ALBERT

Description: Time-calibrated balanced-cross sections of the eastern Fuegian Thrust–Fold Belt reveal many complex pro- and retro-vergent structures, rooted at the base of Cretaceous and within Paleocene rocks. These structures involve the unconformity-bounded syntectonic sequences of the Austral foreland basin, and accommodate a minimum shortening of c. 41.8 km. The complex kinematics of the thrust–fold belt are recorded by: (1) propagation of the basal décollement into the foreland, and forward-directed thrusting during the Ypresian; (2) out-of-sequence thrusting in the Lutetian; (3) subsidence and sedimentation from the Late Lutetian to the Oligocene; (4) backthrusting during the Oligocene; and (5) a renewed stage of forward-directed thrusting between the latest Oligocene and the Early Miocene, probably related to accretion below the sole fault in the hinterland. This thrust sequence is interpreted as the result of critical Coulomb wedge behaviour during the first stage of thrust–fold belt expansion, with accretion of new material that led to a taper decrease. The subsequent period of internal deformation corresponds to a subcritical stage, during which backthrusting accommodates significant shortening (c. 15%). After growth and taper increase, the last period of forward thrusting at the wedge's front marks the inception of a new critical stage.

Description: The Forcarei Synform is a kilometric fold developed in the hinterland of the NW Iberian Variscan belt. A detailed analysis of the synform, based on quartz fabrics and kinematic markers, shows pervasively deformed rocks that have been continuously deformed during the last two main Variscan deformation phases (D2 and D3).Variscan D2 minor structures related to the synform were formed under general non-coaxial flow and have a sub-horizontal maximum finite stretching toward the SSE. Later a coaxial D3 produced a sub-vertical crenulation cleavage, and type 2 and 3 refolded folds figures at the meso- and micro-scale. Consequently, the strike of the foliations (S2 and S3) become sub-parallel and lineation (L2 and L3) are sub-horizontal. The geometry of the synform and the related structures can be interpreted in the context of D3. However the dominantly sinistral shear sense indicators, observed in both limbs of the synform (in map view), seem to be most probably developed during D2. A model is proposed involving the progressive clockwise rotation of a sub-horizontal shear, with general top-to-the-south sense, during the simultaneous development of shear zone and foliation in agreement with the kinematic indicators.

Description: The Aracuai orogen extends from the eastern edge of the Sao Francisco craton to the Atlantic margin, in southeastern Brazil. Orogenic igneous rocks, formed from c. 630 to c. 480 Ma, cover one third of this huge area, building up the Eastern Brazilian Pegmatite Province and the most important dimension stone province of Brazil. G1 supersuite (630-585 Ma) mainly consists of tonalite to granodiorite, with mafic to dioritic facies and enclaves, representing a continental calc-alkaline magmatic arc. G2 supersuite mostly includes S-type granites formed during the syn-collisional stage (585-560 Ma), from relatively shallow two-mica granites and related gem-rich pegmatites to deep garnet-biotite granites that are the site of yellow dimension stone deposits. The typical G3 rocks (545-525 Ma) are non-foliated garnet-cordierite leucogranites, making up autochthonous patches and veins. At the post-collisional stage (530-480 Ma), G4 and G5 supersuites were generated. The S-type G4 supersuite mostly consists of garnet-bearing two-mica leucogranites that are the source of many pegmatites mined for tourmalines and many other gems, lithium (spodumene) ore and industrial feldspar. G5 supersuite, consisting of high-K-Fe calc-alkaline to alkaline granitic and/or charnockitic to dioritic/noritic intrusions, is the source of aquamarine-topaz-rich pegmatites but mainly of a large dimension stone production.

Description: A new sequence of Variscan deformations is proposed for the Palaeozoic rocks of the Central Pyrenees. The non-metamorphic units include south-directed thrust systems and related folds with a poorly developed cleavage. In the metamorphic units north-verging, recumbent to inclined folds (D1), associated with a subhorizontal to south dipping cleavage, are refolded by south-verging, upright to inclined folds (D2), with a subvertical to north-dipping axial plane cleavage, and offset by south-directed thrusts approximately coeval with D2. The structural evolution of these units suggests a subdivision of the Variscan Central Pyrenees into two different regions consistent with the zones known for a long time in the core of the Ibero-Armorican or Asturian arc (northern part of the Iberian Variscan Massif). The structure of the Pyrenean non-metamorphic units has foreland affinities and is comparable to that of the Cantabrian Zone, whereas the deformation observed in the Pyrenean metamorphic units is characteristic of the hinterland and is consistent with the features of the West Asturian–Leonese Zone or Central–Iberian Zone. Since the Pyrenean non-metamorphic units are located southwards of the metamorphic ones and the Variscan thrusts are south-directed, we tentatively correlate the Variscan Pyrenees with the northern branch of the Ibero-Armorican or Asturian arc.

Description: Deep-seated gravitational slope deformation (DSGSD) is a common and widespread type of large slope instability in the Alps. In the Aosta Valley region in NW Italy, DSGSDs occupy at least 13.5% of the regional territory. In this study, regional distribution analyses have been coupled with local detailed geological and geomorphological surveys of individual phenomena to detect the controlling factors, deformation processes and evolution stages of DSGSD. Data and maps from field and remote-sensing investigations have been supported by drill data and geomechanical and hydrogeochemical analyses from project studies for hydroelectric plants and tunnels. Several phenomena related to DSGSD have been studied thoroughly: gravity-induced stresses, tectonic–metamorphic setting, morphostructural relations, glacial and periglacial morphodynamics, recent tectonic evolution, hydrogeological conditions and karst phenomena have been generically indicated as controlling factors. In the studied area three of the controlling factors were crucial in differentiating the form and evolution of DSGSDs: deep dissolution, surface tectonics, and tectonostructural setting. They are presented as possible end members of a classification scheme for DSGSDs.

Description: Structural geology has recently become a key topic in landslide research. However, the link between regional structures, their cumulative contribution to rockslide development and their significance in a spatial framework is uncertain. We examine the influence of structures on rockslide susceptibility in the Storfjorden area, a 900 km2 fjord complex in western Norway that includes the monitored rockslide sites of Åknes and Heggursaksla. We have newly identified 52 potential rockslide sites from aerial photographs. The structural features critical for the development of large rockslides (fjord-dipping foliation, basal shear plane and breccia, extensional fracture and transfer fault) have a spatial bias in orientation. Rockslides are more likely to develop in specific fjord orientations that have favourably oriented structures. Therefore, the development of rockslides has a marked spatial distribution that we describe qualitatively with an inventory of structural features. Sites with the full plethora of features display the most movement, the largest volumes and are already under the closest scrutiny with regard to monitoring. These sites are also spatially biased, the largest clustering occurring in west Sunnylyvsfjorden. The utilization of structural criteria can show trends in spatial distribution of rockslide potential and on a regional scale can be an important tool in susceptibility analysis.

Description: Our study area is located in northwestern Argentina. It is a semiarid valley in which developed agricultural pre-Columbian settlements were located. The objectives of our research were to establish the geomorphological characteristics of the area, its relative chronological development, and the relationships between geomorphological development and pre-Columbian settlements.Pre-Quaternary lithologies are represented by a metamorphic basement that is commonly exposed on slopes and belongs to the Precambrian and Cambrian periods. Tertiary sediments from several formations are exposed over an extensive surface forming cuesta relief landforms. Quaternary landscape units were classified according to their genesis into structural–denudational landforms (denudational slopes and structural scarps), denudational landforms (covered glacis), fluvio-alluvial landforms (alluvial fans, fluvial fans, and fluvial terraces) and aeolian forms (stabilized dunes).Archaeological sites belonging to the Formative (500 BC–AD 1000) and Regional Development (AD 1000–1500) periods were identified. The main archaeological sites are located on the surfaces of debris-flow deposits and some covered glacis. They are characterized by the presence of residential units together with agricultural structures (terraces and irrigation channels). The earlier settlements (Formative period) are restricted to alluvial fan landforms (debris-flow deposits), where present hydrological supply is lower than in the rest of the study area. Later settlements (Regional Development period) are juxtaposed with earlier settlements in the south of the area, where present hydrological supply is higher owing to larger river catchments and moisture-laden winds from the SE.

Description: Palaeoenvironmental records from the Northern Plains of North America attest to an extended period of Middle Holocene warming and drying, making this a useful region and period for research on long-term human response to marked climate change. However, archaeological perspectives on human–environment interaction during this episode have remained preoccupied with a refugial model that incorporates limited latitude for dynamic human adaptation. In part, this situation reflects the challenging geomorphological and typological obstacles faced by those studying this period. However, this paper argues that our failure to develop new perspectives also reflects a longstanding and continued conservatism that casts Northern Plains lifeways as inflexible and unchanging, rather than dynamic and adaptable.

Description: Tepe Pardis, a significant Neolithic–Chalcolithic site on the Tehran Plain in Iran, is, like many sites in the area, under threat from development. The site contains detailed evidence of (1) the Neolithic–Chalcolithic transition, (2) an Iron Age cemetery and (3) how the inhabitants adapted to an unstable fan environment through resource exploitation (of clay deposits for relatively large-scale ceramic production by c. 5000 BC, and importantly, possible cutting of artificial water channels). Given this significance, models have been produced to better understand settlement distribution and change in the region. However, these models must be tied into a greater understanding of the impact of the geosphere on human development over this period. Forming part of a larger project focusing on the transformation of simple, egalitarian Neolithic communities into more hierarchical Chalcolithic ones, the site has become the focus of a multidisciplinary project to address this issue. Through the combined use of sedimentary and limited pollen analysis, radiocarbon and optically stimulated luminescence dating (the application of the last still rare in Iran), a greater understanding of the impact of alluvial fan development on human settlement through alluviation and the development of river channel sequences is possible. Notably, the findings presented here suggest that artificial irrigation was occurring at the site as early as 6.7±0.4 ka (4300–5100 BC).

Description: Palaeoenvironmental investigations were carried out in the Siedlungskammer (prehistoric settlement area) Burgweinting (Regensburg, Bavaria, Germany) to reveal past settlement conditions and human impact on the environment. Two sequences were obtained from the Islinger Mühlbach Fen, in close proximity to the archaeological excavation site in Burgweinting, which documents an almost continuous settlement history since the Neolithic Period. The analyses of the sequences comprise stratigraphic, geochemical and microscopic charcoal analyses. For chronological information, radiocarbon dating was conducted on a total of 10 samples. Thus, the first long-term fire record was reconstructed for the investigation area, and the results were correlated, based on radiocarbon dating, with the available environmental information and settlement history in the Siedlungskammer Burgweinting. The fire record reveals an almost continuous, but alternating fire history. Furthermore, it shows that fire played an important role in the Siedlungskammer Burgweinting and that most probably as early as the Mesolithic hunterer–gatherers deliberately used fire.

Description: Palaeomagnetic, rock magnetic and geochronological investigations were carried out on the Abor volcanics of Arunachal Pradesh, NE India. A Late Palaeozoic formation age for part of the Abor volcanics cannot be excluded based on K–Ar whole rock dating. Low-temperature thermochronometers – zircon (U–Th)/He and fission track analyses – yield a maximum burial temperature of c. 150–170 °C during Late Miocene. ZFT thermochronology of the Yinkiong and Miri Fms. indicates a post-Paleocene and post-Jurassic deposition age, respectively. This infers that the volcanic rocks intercalating or intruding them are not part of the Late Palaeozoic sequence but represent one or more, latest Cretaceous to Tertiary event(s). Therefore the Abor volcanics are connected to at least two separate events of volcanism. From palaeomagnetic sites, two characteristic magnetic remanence components were separated: a low-coercivity-component demagnetized below 20 mT and a high-coercivity-component demagnetized between 15 and 100 mT. Fold tests support a secondary origin of both components. Thermochronological and rock magnetic analyses indicate a low-grade overprint event between India–Asia collision and Miocene, which probably represents the time of remanence acquisition. The high-coercivity-component shows a trend of clockwise declinations, which is likely related to vertical-axis rotations of the eastern Himalayas due to eastward extrusion of the Tibetan Plateau.

Description: A range of cold desert landforms are found on the Martian surface that have been interpreted to indicate prevailing frozen and hyper-arid conditions for at least the past several million years. These cold desert conditions are punctuated by brief periods of localized surficial liquid water flow. Sediment transport pathways operate under these conditions of extreme cold and aridity and the processes involved generate permafrost landforms that are recognizable from spacecraft at local, regional and global scales. Thermal-contraction-crack polygons are associated with hemisphere-spanning mantle units that contain excess ice in the immediate subsurface. Sublimation is the dominant phase transition rather than melting under present Martian conditions. Evidence is presented for melting of near-surface snow, frost and/or ground ice in protected gully alcove microclimates during the most recent several million years.

Description: The volume focuses on the analysis of glacial clastic sedimentary deposits, both ancient and recent. The papers range from reviews of glacial systems and cold-climate weathering products and processes to conceptual and field studies of specific ice-marginal and cold-climate sediments. Papers are included that deal with tidewater glaciers, mountain settings on Earth, permafrost areas on both Earth and Mars and detailed regional analyses of cold-climate sediments of Late Pleistocene and Holocene age. The identification of sedimentary facies allows an accurate reconstruction of many of the developmental processes that are involved in ice-marginal and periglacial environments. Lithostratigraphic characteristics of clastic deposits also constitute circumstantial evidence for the previous existence of ancient, and certainly pre-Quaternary, cold-climate systems. This is demonstrated by a study on putative Palaeozoic glacial deposits in Saudi Arabia.

Description: Anisotropy of magnetic susceptibility (AMS) combined with structural analysis are used in this work with the aim to characterize the tectonic evolution of the Triassic flysch within the eastern Tethyan Himalaya Thrust Belt in SE Tibet. The attitude of the magnetic foliation and lineation are concordant with the planar and linear structures of tectonic origin defined by the preferred orientation of the iron-bearing silicates. Two different tectonic domains can be defined: (a) the southern domain is controlled by the Eohimalayan tectonic foliation (S1) recorded in the magnetic foliation which trends east–west and dips to the north; (b) the northern domain is dominated by the Neohimalayan magnetic foliation with WNW–ESE strike and dips to the south opposite to the vergence of the main structures. A slightly prolate magnetic ellipsoid has been found in between the two domains recording the intersection of S1 and the subtle development of the S2 tectonic foliation. Hinterland propagation of the deformation lead to the Great Counter backthrust generation, pointed out by the SSW steeply plunging magnetic lineation. Furthermore different orientations of magnetic foliation may indicate an Early Miocene c. 20° clockwise vertical-axis rotation.

Description: Fold-and-thrust (FAT) belts occur worldwide and have long been the focus of research of structural geologists who have devised a variety of techniques to image, characterize and model their main structural features. This introductory chapter reviews the principal geological features of FAT belts formed in different settings, emphasizing aspects related to their kinematic evolution and structural styles. Despite great advances, challenges remain, particularly in the understanding of the spatial and temporal evolution (4D) of FAT belts and their controlling factors. These research efforts are being assisted by the growing availability to researchers of relatively new tools to collect field data, high quality 3D seismic data, and computer and laboratory modelling tools. This volume includes technical papers presented in the conference ‘International Meeting of Young Researchers in Structural Geology and Tectonics (YORSGET-08)’ held in Oviedo (Spain), together with other papers on the same theme. These papers deal with FAT belts in different parts of the world and cover a broad range of different aspects, from detailed structural analysis of single structures to regional issues, and from studies based on classical field structural geology to modelling.

Description: In the South Portuguese Zone (Iberian Massif), thin-skinned tectonics linked to the collision with the Ossa-Morena Zone produced the inversion of previous extensional basins in Carboniferous times. Its central domain, namely the Iberian Pyrite Belt, underwent two deformation phases at mostly low-grade metamorphic conditions linked to a progressive deformation migrating upwards from a basal detachment and from north to south. The Puebla de Guzmán Antiform is one of the most outstanding cartographic structures in the Iberian Pyrite Belt, representing a imbricate fan thrust system developed during the second regional deformation phase. In the Puebla de Guzmán Antiform, the first deformation phase gave rise to a penetrative slaty cleavage (S1), which is also recognized in the whole Iberian Pyrite Belt and constitutes the main foliation all over the region. Its genesis is possibly linked to the coetaneous development of thrusts at deeper crustal levels and SSW-vergent folds at all levels above these thrusts. First phase structures were deformed by large-scale imbricated thrust systems with lateral (NNE–SSW) and frontal (WNW–ESE) ramps, which constitute the most relevant regional cartographic structures. This second deformation phase generated thrusts, two set of folds with WNW–ESE and NNE–SSW-oriented axes, as well as two related axial plane crenulation cleavages. These relatively brittle to ductile-brittle second phase structures have been identified in many areas of the Iberian Pyrite Belt, and especially in the southern limb of the Puebla de Guzmán Antiform. The second phase thrusts reported from the Puebla de Guzmán Antiform have not been folded according to both the geological map of the area and the analysis of maximum shortening and stretching axes.

Description: This volume brings together a collection of papers that summarize current ideas and recent progress in the study of granite-related mineralization systems. They provide a combination of field, experimental and theoretical studies. Papers are grouped according to the main granite-related ore systems: granite-pegmatite, skarn and greisen-veins, porphyry, orogenic gold, intrusion-related, epithermal and porphyry-related gold and base metal, iron oxide-copper-gold (IOCG), and special case studies. The studies provide a broad spread in terms of both space and time, highlighting granite-related ore deposits from Europe (Russia, Sweden, Croatia and Turkey), the Middle East (Iran), Asia (Japan and China) and South America (Brazil and Argentina) and spanning rocks from Palaeoproterozoic to Miocene in age.

Description: Since c. 3.1 Ga, pegmatite mineral deposits in orogenic areas have been formed throughout geological time in pulses, alternating with total absence of generating activity. The higher activity peaks of 2.65-2.60, 1.90-1.85, 1.00-0.95, and 0.30-0.25 Ga suggest a quasi-regular periodicity of 0.8{+/-}0.1 Ga. This series is dominated by pegmatites of Laurasian blocks. The lower peaks at 2.85-2.80, 2.10-2.05, 1.20-1.15, and the higher one at 0.55-0.50 make up another series represented by pegmatites in Gondwanan blocks only. Each pegmatite class is characterized by a life cycle of its own, from inception to peak through to decline and eventual extinction. The longest cycle is recorded for the rare-metal class deposits, which first appeared in the Mesoarchaean and persisted through all the later eras, deteriorating gradually after the Early Precambrian. Muscovite pegmatites first appeared in the Palaeoproterozoic and reached the end of their life cycle at the Palaeozoic-Mesozoic boundary. The miarolitic class of pegmatite deposits in orogenic setting first came into being in the terminal Mesoproterozoic and dominated the pegmatite metallogeny of many Phanerozoic belts. The evolution of the pegmatite classes was controlled by the general cooling of the Earth and by associated changes in the tectonics of the lithosphere. Supplementary materialGeochronological data used is available at http://www.geolsoc.org.uk/SUP18435.

Description: The Algtrask intrusive hosted Au deposit, Skellefte district, northern Sweden, is situated in the oldest, most heterogeneous part of the c. 1.89-1.86 Ga Jorn granitoid complex, which intruded a complex volcano-sedimentary succession in an island arc or continental margin arc environment. The Tallberg porphyry Cu deposit, situated only 3 km west of Algtrask, is associated with quartz feldspar porphyritic dykes. These dykes are suggested to be genetically related to similar porphyry dykes in Algtrask and the tonalitic host rock in Tallberg. The granodiorite hosting the Algtrask Au-deposit does not appear to be genetically related to the tonalite or the porphyry dykes.

Description: Usually geomorphology, structural geology and engineering geology provide descriptions of slope instability in quite distinctive ways. This new research is based on combined approaches to providing an integrated view of the operative slope processes. ‘Slope Tectonics’ is the term adopted here to refer to those deformations that are induced or fully controlled by the slope morphology, and that generate features which can be compared to those created by tectonic activity. Such deformation can be induced by the stress field in a slope which is mainly controlled by gravity, topography and the geological setting created by the geodynamic context.The content of this book includes slope-deformation characterization using morphology and evolution, mechanical behaviour of the material, modes of failure and collapse, influence of lithology and structural features, and the role played by controlling factors. The contributions cover broad aspects of slope tectonics that attempt to underline a multidisciplinary approach, which should create a better framework for studies of slope instability.

Description: The calc-alkaline Karacaali Magmatic Complex (KMC), in the Central Anatolian Crystalline Complex, is an example of an Upper Cretaceous post-collisional I-type, plutonic-volcanic association. Volcanic rocks grade from basalt to rhyolite, whilst coeval plutonic rocks range from gabbro to leucogranite. In this paper we document evidence for the occurrence of both mixing and unmixing during the evolution of this igneous complex. Mixing of mafic and felsic magmas was observed in petrographic properties at microscopic to macroscopic scales and is further supported by mineral chemistry data. The occurrence of unmixing is evidenced in the Fe and Cu-Mo mineralization hosted in the KMC. The iron mineralization in basaltic-andesitic rocks consists mostly of magnetite. Magnetite has been grouped into four settings: (1) matrix type; (2) vein-filling type; (3) breccia matrix type; and (4) vesicle-filling type. In contrast, Cu-Mo mineralization is related to vertical north-south trending quartz-, quartz-calcite-, and quartz-tourmaline veins crosscutting monzonitic and granitic rocks. We propose that the intrusion of an oxidized, Fe- and Cu-rich basic magma into a partially crystallized acid magma resulted in partial mixing and may have triggered the abrupt separation of an iron-oxide-rich melt. Our results highlight the importance of magma mixing and metal unmixing, possibly associated with stress relaxation during post-collisional evolution. Supplementary materialElectron microprobe analyses of plagioclase in monzonitic rocks, MMEs and electron microprobe analyses of K-feldspar in monzonitic rocks are available at http://www.geolsoc.org.uk/SUP18434.

Description: The Zaglic and Safikhanloo epithermal gold prospects are located in the Arasbaran zone, to the west of the Cenozoic Alborz-Azarbaijan magmatic belt in NW Iran. Mineralization is mainly restricted to quartz and quartz -carbonate veins and veinlets. Pyrite is the main sulphide, associated with subordinate chalcopyrite and bornite. Gold occurs as microscopic and submicroscopic grains in quartz and pyrite. The country rocks are Tertiary intermediate-mafic volcanic and volcaniclastic rocks of andesite to trachy-andesite composition intruded by a composite granitic to syenitic pluton. They are medium- to high-K, calc-alkaline and alkaline rocks and display fractionated REE (rare earth element) patterns, with light rare earth elements (LREE) significantly enriched relative to the heavy rare elements (HREE). On primitive mantle normalized plots, they display depletions in Nb, Ti and P, and enrichments in Pb, which are common characteristics of arc-related magmas worldwide. Hydrothermal alteration minerals developed in the wall rocks include quartz, calcite, pyrite, kaolinite, montmorillonite, illite, chlorite, and epidote. Minor alunite occurs in Safikhanloo. Gold is locally enriched in the altered rocks immediate to the veins. The ore-stage quartz from both prospects is dominated by liquid-rich fluid inclusions; vapour-rich inclusions are rare. The homogenization temperature varies between 170-230 and 170-330 {degrees}C and salinity varies between 1.4 to 9.5 and 〈1 to 6.7 wt% NaCl equivalent, for Safikhanloo and Zaglic, respectively. The occurrence of hydrothermal breccias, bladed calcite, adularia, and rare coexisting vapour- and liquid-dominant inclusions suggest that boiling occurred in the course of the evolution of the ore fluids. The large variations in Th and the salinity values can be explained by boiling and/or mixing. Lack of sulphate minerals in the veins suggests that sulphides and gold precipitated from a reduced, H2S-dominant fluid. Calculated {delta}34S values for the ore fluid vary between -4.6 and -9.3{per thousand}. Sulphur could have been derived directly from magmatic sources, or leached from the volcanic and plutonic country rocks. Ore formation in Zaglic and Safikhanloo occurred in response to mixing, boiling, and interactions with wall rocks. Considering the intermediate-argillic alteration, the low contents of base metal sulphides, and the overall low salinities, the Zaglic and Safikhanloo can be classified as low-sulphidation epithermal systems.

Description: In the Sierra de Velasco, northwestern Argentina, undeformed Lower Carboniferous granitoids (350-334 Ma) intrude deformed Lower Ordovician granites and have been emplaced by passive mechanisms, typical of tensional environments. The semi-elliptic, about 300 km2 shallow-emplaced San Blas pluton is 340-330 Ma old, with {varepsilon}Ndt between -1.3 and -1.8 which indicates that, different from the nearby Famatinian-Ordovician granitoids, the San Blas pluton had a relatively brief crustal residence, with an interaction between asthenospheric material and greywackes. The cupola of the pluton was almost totally eroded down during the Upper Carboniferous. The San Blas pluton is a porphyritic granite composed mainly of monzogranite to syenogranite and shows graphic intergrowth and miarolitic cavities up to 5 cm in diameter, filled with quartz. Two different textures are recognized: perthitic microcline megacrysts (30-45 vol%) set in a medium- to coarse-grained groundmass of quartz, microcline and oligoclase, with sericitic alteration. Biotite, muscovite, apatite, zircon, fluorite and opaque minerals are the accessory phases. The other textural variation consists in microcline megacrysts (10%-15 vol%) and a fine-grained groundmass, of quartz, microcline and oligoclase, biotite, apatite, muscovite, zircon and magnetite. The average SiO2 content in this pluton is 74.94%, the ASI=1.1, CaO and MgO are less than 1%, total Fe2O3 and P2O5 contents are low, and K2O〉Na2O. Low Ba, Sr and high Rb contents, coupled with Sn contents (c. 15 ppm), W (c. 380 ppm), Nb, Y, Ta, Th and U confirm this is a special granite. The K/Rb ratio (c. 75) indicates that Rb has been fractionated to the residual melt whereas the Zr/Hf (c. 25) demonstrates that hydrothermal alteration occurred. The Sr/Eu ratio of c. 75 along other geochemical features characterize this pluton as a fertile evolved granite. The chondrite-normalized rare earth element (REE) diagram shows the tetrad effect that allows the subdivision of the lanthanides into four groups. In general, the tetrad effect is recognized in evolved granites and products of hydrothermal alteration such as greisens. The above-mentioned features show that the San Blas granite is fertile, and the absence of ore deposits has been probably caused by erosion of a mineralized cupola during Carboniferous and Cenozoic exhumation. The finding of alluvial cassiterite and wolframite in drainage systems is the first evidence of the fertile character of this granite.

Description: Evidence of deep-seated gravitational slope deformations (DSGSD) and of large prehistoric landslides is fairly widespread within the Central Apennines (Italy). These gravity-induced processes accompanied the intense Plio-Quaternary uplift phases that affected the mountain chain. In this study a multidisciplinary approach has been adopted in order to better constrain the relationship between the tectonic evolution and the gravitational morphogenesis of a typical Apennine morphostructure, such as the Caramanico Valley. For this purpose a conceptual model of the morphostructural evolution of the area has been reconstructed, on the basis of geological constraints derived by the integration of detailed geological–structural and geomorphological surveys with available literature data. Based on this evolutionary model, a multistage numerical modelling using the finite difference method code FLAC 6.0 has been performed in order to: (i) evaluate the effect of the uplift-related morphological changes of the valley–slope system; and (ii) assess the role of the horizontal/vertical stress ratio variations due to geodynamic regime shifts. The results of the numerical model show a good fit with the actual geomorphical evidence and also confirm the presence during some evolutionary stages of stress–strain conditions compatible with those necessary to produce the massive rock slope failures testified by the presence of large palaeo-landslide deposits.

Description: Stress distribution in mountainous areas is influenced by local morphology. Valley morphology and the relationship between main and tributary valleys strongly depend on geological characteristics and evolution. They may control the evolution of slope instabilities, especially when interacting with pervasive structural features.We performed parametric three-dimensional (3D) numerical modelling of simplified slope geometries with variable slope angle (from 21° to 35°), length, combining different orientations for different slope sectors and changing attitude of pervasive planes of anisotropy (foliation, schistosity, bedding). Data used in the 3D models are the initial slope geometry, rock mass properties and internal anisotropy. We assumed Mohr–Coulomb behaviour, with the presence of ubiquitous joints and different piezometric levels.The model results show that plastic deformation initiates near the highest ridge just after deglaciation commences. A shear zone develops and propagates toward the toe of the slope, and its shape is strongly controlled by slope geometry, anisotropy and in situ stresses. The thickness of the failing mass, for model slope reliefs up to 3200 m, increases from 50 m to some hundreds of metres during glacier retreat, and it depends on geometry of slopes, anisotropy and in situ stresses. Results are compared to examples of deep-seated slope deformations from the Alps, which helps in the interpretation of such phenomena and in the understanding of their influence on valley evolution.

Description: Intensive agricultural development of the forest zone of the East European Plain started in the second part of the first millennium AD. Although the majority of the mediaeval population were peasants, archaeological study of ancient rural settlements is much less developed than that of ancient towns. The analysis of interrelationships between environmental conditions and the agricultural pattern across space, including the corresponding pattern of rural settlements, helps us to delimit the spatial frame in which it is possible to find rural settlements of different historical epochs, even if they have since disappeared. Five areas with different historical types of agricultural landscapes were revealed, based on their geological and climatic characteristics. Another analysis essential for archaeology deals with the age of contemporary agricultural landscapes and rural settlements along with the factors and laws that control their changes through time and space.

Description: Human impact on our environment is not a new phenomenon. For millennia, humans have been coping with – or provoking – environmental change. We have exploited, extracted, over-used, but also in many cases nurtured, the resources that the geosphere offers. Geoarchaeology studies the traces of human interactions with the geosphere and provides the key to recognizing landscape and environmental change, human impacts and the effects of environmental change on human societies. This collection of papers from around the world includes case studies and broader reviews covering the time period since before modern human beings came into existence up until the present day. To understand ourselves, we need to understand that our world is constantly changing, and that change is dynamic and complex. Geoarchaeology provides an inclusive and long-term view of human–geosphere interactions and serves as a valuable aid to those who try to determine sustainable policies for the future.

Description: In 2002 and 2004–2005 archaeological investigations were undertaken on middens exposed by coastal erosion at West Voe in the south of Mainland Shetland, UK. This work established that the site dated from c. 4000 cal BC to c. 3250 cal BC and was of major importance for two reasons: (1) as the first of Mesolithic date to be found on Shetland; (2) as the first site to be found in the Northern Isles that spanned the Mesolithic–Neolithic transition. This paper describes investigations into the origin of sands deposited around 3500 cal BC and their potential effect on human settlement. The sands in question lie between two midden deposits, the lower of which accumulated over the period 4000–3500 cal BC and the upper 3500–3250 cal BC. The sands, therefore, dated to the period shortly after the adoption of agriculture on the archipelago, represented in the lower midden by the appearance of domesticated species and ceramics at around 3700–3600 cal BC, and represented a disruption in human occupation at a critical point in the development of a changing use of the landscape.

Description: To understand the human behaviour reflected in stone tool assemblages, we must take into account the characteristics of the lithic resources, their distribution across the landscape, the characteristics of the landscape itself, the distribution of other resources such as water and food, and human strategies of mobility and resource exploitation. The assemblage from one layer of a Middle Palaeolithic rock shelter site, the Bau de l'Aubesier, shows that raw materials from different areas were used in different ways: they are more or less common in the assemblage, and they are more or less likely to have been brought in as raw material and knapped in situ. Various factors may have influenced this pattern. Measures of terrain difficulty and energy expenditure, the raw material quality, and characteristics of the sources are woven together to determine the attractiveness of each source. This is then placed in the context of the geology and geography of the area to distinguish a ‘main’ or core territory from a more extended territory visited during longer trips. The results show the value of taking a geoarchaeological perspective, which sees nature and culture as inextricably intertwined.

Description: Beginning with the earliest organized habitation sites the options provided by the regional environment have largely or partially governed the location and relocation of human settlements. The settlement system in second millennium BCE Henan Province, China, evolved during a period of significant climatic change and shifting river courses but relative soil stability. Human–environment interactions across the landscape have left ample remains for investigation by scholars of social and cultural change and by natural scientists. The social effects of climate and geomorphological change during this period are complex and only partially understood. It is well documented that long-term soil stability before and during the second millennium BCE gave rise to the development of good agricultural soils, without which population expansion probably could not have taken place. This paper summarizes some of the recent research in climate change and, from two of our own projects, in geomorphology and ecology that underlie environmental impacts on the evolving state-level societies, especially related to settlement location and relocation. For example, the Shang possibly relocated one or more capital sites in response to disastrous floods.

Description: A seismic velocity cross-section down to 700 km depth beneath the Tibetan Plateau has been constructed. Beneath the cover layer, felsic rocks rich in a quartz exist down to 15–25 km depth. Beneath these depths, temperatures are probably high enough for ductile flow and partial melting to occur. The velocity increase across the boundary at 30–40 km depth marks the interface between felsic upper crust and more mafic lower crust. Crustal thickness is greatest (c. 74 km) south of c. 31.5°N, where Indian lower crust forms the basal layer. Northwards, crustal thickness decreases to c. 66 km around 33°N, before increasing to c. 70 km beneath northern Tibet. Crossing the Kunlun, the crust thins to c. 54 km beneath the Qaidam basin. High-velocity, dense, cold Indian lithospheric mantle extends northwards until about the Banggong-Nujiang suture, where it downwells to 350–400 km depth. The lithosphere–asthenosphere boundary occurs at 160–225 km depth. The apparent northwards deepening of the 410 and 660 km discontinuities implies that the upper mantle beneath northern Tibet is slower, less dense and warmer than under southern Tibet which, in turn, could provide some of the isostatic support for the high elevations in northern Tibet where the crust is thinner than under southern Tibet.

Description: Geoarchaeological research within Sicily continues to characterize the effects of anthropogenic and geological processes upon the island's Holocene alluvial landscape developments. Interdisciplinary approaches have been used including geomorphological mapping, archaeological survey and excavations to characterize land-use practices though the mid- to late Holocene. Landscape development changes are recorded in the alluvial sediments as a consequence of land use by the indigenous and Roman settlers of Sicilian valleys in the Nebrodi and Polizzo Mountains. A marked change in erosion has been identified during the late Roman occupation of Sicily, probably as a product of intensive pastoralism and land clearing. Sedimentation during indigenous hilltop occupation of north–central and western Sicily was dominated by coarse-grained (cobble or boulder) deposits attributed to flash-flooding. Sedimentation that temporally coincided with the Greek and later Roman occupation of the adjacent valleys is marked by fine-grained deposits. These data continue to support the geological and archaeological interpretations of human–landscape interactions in Sicily. Furthermore, such geoarchaeological data may be used in models to strengthen our present and future landscape conservation methods.

Description: The Selin Co basin in the northern Lhasa terrane includes more than 3000 m of upward coarsening Lower Cretaceous strata, and the sedimentary sequence from the flysch to the molasse indicates the evolution of a foreland basin. Petrographic analysis shows that sandstones are rich in volcanic and sedimentary lithics and most of them fall into recycled orogen and magmatic arc.Uranium–lead (U–Pb) ages were determined for 435 detrital zircons from the Lower Cretaceous strata in the Selin Co basin. Relative probability of detrital zircon ages shows the Eshaerbu Formation was rich in zircon grains with the age of 125–140 and 160–180 Ma, and the Duoni Formation was dominated by one main age cluster of 125–150 Ma. Analysis of the potential provenances suggests the Early Cretaceous zircon grains were primarily derived from the Gangdese magmatic arc to the south. The youngest zircon ages in the lowermost exposure of the Eshaerbru Formation are c. 130 Ma, providing a maximum depositional age of sediments in the Selin Co basin.Collectively, our studies, together with previously documented Cretaceous thrusting in the Lhasa terrane, suggest the Lower Cretaceous Selin Co basin was deposited in a retroarc foreland basin. From 145–90 Ma, a retroarc foreland basin was presumed to develop in the Lhasa terrane, migrating from the south to the north. Crustal thickening, likely associated with the evolution of the retroarc foreland basin, was speculated to start in the Early Cretaceous in the Lhasa terrane.

Description: The endorheic Gaxun Nur Basin (GNB, local name: Ejina basin), which is located north of the Tibetan Plateau between the tectonic stress fields of the Qilian Shan and the Gobi-Tienshan, has evolved as a large inland basin filled with deltaic sediments during the past 250 ka. Here we present selected examples of geomorphological, sedimentological and geophysical evidence of tectonic activity and discuss a possible time frame of selected occurrences.We used medium-scale geomorphological mapping supported by analyses of Landsat ETM images, Corona images and an Aster Digital Terrain Model (Aster-DTM), combined with field surveys, dated sediment sections, and geophysical investigations using electromagnetic methods.The spatio-temporal distribution of radiocarbon-dated lake sediments within the northern GNB indicates a non-even distribution of neotectonic activity with west–east increasing amplitude of subsidence rates from 0.8–1.1 m/ka in the western part and more than three times higher rates in the eastern part.Our data indicate that tectonic has strongly amplified climate-induced environmental changes and may be regarded as an example of non-climatic pulses affecting lake-hydrology and basin development.

Description: Sediments at Pias (Galicia) provide evidence of Upper Pleistocene glacial activities at a valley junction in the north-western mountains of Spain. The sedimentary sequence consists of lower, predominately fine-grained lacustrine deposits with few lonestones, overlain by poorly sorted, sandy gravels interstratified with massive diamicton deposited during mid-Weichselian times (MIS 3) (marine isotope stage 3). The lacustrine sediments were deposited in a glacial valley temporarily dammed by a confluent glacier. The presence of active ice is suggested by massive diamicton layers best interpreted as till, rafted sediments in lacustrine deposits and deformation structures indicative of loading and kettle formation. Frozen ground conditions are suggested by a few involution-like structures. The Pias area contains one of the few western-Spain sedimentary records of Upper Pleistocene glaciation at relatively low latitude (about 42°N) and low altitude (less than 1000 m a.s.l.). A southern dip of the Polar front to 40–45°N latitudes, as occurred during Last Glacial Maximum, could have cut moisture to the northern Fennoscandinavian ice sheets. At the same time, however, sufficient precipitations would have persisted in north-western Spain to sustain extensive ice caps and their outlets to elevations as low as c. 900 m a.s.l.

Description: The effects of Pleistocene cold-climate geomorphology are distributed across the weathered and eroded Mid-Atlantic Coastal Plain uplands from the Wisconsinan terminal moraine south to Tidewater Virginia. Cold-climate deposits and landscape modifications are superimposed on antecedent landscapes of old, weathered Neogene upland gravels and Pleistocene marine terraces that had been built during warm periods and sea-level highstands. In New Jersey, sequences of surficial deposits define a long history of repeating climate change events. To the south across the Delmarva Peninsula and southern Maryland, most antecedent topography has been obscured by Late Pleistocene surficial deposits. These are spatially variable and are collectively described as a cold-climate alloformation. The cold-climate alloformation includes time-transgressive details of climate deterioration from at least marine isotope stage (MIS) 4 through the end of MIS 2. Some deposits and landforms within the alloformation may be as young as the Younger Dryas. Southwards along the trend of the Potomac River, these deposits and their climatic affinities become diffused. In Virginia, a continuum of erosion and surficial deposits appears to be the product of ‘normal’ temperate, climate-forced processes. The cold-climate alloformation and more temperate deposits in Virginia are being partly covered by Holocene alluvium and bay mud.

Description: SE Asia comprises a collage of Gondwana-derived continental blocks assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones. Two major biogeographical boundaries, the Late Palaeozoic Gondwana–Cathaysia divide and the Cenozoic-Recent Australia–Asia divide (Wallace Line) are present. Palaeozoic and Mesozoic evolution involved the rifting and separation of three collages of continental terranes from eastern Gondwana and the opening and closure of three successive ocean basins, the Palaeo-Tethys (Devonian–Triassic), Meso-Tethys (Permian–Cretaceous) and Ceno-Tethys (Late Triassic–Cenozoic). This led to the opening and closing of ocean gateways and provision of shallow-marine and terrestrial land bridges and stepping-stones for biotic migration. The SE Asia core (Sundaland) comprises a western Sibumasu block, an eastern Indochina–East Malaya block, and the Sukhothai Island Arc terrane between. The Jinghong, Nan-Uttaradit and Sra Kaeo sutures represent the Sukhothai closed back-arc basin. The Palaeo-Tethys is represented by the Changning-Menglian, Chiang Mai/Inthanon and Bentong-Raub suture zones. The West Sumatra and West Burma blocks were accreted to the Sundaland core in the Late Permian–Early Triassic. SW Borneo and/or East Java–West Sulawesi are now identified as the missing ‘Argoland’ that separated from NW Australia in the Jurassic and accreted to SE Sundaland in the Cretaceous.

Description: Collision between Australia and SE Asia began in the Early Miocene and reduced the former wide ocean between them to a complex passage which connects the Pacific and Indian Oceans. Today, the Indonesian Throughflow passes through this gateway and plays an important role in global thermohaline flow. The surrounding region contains the maximum global diversity for many marine and terrestrial organisms. Reconstruction of this geologically complex region is essential for understanding its role in oceanic and atmospheric circulation, climate impacts, and the origin of its biodiversity.The papers in this volume discuss the Palaeozoic to Cenozoic geological background to Australia and SE Asia collision. They provide the background for accounts of the modern Indonesian Throughflow and oceanographic changes since the Neogene, and consider aspects of the region's climate history.

Description: A new long-offset, long-record crustal-scale seismic survey of 9600 km called JavaSPAN was acquired in the Java Sea and Makassar Strait. The East Java Sea is underlain by continental basement with a prolonged multiphase history of deposition punctuated by extensional and compressional events. This East Java Terrane is a major component of SE Sundaland lying between the Meratus suture, the contemporary Java arc, and the west Sulawesi orogenic belt, but is poorly constrained on the north under the North Makassar Basin and in Kalimantan. A Precambrian to Permo-Triassic sedimentary section up to some 8.5 km in thickness overlies crystalline basement in a number of fault blocks and synformal structures below a strong angular unconformity. A thin overlap assemblage of Cretaceous to early Cenozoic sediments overlies that unconformity. Middle Eocene to Neogene clastic and carbonate rocks overlie another angular unconformity that marks the initiation of a well known history of Palaeogene extension, sag, and Neogene inversion. The East Java Terrane rifted from the Bonaparte-Arafura sector of northern Australia in the Jurassic and accreted onto a magmatic arc on the SW flank of what is now Kalimantan in the Cretaceous.

Description: The existence of El Niño/Southern Oscillation (ENSO) variability in past climates is still debated. Based on evidence from geological records indicating a different long-term mean climate in the tropical Pacific, a permanent El Niño state has been hyothesized to exist prior to the Plio-Pleistocene transition. However, model studies of past climate and geological records suggest that ENSO variability has existed on Earth as far back as in the Eocene and the Miocene. In the early-to-middle Miocene, climate was not only warmer than today, but oceanic gateways such as the Indonesian Passage and the Central American Seaway established deep connections between the main ocean basins. Here, we analyse the effect of increased levels of atmospheric greenhouse gases and open tropical gateways on the amplitude, period and pattern of ENSO variability using results of fully coupled climate model simulations. While our model shows only small changes in ENSO variability under increased greenhouse gas levels, it suggests a significantly stronger and less frequent ENSO due to altered oceanic gateways. In particular, a deeper and more open Indonesian Passage does not prevent a Western Pacific warm pool from developing, but it allows the warm pool to shift into the Indian Ocean.

Description: The Neogene climate history of the Makassar Straits has been assessed by combining palynological studies of two Late Quaternary cores from the ocean floor with analyses of petroleum exploration wells from the Makassar Straits, Indonesia, penetrating the Early Pleistocene to Middle Miocene.The two Late Quaternary cores span 30 ka, located offshore the Mahakam Delta, east Kalimantan, and 95 ka, from offshore south Sulawesi. The first provides a record of the vegetation and climate history of the Mahakam catchment, and indicates rain forests through the last 30 ka, but with a cooler last glacial maximum, whereas the second provides a record of vegetation of the Java Sea region and south Sulawesi, and indicates extensive grasslands, suggesting a distinctly seasonal climate, during the last glacial maximum.Based on a climate model constructed from the cores which link sea level change with changes of temperature and seasonality, the history of vegetation and climate for the Makassar Straits is then extrapolated back to the Middle Miocene using the record obtained from the two exploration wells. Results show that the equatorial climate has been everwet since the Middle Miocene, but at subequatorial latitudes seasonal climates became established from the Late Pliocene onward.

Description: Rich palynomorph assemblages have been obtained through a marine Oligocene succession from the East Java Sea (Indonesia) and provide the first instance of an independently dated Oligocene succession from SE Asia that has yielded a good quality palynological record. The succession has been independently dated by nannofossils and foraminifera.The palynomorph succession suggests climatic control on Oligocene vegetation, on which basis a regionally applicable zonation is proposed. The Early Oligocene is characterized by common rain forest elements, suggesting an everwet, rain forest climate. The early part of the Late Oligocene contains much reduced rain forest elements with grass pollen, indicating a more seasonal climate, whereas for the latest Late Oligocene, rain forest elements return in abundance, suggesting a superwet rain forest climate. This palynological succession is similar to that from the Sunda Basin in the West Java Sea, allowing the Sunda Basin succession to be dated by correlation.The study also extends the stratigraphic range of Dacrydium and Casuarina, two plant taxa previously thought to have dispersed from the Australian Plate into SE Asia at the time of the collision with Sunda, to well before the time of collision. A different means of dispersal for these taxa is proposed.

Description: This study reviews how shallow water carbonates are revealing environmental and climatic changes on all scales through the last 50 million years in SE Asia. Marine biodiversity reaches a global maximum in the region, yet the environmental conditions are at odds with the traditional view of ‘blue-water’ reefal development. The region is characterized by complex tectonics, major volcanism, high terrestrial runoff, nutrient influx, everwet and monsoonal climates, low salinities, major currents and ENSO (El Niño Southern Oscillation) fluctuations. Terrestrial runoff, nutrient upwelling, tectonics, volcanism and recent human activities are major influences on the modern development of carbonate systems. Coral sclerochronology is revealing how these factors vary locally over annual and decadal scales. The strong impact of vertical tectonic movements and the interplay with eustasy is evaluated from Quaternary and Pleistocene coral reef terraces. Isotopic data from terrace deposits indicates that interglacials may have been up to 3–6 °C warmer than glacials, consistent with the region's record from terrestrial and deep marine deposits. Study of outcrop and subsurface carbonate deposits reveals the impact of tectonics, siliciclastic, nutrient influx, eustasy and oceanography on individual systems over millennial timescales. Major changes in oceanography, plate tectonics, climate change and perhaps fluctuating CO2 levels impacted Cenozoic regional carbonate development. Results of studies from terrestrial and deep marine realms are comparable with those from the carbonates, but have yielded higher resolution records of changing currents, precipitation and the monsoons. There is considerable scope for further research, however, SE Asian carbonates are powerful tools in evaluating past environmental change in the equatorial tropics.

Description: Mars is the fourth planet in our Solar System and orbits roughly 230×106 km from the Sun. It has an orbital period of 687 Earth days and a solar day that is approximately 40 min longer than an Earth day. Mars is less dense and has half the radius of the Earth, and so has about one-tenth the mass; hence, the surface gravity of Mars is about four-tenths that of the Earth. Mars has no oceans and its surface area is therefore almost as large as that of Earth's continents. In this chapter, we present a summary of the Martian environment, global geography and geology, and provide some background on the missions and instruments that have played a role in developing our current understanding. Our aim is to provide a broad overview for those unfamiliar with Mars, rather than providing an exhaustive summary of every aspect of the planet's evolution.

Description: The surface of Phobos, the 27×22×18 km inner moon of Mars, is dominated by several families of parallel grooves. At least seven different groups of hypotheses have been advanced to explain their origin, but studies have always been limited by the fact that, until recently, much of Phobos was imaged at a resolution too low to show grooves. Now, however, the High Resolution Stereo Camera (HRSC) on board the European Mars Express mission has made 134 imaging fly-bys past Phobos. The pictures of the previously poorly imaged regions and much of the rest of the satellite have been returned with resolutions down to a few metres, facilitating the construction of a more complete map of the grooves. Each of the seven hypotheses was tested against the new data on groove morphology, positions and orientations, and it was found that six of the previous hypotheses could be discarded. The only hypothesis to pass all tests was that they are chains of secondary impact craters from primary impacts on Mars. An implication of these results is that previous estimates of an unusually thick Phobos regolith of 100–200 m depth are no longer necessary, and our conclusions place no constraints on the interior of Phobos, so recent evidence that Phobos is a ‘rubble pile’ is consistent with our work. The preferred hypothesis also sheds light on the origin of crater chains on Eros, and on impact processes in the early stages of crater excavation.

Description: A systematic survey was undertaken and an investigation carried out into the geomorphological characteristics of lobate debris aprons in the Tempe Terra region of Mars. Based on the most recent high-resolution (sub 15 m per pixel) imagery and on new topography data, this study endeavoured to raise and discuss questions regarding their formation (emplacement) and modification (deformation sequence), as well as the role of a mantling deposit found at mid-latitude locations on Mars. Furthermore, a model for the formation of debris aprons in the Tempe Terra–Mareotis Fossae settings is proposed. Image survey, in combination with basic morphometric observations within a geomorphological context, provided additional insights into the source, emplacement and modification of hillslope debris material. Our results imply that lobate debris aprons are not mainly relicts of remnant degradation but are substantially composed of mantling material probably deposited episodically in the course of planetary obliquity changes and over a long timespan, as derived erosion rates suggest. Crater-size frequency statistics and the derivation of absolute ages show ages of sub-recent modification and document earlier resurfacing events.

Description: Possible periglacial and relict glacial landforms in the ancient mountain range of the Thaumasia Highlands, Mars, are described. The landforms include large-scale mantling, lineated crater and valley-fill materials, debris aprons, protalus lobes and ramparts. The most pristine ice-related landforms appear to be small-scale protalus lobes and ramparts with no visible distinct impact craters at both medium (High Resolution Stereo Camera (HRSC)) and high (Mars Orbiter Camera (MOC) narrow angle (NA), Context Camera (CTX)) spatial resolution. These small landforms are possibly active at present and post-date more extensive features such as crater fills, possibly formed during high obliquity climatic periods.In contrast to the rock glacier-like landforms with distribution preferentially occurring on south-facing slopes, possibly controlled by enhanced exposure to the Sun, older, less pristine lineated fill materials show a less systematic distribution of flow directions, suggesting a more generalized periglacial and possibly glacial environment in the Thaumasia Highlands.

Description: The confirmation of near-surface ground ice and perchlorates at the Phoenix landing site suggest that high-latitude ground-ice thaw may be more easily achieved than previously envisaged, providing the potential to drive significant, distinctive morphogenesis. We describe the results of a survey of 23 High Resolution Imaging Science Experiment (HiRISE) images covering 337° of longitude between latitudes 59°N and 79°N in which such morphogenesis is apparent, confirming that thaw has been a regionally important morphological agent. Some of the strongest geomorphological indicators of cyclical ground-ice thaw described are assemblages of sorted landforms, including clastic patterned ground resulting from cryoturbation of ice-rich regolith and lobate forms reflecting solifluction. Also described are braided gully-fan systems sourced at thermokarst pits and channels that have evolved from enlarged thermal contraction cracks. Not only are these landforms indicative of thaw and flowing liquid but the incision of solifluction lobes by thermokarst gullies demonstrates that thaw has been responsible for polycyclic morphogenesis. The presence of these landforms across the high northern latitudes of Mars indicates that the regional importance of thaw has been underestimated. This in turn has important implications for the development of better climate models and the search for life on Mars.

Description: Periglacial landforms on Spitsbergen (Svalbard, Norway) are morphologically similar to landforms on Mars that are probably related to the past and/or present existence of ice at or near the surface. Many of these landforms, such as gullies, debris-flow fans, polygonal terrain, fractured mounds and rock-glacier-like features, are observed in close spatial proximity in mid-latitude craters on Mars. On Svalbard, analogous landforms occur in strikingly similar proximity, which makes them useful study cases to infer the spatial and chronological evolution of Martian cold-climate surface processes. The analysis of the morphological inventory of analogous landforms on Svalbard and Mars allows the processes operating on Mars to be constrained. Different qualitative scenarios of landscape evolution on Mars help to better understand the action of periglacial processes on Mars in the recent past.

Description: Sublimation-related landforms are ubiquitous on Mars, especially at mid to high latitudes. This paper reviews the main landforms interpreted to form due to sublimation of subsurface ice on Mars. Pits, knobs and dissected terrains are classical landforms thought to form due to subsurface ice sublimation as observed with high-resolution imagery. Sublimation-related processes on Mars are strongly latitude dependent, with sublimation being increasingly important from high (〉60°) to low latitudes (down to 25°) due to correspondingly higher mean annual temperatures. Equatorial regions (within 25° latitude) are mainly devoid of any sublimation-related landforms, reflecting an ice-free shallow subsurface. Mean temperatures and water vapour pressure strongly control the sublimation rate, but diffusion and water adsorption are fundamental and vary depending on the regolith porosity and composition, leading to variations in the theoretical depth at which water ice becomes stable. From a geomorphological point of view, this review highlights the importance of subsurface structure (fractures, layering) in the shaping of landforms and in the control of sublimation rates, in addition to usual physicochemical parameters.

Description: The latest Mars missions are returning data of unprecedented fidelity in their representation of the martian surface. New data include images with spatial resolution better than 30 cm per pixel, stereo imaging-derived terrain models with one meter postings, high-resolution imaging spectroscopy, and RADAR data that reveal subsurface structure. This book reveals how this information is being used to understand the evolution of martian landscapes, and includes topics such as fluvial flooding, permafrost and periglacial landforms, debris flows, deposition and erosion of sedimentary material, and the origin of lineaments on Phobos, the larger martian moon. Contemporary remote sensing data of Mars, on a par with those of Earth, reveal landscapes strikingly similar to regions of our own planet, so this book will be of interest to Earth scientists and planetary scientists alike. An overview chapter summarising Mars’ climate, geology and exploration is included for the benefit of those new to Mars.

Description: The African continental crust was assembled by a series of orogenies over a period of billions of years mainly in Precambrian times. Tracing the build-up history of this stable crust is not always straightforward due to multiphase deformation and regions with poor outcrop. Episodes of metamorphism and magmatism associated with multiple Wilson cycles are recorded in zircons, which found their way into sediments derived from the hinterland. Dating of zircon populations in detrital rocks can hence provide age spectra which reflect the metamorphic and magmatic events of the region. Microbeam dating of detrital zircon is used to characterize the crustal development history of the Rehoboth Province of southern Africa. We investigated a quartzite of the Late Palaeo-Early Mesoproterozoic Billstein Formation, formed in a continental basin, and a quartz-feldspar arenite layer of the late Mesoproterozoic Langberg Formation conglomerates, immature sediments formed within a felsic volcanic system (both close to Rehoboth Town). The combined data indicate three episodes of crustal evolution in the Rehoboth Province. The oldest phase is only documented in the Billstein quartzite by three 2.98–2.7 Ga Archaean zircons. A Palaeoproterozoic phase between 2.2 and 1.9 Ga is older than any known exposures of the Rehoboth Province. The Billstein quartzite shows a main peak at 1.87 Ga, corresponding to the 1863±10 Ma Elim Formation. The Langberg sample reflects magmatism related to the entire Namaqua–Natal Wilson cycle between c. 1.32 and 1.05 Ga. The absence of zircons of that age range in the Billstein quartzite indicates a pre-Namaqua age for the Billstein Formation. Our data shows that there were at least three episodes of crustal development at 2.98–2.7 Ga, 2.05–1.75 and 1.32–1.1 Ga. We have documented the existence of a previously unrecognized 2.98–2.7 Ga Archaean crustal component, which was probably exposed in the Rehoboth Province during the Palaeoproterozoic and thus indicates a much longer geological history for the Rehoboth Province than previously known.

Description: Sr and Nd isotopic compositions are presented for a Miocene bimodal basalt–rhyolite suite from north Shewa, central Ethiopian plateau. Whole-rock Rb–Sr isochron of the rhyolites yields an age of 20.7±2.4 Ma, marking the onset of volcanism in central Ethiopia c. 20 Ma, 10 Ma after initial magmatism in the northern Ethiopian plateau. Initial 87Sr/86Sr ratios slightly vary in the basalts as well as in the rhyolites, ranging from 0.70440 to 0.70641 and from 0.70563 to 0.70658, respectively. Initial 143Nd/144Nd ratios show significant variations in the basalts (0.51248–0.51274), but remain nearly constant in the rhyolites (0.51273–0.51278). The Sr and Nd isotopic ratios of the basalts are interpreted to reflect their derivation from Afar plume contaminated by crustal materials (up to 15% contamination). The rhyolites evolved dominantly by fractional crystallization of mantle-derived basaltic magmas similar in composition to the exposed flood basalts.

Description: Subalkaline basalts from NE Egypt represent an episode of magmatism at c. 24 Ma, coincident with widespread eruptive activity in northern Africa. New geochemical data provide insight into the mineralogical and isotopic characteristics of the underlying mantle. The basalts show little geochemical variation, with incompatible trace element abundances similar to those of ocean island basalts. They display fairly smooth primitive mantle-normalized incompatible trace element patterns. Trace element abundances and Sr–Nd–Pb–Hf isotopic signatures are consistent with contributions from two distinct source regions, one similar to the Afar plume and the other located within the metasomatized spinel-facies subcontinental lithosphere. Mixing of melts from these two domains was followed by minor crustal contamination during prolonged ascent or emplacement. Integrating the geochemical data with available tomographic information allows us to develop a framework for understanding mid-Tertiary magmatic activity throughout northern Africa. A model for this widespread volcanism involves ascent of upwelling mantle derived from the margins of the South African Superplume rooted at the core–mantle boundary and/or through small-scale convection at the 660 km discontinuity. Ascent of magmas to the surface was facilitated by pre-existing structures within the lithosphere, including those associated with incipient rifting of the Red Sea.Supplementary material: Mineral chemistry data are available at http://www.geolsoc.org.uk/SUP18483.

Description: The crustal structure of northern Africa is puzzling, large areas being of difficult access and concealed by the Sahara. The new global gravity models are of unprecedented precision and spatial resolution and offer a new possibility to reveal the structure of the lithosphere beneath the Sahara. The gravity gradients correlate better than gravity with geological features such as rifts, fold belts and magmatic deposits and intrusions. They are an ideal tool to follow geological units (e.g. basement units) below a stratigraphic layer of varying density (e.g. sediments). We focus on the Chad lineament, a 1300 km arcuate feature located between the west and central African rift system. The gravity fields show differences between the lineament and the west and central African rift system. Along the centre of the lineament high-density rocks must be present, which relate to either magmatic or metamorphic rocks. This is very different to the lineaments of the western and central-west African rift system which are filled with sediments. Considering present models of rifting and the absence of topography, the lineament cannot be coeval to the west and central African rift system and is most likely older. We suggest that the lineament is a structural element of the Saharan Metacraton.

Description: Explaining the cause and support of Africa's varied topography remains a fundamental question for our understanding of the long-term evolution of the continent. As geodynamical modelling becomes more frequently used to investigate this problem, it is important to understand the seismological results that can be incorporated into these models. Crustal thickness estimates are crucial for calculating components of topography that are isostatically compensated. Variations in seismic velocity help constrain variations in subsurface temperature and density and thus buoyancy; measurements of anisotropy can also be used to determine the contribution of the mantle flow field to dynamic topography. In this light, we review the results of passive seismic studies across Africa. At the continental scale there are significant differences in crustal models, meaning large uncertainties in corrections for isostatic topography. In east Africa, multiple seismic experiments have provided firm constraints on crustal and mantle structure. Tomographic images illuminate a broad (c. 500 km wide) low-velocity region in the upper mantle, with possible connection to the African Superplume in the lower mantle. These observations, alongside the variations in radial anisotropy, strongly suggest that the mantle flow field contributes significantly to the uplift of the region. Beneath southern Africa, low velocities are observed near the base of the continental lithosphere; the depth to transition zone discontinuities however suggests that they are not linked to the superplume beneath. It is thus less clear what role the sublithospheric mantle plays in supporting the region's high topography. Many of Africa's secondary topographic features (e.g. Atlas, Hoggar, Bie Dome) are underlain by slow velocities at depths of 100–150 km and are adjacent to rapid changes in lithospheric thickness. Whether these variations in lithospheric structure promote small-scale convection or simply guide the larger-scale mantle flow field remains ambiguous.

Description: Two lava flows with interbedded palaeosols outcrop c. 40 km SW of Mount Kenya, near the Amboni River north of Mweiga, Kenya along the Nyeri/Thompson Falls Road, at 0°18'S; 37°48'E. These flows, overlain by loess, are principally trachyandesite and form the base of the Mount Kenya Volcanic Series which, in the early literature, is described as being of probable Miocene/Pliocene age. Here we report 39Ar/40Ar dates (c. 5.2–5.5 Ma) and reversed magnetizations which establish a Latest Miocene to Earliest Pliocene age for these flows. Weathering characteristics of palaeosols interbedded with the lavas indicate generally dry climatic conditions during the Late Miocene, punctuated with humid events during the Pliocene and Quaternary. These Late Miocene–Quaternary palaeosols depict a relatively long and complex weathering history, followed by loess deposition. The palaeosols appear to have been episodically deflated, initially in phase with the deposition of lavas when surfaces were devoid of vegetation and later during periods of climatic deterioration when wind systems intensified. Such weathering histories within palaeosol profiles are also documented on nearby Mount Kenya, where well-weathered lower palaeosol horizons developed on Matuyama-age tills are overlain by much younger less-weathered horizons developed on Brunhes-age loess. The geochronology of Late Miocene lavas reported here provides maximum ages for weathering histories of palaeosols formed in a xeric tropical highland climate.

Description: High-energy seismicity is historically recorded in Tripolitania, Libya suggesting that this area, far from Mediterranean convergent margin, is currently deforming. How this deformation relates to surrounding tectonics of the Africa-Europe convergence is still poorly known. Here, we use remote sensing image analysis and structural survey to show the recent deformation history that affected Tripolitania and reactivated the western bordering structures of Sirte Basin. This tectonic regime onset long after the Paleocene–Oligocene deformation correlated to the Hellenic subduction evolution (Libyan tectonics have been quiescent since then) and is compatible with age and trends of the Sicily Channel rift zone, a deformational belt that developed across the Maghrebian chain. We show that the continuity of this belt reaches farther than that previously acknowledged, as far as c. 1400 km from the collisional front. We speculate on the causes of deformation in this remote area, suggesting that the extensional belt formed in response to the strong slab-pull gradients at the central Mediterranean subduction margin which followed the progressive closure of the oceanic basin.

Description: Taiwan and the Southern Alps of New Zealand are both young transpressive orogens characterized by rapid uplift and exhumation, high heat flow and vigorous surface processes. However, the distribution of heat flow, hot springs and veins in the two orogens is different. Taiwan has higher heat flow, distributed hot springs and localized veining. The Southern Alps has a narrow heat-flow anomaly, localized warm springs and widespread veining. Both orogens have two fluid-flow systems centred about the drainage divide. Shallow topographically driven meteoric water is restricted to the top 2–4 km. Deep flow is dominated by mineralizing rock-exchanged fluids. Extensional deformation occurs in the divide region of both orogens. At depth, vertical stretching produces subhorizontal veins. At shallower levels, stretching is horizontal and veins are steep. Veins in Taiwan are rare with zones of intense veining where flow has been localized into one site during exhumation from metamorphic to near-surface conditions. Fracturing and veining of the initially weak Slate Belt rocks causes a rheological change, increasing the tensile strength and making it more prone to fracturing, thus focusing fluid flow into the same locale. More uniform rheology in the Southern Alps leads to distributed veining.

Description: For the past two decades geodetic measurements have quantified surface displacement fields for the continents, illustrating a general complexity. However, the linkage of geodetically defined displacements in the continents to mantle flow and plate tectonics demands understanding of ductile deformations in the middle and lower continental crust. Advances in seismic anisotropy studies are beginning to allow such work, especially in the Himalaya and Tibet, using passive seismological experiments (e.g. teleseismic receiver functions and records from local earthquakes). Although there is general agreement that measured seismic anisotropy in the middle and lower crust reflects bulk mineral alignment (i.e. crystallographic preferred orientation, CPO), there is a need to calibrate the seismic response to deformation structures and their kinematics. Here, we take on this challenge by deducing the seismic properties of typical mid- and lower-crustal rocks that have experienced ductile deformation through quantitative measures of CPO in samples from appropriate outcrops. The effective database of CPO and hence seismic properties can be expanded by a modelling approach that utilizes ‘rock recipes’ derived from the as-measured individual mineral CPOs combined in varying modal proportions. In addition, different deformation fabrics may be diagnostic of specific deformation kinematics that can serve to constrain interpretations of seismic anisotropy data from the continental crust. Thus, the use of ‘fabric recipes’ based on subsets of individual rock fabric CPO allows the effect of different fabrics (e.g. foliations) to be investigated and interpreted from their seismic response. A key issue is the possible discrimination between continental crustal deformation models with strongly localized simple-shear (ductile fault) fabrics from more distributed (‘pure-shear’) crustal flow. The results of our combined rock and fabric-recipe modelling suggest that the seismic properties of the middle and lower crust depend on deformation state and orientation as well as composition, while reliable interpretation of seismic survey data should incorporate as many seismic properties as possible.

Description: First-order splay faults are secondary faults that form at acute angles to the primary fault when the latter becomes critically misaligned with the direction of maximum principal stress. They are first order in the sense that their slip rate is of the same order as their primary fault. First-order splay faults have been previously described for strike-slip faults and examples are here shown of first-order dip-slip splay faults. For dip-slip faults in sedimentary sequences, friction is often anisotropic, being lower parallel to, rather than oblique to, bedding, and the position of the primary fault is often controlled by a décollement guided by a layer of particularly low friction or a structural feature. In this latter situation, the primary fault may become frictionally misaligned with the direction of maximum principal stress and first-order splay faults may then form. Examples shown are megasplays in subduction zones, ramp faults in fold and thrust belts, and synthetic and antithetic splays of low-angle normal faults.

Description: The Nanga Parbat Massif (NPM), Pakistan Himalaya, is an exhumed tract of Indian continental crust and represents an area of active crustal thickening and exhumation. While the most effective way to study the NPM at depth is through seismic imaging, interpretation depends upon knowledge of the seismic properties of the rocks. Gneissic, ‘mylonitic’ and cataclastic rocks emplaced at the surface were sampled as proxies for lithologies and fabrics currently accommodating deformation at depth. Mineral crystallographic preferred orientations (CPO) were measured via scanning electron microscope (SEM)/electron backscatter diffraction (EBSD), from which three-dimensional (3D) elastic constants, seismic velocities and anisotropies were predicted. Micas make the main contribution to sample anisotropy. Background gneisses have highest anisotropy (up to 10.4% shear-wave splitting, AVs) compared with samples exhibiting localized deformations (e.g. ‘mylonite’, 4.7% AVs; cataclasite, 1% AVs). Thus, mylonitic shear zones may be characterized by regions of low anisotropy compared to their wall rocks. CPO-derived sample elastic constants were used to construct seismic models of NPM tectonics, through which P-, S- and converted waves were ray-traced. Foliation orientation has dramatic effects on these waves. The seismic models suggest dominantly pure-shear tectonics for the NPM involving horizontal compression and vertical stretching, modified by localized ductile and brittle (‘simple’) shear deformations.

Description: This paper presents the background for the calculation of physical properties of an aggregate from constituent crystal properties and the texture of the aggregate in a coherent manner. Emphasis is placed on the important tensor properties of 2nd and 4th rank with applications in rock deformation, structural geology, geodynamics and geophysics. We cover texture information that comes from pole figure diffraction and single orientation measurements (electron backscattered diffraction or EBSD, electron channelling pattern, Laue pattern, optical microscope universal-stage). In particular, we provide explicit formulae for the calculation of the averaged tensor from individual orientations or from an orientation distribution function (ODF). For the latter we consider numerical integration and an approach based on the expansion into spherical harmonics. This paper also serves as a reference paper for the mathematical tensor capabilities of the texture analysis software MTEX, which is a comprehensive, freely available MatLab toolbox that covers a wide range of problems in quantitative texture analysis, for example, ODF modelling, pole figure to ODF inversion, EBSD data analysis and grain detection. MTEX offers a programming interface which allows the processing of involved research problems as well as highly customizable visualization capabilities; MTEX is therefore ideal for presentations, publications and teaching demonstrations.

Description: Large parts of the mantle wedge near subduction boundaries are likely to be hydrated and contain antigorite. This mineral is acoustically highly anisotropic and potentially has a strong influence on seismic properties of the wedge. The Higashi–Akaishi body of SW Japan is an exhumed sliver of partially serpentinized forearc mantle, ideal for studying the effects of antigorite on the development of tectonic fabrics in the mantle. Samples with less than 1% antigorite show strong B-type olivine crystallographic preferred orientation (CPO) patterns. In contrast, samples with 〉10% antigorite deformed during the same tectonic event show much weaker olivine CPO patterns lacking the flow-normal a-axis concentration. These microstructural data suggest that the development of antigorite during deformation weakens olivine CPO due to phase boundary slip and associated rigid-body rotation of olivine grains. Antigorite and similar sheet silicates are likely to be present to some extent in the mantle wedge of all convergent margins. Our results suggest that even if this amount is only a few percent, strong olivine CPO is unlikely to develop and any pre-existing CPO is likely to be destroyed. Under these conditions, olivine CPO is unlikely to contribute significantly to seismic anisotropy in the mantle wedge.

Description: The relationships between elastic wave velocities and petrofabrics were studied in two antigorite-bearing serpentinite mylonites. Rock samples with antigorite content of 37 and 80 vol% were collected from the Happo ultramafic complex, Central Japan. Compressional and shear-wave velocities were measured by the pulse transmission technique at room temperature and confining pressures of up to 180 MPa. Petrofabrics were examined by optical microscopy and scanning electron microscopy with electron backscattered diffraction (SEM-EBSD). Olivine a- and c-axes are weakly oriented perpendicular to the foliation and parallel to the lineation, respectively. Antigorite b- and c-axes are distinctly oriented parallel to the lineation and perpendicular to the foliation, respectively. Both samples show strong anisotropy of velocity. The compressional wave velocity is fastest in the direction parallel to the lineation, and slowest in the direction perpendicular to the foliation. The shear wave oscillating parallel to the foliation has higher velocity than that oscillating perpendicular to the foliation. As the antigorite content increases, the mean velocity decreases but both azimuthal and polarization anisotropies are enhanced. Measured velocities were compared with velocities calculated from petrofabric data by using Voigt, Reuss and Voight-Reuss-Hill (VRH) averaging schemes. All averaging schemes show velocity anisotropy qualitatively similar to measurements. There are large velocity differences between Voigt and Reuss averages (0.7–1.0 km/s), reflecting the strong elastic anisotropy of antigorite. Measured velocities are found between Reuss and VRH averages. We suggest that the relatively low velocity is due to the platy shape of antigorite grains, the well-developed shape fabric and their strong elastic anisotropy. The configuration of grains should be an important factor for calculating seismic velocities in an aggregate composed of strongly anisotropic materials, such as sheet silicates.

Description: Anhydrite-rich layers within foreland fold and thrust belts are frequently observed to be the weakest horizon of the sequence. Characterizing the microstructure of anhydrite is therefore important for interpreting the larger-scale deformation history of these rocks. Two microstructures from naturally deformed, fine-grained (〈15 µm mean grain size) anhydrite samples from the Triassic Evaporites of the Umbria–Marche Apennines, Italy were analysed using electron backscatter diffraction (EBSD). Microstructural observations, misorientation analysis and crystallographic preferred orientation (CPO) determination were carried out on these samples. Both samples have a CPO characterized by alignment of 〈001〉 and distribution of 〈100〉 and 〈010〉 on a great circle normal to this. This anhydrite 〈001〉 ‘fibre texture’ has not been described before. Microstructure A is characterized by a moderate to weak CPO and a weak shape preferred orientation at 55° to 70° from the trace of the 〈001〉 maximum. Low-angle boundaries are revealed by misorientation analysis. A change in grain size from c. 10 to c. 7 µm corresponds to reduction in strength of CPO and reduction in the number of low-angle grain boundaries. Microstructure B is characterized by a very strong CPO. The orientation of the CPO changes between different microstructural domains. The 〈001〉 maximum is always perpendicular to the trace of a strong grain elongation and high-angle grain boundaries have misorientations close to 〈001〉, suggesting that the CPO is geometrically controlled: anhydrite grains are platy with 〈001〉 short axes. The origin of the CPO is therefore unclear but it need not relate to dislocation creep deformation. Whether or not CPO relates to dislocation creep, both samples have a high number of lower-angle grain boundaries and internal grain distortions with 〈010〉 and 〈001〉 misorientation axes. These are indicative of dislocation activity and the data are best explained by slip on either (100)[010] (dominant) and (001)[100] or a combination of these. Neither of these slip systems has been recognized before. Both microstructures are interpreted to have undergone dynamic recrystallization, and the weakening of the CPO with decreasing grain size in microstructure A is suggested to be indicative of a grain-boundary sliding mechanism becoming active. Comparison with experimental data shows that creep mechanisms involving dislocations at the observed grain sizes require the differential stress magnitudes driving deformation to be greater than c. 100 MPa.

Description: A description of the systematic errors associated with the measurement of the vorticity number from poryhroclasts in natural systems is presented and discussed. We show that strong biases and systematic errors could derive both from some erroneous physical (i.e. no slip across clast/matrix boundary, homogeneity within the matrix) as well as geometrical assumptions (i.e. the radius ratio and angular measurements carried out in two dimensions on outcrop surfaces and thin section). By comparing natural datasets of porphyroclast shape preferred orientation (SPO) with different theoretical curves plots, we suggest that at least one of the Jeffery physical assumptions can be tested when applying vorticity techniques. The comparison of different possible sources of systematic errors indicates that, for medium-to-low vorticity numbers (Wm〈0.8), vorticity data are strongly biased and that a minimum systematic error of 0.2 should be taken into account. Finally, we use data from natural shear zones from the Southern Variscan Belt in Sardinia to test and discuss the starting assumptions of the Jeffery model.

Description: This paper extends previous work by us to gain a fuller appreciation of the physical factors that affect polycrystal diffusion-creep simulations of fibrous pressure-shadow growth around a pyrite inclusion. The earlier work dealt with the effect of diffusion ratio or diffusional conductance of the inclusion/matrix interface. The new work also examines the effects of inclusion geometry: a smaller inclusion of similar smoothness to the original, a regularly serrated inclusion the same size as the original and a coarse irregular inclusion of the same size. The results show: (1) significant enhancement of fibrous pressure-shadow growth and change of matrix strain pattern with decreased inclusion size, similar to an increase in diffusion ratio; (2) approach towards a maximum fibrous pressure-shadow growth at high diffusion ratios in the small-pyrite model; (3) little influence of the model serrations; (4) significant sliding on the interface at low diffusion ratios in all of the models; and (5) enhanced sliding in the irregular-pyrite model at low diffusion ratios. The results are qualitatively consistent with diffusion creep of a single grain interacting with a deforming medium. They demonstrate factors that may influence development of the natural structures under similar conditions in rocks.

Description: Extreme grain-size reduction due to cataclasis, neocrystallization or phase change results in a switch to diffusion creep and dramatic weakening in deforming rocks. Grain growth increases strength until dislocation creep becomes a significant deformation mechanism. We quantify the ‘lifetime’ of diffusion creep by substituting the normal grain growth law into the diffusion creep flow law to calculate the time taken for dislocation creep to become significant. Stress-temperature and strain-rate-temperature space is outlined where diffusion creep may accommodate significant strain: these regions have an upper temperature limit beyond which grain growth is fast enough to move the rock quickly into the dislocation creep field. For plagioclase the limit lies in the amphibolite facies. Rocks in a mantle upwelling experience grain-size reduction during phase changes. Pressure-dependent grain growth limits the deformation that can be accommodated by diffusion creep. This time limit and associated strain limit is independent of starting grain size with a small dependence on upwelling rate and plume width. In both these tectonic environments, second phases are likely to play a role in the maximum achievable grain size due to grain-boundary pinning. Hence we predict the minimum lifetimes of diffusion-creep-dominated deformation following extreme grain-size reduction.

Description: The presence of two different coeval pre-flysch carbonate facies juxtaposed in numerous profiles in the southern part of the Moravian Karst proves that the Variscan nappe tectonics affected the pre-flysch basement of the main Culmian flysch nappes. Two main thrust events were recognized: (1) a ‘thin-skinned’ event, during which two sedimentary facies were juxtaposed along bedding sub-parallel thrusts, and (2) a ‘thick-skinned’ event, which generated younger thrusts oblique to bedding, involved crystalline rocks of the Brno Massif, and resulted in refolding of the older thrusts.

Description: The Pavlov Hills are formed by separated limestone blocks previously identified as klippen. A new flat-ramp-flat thrust model of the Pavlov Hills is formulated in this paper. The main tectonic detachment is located at the base of the limestone plate and other subsidiary detachments are located within the nodular limestone horizon and also at the base and top of the Upper Cretaceous deposits. The ramps are situated in the Klentnice Fm and Ernstbrunn Lst. The ramp angle was determined by structural evidence combined with interpretation of seismic profiles. Two parallel antiformal structures plunging to the NE are recognized within the study area. The antiformal fold axes are gently plunging to the NE so the anticlines are not ideal for 3-point hydrocarbon trap setting. These anticlines were subsequently cut by sinistral strike-slip faults perpendicular to the fold axis which resulted in the formation of a large-scale pseudo en-echelon structure in an approximate north–south direction.

Description: The origin of tourmaline nodules, and of their peculiar textures found in peripheral parts of the Moslava[c]ka Gora (Croatia) Cretaceous peraluminous granite are connected with the separation of a late-stage boron-rich volatile fluid phase that exsolved from the crystallizing magma. Based on field, mineralogical and textural observations, tourmaline nodules were formed during the final stage of granite evolution when undersaturated granite magma intruded to shallow crustal horizons, become saturated and exsolved a fluid phase from residual melt as buoyant bubbles, or pockets. Calculated P-T conditions at emplacement level are c. 720 {degrees}C, 70-270 MPa, and water content in the melt up to 4.2 wt%. Two distinct occurrence types of tourmalines have been distinguished: disseminated and nodular tourmalines. Disseminated tourmaline, crystallized during magmatic stage, is typical schorl while nodular tourmaline composition is shifted toward dravite. The increase of dravite in nodular tourmaline is attributed to mixing of the fluid phase from the residual melt with fluid from the wall rocks. The pressure decrease and related cooling at shallow crustal levels can be considered as a major factor controlling fluid behaviour, formation of a volatile phase, and the crystallization path in the Moslava[c]ka Gora granite body.

Description: This paper presents a tool for analysing the element distribution and mineralization intensity. The Hurst exponents and a-f(a) multifractal spectrum are utilized to analyse the irregular element distribution in Shizishan skarn orefield, China. The Hurst exponents reveal the Cu, Ag, Au and Zn distributions in the skarn-dominated drill cores are persistent and those in marble-dominated drill core are nearly random; the persistence indicates the mineralized segments are repeatedly developed, with accordance to multi-layer structure of the ore-controlling bedding faults and orebodies. The small amin (minimum multifractal singularity) of the Cu, Ag and Au in M1 reflect bare mineralization. The amin also displays that the mineralization intensities are varied for distinct elements and for different locations, yet the similarity of the distinct ore-forming processes is manifested by constant amin/f(amin) ratio. The constant ratio indicates the wider mineralization range denotes a more compact concentration distribution. The compact distributions represent the wide Cu, Ag and Au mineralization in skarns, and the loose distributions reflect the bare Cu, Ag and Au mineralization in marbles. Moreover amin shows a positive correlation with Hurst exponents in the Shizishan skarn orefield. Using fractal analysis the author's show that although the mineralization intensities for different elements and different locations along the Shizishan skarn orefield is not consistent, similar mineralization processes can be correlated to similar fractal exponents.

Description: A giant rockslide occurred on the southern side of an Upper Tertiary shield volcano in central Nicaragua in the Holocene. The failure caused tectonic-like deformation of rock masses and changed the local stress regime. The lower, compressional part of the rockslide produced a stress field with the axis of maximum stress (s1) parallel to the displacement vector of the main body. The upper part of the rockslide was gravity-driven with s1 vertical and s3 horizontal, and oriented SE–NW. The mass tended to move SE. In the crown, the stress field had a subvertical s1 steeply dipping towards the west. Data at the base of the Santa Lucia Depression, where east- and west-dipping reverse and thrust faults developed, showed that the compressional stress, s1, was nearly horizontal and east–west oriented, the horizontal s2 was north–south oriented, and the s3 was subvertical. These compressional conditions resulted from the collapse of the crown after the main slope failure phase. Simultaneously, along with the gravity relaxation of the main displaced mass, the slopes and mountain slopes along the main scarp depression underwent deep-seated sliding, sagging and flowing.

Description: Catastrophic deep-seated landslides (DSL) are generally considered to be the result of large slope deformations also known as deep-seated gravitational slope deformation (DSGSD). This paper aims to build a synthesis of multiple studies made in the Tinée Valley (southern French Alps) to assess the geometrical, kinematical, mechanical and chronological relationships between these two gravitational processes.At the scale of the valley, data issued from geological, geomorphological and 10Be dating indicate a clear geometrical link between DSGSD and DSL occurring at the base of the slope and suggest that gravitational slope evolution began after the glacial retreat (13 ka BP). This is supported by the example of the well-documented La Clapière slope. A continuous evolution process is characterized geometrically and temporally from geomorphic observations and analogue modelling. Coupling structural, geomorphological, physical and chronological studies allowed us to propose a four-dimensional (4D) deformation model mechanically correlated with progressive failure concept. The validity and variability of this reference site are discussed at the valley scale (taking Isola and Le Pra slope deformation as examples).It allows a rough estimation of the state of slope deformation at the valley scale to be constructed and the slope evolution with time to be considered. This 4D model could then be considered as a reference for other deep-seated gravitational slope deformations in comparable Alpine valleys.

Description: Coastal areas have been prime locations for habitation and commerce. Early authors such as Pausanias (second century CE), and Strabo (64 or 63 BCE–24 CE) noted the impacts of shoreline changes. Geomorphological and subsurface geological data, combined with archaeological excavation and ancient texts, indicate a long interplay between natural processes of estuarine infilling by sediments from the Küçük Menderes River (ancient Cayster River) and multiple attempts of human intervention to preserve the harbours of Ephesus. Strabo noted that harbour engineering efforts there, such as the construction of a mole to prevent siltation, instead created a sediment trap that made things worse. The pre-Holocene river valley was inundated by Holocene sea-level rise that formed the ancient Gulf of Ephesus. Extensive palaeogeographical studies, based on sediment coring, geomorphology, archaeology and history, have provided details of the problems the inhabitants faced in keeping vital harbours in operation. Dating and analysis of sedimentary deposits has allowed the description of shifting river courses, floodplain changes, human intervention, and anthropogenic deposits at Ephesus. During and following Classical times sediment deposition rapidly began to fill in the embayment, requiring the inhabitants to regularly shift the harbours westward. Ultimately, it was to no avail.

Description: Åknes is an active complex large rockslide of approximately 30–40 Mm3 located within the Proterozoic gneisses of western Norway. The observed surface displacements indicate that this rockslide is divided into several blocks moving in different directions at velocities of between 3 and 10 cm year-1. Because of regional safety issues and economic interests this rockslide has been extensively monitored since 2004.The understanding of the deformation mechanism is crucial for the implementation of a viable monitoring system. Detailed field investigations and the analysis of a digital elevation model (DEM) indicate that the movements and the block geometry are controlled by the main schistosity (S1) in gneisses, folds, joints and regional faults. Such complex slope deformations use pre-existing structures, but also result in new failure surfaces and deformation zones, like preferential rupture in fold-hinge zones.Our interpretation provides a consistent conceptual three-dimensional (3D) model for the movements measured by various methods that is crucial for numerical stability modelling. In addition, this reinterpretation of the morphology confirms that in the past several rockslides occurred from the Åknes slope. They may be related to scars propagating along the vertical foliation in folds hinges. Finally, a model of the evolution of the Åknes slope is presented.

Description: Specialists and the general public alike are very aware of human impacts on our environment. Climate change, deforestation, desertification, soil erosion and other topics are currently much in the news, but human influence on the environment is not a new phenomenon. Geoarchaeologists study the traces of human interactions with the geosphere dating back to ancient times, as well as up to and in the present. Geoarchaeological investigations provide the key to recognizing landscape and environmental change within a region, as well as reconstructing ancient landscapes and palaeoclimatic regimes. Such an interdisciplinary approach makes it possible to interpret the ways that humans affect the geosphere, through such things as subsistence and resource exploitation activities, settlement location, and local and regional land-use patterns. This approach also allows us to determine the effects of environmental change on human societies. For millennia, humans have been coping with, or provoking, environmental change. We have exploited, extracted, over-used but also in many cases nurtured the resources that the geosphere offers. In the geoarchaeological perspective, human life has never been separate from nature. Geoarchaeology can thus provide a more inclusive and longer-term view of human–geosphere interactions, and serve as a valuable aid to those who try to determine sustainable policies for the future.

Description: Measurements of d13C and d18O values of the riverine tufa samples dated by the accelerating mass spectrometry-14C method have been used for discussion of land-cover change in the catchment area of the Xiangshui River, SW China during the late Holocene. The results show that tufa was deposited in this short river only between c. 4280 and c. 110 years BP. Based on the characteristics of d13C values of the complete tufa profile in the river, three stages of land-cover conditions in the headwater area could be identified. The earliest, Stage I, contained the most extensive vegetation cover with mainly C3 plants, as shown by the lightest d13C value, whereas the latest, Stage III, had the least land cover, reflected by the heaviest d13C value. By comparison of speleothem and historical records, it was found that the land cover in Stage I was controlled mainly by climate change, whereas the land-cover changes in the later two stages were most probably related to major human disturbance (land use), especially since the Qin Dynasty and Ming Dynasty, in the headwater area of the river.

Description: Despite agreement on first-order features and mechanisms, critical aspects of the origin and evolution of the Tibetan Plateau, such as the exact timing and nature of collision, the initiation of plateau uplift, and the evolution of its height and width, are disputed, untested or unknown. This book gathers papers dealing with the growth and collapse of the Tibetan Plateau. The timing, the underlying mechanisms, their interactions and the induced surface shaping, contributing to the Tibetan Plateau evolution are tightly linked via coupled and feedback processes. We present interdisciplinary contributions allowing insight into the complex interactions between lithospheric dynamics, topography building, erosion, hydrological processes and atmospheric coupling. The book is structured in four parts: early processes in the plateau formation; recent growth of the Tibetan Plateau; mechanisms of plateau growth; and plateau uplift, surface processes and the monsoon.

Description: We present a review and synthesis of the tectonic geomorphology along the eastern margin of the Tibetan Plateau adjacent to and north of the Sichuan Basin. Re-evaluation of spatial variations in the form of fluvial longitudinal profiles provides a refined image of the distribution of anomalously steep channels. Three new analyses demonstrate that these variations in channel steepness reflect variations in the locus and rate of differential rock uplift. First, measurements of channel width along trunk streams reveal systematic co-variations in channel hydraulic geometry and slope that suggests channels are dynamically adjusted to spatial variations in erosion rate. Second, recent determinations of the functional relationship between channel steepness indices and erosion rate allow a quantitative estimation of erosion rate from channel profile form. Third, comparison of rock uplift patterns to variations in the distribution of slip associated with the 2008 Wenchuan earthquake confirms that channel gradients reflect differential rock uplift. Our analysis suggests that reactivated fault systems adjacent to the Sichuan Basin are primarily responsible for accommodating differential rock uplift, but that rock uplift northward along the margin is not associated with active faults and is likely sustained by flow and thickening in the deep crust.

Description: The youngest deformation structures on the Tibet Plateau are about NNE-trending grabens. We first combine remote-sensing structural and geomorphological studies with structural field observations and literature seismological data to study the Muga Purou rift that stretches at c. 86°E across central Tibet and highlight a complex deformation field. ENE-striking faults are dominated by sinistral strike–slip motion; NNE-striking faults have normal kinematics and outline a right-stepping en-echelon array of grabens, also suggesting sinistral strike–slip; along NW-striking fault sets, the arrangement of grabens may indicate a dextral strike–slip component. Thus, in central Tibet, rifts comprise mostly grabens connected to strike–slip fault zones or are arranged en-echelon to accommodate sinistral wrenching; overall strain geometry is constrictional, in which NNE–SSW and subvertical shortening is balanced by WNW–ESE extension. The overwhelmingly shallow earthquakes only locally outline active faults; clusters seem to trace linkage or propagation zones of know structures. The earthquake pattern, the neotectonic mapping, and the local fault–slip analyses emphasize a distributed, heterogeneous pattern of deformation within a developing regional structure and indicate that strain concentration is weak in the uppermost crust of central Tibet. Thus, the geometry of neotectonic deformation is different from that in southern Tibet. Next, we use structural and palaeomagnetic data along the Zagaya section of southern central Tibet to outline significant block rotation and sinistral strike–slip SE of the Muga Purou rift. Our analysis supports earlier interpretations of reactivation of the Bangong–Nujiang suture as a neotectonic strike–slip belt. Then, we review the existing and provide new geochronology on the onset of neotectonic deformation in Tibet and suggest that the currently active neotectonic deformation started c. 5 Ma ago. It was preceded by c. north–south shortening and c. east–west lengthening within a regime that comprises strike–slip and low-angle normal faults; these were active at c. 18–7 Ma. The c. east-striking, sinistral Damxung shear zone and the c. NE-trending Nyainqentanghla sinistral-normal detachment allow speculations about the nature of this deformation: the ductile, low-angle detachments may be part of or connect to a mid-crustal décollement layer in which the strike–slip zones root; they may be unrelated to crustal extension. Finally, we propose a kinematic model that traces neotectonic particle flow across Tibet and speculate on the origin of structural differences in southern and central Tibet. Particles accelerate and move eastwards from western Tibet. Flow lines first diverge as the plateau is widening. At c. 92°E, the flow lines start to converge and particles accelerate; this area is characterized by the appearance of the major though-going strike–slip faults of eastern-central Tibet. The flow lines turn southeastward and converge most between the Assam–Namche Barwa and Gongha syntaxes; here the particles reach their highest velocity. The flow lines diverge south of the cord between the syntaxes. This neotectonic kinematic pattern correlates well with the decade-long velocity field derived from GPS-geodesy. The difference between the structural geometries of the rifts in central and southern Tibet may be an effect of the basal shear associated with the subduction of the Indian plate. The boundary between the nearly pure extensional province of the southern Tibet and the strike–slip and normal faulting one of central Tibet runs obliquely across the Lhasa block. Published P-wave tomographic imaging showed that the distance over which Indian lithosphere has thrust under Tibet decreases from west to east; this suggests that the distinct spatial variation in the mantle structure along the collision zone is responsible for the surface distribution of rift structures in Tibet.Supplementary material: Containing supporting data is available at http://www.geolsoc.org.uk/SUP18446.

Description: The metamorphic conditions and the age of thermal overprint were determined in metapelites, metaarenites and metabasites of the Tethyan Himalayan Sequence (THS) in SE Tibet using Kübler Index and vitrinite reflectance data and applying thermobarometrical (Thermocalc and PERPLEX) and geochronological methods (illite/muscovite K–Ar and zircon and apatite (U–Th)/He chronology). The multiple folded thrust pile experienced a thermal overprint reaching locally peak conditions between the diagenetic stage (c. 170 °C) and the amphibolite facies (c. 600 °C at 10 kbar). Burial diagenesis and heating due to Early Cretaceous dyke emplacement triggered the growth of illite in the metapelites. Eocene collision-related peak metamorphic conditions have been reached at c. 44 Ma. During collision the different tectonic blocks of the THS were tectonically buried to different structural levels so that they experienced maximum greenschist to amphibolite facies metamorphism. Later, during Oligocene to Miocene times the entire THS underwent anchi- to epizonal metamorphic conditions, probably associated to continuous deformation in the flysch fold-thrust-system. This period terminated at c. 24–22 Ma. Adjacent to the north Himalayan metamorphic domes, the base of the THS was metamorphosed during Miocene times (c. 13 Ma). Post-metamorphic cooling below c. 180 °C lasted until Late Miocene and took place at different times.

Description: The Late Quaternary geomorphology and stratigraphy of the Big Fork River valley, within the Rainy River basin of northern Minnesota, reveals evidence of prehistoric human interaction with late Holocene riverine environments. By 11 000 14C BP, deglaciation made the region inhabitable by human groups using Clovis artefacts. Human habitation would also have been possible during the Moorhead low-water stage of glacial Lake Agassiz, starting at 10 500 14C BP. Near its confluence with the Rainy River, the valley floor of the Big Fork valley consists of a floodplain complex and two terraces. The multi-component stratified Hannaford site is situated within the active floodplain. Overbank deposits contain artefacts in primary context, whereas artefacts within the point bar deposits are in secondary archaeological context; these deposits are associated with changing alluvial settings as the river moved eastward. Aggradation of the valley fill beneath the lowest surface (T0, floodplain complex) began by 3000 years ago and is associated with human activities focused on seasonal fishing and the use of riparian resources from 1300 to 650 14C BP.

Description: Low-velocity zones (‘bright spots’) imaged by the INDEPTH seismic experiment in southern Tibet are extensively interpreted as widespread partial melt within the crust, which has given a strong support for the channel flow model. These suggest that a continuous seismic low-velocity zone underlies Tibet on the large scale. Here we take advantage of the Hi-CLIMB seismic experiment which includes a dense south–north profile and a lateral 2D seismic network to assess the vertical and the horizontal extension of low-velocity zones in southern Tibet. Several approaches including migration, amplitude analysis and waveform inversion of receiver functions are performed to detect crustal low-velocity zones using this new seismological dataset. Our results reveal localized and discontinuous low-velocity zones in Tibet. They indicate that the vertical extension of the low-velocity zones is about 10 km, and their maximum horizontal length appears to be c. 50 km. Our study suggests a partial correlation between the location of these low-velocity zones and the spatial distribution of Tibetan grabens. These results, especially the non-continuity of low-velocity zones, together with the observed regular value of mean crustal VP/VS ratio, question the existence of widespread partial melt of the southern Tibetan crust and, therefore, the viability of the channel flow model.

Description: We present a synthesis of the tectonic and thermochronological evolution of the Eastern Tibet since the Triassic. The long-term cooling histories obtained on magmatic and metamorphic rocks of the South Songpan-Garzê, Kunlun and Yidun blocks are similar showing a very slow and regular cooling during Late Jurassic and Cretaceous, confirming the suspected lack of major tectonic events between c. 150 and 30 Ma. The exhumation linked to the Tertiary growth of the Tibetan Plateau initiated around 30 Ma and concentrates at the vicinity of the major tectonic structures. Exhumation rates increased again from about 7 Ma in the Longmen Shan.To interpret this very slow cooling rate between Late Jurassic and Early Cenozoic from granites of this area, we use a simple 1D thermal model that takes into account the thermal properties of both sediments and crust. The results suggest that: (1) high temperature (500 °C) can be kept over a long period of time; (2) during Cretaceous, cooling is mostly controlled by the thermal properties of sediments of continental origin; and (3) the initial Late Triassic rapid cooling rate was caused by the large thermal contrast between the granite body and the sedimentary rocks rather than by a high exhumation rate.

Description: The mechanical and chemical effects of lichens on the outer and inner surfaces of tafoni features were investigated through a multidisciplinary approach at two locations (Oasi 74°42'S, 164°07'E, 40–250 m a.s.l.; Mount Keinath, 74°32'S; 163°58'E; 850 m a.s.l.) close to the Italian Antarctic station (Mario Zucchelli). Outer tafoni roof surfaces show low values of effective porosity coupled with pervasive hyphal penetration and an extensive reddish-brown weathering rind. Inner tafoni surfaces show higher values of effective porosity, which correspond with an almost absent weathering rind and low hyphal penetration. Our observations indicate that: (a) iron oxy-hydroxides, particularly concentrated where hyphal patches and bundles contact biotite, consist of hematite; (b) the microcosms of lichen hyphae and their precipitates fill voids to form case hardening on outer surfaces; and (c) on inner surfaces biological action is less active, most likely because of more intense thermal stress and salt action.

Description: Stratified slope deposits occur on or at the base of slopes within a wide range of hilly or mountainous environments. Gelifraction, a lack of vegetation, and snowmelt-derived slopewash are thought to be important factors in their development. The relatively fine-grained grèzes litées found at many sites within the French Charente region are the prototype of this kind of deposit. The original, strictly limited and genetically intended definition has been enlarged by mainly non-French authors causing considerable confusion.Other assemblages of cold-climate slope deposits are more heterogeneous, sometimes less clearly stratified, and show much larger variation in grain sizes and sedimentary structures than grèzes litées. The most important of these are stone-banked solifluction (sheets or lobes), rock fall, (dry) grain flow, frost-coated clast flow, debris flow, snow avalanching and, to a lesser degree, rain-generated overland flow and (niveo-) aeolian activity. Many of these processes are azonal and occur under a wide range of environmental conditions. A periglacial context may nevertheless influence process activity in these cases, for instance with regard to their magnitude and/or frequency.

Description: This review concentrates on the characteristics of wind processes and products in cold lowland deserts. Its main aims are: to show how difficult it can be to separate wind-generated from water-generated processes and features without detailed study of lamination types; to suggest cold aeolian interpretations for some ancient pre-Quaternary rocks; and to encourage students to revisit many ancient deposits with such interpretations in mind. Although upper Quaternary and Recent cold-climate aeolian deposits have been studied for many years there are very few older examples described. Martian features are included since Mars is now one of the most exciting areas of study for geologists.

Description: Indian Ocean crust subducted northwards at the Banda Trench from about 12 to 4 Ma. The Australian continental margin collided with the Asian fore-arc at about 4 Ma. Gradually the Banda Trench was transformed into the fold and thrust mountains of Timor Island. Tectonic collision processes developed when all ocean crust had been subducted and Australian continental crust was refused entry to the subduction path below the Asian fore-arc. The Banda Trench was then gradually converted into a Tectonic Collision Zone (TCZ) progressively filled by two highly deformed Australian continental upper crust mega-sequences. Slowing subduction of Australian sub-crustal lithosphere after c. 2.5 Ma led to uplift of the TCZ that raised Timor 3 km above sea level. Asian Banda fore-arc deformation is linked to c. 30 km southeastwards rollback of the subducting Australian mantle lithosphere. Two Asian fore-arc nappes were thrust southwards from the Banda fore-arc onto the older of two highly deformed Australian continental margin upper crust mega-sequences. The Wetar Suture was created as a thrust at the base of Australian partially detached continental lower crust propagated into the Asian fore-arc. Re-interpretation of BIRPS seismic and gravity data for the Timor region supports this collision model.

Description: The formation process of recent gullies on Mars is currently under debate. This study aims to discriminate between the proposed formation processes – pure water flow, debris flow and dry mass wasting – through the application of geomorphological indices commonly used in terrestrial geomorphology. High-resolution digital elevation models (DEMs) of Earth and Mars were used to evaluate the drainage characteristics of small slope sections. Data from Earth were used to validate the hillslope, debris-flow and alluvial process domains previously found for large fluvial catchments on Earth, and these domains were applied to gullied and ungullied slopes on Mars. In accordance with other studies, our results indicate that debris flow is one of the main processes forming the Martian gullies that were being examined. The source of the water is predominantly distributed surface melting, not an underground aquifer. Evidence is also presented indicating that other processes may have shaped Martian crater slopes, such as ice-assisted creep and solifluction, in agreement with the proposed recent Martian glacial and periglacial climate. Our results suggest that, within impact craters, different processes are acting on differently oriented slopes, but further work is needed to investigate the potential link between these observations and changes in Martian climate.

Description: The circum north-polar Rupes Tenuis unit forms the polar-proximal basal stratigraphical and morphological units that delineate the north polar cap between 180° and 300°E. In the region of the mouth of the Chasma Boreale re-entrant, the Rupes Tenuis unit is likely to extend further southwards into the northern plains. This is suggested by the occurrence of isolated remnants that have been interpreted as basaltic shield volcanoes, maar craters or mud volcanoes in the past.As key elements of this study, we assessed the quantitative characteristics of this unit using layer attitudes derived from high-resolution images and terrain-model data, and by performing cross-correlations of prominent layers whose outcrops are observed at eight cone-like remnants. The identification and unambiguous correlation of characteristic layers across the study area provided a reasonable basis for introducing at least three additional stratigraphical subunits of the Rupes Tenuis unit. Extrapolation of altitude data indicates a gentle southward dip of remnant layers, suggesting that the unit had a much larger areal extent in Martian history. The palaeo-layer contact between two subunits of the Rupes Tenuis unit correlates well with elevation values of the Hyperborea Lingula surface. Both results disagree with an interpretation of a volcanic origin for isolated mesas but underpin that they are erosional relicts of the Rupes Tenuis unit. Average erosion rates of 2.5×10-4±4×10-5 mm year-1 are relatively high when compared to Amazonian rates but are not exceptional for areas undergoing deflation. They also corroborate the idea of aeolian denudation of the Rupes Tenuis unit.

Description: Interior layered deposits (ILDs) of the eastern Valles Marineris and adjacent chaos regions were analysed using high-resolution imagery, topography and spectral data in order to detect possible correlations. We find that ILDs are susceptible to erosion and weathering, as proven by their shapes (mesa, buttes), surface structures (pitted, fluted, yardangs), stair-stepped morphologies at different scales, and metre-sized boulders and talus. ILDs bear hydrated sulphates; consequently, we conclude that aqueous conditions dominated during their formation. Subhorizontal layering and parallel bedding of the ILDs could then indicate that deposition took place under low-energy aquatic conditions. Their superposition on chaotic terrain suggests that they are younger than chaotic terrain and, hence, younger than Late Hesperian. For the hydrated ILDs, which show polyhydrated on top of monohydrated sulphates, we think that formation within an evaporative body is not conceivable and we assume instead that a conversion of sulphates by post-formational humidity changes took place. As hydrated ILDs correlate well with rock fragmentation, we suppose that volume changes due to water content are responsible for rock fragmentation. Despite the different ILD settings, the basic conditions during sedimentation and erosion of ILDs could not have varied greatly because comparable mineralogies and morphologies are found among ILDs.

Description: Northern Ethiopia is marked by a fanning system of thrust planes with NW-dipping structures in the east and southeast-dipping in the west. The central zone of this large-scale (200 km long) structure is formed by a c. 10 km wide zone of localized strain and amphibolites facies metamorphic conditions (680 °C and 3.4 kbar) referred to as the Central Steep Zone (CSZ). The CSZ comprises a mafic rock assemblage of amphibolite, serpentinite showing ocean-floor characteristics and calc-silicate schist. A monzonite intrusion in the central part of the CSZ post-dates the deformation and is related to partial melting of the mafic rocks. Magnetic fabric measurements reveal NE-trending (043°) steep foliations in the CSZ with vertical orientation of lineation, parallel to the axes of micro-folds. This high-strain zone is interpreted as central zone of a positive flower structure on the basis of simultaneous flattening and shear movement, typical for transpressive kinematics. The CSZ has a northern continuation into the Nafka terrane of Eritrea where it can be traced over a distance of 200 km. This high-strain belt forms a major structure in the context of Arabian–Nubian Shield (ANS) collision tectonics during the closure of the Mozambique Ocean and assembly of Gondwana.

Description: Our recent geological survey of the basement of central and northern Madagascar allowed us to re-evaluate the evolution of this part of the East Africa–Antarctica Orogen (EAAO). Five crustal domains are recognized, characterized by distinctive lithologies and histories of sedimentation, magmatism, deformation and metamorphism, and separated by tectonic and/or unconformable contacts. Four consist largely of Archaean metamorphic rocks (Antongil, Masora and Antananarivo Cratons, Tsaratanana Complex). The fifth (Bemarivo Belt) comprises Proterozoic meta-igneous rocks. The older rocks were intruded by plutonic suites at c. 1000 Ma, 820–760 Ma, 630–595 Ma and 560–520 Ma. The evolution of the four Archaean domains and their boundaries remains contentious, with two end-member interpretations evaluated: (1) all five crustal domains are separate tectonic elements, juxtaposed along Neoproterozoic sutures and (2) the four Archaean domains are segments of an older Archaean craton, which was sutured against the Bemarivo Belt in the Neoproterozoic. Rodinia fragmented during the early Neoproterozoic with intracratonic rifts that sometimes developed into oceanic basins. Subsequent Mid-Neoproterozoic collision of smaller cratonic blocks was followed by renewed extension and magmatism. The global ‘Terminal Pan-African’ event (560–490 Ma) finally stitched together the Mid-Neoproterozoic cratons to form Gondwana.

Description: Structural investigations and U–Pb sensitive high-resolution ion microprobe (SHRIMP) dating of rocks from the southwestern Central Zone of the Damara Belt, Namibia, reveal that a major SE-verging deformation event (D2) occurred at between 520 and 508 Ma. During D2, SE-verging simple shear and NE–SW pure shear extension in a constrictional stress field produced recumbent, south- to SE-verging, kilometre-scale folds and ductile shear zones, a NE–SW extensional lineation and conjugate shear bands, and was coeval with granitoid emplacement and high-grade metamorphism. The timing of this event is constrained by anatectic leucosomes in D2 shear zones (511±18 Ma) and extensional shear bands (508.4±8.7 Ma) as well as by syntectonic grey granites (520.4±4.2 Ma), and is similar to ages for high-grade metamorphism in the Central Zone. An upright folding event (D3) occurred at c. 508 Ma, resulting in the formation of basement-cored fold interference domes. The timing of deformation and metamorphism at 520–508 Ma in the mid-crustal SW Central Zone contrasts with ages of 560–540 Ma for shallow crustal NW-verging folding and thrusting elsewhere in the Central Zone that was concomitant with voluminous magmatism. This magmatism led to metamorphism and anatexis of the basement and the emplacement of anatectic red granites at 539±17 to 535.6±7.2 Ma, which contain 1013±21 Ma inherited zircons. The Central Zone therefore contains a record of crustal thickening, heating of the mid-crust, exhumation and orogen-parallel extension over the life of an orogen.