italian oil reservoir) complete the paper.

Description: Ground penetrating radar (GPR) surveys were used to identify three distinct sea-level highstands within the oxygen isotope stage (OIS) 5-equivalent sediments of the Quaternary Cape May Formation in southern New Jersey. The three units, QCM1a, QCM1b, and QCM1c, are designated as submembers of the Cape May 1 member. The transgressive ravinement surfaces (TRS) forming the bounding unconformities of these units are recognized as laterally extensive reflections on the radar records and have been corroborated as gravel lag deposits and associated lithological discontinuities in continuous vibracores and hand-augered boreholes. GPR and lithological data have been used to interpret these highstand deposits in a sequence-stratigraphic framework. These units are thin (3 m or less), lithologically similar and present limited geomorphic expression of their individual existence beneath a low terrace (+6 m to mean sea level/MSL) on the northern margin of Delaware Bay. In the upper two units, QCM1b and QCM1a, radar surveys across subtle, bay-margin parallel, sublinear topographic highs of 3 m relief or less in the Jones Island area reveal internal structures consistent with geomorphic interpretation as stranded estuarine shorelines. The newly identified shoreline complexes are located well bayward of, and lower in elevation than, the commonly accepted +5 m to +6 m MSL OIS 5e shoreline. This older shoreline abuts the Cedarville Scarp and is attributed to the sea-level highstand associated with QCM1a. GPR was also used to accurately place vibracores for gathering samples of the three units for optically stimulated luminescence dating. Together, these three highstand deposits record sea-level fluctuations within OIS 5, at time scales shorter than those commonly recognized in the mid-Atlantic region.