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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Arctic Ocean
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Arctic region
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Invertebrata
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Vermes (1)
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Plantae
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ophiolite (1)
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framework silicates
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orthosilicates
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sheet silicates
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sulfates
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Primary terms
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absolute age (2)
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Arctic Ocean
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Arctic region
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Svalbard
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Spitsbergen (1)
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Asia
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Far East
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Japan
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Honshu
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Mino Belt (1)
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Himalayas
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Indian Peninsula
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Tamil Nadu India (1)
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Pakistan (2)
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Middle East
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Turkey
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Pontic Mountains (1)
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Atlantic Ocean
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North Sea (1)
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atmosphere (1)
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Australasia
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Australia
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Yilgarn (1)
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bitumens
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Canada
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carbon
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organic carbon (1)
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Caribbean region (1)
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catalogs (1)
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Cenozoic
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Bronze Age (1)
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Quaternary
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upper Holocene
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Roman period (1)
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Tertiary
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Neogene
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Miocene
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Paleogene
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Eocene
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middle Eocene (1)
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Oligocene (2)
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upper Cenozoic (1)
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ceramic materials (1)
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chemical analysis (1)
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Chordata
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Vertebrata
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Reptilia
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volcanic rocks
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intrusions (3)
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Invertebrata
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Vermes (1)
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isotopes
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stable isotopes
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maps (1)
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Mesozoic
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Cretaceous
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Lower Cretaceous
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Agrio Formation (1)
-
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Upper Cretaceous
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Hell Creek Formation (1)
-
-
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Jurassic
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Upper Jurassic
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Portlandian (1)
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Tithonian (1)
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-
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Triassic
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Lower Triassic (1)
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Middle Triassic
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Anisian (1)
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Ladinian (1)
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-
Upper Triassic
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Carnian (1)
-
-
-
Vaca Muerta Formation (1)
-
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metal ores
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copper ores (4)
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gold ores (4)
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lead ores (1)
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lead-zinc deposits (1)
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silver ores (2)
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zinc ores (2)
-
-
metals
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actinides
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Pu-239 (1)
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alkaline earth metals
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barium (1)
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platinum group
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ytterbium (1)
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zinc (2)
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metamorphic rocks
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cataclasites (1)
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eclogite (1)
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lapis lazuli (1)
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metasomatic rocks
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skarn (1)
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migmatites (1)
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mylonites
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metamorphism (2)
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mineralogy (1)
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Moon (1)
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noble gases
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helium
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He-3 (1)
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North America
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Appalachians
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Blue Ridge Mountains (1)
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Piedmont (1)
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Great Lakes region (1)
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Gulf Coastal Plain (1)
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Ocean Drilling Program
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Leg 120
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ODP Site 747 (1)
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oil and gas fields (2)
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orogeny (1)
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oxygen
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O-18/O-16 (1)
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paleoclimatology (1)
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paleoecology (1)
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paleogeography (1)
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Paleozoic
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Devonian
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Ordovician
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Lower Ordovician (1)
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Middle Ordovician
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Black River Group (1)
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Trenton Group (1)
-
-
Permian
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Upper Permian (1)
-
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Silurian
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Upper Silurian (1)
-
-
-
palynomorphs
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miospores
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pollen (1)
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-
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paragenesis (1)
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petroleum (3)
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petrology (2)
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Phanerozoic (1)
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phase equilibria (1)
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Plantae
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Spermatophyta
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Angiospermae (3)
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plate tectonics (5)
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sea-level changes (2)
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Andes
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Argentina
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Neuquen Basin (1)
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Bolivia (1)
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United States
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rock formations
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sedimentary rocks
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sedimentary rocks
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sediments
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clastic sediments
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silt (1)
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marine sediments (1)
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peat (1)
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soils
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soils
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Alluvial soils (1)
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SERC
Selecting the location, and the initial investigation of the SERC soft clay test bed site
Fragments of Ge-bearing lignites in poorly lithified sandstones of the Serc...
Earth, Mind, and Paper: Field Sketches as Expert Representations of the Hat Creek Fault Zone
Abstract Sketching, particularly in field settings, is a common but powerful means of communication and visualization in the geosciences. Here, we investigate the range of sketch types and annotations made by expert geoscientists and non-geoscientists during a field trip to the Hat Creek fault zone (northern California) taken during the 2013 AAPG Hedberg Research Conference. Participants (N=42) included geologists and seismic interpreters employed in the oil and gas industry (n=20), geologists employed in academia (n=16), and non-geoscientist software developers and cognitive scientists (n=6). A total of 361 sketches of the normal fault system were collected during stops at three field modules. Sketches were thematically coded by sketch type (e.g., map, perspective landscape view, cross-section, three-dimensional [3-D] block diagram) and annotation type (e.g., fault symbols, reference locations, questions, labels). Overall, two-dimensional (2-D) perspective sketches and maps were the most common representation type, whereas 3-D block diagrams were rare. Statistical analysis of code counts suggests that the choice of sketch and annotation types is largely driven by characteristics of the field trip stop and/or the particular task required. Non-geoscientists more frequently produced perspective sketches from their actual viewpoint, but were less likely to annotate diagrams. As compared to industry peers, academic geoscientists were more likely to create related sets of sketches. Conversely, industry geoscientists were more likely to explain their thinking and provide alternate explanations. This work is a first step in exploring geoscientists’ sketching practices in the field, and may have implications for both undergraduate education and industry training.
A geochemical investigation (major cations and anions, stable isotopes of oxygen and hydrogen, pH, and salinity) was conducted to identify the sources of groundwater recharge to the surficial aquifer system in Everglades National Park. The weighted mean values of δ 18 O and δD of rainfall were −2.83‰ and −10.59‰, respectively. A mean deuterium excess value of 12 suggests that evaporation of Everglades surface water contributes between 7% and 12% to the local precipitation. Most shallow groundwater in the surficial aquifer system (<28 m) is recharged throughout the year by Everglades surface water and or canal water exposed to evaporation. Recharge rates between 2 cm/yr and 12 cm/yr were obtained, with the higher rates in areas of little to no standing water. Deep groundwater in the surficial aquifer system (>28 m) is recharged directly from rainfall far upgradient of the northern boundary of Everglades National Park. Groundwater from the underlying Hawthorn Group is geochemically distinct from the surficial aquifer system and recharges the surficial aquifer system from below. There is no geochemical evidence of surface water or shallow groundwater flow between the two major waterways (Shark Slough and Taylor Slough) in Everglades National Park. In this investigation, a combination of stable isotopes (δ 18 O and δD) and major-ion data was necessary to identify different sources of groundwater recharge to the karst aquifer. The stable isotopes (δ 18 O and δD) were most useful in deciphering between rainfall and surface-water recharge to the shallow aquifer, whereas the major-ion data were used to identify recharge from deeper aquifers and seawater intrusion.
Structural variations in chrysotile asbestos fibers revealed by synchrotron X-ray diffraction and high-resolution transmission electron microscopy
Abstract While the Triassic is comparatively a tectonically quiescent period in the dynamic development of the Barents Shelf, the depositional infill was strongly influenced by structural elements and there is a marked difference between lower and middle Triassic sedimentation. Southwards-propagating uplift of north–south-orientated elements along the incipient North Atlantic margin, from the mid-Carboniferous to the Early Triassic, generated uplift, tilt and erosion of the Sørkapp–Hornsund and palaeo-Stappen highs, and the Ringsel and Selis ridges. Progressive onlap along the flanks with probably no deposition until the Ladinian, which is probably condensed/partly missing, characterized the ensuing sedimentation. Late Permian–Early Triassic uplift of the Selis Ridge was concurrent with uplift and erosion of the Capria Ridge. Both elements also experienced a phase of Anisian–Ladinian erosion. The Gardarbanken High underwent a later Early Triassic uplift and a complex, probably condensed, deposition associated with the infill of advancing deltaic systems. The Ladinian, and more dominantly the Carnian, saw even blanketing of large parts of the Barents Shelf, almost wholly unaffected by the structural elements. The most noticeable influence at the time is the thinning of the progradational system approaching the Svalbard Platform, which remained comparatively shallow, as witnessed by the lowered clinoform angle and rapid deposition.
Core complex fault rocks of the Silurian to Devonian Keisarhjelmen detachment in NW Spitsbergen
ABSTRACT A Silurian–Devonian metamorphic core complex has recently been recognized in northwest Spitsbergen, on the northwest corner of the Barents Shelf at the junction between the Atlantic and Arctic oceans. The associated Keisarhjelmen detachment, a major, ductile-brittle fault zone, is 200–500 m thick and has a map trace >150 km. A top-to-the-north transport direction is parallel to the axis of a large-scale, shallowly north-plunging, detachment corrugation. This detachment zone separates overlying faulted Silurian–Devonian aged cover strata from underlying migmatitic rocks in the core. The detachment shows a diverse array of fault and metamorphic rocks with structural ascent, ranging from sheared migmatite, mylonite, ultramylonite, foliated cataclasite, pseudotachylite, and breccia. Footwall post-kinematic granitic intrusions occurred shortly prior to, and likely during, deposition of the older cover strata. Variably deformed, syn-kinematic granitic sheets and veins within the detachment zone are considered coeval. Thin sections show significant grain size reduction, porphyroclasts, and well-developed composite fault surfaces. Relict garnet sigma porphyroclasts associated with chlorite and sericite indicate retrogression. Feldspar porphyroclasts show significant sericite alteration, undulose extinction and limited recrystallization low in the detachment, and brittle deformation throughout. Quartz deformation textures and grain size vary considerably within and between samples. Deformation during retrogression continued into the brittle realm with the development of thick foliated cataclasites, fault breccias, and local pseudotachylites concentrated at the top of the detachment. Biotite in particular shows grain size reduction, concentration along C-surfaces, and shredding and redistribution, suggesting it played a significant role in both ductile and brittle faulting. Veins, micro-veins, and fluid inclusion planes are ubiquitous throughout the detachment, indicating substantial fault-related fluid flow. Given existing geochronologic and P-T (pressure-temperature) data from the basement rocks of the area, the kinematics, retrogression, and ductile-brittle transition are consistent with exhumation of a core complex developing by orogen-parallel extension associated with transtension during the Late Silurian and Early to Middle Devonian in northwest Spitsbergen. Remaining questions include how this core complex connects with coeval plate-scale strike-slip faults in Svalbard, and its relationship to mainland Norwegian core complexes and Devonian basins to the south.
Lower Cretaceous Barents Sea strata: epicontinental basin configuration, timing, correlation and depositional dynamics
Dynamics of the Polish and Eastern Slovakian parts of the Carpathian accretionary wedge:: insights from palaeostress analyses
Abstract The arcuate Outer Carpathian accretionary wedge formed in front of the East Alpine-Carpathian-Pannonian (ALCAPA) megablock during the Eocene-Sarmatian. The wedge accreted sediments of the subducting remnants of the Carpathian Flysch Basin, a large oceanic tract left in front of the Alpine orogen. The palaeostress data for the orogenic hinterland (particularly the data related to the Early Miocene extension that was expanding towards the NE), combined with coeval subduction-related volcanism that was expanding towards the NE, indicate that the uneven roll-back of the subduction zone was the main mechanism controlling the development of the northern West Carpathian arc. The palaeostress data for the Tertiary accretionary wedge from the same time period are characterized by outward-fanning σ 1 trajectories that changed gradually during the wedge development. In contrast, the palaeostress data for the hinterland are characterized by preferred-directional stress events that changed abruptly during the wedge development. These palaeostress results are in accordance with the behaviour of the wedge and the hinterland, as the wedge behaved as a weak continuum and the hinterland behaved as a block mosaic with weak boundaries. The fault traces of the northern West Carpathian arc converge to both ends of the arc and suggest that the pre-existing basin was the factor that controlled the arc location. These fault trace patterns are asymmetric, indicating a slightly oblique overall convergence in a NE-SW direction. In accordance with this convergence, the palaeostress data for the accretionary wedge indicate that the western part of the wedge, which is characterized by NW-SE-oriented maximum principal compressional stress σ 1 , was undergoing sinistral transpression. Meanwhile, the eastern part, which is characterized by NE-SW-oriented σ 1 , was undergoing compression. Apparently, the dynamics of the accretionary wedge was further influenced by the shape of an elongated NE-SW-trending ALCAPA megablock, which was located behind the wedge and advanced in the direction of the general Early Miocene convergence during the most pronounced stages of the wedge development. This megablock served as the local indenter, as its strength surpassed that of the accretionary wedge located to its front. Further dynamic complexities were added because of the complex shape of the Magura Unit, which was located in the most proximal portion of the wedge and was stronger than the units in front of it. Wedge outcrops indicate that the large-scale shortening, which is characterized by the development of detachments and ramps, was preceded by an initial layer-parallel shortening. This is indicated by scaly fabrics and minor reverse faults that rotated into locked positions during the later accretion. Several outcrops with a wedge detachment fault indicate that there was a relatively low amount of friction during its development. The décollement zone is several hundred metres thick and shows evidence of transient fluid flow that was driven by pressure gradients. This is documented by frequent hydrofracturing, sandstone dykes and fibrous veins that opened against the weight of the whole wedge, all of which indicate cycles of higher pore fluid pressures that lowered the basal friction.