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- Volume 21, Issue 3, 2009
Basin Research - Volume 21, Issue 3, 2009
Volume 21, Issue 3, 2009
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Evolution of basin architecture in an incipient continental rift: the Cenozoic Most Basin, Eger Graben (Central Europe)
Authors Michal Rajchl, David Uličný, Radomír Grygar and Karel MachABSTRACTThe Oligo‐Miocene Most Basin is the largest preserved sedimentary basin within the Eger Graben, the easternmost part of the European Cenozoic Rift System (ECRIS). The basin is interpreted as a part of an incipient rift system that underwent two distinct phases of extension. The first phase, characterised by NNE–SSW‐ to N–S‐oriented horizontal extension between the end of Eocene and early Miocene, was oblique to the rift axis and caused evolution of a fault system characterised by en‐échelon‐arranged E–W (ENE–WSW) faults. These faults defined a number of small, shallow initial depocentres of very small subsidence rates that gradually merged during the growth and linkage of the normal fault segments. The youngest part of the basin fill indicates accelerated subsidence caused probably by the concentration of displacement at several major bounding faults. Major post‐depositional faulting and forced folding were related to a change in the extension vector to an orthogonal position with respect to the rift axis and overprinting of the E–W faults by an NE–SW normal fault system. The origin of the palaeostress field of the earlier, oblique, extensional phase remains controversial and can be attributed either to the effects of the Alpine lithospheric root or (perhaps more likely because of the dominant volcanism at the onset of Eger Graben formation) to doming due to thermal perturbation of the lithosphere. The later, orthogonal, extensional phase is explained by stretching along the crest of a growing regional‐scale anticlinal feature, which supports the recent hypothesis of lithospheric folding in the Alpine–Carpathian foreland.
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Morphology and sedimentary systems in the Central Bransfield Basin, Antarctic Peninsula: sedimentary dynamics from shelf to basin
Authors Marga García, Gemma Ercilla and Belén AlonsoABSTRACTA detailed regional characterization of the physiography, morphology and sedimentary systems of the Central Bransfield Basin (CBB) was carried out using swath bathymetry and high‐ and very high‐resolution seismic profiles. The basin margins show continental shelves with numerous glacial troughs, and continental slopes where relatively wide and flat slope platforms represent the middle domain in an atypical physiographic scenario in glaciated margins. Although the CBB is tectonically active, most of the morphologic features are sedimentary in origin, and can be classified into four sedimentary systems: (1) glacial‐glaciomarine, composed of erosional surfaces, glacial troughs, furrows and draping sheets; (2) slope‐basin, formed by trough mouth fans, slope aprons, the Gebra‐Magia instability complex and turbidity systems; (3) seabed fluid outflow system composed of pockmark fields; and (4) contourite, composed of drifts and moats. The sedimentary systems show a clear zonation from shelf to basin and their dynamics reflects the complex interplay among glacial, glaciomarine, marine and oceanographic processes involved in the entire shelf‐to‐basin sediment distribution. The CBB morphology is primarily controlled by glacial/interglacial cyclicity and physiography and to a lesser extent by tectonics and oceanography. These factors have affected the South Shetland Islands (SSI) and Antarctic Peninsula (AP) margins differently, creating a relatively starved SSI margin and a more constructional AP margin. They have also created two entire sediment‐dispersal domains: the shelf‐to‐slope, which records the glaciation history of the CBB; and the lower slope‐to‐basin, which records the imprint of local factors. This study provides a ‘source‐to‐sink’ sedimentary scheme for glaciated margins, which may be applied to the basin research in other margins, based on the characterization of sedimentary systems, their boundaries and the linkages among them. This approach proves to be adequate for the identification of global and local factors governing the CBB and may therefore be applied to other study areas.
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Distribution of Palaeozoic reworking in the Western Arunta Region and northwestern Amadeus Basin from 40Ar/39Ar thermochronology: implications for the evolution of intracratonic basins
ABSTRACTThe Centralian Superbasin in central Australia is one of the most extensive intracratonic basins known from a stable continental setting, but the factors controlling its formation and subsequent structural dismemberment continue to be debated. Argon thermochronology of K‐feldspar, sensitive to a broad range of temperatures (∼150 to 350 °C), provides evidence for the former extent and thickness of the superbasin and points toward thickening of the superbasin succession over the now exhumed Arunta Region basement. These data suggest that before Palaeozoic tectonism, there was around 5–6 km of sediment present over what is now the northern margin of the Amadeus Basin, and, if the Centralian superbasin was continuous, between 6 and 8 km over the now exhumed basement. 40Ar/39Ar data from neoformed fine‐grained muscovite suggests that Palaeozoic deformation and new mineral growth occurred during the earliest compressional phase of the Alice Springs Orogeny (ASO) (440–375 Ma) and was restricted to shear zones. Significantly, several shear zones active during the late Mesoproterozoic Teapot Orogeny were not reactivated at this time, suggesting that the presence of pre‐existing structures was not the only controlling factor in localizing Palaeozoic deformation. A range of Palaeozoic ages of 440–300 Ma from samples within and external to shear zones points to thermal disturbance from at least the early Silurian through until the late Carboniferous and suggests final cooling and exhumation of the terrane in this interval. The absence of evidence for active deformation and/or new mineral growth in the late stages of the ASO (350–300 Ma) is consistent with a change in orogenic dynamics from thick‐skinned regionally extensive deformation to a more restricted localized high‐geothermal gradient event.
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Stratigraphic evolution of the Triassic–Jurassic succession in the Western Southern Alps (Italy): the record of the two‐stage rifting on the distal passive margin of Adria
ABSTRACTThe Triassic–Lower Jurassic succession of the Southern Alps is characterized by rapid thickness changes, from an average of about 5000 m east of Lago Maggiore to about 500 m in the Western Southern Alps. The stratigraphy reflects the Triassic evolution of the Tethyan Gulf and the Early Jurassic rifting responsible for the Middle Jurassic break‐up of Adria from Europe. The succession of the Western Southern Alps starts with Lower Permian volcanics directly covered by Anisian sandstones. The top of the overlying Ladinian dolostones (300 m) records subaerial exposure and karstification. Locally (Gozzano), Upper Sinemurian sediments cover the Permian volcanics, documenting pre‐Sinemurian erosion. New biostratigraphic data indicate a latest Pliensbachian–Toarcian age for the Jurassic synrift deposits that unconformably cover Ladinian or Sinemurian sediments. Therefore, in the Western Southern Alps, the major rifting stage that directly evolved into the opening of the Penninic Ocean began in the latest Pliensbachian–Toarcian. New data allowed us to refine the evolution of the two previously recognized Jurassic extensional events in the Southern Alps. The youngest extensional event (Western Southern Alps) occurred as tectonic activity decreased in the Lombardy Basin. During the Sinemurian the Gozzano high represents the western shoulder of a rift basin located to the east (Lombardy). This evolution documents a transition from diffuse early rifting (Late Hettangian–Sinemurian), controlled by older discontinuities, to rifting focused along a rift valley close to the Pliensbachian–Toarcian boundary. This younger rift bridges the gap between the Hettangian–Sinemurian diffuse rifting and the Callovian–Bathonian break‐up. The late Pliensbachian–Toarcian rift, which eventually lead to continental break‐up, is interpreted as the major extensional episode in the evolution of the passive margin of Adria. The transition from diffuse to focused extension in the Southern Alps is comparable to the evolution of the Central Austroalpine during the Early Jurassic and of the Central and Northern Atlantic margins.
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Differential compaction due to the irregular topology of a diagenetic reaction boundary: a new mechanism for the formation of polygonal faults
Authors R. J. Davies, M. T. Ireland and J. A. CartwrightABSTRACTWe propose a new mechanism for the formation of some polygonal fault arrays. Seismically imaged opal‐A (biogenic silica) to opal‐CT (cristobalite and tridymite) diagenetic boundaries from two regions offshore of Norway have developed regular wavelength patterns. The pattern consists of cell‐shaped elevations that are 200–2600 m wide and up to 200 m high, separated by troughs. The cells represent regions that undergo diagenesis at shallower burial depths, earlier than adjacent areas. The chemical change leads to mechanical compaction and porosity reduction; therefore subsidence occurs above the cells in the overburden. Roughly circular depressions form above the cells, and a network of folds form above inter‐cell areas. Networks of normal faults form on the crests and margins of the folds as a result of flexure during the folding. The progressive lateral growth of the cells causes the depressions to widen and intervening folds to narrow resulting in new differential compaction‐induced faults to form with variable strike orientations. Lateral and vertical growth of cells leads to cells conjoining and the re‐establishment of a uniform planar reaction boundary. This novel but simple mechanism can explain some polygonal fault arrays that form above opal‐A to opal‐CT reaction boundaries and in these settings the mechanism should be considered in addition to syneresis, density inversion or low coefficients of residual friction which are the most commonly cited drivers for polygonal fault systems.
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Volumes & issues
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Volume 36 (2024)
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Volume 35 (2023)
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Volume 34 (2022)
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Volume 33 (2021)
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Volume 32 (2020)
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Volume 31 (2019)
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Volume 30 (2018)
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Volume 29 (2017)
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Volume 28 (2016)
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Volume 27 (2015)
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Volume 26 (2014)
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Volume 25 (2013)
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Volume 24 (2012)
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Volume 23 (2011)
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Volume 22 (2010)
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Volume 21 (2009)
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Volume 20 (2008)
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Volume 19 (2007)
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Volume 18 (2006)
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Volume 17 (2005)
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Volume 16 (2004)
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Volume 15 (2003)
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Volume 14 (2002)
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Volume 13 (2001)
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Volume 12 (2000)
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Volume 11 (1999)
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Volume 10 (1998)
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Volume 9 (1997)
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Volume 8 (1996)
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Volume 7 (1994)
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Volume 6 (1994)
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Volume 5 (1993)
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Volume 4 (1992)
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Volume 3 (1991)
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Volume 2 (1989)
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Volume 1 (1988)