ALBERT

Beschreibung: In most hot deserts Quaternary environmental changes have left their imprint on ground conditions, creating a legacy of materials that often reflect past as well as contemporary processes, and can appear unusual to geologists trained in temperate environments. Attention is drawn in this article to three near-surface features (duricrusts, palaeolakes and sulphate-rich soils) that reflect changing environmental conditions and that are of potential significance to engineering investigation, design and construction.

Beschreibung: The results of 61 in situ UK thermal response tests, derived from three commercial test-rigs, have been analysed. Derived values of thermal conductivity yield a median of 2.25 W m K –1 , with 25th and 75th percentiles of 1.86 and 3.0 W m K –1 . The lowest single values are derived from Northern Irish basalt (1.1 W m K -1 ) and from Mesozoic and Tertiary argillites (often in the range 1.43–2 W m K –1 ), whereas the highest (〉5 W m K –1 ) are from Sherwood Sandstone and Coal Measures strata where advective heat transport with groundwater flow may have led to an elevated apparent conductivity. Borehole thermal resistance exhibits 25th percentile, median and 75th percentile values of 0.09, 0.11 and 0.14 K m W –1 and correlates with borehole heat exchanger diameter and configuration. Undisturbed ground temperature exhibits 25th percentile, median and 75th percentile values of 11.7, 12.3 and 13.2 °C and exhibits a latitude dependence.

Beschreibung: The Whitby Mudstone Formation has one of the highest landslide densities in the UK with 42 landslides per 100 km 2 . Landsliding at Hollin Hill in North Yorkshire, UK is complex and continuing, and includes shallow, retrogressive rotational failure on the upper slope, translation, and flow from the base of the Whitby Mudstone Formation over the scarp slope of the Staithes Sandstone Formation. Surface observations augmented by information relating to lithological, moisture and strength variation with depth allowed rapid initial interpretation of the masses affected by movement. These were provided by a single person operating portable probes providing depth logs of cone penetration resistance and soil moisture based upon dielectric property measurements in conjunction with a sampling auger. The gathered information was used to guide the design of further invasive site investigation and the configuration of permanent systems to monitor changes in dynamic moisture distribution and direct movement. At Hollin Hill, the near-surface materials in the upper 5 m interval are distinctly weathered or destructured, predominantly comprising silty clay in the Whitby Mudstone Formation, and fine silty, clayey sand and silty clay in the Staithes Sandstone Formation. Direct and secondary evidence was observed showing high moisture variation to be related to narrow intervals within the upper 5 m. Cyclic variation in moisture has played a key role in the movement and break-up of sliding materials, especially within the prograding lobes resulting from flow over the Staithes Sandstone Formation. Since these observations, permanent monitoring systems have been installed, including electrical resistivity tomography (ERT) arrays, which have successfully mapped the distribution of the Whitby Mudstone and the Staithes Sandstone, but will also be used in time lapse mode to image the near-surface moisture movement driving the landsliding processes. ERT array installations included a large area, low spatial resolution grid designed to investigate the potential coupling between the upper and lower slope hydrogeological processes and a small area, high spatial resolution grid designed to investigate the hydrogeological processes driving the earth flow.

Beschreibung: Publication date: Available online 24 September 2013 Source: Quaternary Research Author(s): Daniel E. Karig , Norton G. Miller Areal mapping of the middle Wisconsin varved clay site along Sixmile Creek near Ithaca, New York, has revealed a much more widespread and varied array of sediments than previously thought. Lacustrine clays, some varved, are interbedded with sands and gravels interpreted as sub-aqueous fan deposits, and both are overlain by a deformation till. Nine radiocarbon dates indicate a 34–37 14 C ka BP age for the lacustrine sediment, with the deformation till less than a few thousand years younger. Beneath this sequence is a deposit dated at ± 42 14 C ka BP. Both strata represent a tundra climate with a mean July temperature of about 10°C. The Sixmile Creek deformation till must correlate with the 35 14 C ka BP till along the Genesee River, 125 km to the NW, and defines a Cherrytree stade glacial advance into the Appalachian Plateau, much further south than what has generally been accepted. Such an advance would require drainage from a proglacial lake in the western Ontario basin to flow westward instead of northeastward. The Sixmile strata suggest a colder than accepted middle Wisconsin stage. Recent data indicate that this stage is one of progressive cooling, with large climatic fluctuations.

Beschreibung: Publication date: Available online 25 September 2013 Source: Quaternary Research Author(s): Denis Geraads , Fethi Amani , Abdelouahed Ben-Ncer , Shannon P. McPherron , Jean-Paul Raynal , Jean-Jacques Hublin The rodents from the late middle Pleistocene hominin-bearing locality of J'bel Irhoud include the following species: Meriones shawii , Gerbillus grandis , Dipodillus campestris , Paraethomys ras , Lemniscomys barbarus , Mus cf. spretus , and Eliomys sp. We consider M. shawii , a living species, as identical with the middle Pleistocene Meriones maghrebianus . The mouse differs from the domestic Mus musculus but does not clearly fit into Mus spretus , either. The rare G. grandis looks identical with the form from the middle Pleistocene of Thomas quarries, which may suggest a rather early age for Irhoud. This is in agreement with the occurrence of Paraethomys , a genus unknown in the upper Pleistocene of Morocco, but the absence of the arvicolid Ellobius suggests that the site is younger than other middle Pleistocene sites, Doukkala II, Sidi Abderrahmane D2, and Irhoud-Derbala-Virage. Paleoecological indicators, such as the taxonomic habitat spectrum, or the relative abundances of Gerbillinae and Murinae, suggest a less xeric environment than in many earlier and later sites. Diversity indices, comparable to those of other middle Pleistocene sites, point to similarly favorable conditions before the major climatic crisis close to the middle/upper Pleistocene boundary that drastically reduced rodent diversity in North Africa.

Beschreibung: The thermal springs of Bath, England, produce 1.25 Ml day –1 of water at 46.5 °C. The spring at Hotwells, Bristol, England, 15 km to the west, is estimated to produce between 0.17 and 0.39 Ml day –1 of water at a temperature between 22.8 and 24.4 °C. Published research suggests that the waters originate in the Mendip Hills, SW of Bath and Bristol, and are heated by geothermal energy within the Carboniferous Limestone basin (‘The Mendips Model’). The exact paths of the waters to the springs have not been established. We interpreted seismic reflection data for the urban district of Bath and for the Radstock Basin to the south of Bath. By combining the geophysical interpretations with published geological data we have established a potential route through the Carboniferous Limestone reaching sufficient depths for the waters to attain the required temperatures. We imaged a steeply dipping, fractured region of Carboniferous Limestone coincident with the valley of the River Avon and propose that this is the feature by which the thermal waters can rise rapidly to the surface, providing an explanation for the existence of these unique springs. We have incorporated these new aspects of the Mendip Model into the ‘Mendip–Avon Fracture Zone Model’.

Beschreibung: Publication date: Available online 25 September 2013 Source: Quaternary Research Author(s): Mikael Ohlson , Isabella Kasin , Anveig Nordtug Wist , Anne E. Bjune Forest fires convert a proportion of the burning vegetation into charcoal that is stored in forest soils and lake sediments. In this paper we use a geostatistical approach to present a detailed analysis of the size of the charcoal pool and its spatial variation in a boreal forest watershed including its lake sediment. The amount of soil charcoal averaged 179 g/m 2 and ranged from 0 to 3600 g/m 2 in the watershed. There was an extreme variation in the size of the charcoal pool over fine (cm) spatial scales. For example, the amount of charcoal in the soil could range from 34 to 1646 g/m 2 within a distance of 10 cm. Individually dated soil charcoal particles had radiocarbon ages that varied from 630 to 2930 cal yr BP. The lake sediment began accumulating at 10,600 cal yr BP and charcoal accumulation has been practically continuous ever since then, with the largest peak occurring at 6900 cal yr BP. The lake sediment contained more charcoal, 360 g/m 2 , than the average for forest soil. We interpret this as an indication of a relatively rapid degradation of charcoal in boreal forest soils.

Beschreibung: Publication date: Available online 29 September 2013 Source: Quaternary Research Author(s): Julien Carcaillet , Isandra Angel , Eduardo Carrillo , Franck A. Audemard , Christian Beck In the tropical Mérida Andes (northwestern Venezuela), glacial landforms were found at altitudes between 2600 and 5000 m, corresponding to 600 km 2 of ice cover during the maximum glacial extension. However, the lack of sufficient absolute age data prevents detailed reconstruction of the timing of the last deglaciation. On the northwestern flank of the Mucuñuque Massif, successive moraines and striated eroded basement surfaces were sampled for cosmogenic 10 Be investigation. Their compilation with published data allows the establishment of a detailed chronology of the post-LGM glacier history. The oldest moraines (18.1 and 16.8 ka) correspond to the Oldest Dryas. Successive moraine ridges indicate stops in the overall retreat between the LGM and the Younger Dryas. The cold and short Older Dryas stadial has been identified. Results indicate that most of the ice withdrew during the Pleistocene. The dataset supports an intensification of the vertical retreat rate from ~ 25 m/ka during the late Pleistocene to ~ 310 m/ka during the Pleistocene/Holocene. Afterwards, the glacier was confined and located in the higher altitude zones. The altitude difference of the Younger Dryas moraines in the Mucubají, La Victoria and Los Zerpa valleys indicates a strong effect of valley orientation on the altitude of moraine development.

Beschreibung: Publication date: Available online 3 October 2013 Source: Quaternary Research Author(s): Nicole E. Spaulding , John A. Higgins , Andrei V. Kurbatov , Michael L. Bender , Steven A. Arcone , Seth Campbell , Nelia W. Dunbar , Laura M. Chimiak , Douglas S. Introne , Paul A. Mayewski Terrestrial meteorite ages indicate that some ice at the Allan Hills blue ice area (AH BIA) may be as old as 2.2 Ma. As such, ice from the AH BIA could potentially be used to extend the ice core record of paleoclimate beyond 800 ka. We collected samples from 5 to 10 cm depth along a 5 km transect through the main icefield and drilled a 225 m ice core (S27) at the midpoint of the transect to develop the climate archive of the AH BIA. Stable water isotope measurements (δD) of the surface chips and of ice core S27 yield comparable signals, indicating that the climate record has not been significantly altered in the surface ice. Measurements of 40 Ar atm and δ 18 O atm taken from ice core S27 and eight additional shallow ice cores constrain the age of the ice to approximately 90–250 ka. Our findings provide a framework around which future investigations of potentially older ice in the AH BIA could be based.

Beschreibung: Publication date: Available online 3 October 2013 Source: Quaternary Research Author(s): Yurena Yanes , María P. Asta , Miguel Ibáñez , María R. Alonso , Christopher S. Romanek Land snail shell δ 13 C value is often used as a paleovegetation proxy assuming that snails ingest all plants in relation to their abundance, and that plants are the only source of carbon. However, carbonate ingestion and variable metabolic rates complicate these relationships. We evaluate if live-collected snails from Lanzarote (Canary Islands) reflect the abundance of C 3 and CAM plants. Snails were collected on either CAM or C 3 plants for isotope analysis of shell and body, and shell size. Respective shell and body δ 13 C values of snails collected on CAM plants averaged − 8.5 ± 1.7‰ and − 22.8 ± 1.6‰, whereas specimens from C 3 plants averaged − 10.1 ± 0.7‰ and − 24.9 ± 1.1‰. A flux balance model suggests snails experienced comparable metabolic rates. A two-source mass balance equation implies that snails consumed ~ 10% of CAM, which agrees with their abundance in the landscape. Snails collected on CAM plant were smaller than those on C 3 plants. Conclusively: 1) snails consume CAM plants when they are available; 2) migration of snails among C 3 and CAM plants is a common phenomenon; and 3) C 3 plants may be a more energetic food for growth than CAM plants. This study shows that shell δ 13 C values offer approximate estimates of plants in C 3 –CAM mixed environments.

Beschreibung: Publication date: Available online 7 June 2013 Source: Quaternary Research Author(s): William R. Dickinson Unlike most tropical Pacific islands, which lie along island arcs or hotspot chains, the Loyalty Islands between New Caledonia and Vanuatu owe their existence and morphology to the uplift of pre-existing atolls on the flexural forebulge of the New Hebrides Trench. The configuration and topography of each island is a function of distance from the crest of the uplifted forebulge. Both Maré and Lifou are fully emergent paleoatolls upon which ancient barrier reefs form highstanding annular ridges that enclose interior plateaus representing paleolagoon floors, whereas the partially emergent Ouvea paleoatoll rim flanks a drowned remnant lagoon. Emergent paleoshoreline features exposed by island uplift include paleoreef flats constructed as ancient fringing reefs built to past low tide levels and emergent tidal notches incised at past high tide levels. Present paleoshoreline elevations record uplift rates of the islands since last-interglacial and mid-Holocene highstands in global and regional sea levels, respectively, and paleoreef stratigraphy reflects net Quaternary island emergence. The empirical uplift rates vary in harmony with theoretical uplift rates inferred from the different positions of the islands in transit across the trench forebulge at the trench subduction rate. The Loyalty Islands provide a case study of island environments controlled primarily by neotectonics.

Beschreibung: Publication date: Available online 7 June 2013 Source: Quaternary Research Author(s): Thomas R. Lakeman , John H. England The study revises the maximum extent of the northwest Laurentide Ice Sheet (LIS) in the western Canadian Arctic Archipelago (CAA) during the last glaciation and documents subsequent ice sheet retreat and glacioisostatic adjustments across western Banks Island. New geomorphological mapping and maximum-limiting radiocarbon ages indicate that the northwest LIS inundated western Banks Island after ~ 31 14 C ka BP and reached a terminal ice margin west of the present coastline. The onset of deglaciation and the age of the marine limit (22–40 m asl) are unresolved. Ice sheet retreat across western Banks Island was characterized by the withdrawal of a thin, cold-based ice margin that reached the central interior of the island by ~ 14 cal ka BP. The elevation of the marine limit is greater than previously recognized and consistent with greater glacioisostatic crustal unloading by a more expansive LIS. These results complement emerging bathymetric observations from the Arctic Ocean, which indicate glacial erosion during the Last Glacial Maximum (LGM) to depths of up to 450 m.

Beschreibung: Publication date: Available online 10 April 2013 Source: Quaternary Research The distribution of marine-influenced oxygen isotope stage (OIS) 5 to OIS 1 sediments was examined in several late Quaternary boreholes from the southern Changjiang (Yangtze) delta plain, China, using different dating methods including OSL, U-series, AMS 14 C and paleomagnetism. Results demonstrate that coastal and estuarine deposition during OIS 5 and OIS 3 occurred throughout the study area. However, Holocene transgressive sediments were absent on the Taihu block. The burial depth of intertidal to subtidal sediment deposited during OIS 5e records 30–80 m subsidence caused by sediment compaction and tectonic movement since that time. However, coastal sediments formed during the late phase of OIS 3 were buried to a depth of ca. 6–15 m in the Taihu Lake area, while the burial depth increased eastward to ca. 45–60 m on the coastal plain. This phenomenon, combined with the distribution of Holocene marine strata, indicates at least 25–30 m uplift of the Taihu block since the end of OIS 3. We suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post-glacial deposition by the Changjiang and Huanghe Rivers on the continental shelf of east China marginal sea.

Beschreibung: Publication date: Available online 5 September 2013 Source: Quaternary Research Author(s): Vachel A. Carter , Andrea Brunelle , Thomas A. Minckley , Philip E. Dennison , Mitchell J. Power Fire is one of the most important natural disturbances in the coniferous forests of the US Rocky Mountains. The Rocky Mountains are separated by a climatic boundary between 40° and 45° N, which we refer to as the central Rocky Mountains (CRM). To determine whether the fire regime from the CRM was more similar to the northern Rocky Mountains (NRM) or southern Rocky Mountains (SRM) during the Holocene, a 12,539-yr-old sediment core from Long Lake, Wyoming, located in the CRM was analyzed for charcoal and pollen. These data were then compared to charcoal records from the CRM, NRM and SRM. During the Younger Dryas chronozone, the fire regime was characterized as frequent at Long Lake. The early and middle Holocene fire regime was characterized as infrequent. A brief interval from 4000 to 3000 cal yr BP, termed the Populus period, had a frequent fire regime and remained frequent through the late Holocene at Long Lake. In comparison to sites from the NRM and SRM, the fire regime at Long Lake was most similar to the SRM during the past 12,539 cal yr BP. These results suggest the disturbance regime in the CRM has a greater affinity with those of the SRM.

Beschreibung: Publication date: Available online 13 September 2013 Source: Quaternary Research Author(s): Lyudmila S. Shumilovskikh , Helge W. Arz , Antje Wegwerth , Dominik Fleitmann , Fabienne Marret , Norbert Nowaczyk , Pavel Tarasov , Hermann Behling This multiproxy study on SE Black Sea sediments provides the first detailed reconstruction of vegetation and environmental history of Northern Anatolia between 134 and 119 ka. Here, the glacial–interglacial transition is characterized by several short-lived alternating cold and warm events preceding a meltwater pulse (~ 130.4–131.7 ka). The latter is reconstructed as a cold arid period correlated to Heinrich event 11. The initial warming is evidenced at ~ 130.4 ka by increased primary productivity in the Black Sea, disappearance of ice-rafted detritus, and spreading of oaks in Anatolia. A Younger Dryas-type event is not identifiable. The Eemian vegetation succession corresponds to the main climatic phases in Europe: i) the Quercus – Juniperus phase (128.7–126.4 ka) indicates a dry continental climate; ii) the Ostrya – Corylus – Quercus – Carpinus phase (126.4–122.9 ka) suggests warm summers, mild winters, and high year-round precipitation; iii) the Fagus – Carpinus phase (122.9–119.5 ka) indicates cooling and high precipitation; and iv) increasing Pinus at ~ 121 ka marks the onset of cooler/drier conditions. Generally, pollen reconstructions suggest altitudinal/latitudinal migrations of vegetation belts in Northern Anatolia during the Eemian caused by increased transport of moisture. The evidence for the wide distribution of Fagus around the Black Sea contrasts with the European records and is likely related to climatic and genetic factors.

Beschreibung: Adverse reactions between specific aggregate particles and the pore fluids in cement pastes have been widely reported, and have been regarded as responsible for the failure of the structures into which the resulting concrete had been emplaced. The reactivity of aggregates containing various forms of silica has been well understood but similar reactions, apparently taking place between aggregates of limestone, dolostone and ‘dedolomites’, although widely recognized, remain controversial. Here we review the evidence bearing on the latter reactions and suggest a new view of their implications.

Beschreibung: Air at high pressure has recently been encountered during ground investigation borehole drilling for the Thames Tideway project in London. The air was released from within the Upnor Formation (at the base of the Lambeth Group beds), which is at the top of the Lower Aquifer. Cavitation within the granular beds of the Lower Aquifer would have occurred as a consequence of drawdown from the extensive water extraction that began at the start of the nineteenth century, resulting in the water table dropping by almost 70 m. Estimated historical pore pressure profiles are postulated and the cavitation process that occurred, along with the subsequent pressurization of the air during recharge that has occurred in recent years, are discussed using behavioural concepts from unsaturated soil mechanics. The hypotheses are corroborated by a series of simple column experiments where the processes are modelled using analogous soils. Engineering implications of the presence of the pressurized air are discussed: besides the potential for borehole blow-out, another serious consideration is the depletion of oxygen from the trapped air by chemical reaction with the soil, increasing the risk of confined space hypoxia.

Beschreibung: Predictions from laboratory tests of the compression behaviour of peat from 14 sites are compared with full-scale field loading at five sites. Data presented confirm the heterogeneous nature of the deposits. However, for typical engineering works, calculations based on laboratory test data are likely to give reasonable predictions of the magnitude of immediate and primary compression. Standard (20 mm thickness) samples may give misleading data on time for primary consolidation. Thicker samples (e.g. 50 mm) should be used. Sampling by conventional samplers, as used for mineral soils, can cause densification of the peat, resulting in underestimation of actual settlement. Block samples or sample tubes with serrated cutting edges are recommended for peat soils. It was found that the data presented follow the C α / C c law of compressibility. There is also is some evidence to suggest that the H 2 scaling law may be applicable. Good correlations were found between vertical yield stress ( p vy ') and compression index ( C c ) and index parameters such as water content ( w i ). Conventional staged construction with surcharge loading may be successfully applied to peat soils as long as adequate drainage exists to permit consolidation over reasonable time intervals.

Beschreibung: This paper discusses the interpretation of the pore water dissipation curves obtained during a piezocone test with the prime objective of determining the seismic behaviour of fine-grained soil. The pore pressure dissipation approach was attempted to perform a faster diagnosis of liquefiability of fine-grained soils where the ground water table is almost at the surface. Furthermore, because non-plastic silts are very difficult to sample for laboratory testing, such an in situ measurement appears to be the only realistic method for the purpose. Most of the dissipation tests were conducted by using the u 2 filter on the neck of the probe, and the others were performed by using the u 1 filter where the piezometer is located on the cone tip. Penetration was arrested at depths where the presence of silts had been detected by previous sounding and drilling, and t 50 , t 90 and t 100 were determined analytically. The results indicate that t 90 values have a notable potential for diagnosing a potential for liquefaction. This was demonstrated by a t 90 of 300 s or less for liquefiable layers, whereas considerably longer periods are required for non-liquefiable silts similar to clays. This feature is illustrated by the presentation of several types of dissipation curves.

Beschreibung: Publication date: Available online 26 September 2013 Source: Quaternary Research Author(s): Liubing Xu , Shangzhe Zhou The timing of terrace formation relative to the glacial–interglacial cycle and what factors control that timing, such as changes in climate and/or uplift, are controversial. Here we present a study of the terraces along the Yazheku River using electron spin resonance (ESR) dating and analysis of the sedimentary characteristics in order to establish the timing of terrace formation and to assess the forcing mechanisms that have been proposed. The Yazheku River flows in glacial trough leading from the Haizi Shan, on the eastern Tibetan Plateau. The range was uplifted during the Quaternary and repeatedly glaciated by ice caps. The four highest major terraces (T5, T4, T3, and T2) are the result of both climatic and tectonic influences. Strath terraces T5–T2 were created during Haizi Shan glacial expansions during MIS 16, 12, 6 and 3–4, respectively. The major aggradation phases of the four terraces occurred during the deglaciations at the ends of MIS 16, 12, 6, and 2. Down-cutting, which led to the generation of the four terraces, immediately followed the deposition of the T5–T2 gravel units. These incisions occurred during the transitions between MIS 16–15, MIS 12–11, MIS 6–5, and MIS 2–1.

Beschreibung: Publication date: Available online 16 December 2014 Source: Quaternary Research Author(s): Marith C. Reheis , David M. Miller , John P. McGeehin , Joanna R. Redwine , Charles G. Oviatt , Jordon Bright An outcrop-based lake-level curve, constrained by ~ 70 calibrated 14 C ages on Anodonta shells, indicates at least 8 highstands between 45 and 25 cal ka BP within 10 m of the 543-m upper threshold of Lake Manix in the Mojave Desert of southern California. Correlations of Manix highstands with ice, marine, and speleothem records suggest that at least the youngest three highstands coincide with Dansgaard–Oeschger (D–O) stadials and Heinrich events 3 and 4. The lake-level record is consistent with results from speleothem studies in the Southwest that indicate cool wet conditions during D–O stadials. Notably, highstands between 43 and 25 ka apparently occurred at times of generally low levels of pluvial lakes farther north as interpreted from core-based proxies. Mojave lakes may have been supported by tropical moisture sources during oxygen-isotope stage 3, perhaps controlled by southerly deflection of Pacific storm tracks due to weakening of the sea-surface temperature gradient in response to North Atlantic climate perturbations.

Beschreibung: This article is currently available as a free download on ingentaconnect

Beschreibung: This article is currently available as a free download on ingentaconnect

Beschreibung: This article is currently available as a free download on ingentaconnect

Beschreibung: In the southern winter of 1970, a phreatomagmatic eruption occurred in the northern part of Deception Island (South Shetland Archipelago, Antarctic Peninsula). The eruption, with no eye-witnesses to the event, occurred in the same general area as the 1967 eruption, but with new, more widely distributed vents. Two contrasting groups of craters were formed in the 1970 eruption, showing that different active fissures and eruptive dynamics were operating. One group consists of ‘maar-like’ craters, whereas the other comprises conical edifices. The 1970 eruption can be classified as volcanic explosivity index (VEI) 3, with mainly phreatomagmatic phases that generated a bulk volume of about 0.1 km 3 of pyroclastic material and an eruptive column at least 10 km high, from which fallout deposits are recognized more than 100 km to the NE. The 1970 eruption was similar to that of 1967 and together these two eruptive events show how eruption dynamics can be controlled by the uppermost part of the volcano substrate and the width and orientation of the eruptive fissure. These influence magma–water interaction and hence may imply different eruptive phases and associated volcanic hazards. Supplementary material: Granulometric and component histograms of the samples that are not shown in Figure 4 are available at http://www.geolsoc.org.uk/SUP18761 .

Beschreibung: Neoproterozoic oceans provided the setting for the rise of animals, yet little is known of their chemical composition. Marine carbonates from the Cryogenian Oodnaminta Reef Complex, South Australia, reveal the chemical structure of a Neoproterozoic ocean. Pseudo-depth profiles from shallow- to deep-water reef facies have been constructed from geochemical and sedimentological analysis of marine cements. Evidence suggests that under a peritidal oxic–anoxic chemocline, the water column was largely anoxic, strongly ferruginous and had a chemistry profoundly different from that of modern seawater. These geochemical data suggest early Archaean-like conditions for this late Cryogenian ocean, posing problems for metazoan evolution in extremely anoxic conditions. Supplementary material: Detailed methods and data tables are available at www.geolsoc.org.uk/SUP18764 .

Beschreibung: U–Pb ages and Hf isotope data were obtained for zircon from amphibole-rich mafic to ultramafic rocks from the Adamello batholith and the Bergell pluton, the largest Palaeogene intrusions of the Alpine Orogen. The 206 Pb/ 238 U age pattern of U–Pb concordant dates from the Adamello mafic rock shows a major crystallization event at c . 41 Ma and older age peaks at c . 50 and c . 45 Ma. Hornblendite and amphibole gabbro samples of the Adamello batholith have zircon with initial Hf of c . +9.0 and c . +7.0, respectively. Amphibole gabbro and diorite samples of the Bergell pluton yield a younger age of c . 31 Ma and have zircon with lower initial Hf ( c . +4.0). We propose that the amphibole-rich rocks from the Adamello batholith originated from a depleted mantle source activated by the subduction of the Ligurian–Piedmontese Basin. The amphibole-rich rocks from the Bergell pluton formed 10–15 Ma later than the Adamello counterparts by melts derived from a mantle sector metasomatized by the subduction of the Valais Basin. The enriched Hf isotopic signature of the amphibole-rich rocks from the Bergell pluton is therefore interpreted to reflect the peculiar lithostratigraphy of the Valais Basin or a primary feature of the newly activated mantle source. Supplementary material: (1) A map showing the location of analysed samples and table with GPS coordinates of the samples, (2) data tables for U–Pb in zircon determined by LA-ICP-MS, (3) data tables for Hf isotopes in zircon, (4) U–Pb and Hf isotope analytical methods, (5) cathodoluminescence images of analysed zircon from the amphibole-rich mafic rocks of the Adamello and Bergell intrusions, and (6) a U–Pb concordia diagram for zircon of the Adamello amphibole gabbro are available at www.geolsoc.org.uk/SUP18763 .

Beschreibung: The only place where Neogene–Quaternary rocks crop out for the entire Tuscan Archipelago in the Northern Tyrrhenian Sea is the island of Pianosa. In particular, the Miocene deposits record the depositional and tectonic evolution of the Northern Tyrrhenian region during this time period. These deposits are subdivided into two successions separated by a low-angle unconformity. The older, middle Burdigalian succession represents a calciturbidite shallow marine system, whereas the younger late Tortonian–early Messinian succession comprises a continental alluvial system that evolves upwards into a lagoonal–marginal marine environment. Here we present sedimentological, palaeontological and petrographical data that support a new stratigraphic and palaeogeographical framework for reconstructing the opening of the Northern Tyrrhenian back-arc basin. The early Miocene succession records a pre-rift marine depositional phase followed by a late Burdigalian–Langhian erosional phase. This was followed by a period of synrift continental-marginal deposition, as recorded by the late Miocene succession, terminated by an important phase of uplift, probably induced by the start of magmatic activity in the Tuscan Archipelago area.

Beschreibung: Microbial carbonates contain valuable chemical, isotopic and molecular information regarding the Precambrian Earth. They record shallow-water information complementary to deep ocean proxies, such as banded iron formation and black shale. Six groups of well-preserved stromatolites illustrate how the rare earth elements (REE) are used for chemical investigation. The first task is to test whether the REE inventory of carbonate is compromised by clastic, volcanic, or diagenetic contaminants. Once the cleanliness has been verified, the shale-normalized REE pattern can be used to distinguish between marine and lacustrine settings. For marine carbonates, it is possible to distinguish between restricted basin and open marine settings and for thick platform limestones the relative water depth can be inferred from REE systematics. The studied shallow-water stromatolites range in age from 2.52 to 3.45 Ga. They contain no evidence from the behaviour of the redox-sensitive element cerium that free oxygen levels in the shallow sea approached concentrations beyond a trace gas by 2.52 Ga. Compared with abiotic early diagenetic marine carbonate cements, microbial carbonate is strongly enriched in REE. This may itself not yet serve as a biomarker, but it is regarded as a necessary prerequisite for a sample to qualify for biomarker studies.

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Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 8 June 2011 David J., Mallinson , Curtis W., Smith , Shannon, Mahan , Stephen J., Culver , Katie, McDowell The Outer Banks barrier islands of North Carolina, USA, contain a geologic record of inlet activity that extends from ca. 2200calyr BP to the present, and can be used as a proxy for storm activity. Optically stimulated luminescence (OSL) dating (26 samples) of inlet-fill and flood tide delta deposits, recognized in cores and geophysical data, provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data. OSL ages of historical inlet fill compare favorably to historical documentation of inlet activity, providing confidence in the technique. Comparison suggests that the Medieval Warm Period (MWP) and...

Beschreibung: There is a basic assumption that the upper crustal point of magma emplacement overlies the point where magma was generated. This contribution discusses the concept of lateral magma movement in the upper crust based on the Mourne Granite Centres, Northern Ireland. We report anisotropy of magnetic susceptibility fabric data from the Western Mourne Centre that indicate SSW to NNE inflow in this centre, parallel to the Eastern Centre. This suggests that these two centres share a common feeder zone outside the Mourne area c. 20 km to the south, coincident with a c. 50 mGal gravity anomaly that may be caused by an unexposed mafic pluton. The links between mafic and felsic magmas in this region, and the coincidence of the projected Mourne granite feeder zone and the possible buried mafic pluton lead to a model in which the Mourne granites were emplaced in a NNE direction as two gently dipping sheets from this unexposed mafic body. From this we develop a model that incorporates existing geophysics and known tectonic framework and involves an interconnected upper crustal network of Early Palaeogene igneous intrusion pathways fed from a common tectonically controlled, and probably long-lived, deeply penetrating feeder zone.Supplementary material: Anisotropy of magnetic susceptibility data, thermomagnetic analyses and a thin section showing magnetite in biotite cleavage are available at http://www.geolsoc.org.uk/SUP18458.

Beschreibung: Combined U–Pb and Lu–Hf isotope analyses of zircons from 16 tonalite–trondjemite–granodiorite (TTG) gneiss and granite samples from Swaziland reveal that the oldest rocks of the Ancient Gneiss Complex in southern Africa formed by reworking of Early Archaean or perhaps Late Hadean crust at 3.66 Ga, and that new crust was extracted from a depleted mantle source during Palaeoarchaean events between 3.54 and 3.32 Ga. This interpretation is supported by eHft of -1.6 ± 2.0 obtained from 3.66 Ga TTG gneisses, corresponding to hafnium model ages between 3.77 ± 0.18 Ga, for a presumed Hadean–Early Archaean chondritic mantle, and 4.08 ± 0.18 Ga, for a presumed Hadean depleted mantle reservoir, with the first model age being the most likely in the light of recent data from worldwide sources. Furthermore, it is reflected by superchondritic eHft up to +2.2 ± 2.0 for TTGs formed at 3.54, 3.45 and 3.32 Ga. The new datasets additionally show that the Palaeoarchaean crust formed between 3.54 and 3.32 Ga was intensely reworked afterwards, without significant addition of depleted mantle derived material, during orogenic and intracratonic melting processes at 3.23, 3.1 and 2.7 Ga. This is well reflected by an array of decreasing eHft from +2.2 to -7.2 between 3.3 and 2.7 Ga, which can be forced by 176Lu/177Hf of 0.0113, which is similar to that of present-day average continental crust, and might result from lower crust zircon fractionation during Archaean crust reworking.Supplementary material: Results of in situ U–Pb and Lu–Hf isotope zircon analyses and concordia diagrams are available at www.geolsoc.org.uk/SUP18465.

Beschreibung: Dyke thickness datasets offer new insights into the detailed 3D geometry of dyke swarms and an exceptional opportunity to evaluate theoretical emplacement models. The Swartruggens kimberlite dyke swarm extends over 7 km along strike and intrudes a dolerite, quartzite, shale and andesitic lava succession. The Star kimberlite dykes cut shales and sandstones, intersect a large dolerite sill and extend 15 km along strike. Both dyke swarms comprise anastomosing en echelon segments, each several hundred metres long. In total 1532 Swartruggens dyke thickness measurements were taken, to 750 m below the surface over a 250 m depth range, and 3354 Star dyke thickness measurements were taken over a 520 m depth range. The Swartruggens dyke thicknesses are 0.05–1.95 m (mean 0.64 m), whereas the Star kimberlites range from

Beschreibung: The present-day Zagros mountain belt of SW Iran corresponds to the former Arabian passive continental margin of the southern Neo-Tethyan basin, which existed since a Permian–Triassic rifting episode and underwent later collisional deformation in mid- to late Cenozoic time. In West Zagros, the Kermanshah Radiolarian Trough, separated from the Neo-Tethyan basin by the narrow continental platform of the Bisotun Limestone, resulted from the Triassic–Jurassic rifting of the passive margin. Brittle tectonic analyses of syndepositional normal fault slip data have been undertaken to study the extensional history of the passive margin in terms of palaeostress reconstruction. Dominant east–west trends of the inherited rift-related normal faults in West Zagros indicate an approximately north–south trend of extension that prevailed during the entire Mesozoic syn- to post-rift evolution of the radiolarian trough. This extension characterizes a stretched continental margin similar to the present-day passive margin of the British Isles. Considering the structural pattern of the inherited basement faults, as revealed by the present-day earthquake focal mechanisms, an oblique crustal stretching model is proposed for the rifting process.

Beschreibung: Numerous structures and textures, which can be related to magma flow, were observed in felsic dykes intruding late Mesozoic granitoid plutons in the Jiaodong peninsula, in eastern Shandong province, eastern China. These flow structures may be classified into two categories, interior and peripheral. The former group includes magmatic bands, various types of folds (e.g. injection, sheath, similar and disharmonic folds), rotation of phenocrysts, magmatic foliation or lineation, and crenulation, whereas the latter includes hot tool marks and quarrying structures. Magmatic banding resulted from shearing of mingled magma during magma flow in the dykes. The magma seemed to flow rapidly, probably triggering turbulence in some thick dykes. Interaction at the contact between the hot, moving magma and the cold, stationary wallrock sometimes produced the peripheral structures. A few measurements of hot tool marks and of magmatic lineation reveal a roughly horizontal flow of magma within these dykes. For the dominant NE–SW-striking dyke set in the Laoshan granitoid pluton, the felsic magma probably ascended on or to the SW of the pluton to feed the dyke swarm, and then flowed laterally to drive the horizontal propagation of dykes.

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 23 June 2011 Gregory C., Wiles , Daniel E., Lawson , Eva, Lyon , Nicholas, Wiesenberg , R.D., D'Arrigo Two interstadial tree ring-width chronologies from Geikie Inlet, Glacier Bay Southeast, Alaska were built from 40 logs. One of these chronologies has been calendar dated to AD 224–999 (775yr) crossdating with a living ring-width chronology from Prince William Sound, Alaska. Trees in this chronology were likely killed through inundation by sediments and meltwater from the advancing Geikie Glacier and its tributaries ca. AD 850. The earlier tree-ring chronology spans 545yr and is a floating ring-width series tied to radiocarbon ages of about 3000calyr BP. This tree-ring work indicates two intervals of glacial expansion by the Geikie Glacier system toward the...

Beschreibung: An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstätte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental' hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite' intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin.Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463.

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 25 June 2011 Natalie M., Monacci , Ursula, Meier-Grünhagen , Bruce P., Finney , Hermann, Behling , Matthew J., Wooller This study examines a sediment core (SR-63) from a mangrove ecosystem along the Sibun River in Belize, which is subject to both changes in sea-level and in the characteristics of the river's drainage basin. Radiocarbon dates from the core show a decreased sedimentation rate from ~6ka to 1calka BP and a marked change in lithology from primarily mangrove peat to fluvial-derived material at ~2.5calka BP. Changes in the sedimentation rates observed in mangrove ecosystems offshore have previously been attributed to changes in relative sea-level and the rate of sea-level rise. Pollen analyses show a decreased abundance of Rhizophora (red mangrove)...

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 8 June 2011 Jan-Hendrik, May , Jana, Zech , Roland, Zech , Frank, Preusser , Jaime, Argollo , ... Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating (14C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at...

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 12 June 2011 Roderick J., Bale , Iain, Robertson , Matthew W., Salzer , Neil J., Loader , Steven W., Leavitt , ... We present the first near millennium-length, annually resolved stable isotope record from bristlecone pines (Pinus longaeva, D.K Bailey). The carbon isotope ratios from the cellulose of seven trees from the White Mountains of California, corrected for anthropogenic changes in atmospheric chemistry, are used to reconstruct growing season (June through August) precipitation back to AD 1085. Extremely negative isotope results are strongly correlated with proposed severest El Niño events over the last 500yr, and similar values in the first half of the millennium are used to reconstruct a further 13 strong El Niño events, concentrated in the 12th Century and the...

Beschreibung: : In central West Greenland, Palaeogene volcanic sequences deposited during post-rift subsidence are exposed in mountains reaching 2 km above sea level (a.s.l.), with Palaeocene marine deposits within this section at elevations up to 1.2 km a.s.l. This clearly shows that present-day elevated topography of the West Greenland margin is not a remnant of the rifting process but developed later. Integrating such geological constraints with landscape analysis and thermochronological data shows that mountain summits in central West Greenland represent an Oligocene–Miocene peneplain, which is the counterpart of a correlative unconformity offshore separating Eocene from Middle Miocene sedimentary units. Onshore the peneplain has been exhumed, uplifted to its present altitude and progressively dissected since the Late Miocene. Redfield ( Journal of the Geological Society, London , 167 , 261–271, 2010) questioned numerous aspects of this interpretation, suggesting that ‘the AFT model-based hypothesis that [the elevated topography of West Greenland] was constructed in purely Neogene time remains an unproven speculation'. But as we illustrate here, evidence for Neogene uplift is provided by landscape analysis and geological evidence, as well as thermochronology, and integration of these independent lines of investigation provides a consistent synthesis that we regard as highly reliable. The resulting history of episodic burial and exhumation cannot be simply dismissed, and poses a major challenge to accepted tectonic and geomorphological models for the development of rifted continental margins: how do mountains form along passive continental margins millions of years after rifting and breakup?

Beschreibung: : The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a c . 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a c . 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at c . 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus. Supplementary material: Geochemical data and petrography are available at http://www.geolsoc.org.uk/SUP18467 .

Beschreibung: : The Nordfjord region of western Norway hosts an archetypal subducted crustal section, underpinned by ultrahigh-pressure (UHP) eclogite, overlain by Devonian sediments, and cored by a crustal-scale extensional shear zone. Structural mapping reveals two distinct displacement zones that played different roles during the formation and exhumation of this section: (1) the Sandane Shear Zone is a NW-dipping, amphibolite-facies, high-strain zone near the base of the eclogite-bearing crust that separates allochthonous units from underlying crystalline basement; it may have originated during early thrusting, but was overprinted by top-to-the-west extensional fabrics at lower crustal depths; (2) structurally above this, the Nordfjord–Sogn Detachment Zone is a top-to-the-west, amphibolite- to greenschist-facies detachment shear zone within allochthonous units that defines the upper boundary of the eclogitized crust and was responsible for exhumation through at least mid-crustal depths. Muscovite 40 Ar/ 39 Ar ages suggest that amphibolite-facies deformation below the Nordfjord–Sogn Detachment was mostly finished by c . 397 Ma, whereas muscovite ages from the deeper parts of the UHP domain indicate that it cooled after 390 Ma. During exhumation through the middle crust, west-directed stretching was accompanied by north–south folding. Late sinistral transpressional faulting in the middle to upper crust truncated the earlier folds and shear zones. Supplementary material: Complete 40 Ar/ 39 Ar data and a summary geological map of the Nordfjord region are available at http://www.geolsoc.org.uk/SUP18460 .

Beschreibung: : In this paper we present geological evidence of a mid-Cretaceous inversion event in the Polientes basin (northern Iberian plate) based on geological data. Analysis of seismic profiles across the basin indicates that this tectonic event resulted in the uplift of the basin depocentre and the formation of an upright gentle anticline before Cenomanian times. The presence of a pre-Alpine, syntectonic remagnetization in the Jurassic and Lower Cretaceous rocks of the Polientes basin allows us to define the geometry of the basin at the time between this early inversion event and the main Alpine compressional period. The early inversion in the Polientes basin is consistent with a transpressional tectonic setting, contemporaneous with the left-lateral strike-slip movement of Iberia with respect to Europe. This study shows the successful use of two approaches to unravel the geodynamic scenario of the northern Iberian plate during the Cretaceous, which was later obliterated during the Tertiary Pyrenean orogeny.

Beschreibung: : An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstätte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental' hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite' intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin. Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463 .

Beschreibung: : The Steptoean Positive Carbon Isotope Excursion (SPICE) of earliest late Cambrian (Furongian) age is identified in England. The excursion is found within a c . 145 m thick siliciclastic succession within the middle and higher part of the Outwoods Shale Formation of Warwickshire, and reaches a maximum 13 C org amplitude of 4.1 at values of –25.6. Biostratigraphical data show that the excursion occupies the greater part of the Olenus Biozone, an equivalent of the Glyptagnostus reticulatus Biozone that marks the base of the Furongian and coeval base of the Steptoean in North America. The amplitude of the excursion approaches that recorded in limestone-dominated Laurentian successions, and is greater than that recently documented for organic-rich mudstones of palaeocontinental Baltica in southern Sweden. A minor positive excursion above the SPICE may equate with a similar excursion recognized in Siberia. The SPICE in the Outwoods Shale Formation seems closely linked to the widely recognized early Furongian eustatic sea-level rise. There is no evidence in the English succession for slightly later regression, elsewhere considered coincident with the peak of the excursion and pivotal to some previous models explaining the SPICE. Supplementary material: Analytical results, including total organic carbon (TOC) values for each sample, are available at www.geolsoc.org.uk/SUP18455 .

Beschreibung: : The Çaldag ophiolite, in the Bornova Flysch Zone, is a fragment of Neo-Tethys in the Aegean province, western Turkey. The Bornova Flysch Zone is probably of Cretaceous age, and is locally covered by Early Eocene sediments of the Baslamis Formation that show the first evidence of exposure of ultramafic rocks. Field mapping confirms eight tectonic events correlated with the published regional history. The Çaldag ophiolite would have been exposed to weathering only from the Mid-Palaeocene to the Late Miocene and from the Mid-Pliocene until the present. This weathering has resulted in the formation of an average c . 69 m thick oxide-dominated Ni-laterite. Biological, palaeoecological and isotopic records indicate favourable conditions for weathering, comparable with those of regions in which laterites form today. These data suggest that tropical to subtropical climatic conditions dominated through most of the Cenozoic; the Palaeocene–Eocene was significantly warmer than the Oligo-Miocene. Combining the exhumation history with the available climate data better constrains the periods suitable for laterite formation with implications for laterite formation regionally. The data indicate a possible total period of 50 Ma when laterite formation was possible, yet the profile measured at Çaldag is indicative of either a shorter period of actual weathering or partial erosion of the formed profile.

Beschreibung: : There is a basic assumption that the upper crustal point of magma emplacement overlies the point where magma was generated. This contribution discusses the concept of lateral magma movement in the upper crust based on the Mourne Granite Centres, Northern Ireland. We report anisotropy of magnetic susceptibility fabric data from the Western Mourne Centre that indicate SSW to NNE inflow in this centre, parallel to the Eastern Centre. This suggests that these two centres share a common feeder zone outside the Mourne area c . 20 km to the south, coincident with a c . 50 mGal gravity anomaly that may be caused by an unexposed mafic pluton. The links between mafic and felsic magmas in this region, and the coincidence of the projected Mourne granite feeder zone and the possible buried mafic pluton lead to a model in which the Mourne granites were emplaced in a NNE direction as two gently dipping sheets from this unexposed mafic body. From this we develop a model that incorporates existing geophysics and known tectonic framework and involves an interconnected upper crustal network of Early Palaeogene igneous intrusion pathways fed from a common tectonically controlled, and probably long-lived, deeply penetrating feeder zone. Supplementary material: Anisotropy of magnetic susceptibility data, thermomagnetic analyses and a thin section showing magnetite in biotite cleavage are available at http://www.geolsoc.org.uk/SUP18458 .

Beschreibung: : Combined U–Pb and Lu–Hf isotope analyses of zircons from 16 tonalite–trondjemite–granodiorite (TTG) gneiss and granite samples from Swaziland reveal that the oldest rocks of the Ancient Gneiss Complex in southern Africa formed by reworking of Early Archaean or perhaps Late Hadean crust at 3.66 Ga, and that new crust was extracted from a depleted mantle source during Palaeoarchaean events between 3.54 and 3.32 Ga. This interpretation is supported by Hf t of –1.6 ± 2.0 obtained from 3.66 Ga TTG gneisses, corresponding to hafnium model ages between 3.77 ± 0.18 Ga, for a presumed Hadean–Early Archaean chondritic mantle, and 4.08 ± 0.18 Ga, for a presumed Hadean depleted mantle reservoir, with the first model age being the most likely in the light of recent data from worldwide sources. Furthermore, it is reflected by superchondritic Hf t up to +2.2 ± 2.0 for TTGs formed at 3.54, 3.45 and 3.32 Ga. The new datasets additionally show that the Palaeoarchaean crust formed between 3.54 and 3.32 Ga was intensely reworked afterwards, without significant addition of depleted mantle derived material, during orogenic and intracratonic melting processes at 3.23, 3.1 and 2.7 Ga. This is well reflected by an array of decreasing Hf t from +2.2 to –7.2 between 3.3 and 2.7 Ga, which can be forced by 176 Lu/ 177 Hf of 0.0113, which is similar to that of present-day average continental crust, and might result from lower crust zircon fractionation during Archaean crust reworking. Supplementary material: Results of in situ U–Pb and Lu–Hf isotope zircon analyses and concordia diagrams are available at www.geolsoc.org.uk/SUP18465 .

Beschreibung: : Numerous structures and textures, which can be related to magma flow, were observed in felsic dykes intruding late Mesozoic granitoid plutons in the Jiaodong peninsula, in eastern Shandong province, eastern China. These flow structures may be classified into two categories, interior and peripheral. The former group includes magmatic bands, various types of folds (e.g. injection, sheath, similar and disharmonic folds), rotation of phenocrysts, magmatic foliation or lineation, and crenulation, whereas the latter includes hot tool marks and quarrying structures. Magmatic banding resulted from shearing of mingled magma during magma flow in the dykes. The magma seemed to flow rapidly, probably triggering turbulence in some thick dykes. Interaction at the contact between the hot, moving magma and the cold, stationary wallrock sometimes produced the peripheral structures. A few measurements of hot tool marks and of magmatic lineation reveal a roughly horizontal flow of magma within these dykes. For the dominant NE–SW-striking dyke set in the Laoshan granitoid pluton, the felsic magma probably ascended on or to the SW of the pluton to feed the dyke swarm, and then flowed laterally to drive the horizontal propagation of dykes.

Beschreibung: : U–Pb zircon ages obtained by ion microprobe are presented for late Archaean granitoids from the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt. Similar ages of crust formation in the felsic gneisses of the Zimbabwe Craton and the felsic granulites of the North Marginal Zone support the view, previously argued on geological grounds, that they represent the middle and lower crustal layers respectively of the Zimbabwe Craton. Zircons from the southern margin of the Zimbabwe Craton and the northern part of the North Marginal Zone contain old cores, confirming the presence of an old ( c . 3.5 Ga) nucleus to the Zimbabwe Craton and indicating that the areal extent of this old nucleus is greater than has been hitherto supposed. Thus late Archaean crustal growth involved both the reworking of and the addition of new magmas to this old crustal nucleus. At 2.7 Ga crustal growth was contemporaneous with plume volcanism in the greenstone belts. In contrast, crustal growth at 2.74, 2.67, 2.64 and ?2.62 Ga was focused at the margins of the ‘old craton' and may be related to Andean style continental margin magmatism. Lower crustal melting at 2.61–2.59 Ga led to the emplacement of granitoids in the upper crust. Supplementary material: A summary of previously published U–Pb zircon geochronology for the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt, field relationships and sample localities for the samples used in this study, and U–Th–Pb secondary ionization mass spectrometry data are available at www.geolsoc.org.uk/SUP18466 .

Beschreibung: : Structural mapping, nearest neighbour and two-point azimuth statistical analysis of mud volcano vent distributions from nine examples in Azerbaijan and the Lusi mud volcano in east Java are described. Distributions are non-random, forming alignments subparallel to faults within anticlines, ring faults, conjugate faults and detachment faults; this finding confirms a spatial relationship and supports a model for subsurface flow along these features as well as showing fractionation at depth. As fracture and fault orientations are related to structures such as anticlines and the in situ stress state they are therefore predictable. We use vent distributions in Azerbaijan, where the structural geology is well constrained, to propose what controls the distribution of 169 vents at the Lusi mud volcano. This mud volcano system shows evidence for initial eruptions along a NE–SW trend, parallel to the Watukosek fault, changing to eruptions that follow east–west trends, subparallel to regional fold axes. Our analysis indicates that regions east and west of the Lusi mud volcano are more likely to be affected by new vents than those to the north and south, owing to probable onset of elongate caldera collapse within a 10 km diameter of the central vent.

Beschreibung: : The present-day Zagros mountain belt of SW Iran corresponds to the former Arabian passive continental margin of the southern Neo-Tethyan basin, which existed since a Permian–Triassic rifting episode and underwent later collisional deformation in mid- to late Cenozoic time. In West Zagros, the Kermanshah Radiolarian Trough, separated from the Neo-Tethyan basin by the narrow continental platform of the Bisotun Limestone, resulted from the Triassic–Jurassic rifting of the passive margin. Brittle tectonic analyses of syndepositional normal fault slip data have been undertaken to study the extensional history of the passive margin in terms of palaeostress reconstruction. Dominant east–west trends of the inherited rift-related normal faults in West Zagros indicate an approximately north–south trend of extension that prevailed during the entire Mesozoic syn- to post-rift evolution of the radiolarian trough. This extension characterizes a stretched continental margin similar to the present-day passive margin of the British Isles. Considering the structural pattern of the inherited basement faults, as revealed by the present-day earthquake focal mechanisms, an oblique crustal stretching model is proposed for the rifting process.

Beschreibung: : Although subduction–accretion is proposed as a major regime in making new continental crust, how the lithospheric mantle forms remains unclear. Formed after the closure of the Palaeo-Asian Ocean, the Ashele basalt shows normal mid-ocean ridge basalt (N-MORB)-like characteristics with light REE-depleted patterns and extremely low contents of high field strength elements. The low Zr/Y and Nb/Y ratios of the basalt are significantly different from those of asthenosphere-derived melts, and the excess Eu and Sr suggest that the basalt was probably derived from accreted oceanic lithospheric mantle. The presence of the N-MORB-like terrestrial basalt implies that subduction–accretion is an effective mechanism in building the refractory lithospheric mantle of Phanerozoic continents. Supplementary material: A photograph of the outcrop, and age and geochemical data are available at http://www.geolsoc.org.uk/SUP18464 .

Beschreibung: : In the British Isles the majority of volcanic rocks containing upper mantle and lower crustal xenoliths occur in Scotland. Most of the occurrences are of Carboniferous–Permian age. This paper presents new data on the mineral chemistry of spinel lherzolite xenoliths from the five principal Scottish tectonic terranes. Compositional variations among the minerals emphasize the broad lateral heterogeneity of the subcontinental lithospheric mantle across the region. The remarkable range of Al 2 O 3 v. CaO exhibited by the clinopyroxenes compared with data from other ‘xenolith provinces' emphasizes the extremely complex tectonomagmatic history of the Scottish lithosphere. The generalized age increase from southern and central Scotland to the Northern Highland and Hebridean terranes of the north and NW, with concomitant complexity of geological history, is reflected also by trace element and isotopic studies. Reaction relationships in lherzolites from the Hebridean Terrane, owing to pervasive metasomatism, involve secondary growth of sodic feldspar. This, and light REE enrichment of clinopyroxenes, points to involvement of a natro-carbonatitic melt. Most pyroxenitic xenoliths are inferred to form a basal crustal layer with a generally sharp discontinuity above the underlying (dominantly lherzolitic) mantle. A second discontinuity is inferred to separate these ultramafic cumulates from overlying, broadly cognate metagabbroic cumulates.

Beschreibung: : Dyke thickness datasets offer new insights into the detailed 3D geometry of dyke swarms and an exceptional opportunity to evaluate theoretical emplacement models. The Swartruggens kimberlite dyke swarm extends over 7 km along strike and intrudes a dolerite, quartzite, shale and andesitic lava succession. The Star kimberlite dykes cut shales and sandstones, intersect a large dolerite sill and extend 15 km along strike. Both dyke swarms comprise anastomosing en echelon segments, each several hundred metres long. In total 1532 Swartruggens dyke thickness measurements were taken, to 750 m below the surface over a 250 m depth range, and 3354 Star dyke thickness measurements were taken over a 520 m depth range. The Swartruggens dyke thicknesses are 0.05–1.95 m (mean 0.64 m), whereas the Star kimberlites range from 〈0.01 to 1.6 m thick (mean 0.40 m). Two-dimensional models of elastic cracks in a homogeneous, isotropic material subject to constant magmatic over-pressure poorly describe the dyke thickness variation, which is complex and varies along both breadth and length. The Swartruggens dyke segments thicken toward their terminations along strike, which represent regions where stresses were focused. Towards the surface, rock deformation is increasingly difficult to recover as inelastic processes such as host-rock brecciation, stoping, and magma solidification become important.

Beschreibung: : The Andaman ophiolite occurs as thrust slices in the outer arc of the Andaman–Java subduction zone. This ophiolite preserves the mantle sequence, layered ultramafic–mafic rocks, intrusive and extrusive rocks. The mantle sequence is represented by serpentinized lherzolite and harzburgite, hosting dunite and chromitite pods. The low Cr-number (0.2–0.4), Cr-number–TiO 2 relation of the chromites, oxygen fugacity ( f O 2 ) values ( log f O 2 (FMQ) = –1.90) and trace elements of mantle peridotites indicate a mid-ocean ridge basalt–suprasubduction-zone (MORB–SSZ) setting. The MORB mantle underwent a low degree of melting ( c . 10–15%) and interacted with the subduction-zone melts. Melt–rock interaction of the peridotites in a suprasubduction zone is demonstrated by the replacement of pyroxene grains by olivine grains (Fo 90 ), composition of chromites and oxygen fugacity ( log f O 2 (FMQ) = –1.90 to +2.16, where FMQ is the fayalite–magnetite–quartz buffer). The chromite composition of chromitite pods (Cr-number 0.72–0.75), f O 2 levels and trace elements for layered peridotites, and occurrence of the extrusive rocks as low-Ca boninite and island arc tholeiitic (IAT) basalt indicate interplay of both boninite and IAT melts for the Andaman ophiolite. The MORB mantle of the subducting Indian plate accreted into the mantle wedge and then melting of the accreted mantle produced boninite melt at the first stage and tholeiitic melts at the second stage. Supplementary material: Sample co-ordinates from the Andaman ophiolite, mineral analysis data for all the samples, modal compositions of the units of the Andaman ophiolite and details of the laboratory analyses including details of the standard are available at http://www.geolsoc.org.uk/SUP18459 .

Beschreibung: : The Late Neogene and Quaternary sedimentary record within the Maltese islands is very fragmentary and has generally been ignored by sedimentologists. Local stratigraphies for parts of the Quaternary have been erected from vertebrate remains contained in Quaternary cave and fissure deposits of the islands. However, no coherent correlation scheme has been proposed in which to encompass them. The situation is exacerbated by the absence of datable fossils within the majority of Quaternary deposits. Considerable progress in resolving these problems is, however, possible if recourse is made to the post-Messinian (Late Miocene) erosion features evidenced in the topography of the islands. In particular, a hitherto unrecognized marine erosion surface, the San Leonardo Marine Abrasion Surface, is described and dated by reference to the marine deposits (San Leonardo Beds) lying directly above it and similarities to contemporaneous SE Sicily marine deposits. This provides an end-Calabrian Stage (Emilian Sub-Stage) base line upon which to hang fragmentary information on later events that have shaped the topography of the Maltese islands. From this it can be confirmed that a tectonic deformation event spanning latest Messinian to mid- Pliocene times uplifted the islands and reactivated previously incipient graben systems. This deformation episode is shown to have ceased within the islands well before the early Calabrian (before c . 1.6 Ma). Subsequent minor regional uplift and eustacy together with subaerial weathering processes have been the principal agents in shaping the islands. Collectively, these processes have prevented terrestrial animal migrations into the Maltese islands from North Africa since Messinian times. However, the infrequent re-establishment of a marine lowstand isthmus virtually linking Malta with SE Sicily has permitted opportunistic animal migrations into the islands and the presence of these greatly aids in dating the sedimentological events.

Beschreibung: : The Early Palaeozoic stratigraphy and tectonic history of the Eastern Sierras Pampeanas of central Argentina are complicated by metamorphism and deformation resulting from the Pampean (545–510 Ma) and Famatinian (490–440 Ma) orogenies. We report U–Pb sensitive high-resolution ion microprobe dating of detrital zircons in two metasedimentary successions exposed at Quebrada de La Cébila ( c . 28°45'S, 66°25'W): the Ambato and the La Cébila metamorphic complexes. The Ambato zircons record age peaks corresponding to Pampean (530 ± 10 Ma), Brasiliano ( c . 570 and c . 640 Ma), Grenville ( c . 950 to c . 1025 Ma) and minor Neoarchaean ages. Similar peaks are also apparent in the La Cébila sample but it additionally contains Palaeoproterozoic zircons ( c . 2.1 Ga) corresponding to the age of the Rio de la Plata craton, from which they are considered to have been sourced. Our interpretation is that the protolith of the Ambato complex was deposited prior to juxtaposition with the craton and is older than the Early Ordovician La Cébila metamorphic complex. We infer that the craton reached its current relative position in the Mid- to Late Cambrian, after the main Pampean tectonothermal event (530–520 Ma) and before deposition of the La Cébila protolith and the Achavil Formation (Sierra de Famatina), which contain comparable detrital zircon populations.

Beschreibung: : Major fluvial incision (600–1000 m) affecting the Coastal Cordillera and Central Depression of northern Chile is analysed to evaluate supposed coeval uplift of the Altiplano and/or climatic changes in the Atacama Desert. The timing of the beginning of incision is constrained by the age of deposition of the Central Depression top. In the north (18–19°S), this top corresponds to fluvial gravels accumulated between 11.9 ± 0.6 Ma and 8.3 ± 0.5 Ma, which are genetically related to semiarid climate and to an eastward poorly dissected parallel drainage network that developed between 15.0 ± 0.6 and 11.2 ± 0.6 Ma; thus, gravel deposition ended at 11.9–11.2 Ma. To the south (19–20°S), the Central Depression top corresponds to c . 6 Ma alluvial deposits. Stratigraphically determined canyon ages and knickzone locations indicate that southward dissection began later and/or developed under a regime of lower erosion capacity owing to drier climate. Vertical incision rate evolution is compatible with eastward knickzone migration. Dissection required a considerable altitude difference between ancient and present-day river base levels, which was achieved predominantly by basin infill on an already partially elevated bedrock. Therefore subsequent incision would have been triggered by local semiarid climatic periods rather than by contemporaneous surface uplift. Exoreic canyons occur when climatic conditions in the catchments are arid–semiarid whereas endoreism is developed when these conditions in catchments are hyperarid.

Beschreibung: In central West Greenland, Palaeogene volcanic sequences deposited during post-rift subsidence are exposed in mountains reaching 2 km above sea level (a.s.l.), with Palaeocene marine deposits within this section at elevations up to 1.2 km a.s.l. This clearly shows that present-day elevated topography of the West Greenland margin is not a remnant of the rifting process but developed later. Integrating such geological constraints with landscape analysis and thermochronological data shows that mountain summits in central West Greenland represent an Oligocene–Miocene peneplain, which is the counterpart of a correlative unconformity offshore separating Eocene from Middle Miocene sedimentary units. Onshore the peneplain has been exhumed, uplifted to its present altitude and progressively dissected since the Late Miocene. Redfield (Journal of the Geological Society, London, 167, 261–271, 2010) questioned numerous aspects of this interpretation, suggesting that ‘the AFT model-based hypothesis that [the elevated topography of West Greenland] was constructed in purely Neogene time remains an unproven speculation'. But as we illustrate here, evidence for Neogene uplift is provided by landscape analysis and geological evidence, as well as thermochronology, and integration of these independent lines of investigation provides a consistent synthesis that we regard as highly reliable. The resulting history of episodic burial and exhumation cannot be simply dismissed, and poses a major challenge to accepted tectonic and geomorphological models for the development of rifted continental margins: how do mountains form along passive continental margins millions of years after rifting and breakup?

Beschreibung: The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a c. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a c. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at c. 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.Supplementary material: Geochemical data and petrography are available at http://www.geolsoc.org.uk/SUP18467.

Beschreibung: U–Pb zircon ages obtained by ion microprobe are presented for late Archaean granitoids from the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt. Similar ages of crust formation in the felsic gneisses of the Zimbabwe Craton and the felsic granulites of the North Marginal Zone support the view, previously argued on geological grounds, that they represent the middle and lower crustal layers respectively of the Zimbabwe Craton. Zircons from the southern margin of the Zimbabwe Craton and the northern part of the North Marginal Zone contain old cores, confirming the presence of an old (c. 3.5 Ga) nucleus to the Zimbabwe Craton and indicating that the areal extent of this old nucleus is greater than has been hitherto supposed. Thus late Archaean crustal growth involved both the reworking of and the addition of new magmas to this old crustal nucleus. At 2.7 Ga crustal growth was contemporaneous with plume volcanism in the greenstone belts. In contrast, crustal growth at 2.74, 2.67, 2.64 and ?2.62 Ga was focused at the margins of the ‘old craton' and may be related to Andean style continental margin magmatism. Lower crustal melting at 2.61–2.59 Ga led to the emplacement of granitoids in the upper crust.Supplementary material: A summary of previously published U–Pb zircon geochronology for the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt, field relationships and sample localities for the samples used in this study, and U–Th–Pb secondary ionization mass spectrometry data are available at www.geolsoc.org.uk/SUP18466.

Beschreibung: Structural mapping, nearest neighbour and two-point azimuth statistical analysis of mud volcano vent distributions from nine examples in Azerbaijan and the Lusi mud volcano in east Java are described. Distributions are non-random, forming alignments subparallel to faults within anticlines, ring faults, conjugate faults and detachment faults; this finding confirms a spatial relationship and supports a model for subsurface flow along these features as well as showing fractionation at depth. As fracture and fault orientations are related to structures such as anticlines and the in situ stress state they are therefore predictable. We use vent distributions in Azerbaijan, where the structural geology is well constrained, to propose what controls the distribution of 169 vents at the Lusi mud volcano. This mud volcano system shows evidence for initial eruptions along a NE–SW trend, parallel to the Watukosek fault, changing to eruptions that follow east–west trends, subparallel to regional fold axes. Our analysis indicates that regions east and west of the Lusi mud volcano are more likely to be affected by new vents than those to the north and south, owing to probable onset of elongate caldera collapse within a 10 km diameter of the central vent.

Beschreibung: In the British Isles the majority of volcanic rocks containing upper mantle and lower crustal xenoliths occur in Scotland. Most of the occurrences are of Carboniferous–Permian age. This paper presents new data on the mineral chemistry of spinel lherzolite xenoliths from the five principal Scottish tectonic terranes. Compositional variations among the minerals emphasize the broad lateral heterogeneity of the subcontinental lithospheric mantle across the region. The remarkable range of Al2O3 v. CaO exhibited by the clinopyroxenes compared with data from other ‘xenolith provinces' emphasizes the extremely complex tectonomagmatic history of the Scottish lithosphere. The generalized age increase from southern and central Scotland to the Northern Highland and Hebridean terranes of the north and NW, with concomitant complexity of geological history, is reflected also by trace element and isotopic studies. Reaction relationships in lherzolites from the Hebridean Terrane, owing to pervasive metasomatism, involve secondary growth of sodic feldspar. This, and light REE enrichment of clinopyroxenes, points to involvement of a natro-carbonatitic melt. Most pyroxenitic xenoliths are inferred to form a basal crustal layer with a generally sharp discontinuity above the underlying (dominantly lherzolitic) mantle. A second discontinuity is inferred to separate these ultramafic cumulates from overlying, broadly cognate metagabbroic cumulates.

Beschreibung: In this paper we present geological evidence of a mid-Cretaceous inversion event in the Polientes basin (northern Iberian plate) based on geological data. Analysis of seismic profiles across the basin indicates that this tectonic event resulted in the uplift of the basin depocentre and the formation of an upright gentle anticline before Cenomanian times. The presence of a pre-Alpine, syntectonic remagnetization in the Jurassic and Lower Cretaceous rocks of the Polientes basin allows us to define the geometry of the basin at the time between this early inversion event and the main Alpine compressional period. The early inversion in the Polientes basin is consistent with a transpressional tectonic setting, contemporaneous with the left-lateral strike-slip movement of Iberia with respect to Europe. This study shows the successful use of two approaches to unravel the geodynamic scenario of the northern Iberian plate during the Cretaceous, which was later obliterated during the Tertiary Pyrenean orogeny.

Beschreibung: The Andaman ophiolite occurs as thrust slices in the outer arc of the Andaman–Java subduction zone. This ophiolite preserves the mantle sequence, layered ultramafic–mafic rocks, intrusive and extrusive rocks. The mantle sequence is represented by serpentinized lherzolite and harzburgite, hosting dunite and chromitite pods. The low Cr-number (0.2–0.4), Cr-number–TiO2 relation of the chromites, oxygen fugacity (fO2) values (?log fO2 (FMQ) = -1.90) and trace elements of mantle peridotites indicate a mid-ocean ridge basalt–suprasubduction-zone (MORB–SSZ) setting. The MORB mantle underwent a low degree of melting (c. 10–15%) and interacted with the subduction-zone melts. Melt–rock interaction of the peridotites in a suprasubduction zone is demonstrated by the replacement of pyroxene grains by olivine grains (Fo90), composition of chromites and oxygen fugacity (?log fO2 (FMQ) = –1.90 to +2.16, where FMQ is the fayalite–magnetite–quartz buffer). The chromite composition of chromitite pods (Cr-number 0.72–0.75), fO2 levels and trace elements for layered peridotites, and occurrence of the extrusive rocks as low-Ca boninite and island arc tholeiitic (IAT) basalt indicate interplay of both boninite and IAT melts for the Andaman ophiolite. The MORB mantle of the subducting Indian plate accreted into the mantle wedge and then melting of the accreted mantle produced boninite melt at the first stage and tholeiitic melts at the second stage.Supplementary material: Sample co-ordinates from the Andaman ophiolite, mineral analysis data for all the samples, modal compositions of the units of the Andaman ophiolite and details of the laboratory analyses including details of the standard are available at http://www.geolsoc.org.uk/SUP18459.

Beschreibung: The Çaldag ophiolite, in the Bornova Flysch Zone, is a fragment of Neo-Tethys in the Aegean province, western Turkey. The Bornova Flysch Zone is probably of Cretaceous age, and is locally covered by Early Eocene sediments of the Baslamis Formation that show the first evidence of exposure of ultramafic rocks. Field mapping confirms eight tectonic events correlated with the published regional history. The Çaldag ophiolite would have been exposed to weathering only from the Mid-Palaeocene to the Late Miocene and from the Mid-Pliocene until the present. This weathering has resulted in the formation of an average c. 69 m thick oxide-dominated Ni-laterite. Biological, palaeoecological and isotopic records indicate favourable conditions for weathering, comparable with those of regions in which laterites form today. These data suggest that tropical to subtropical climatic conditions dominated through most of the Cenozoic; the Palaeocene–Eocene was significantly warmer than the Oligo-Miocene. Combining the exhumation history with the available climate data better constrains the periods suitable for laterite formation with implications for laterite formation regionally. The data indicate a possible total period of 50 Ma when laterite formation was possible, yet the profile measured at Çaldag is indicative of either a shorter period of actual weathering or partial erosion of the formed profile.

Beschreibung: The Early Palaeozoic stratigraphy and tectonic history of the Eastern Sierras Pampeanas of central Argentina are complicated by metamorphism and deformation resulting from the Pampean (545–510 Ma) and Famatinian (490–440 Ma) orogenies. We report U–Pb sensitive high-resolution ion microprobe dating of detrital zircons in two metasedimentary successions exposed at Quebrada de La Cébila (c. 28°45'S, 66°25'W): the Ambato and the La Cébila metamorphic complexes. The Ambato zircons record age peaks corresponding to Pampean (530 ± 10 Ma), Brasiliano (c. 570 and c. 640 Ma), Grenville (c. 950 to c. 1025 Ma) and minor Neoarchaean ages. Similar peaks are also apparent in the La Cébila sample but it additionally contains Palaeoproterozoic zircons (c. 2.1 Ga) corresponding to the age of the Rio de la Plata craton, from which they are considered to have been sourced. Our interpretation is that the protolith of the Ambato complex was deposited prior to juxtaposition with the craton and is older than the Early Ordovician La Cébila metamorphic complex. We infer that the craton reached its current relative position in the Mid- to Late Cambrian, after the main Pampean tectonothermal event (530–520 Ma) and before deposition of the La Cébila protolith and the Achavil Formation (Sierra de Famatina), which contain comparable detrital zircon populations.

Beschreibung: Although subduction–accretion is proposed as a major regime in making new continental crust, how the lithospheric mantle forms remains unclear. Formed after the closure of the Palaeo-Asian Ocean, the Ashele basalt shows normal mid-ocean ridge basalt (N-MORB)-like characteristics with light REE-depleted patterns and extremely low contents of high field strength elements. The low Zr/Y and Nb/Y ratios of the basalt are significantly different from those of asthenosphere-derived melts, and the excess Eu and Sr suggest that the basalt was probably derived from accreted oceanic lithospheric mantle. The presence of the N-MORB-like terrestrial basalt implies that subduction–accretion is an effective mechanism in building the refractory lithospheric mantle of Phanerozoic continents.Supplementary material: A photograph of the outcrop, and age and geochemical data are available at http://www.geolsoc.org.uk/SUP18464.

Beschreibung: Major fluvial incision (600–1000 m) affecting the Coastal Cordillera and Central Depression of northern Chile is analysed to evaluate supposed coeval uplift of the Altiplano and/or climatic changes in the Atacama Desert. The timing of the beginning of incision is constrained by the age of deposition of the Central Depression top. In the north (18–19°S), this top corresponds to fluvial gravels accumulated between 11.9 ± 0.6 Ma and 8.3 ± 0.5 Ma, which are genetically related to semiarid climate and to an eastward poorly dissected parallel drainage network that developed between 15.0 ± 0.6 and 11.2 ± 0.6 Ma; thus, gravel deposition ended at 11.9–11.2 Ma. To the south (19–20°S), the Central Depression top corresponds to c. 6 Ma alluvial deposits. Stratigraphically determined canyon ages and knickzone locations indicate that southward dissection began later and/or developed under a regime of lower erosion capacity owing to drier climate. Vertical incision rate evolution is compatible with eastward knickzone migration. Dissection required a considerable altitude difference between ancient and present-day river base levels, which was achieved predominantly by basin infill on an already partially elevated bedrock. Therefore subsequent incision would have been triggered by local semiarid climatic periods rather than by contemporaneous surface uplift. Exoreic canyons occur when climatic conditions in the catchments are arid–semiarid whereas endoreism is developed when these conditions in catchments are hyperarid.

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 14 June 2011 Denis, Wirrmann , Anne-Marie, Sémah , Jean-Pierre, Debenay , Magali, Chacornac-Rault Multiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400calyr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes...

Beschreibung: The Nordfjord region of western Norway hosts an archetypal subducted crustal section, underpinned by ultrahigh-pressure (UHP) eclogite, overlain by Devonian sediments, and cored by a crustal-scale extensional shear zone. Structural mapping reveals two distinct displacement zones that played different roles during the formation and exhumation of this section: (1) the Sandane Shear Zone is a NW-dipping, amphibolite-facies, high-strain zone near the base of the eclogite-bearing crust that separates allochthonous units from underlying crystalline basement; it may have originated during early thrusting, but was overprinted by top-to-the-west extensional fabrics at lower crustal depths; (2) structurally above this, the Nordfjord–Sogn Detachment Zone is a top-to-the-west, amphibolite- to greenschist-facies detachment shear zone within allochthonous units that defines the upper boundary of the eclogitized crust and was responsible for exhumation through at least mid-crustal depths. Muscovite 40Ar/39Ar ages suggest that amphibolite-facies deformation below the Nordfjord–Sogn Detachment was mostly finished by c. 397 Ma, whereas muscovite ages from the deeper parts of the UHP domain indicate that it cooled after 390 Ma. During exhumation through the middle crust, west-directed stretching was accompanied by north–south folding. Late sinistral transpressional faulting in the middle to upper crust truncated the earlier folds and shear zones.Supplementary material: Complete 40Ar/39Ar data and a summary geological map of the Nordfjord region are available at http://www.geolsoc.org.uk/SUP18460.

Beschreibung: The Steptoean Positive Carbon Isotope Excursion (SPICE) of earliest late Cambrian (Furongian) age is identified in England. The excursion is found within a c. 145 m thick siliciclastic succession within the middle and higher part of the Outwoods Shale Formation of Warwickshire, and reaches a maximum d13Corg amplitude of 4.1‰ at values of -25.6‰. Biostratigraphical data show that the excursion occupies the greater part of the Olenus Biozone, an equivalent of the Glyptagnostus reticulatus Biozone that marks the base of the Furongian and coeval base of the Steptoean in North America. The amplitude of the excursion approaches that recorded in limestone-dominated Laurentian successions, and is greater than that recently documented for organic-rich mudstones of palaeocontinental Baltica in southern Sweden. A minor positive excursion above the SPICE may equate with a similar excursion recognized in Siberia. The SPICE in the Outwoods Shale Formation seems closely linked to the widely recognized early Furongian eustatic sea-level rise. There is no evidence in the English succession for slightly later regression, elsewhere considered coincident with the peak of the excursion and pivotal to some previous models explaining the SPICE.Supplementary material: Analytical results, including total organic carbon (TOC) values for each sample, are available at www.geolsoc.org.uk/SUP18455.

Beschreibung: The Late Neogene and Quaternary sedimentary record within the Maltese islands is very fragmentary and has generally been ignored by sedimentologists. Local stratigraphies for parts of the Quaternary have been erected from vertebrate remains contained in Quaternary cave and fissure deposits of the islands. However, no coherent correlation scheme has been proposed in which to encompass them. The situation is exacerbated by the absence of datable fossils within the majority of Quaternary deposits. Considerable progress in resolving these problems is, however, possible if recourse is made to the post-Messinian (Late Miocene) erosion features evidenced in the topography of the islands. In particular, a hitherto unrecognized marine erosion surface, the San Leonardo Marine Abrasion Surface, is described and dated by reference to the marine deposits (San Leonardo Beds) lying directly above it and similarities to contemporaneous SE Sicily marine deposits. This provides an end-Calabrian Stage (Emilian Sub-Stage) base line upon which to hang fragmentary information on later events that have shaped the topography of the Maltese islands. From this it can be confirmed that a tectonic deformation event spanning latest Messinian to mid- Pliocene times uplifted the islands and reactivated previously incipient graben systems. This deformation episode is shown to have ceased within the islands well before the early Calabrian (before c. 1.6 Ma). Subsequent minor regional uplift and eustacy together with subaerial weathering processes have been the principal agents in shaping the islands. Collectively, these processes have prevented terrestrial animal migrations into the Maltese islands from North Africa since Messinian times. However, the infrequent re-establishment of a marine lowstand isthmus virtually linking Malta with SE Sicily has permitted opportunistic animal migrations into the islands and the presence of these greatly aids in dating the sedimentological events.

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 7 May 2011 Bryan Keith, Sell , Scott Douglas, Samson Geochemical correlation of ash-fall beds with conventional tephrochronologic methods is not feasible when original glass composition is altered. Thus, alternative correlation methods may be required. Initial studies of heavily altered Paleozoic tephra (K-bentonites) have suggested the potential for employing trace-element concentrations in apatite as ash-fall bed discriminators. To further test the utility of apatite trace-element tephrochronology, we analyzed apatite phenocrysts from unaltered volcanic rocks with an electron microprobe: nine samples from rocks erupted during the Quaternary and one sample from a rock erupted during the Paleogene. The resulting apatite trace-element data provide unique bed discriminators despite within-crystal variability. Each of...

Beschreibung: Publication year: 2011 Source: Quaternary Research, In Press, Corrected Proof, Available online 13 May 2011 Arjen P., Stroeven , Derek, Fabel , Jonathan M., Harbor , David, Fink , Marc W., Caffee , ... Deglaciation chronologies for some sectors of former ice sheets are relatively poorly constrained because of the paucity of features or materials traditionally used to constrain the timing of deglaciation. In areas without good deglaciation varve chronologies and/or without widespread occurrence of material that indicates the start of earliest organic radiocarbon accumulations suitable for radiocarbon dating, typically only general patterns and chronologies of deglaciation have been deduced. However, mid-latitude ice sheets that had warm-based conditions close to their margins often produced distinctive deglaciation landform assemblages, including eskers, deltas, meltwater channels and aligned lineation systems. Because these features were formed or significantly...

Beschreibung: Research Articles Ian Hawes, Karl Safi, Brian Sorrell, Jenny Webster-Brown, David Arscott, Antarctic Science , Volume 23 Issue 03 , pp 235-242 Abstract

Beschreibung: Research Articles G.C. Grobler, A.D.S. Bastos, C.T. Chimimba, S.L. Chown, Antarctic Science , Volume 23 Issue 03 , pp 225-234 Abstract