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- Volume 5, Issue 2, 1993
Basin Research - Volume 5, Issue 2, 1993
Volume 5, Issue 2, 1993
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Lithospheric flexure as a control on stratal geometry and fades distribution in Upper Cretaceous rocks of the Alberta foreland basin
Authors A. GUY Plint, BRUCE S. Hart and W. STEVEN DonaldsonAbstractFacies distributions, stratal geometry and regional erosional bevelling surfaces in Upper Cretaceous (Cenomanian‐Santonian) strata of the Alberta foreland basin are interpreted in terms of high‐frequency (probably eustatic) relative changes in sea level, superimposed on longer‐term basin‐floor warping, related to episodic tectonic loading. Thick marine shales correspond to periods of rapid subsidence whereas thin but extensive strandplain sandstones record rapid progradation during slow subsidence. Westward‐thickening wedges of coastal plain strata were deposited during initial downwarping of a near‐horizontal strandplain, prior to marine transgression. Surfaces of erosional bevelling beneath which between 40 and >160m of strata have been removed extend at least 300 km from the present deformation front and are interpreted to reflect forebulge uplift in the east. Uplift appears to have lagged about 0.25‐0.5 Myr behind the onset of accelerated loading. Thin marine sandstones which grade westward into mudstone are interpreted as material winnowed from the crest of the rising forebulge. Subsidence and/or westward migration of the forebulge allowed the sea to flood westward across the eastern flank of the eroded forebulge. The transgressive shoreface cut asymmetric notches which were later blanketed by marine shales which lap out from east to west. The two unconformities which embody the largest erosional vacuity are veneered locally with oolitic ironstone which accumulated in a shallow, sediment‐starved setting on the crest of the forebulge. The consistent pattern of erosional bevelling and lap‐out of transgressive shales might be interpreted as evidence that the forebulge migrated towards the thrust load over a period of <1 Myr.
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The interaction between normal faulting and drainage in active extensional basins, with examples from the western United States and central Greece
Authors M. R. Leeder and J. A. JacksonAbstractFaulting exerts an important control upon drainage development in active extensional basins and thus helps determine the architecture of the sedimentary infill to a synrift basin. Examples of the interaction between faulting and drainage from the western United States and central Greece may be grouped into a relatively small number of classes based upon the structural position of a drainage catchment: footwall, hangingwall, fault offset and axial. Our examples illustrate the diversity of erosional effects that might arise because of variations in the spacing, orientation and segmentation of faults and their interactions. Where basement lithology is similar, footwall catchments are generally smaller, shorter and steeper than those of the hangingwall. Footwall‐sourced alluvial fans and fan deltas are: generally smaller in area than those sourced from similar lithologies in the hangingwall. Wide fault offsets often give rise to large drainage catchments in the footwall. The development of axial drainage depends upon the breaching of transverse bedrock ridges by headward stream erosion or by lake overflow. Once breaching has occurred the direction of axial stream flow is controlled by the potential developed between basins of contrasting widths. Fault migration and propagation leads to the uplift, erosion and resedimentation of the sedimentary infill to formerly active basins, leading to the cutting of footwall unconformities. The outward sediment flux from structurally controlled catchments is modulated in an important way by lithology and runoff. The greatest contrasts in basement lithology arise when fault migration and propagation have occurred, such that the sedimentary fill to previously active basins is uplifted, incised and eroded by the establishment of large new drainage systems in the footwalls of younger faults. Drainage patterns in areas where faults interact can shed light on the relative timing of activity and therefore the occurrence of fault migration and propagation. Facies and palaeocurrent trends in ancient grabens may only be correctly interpreted when observations are made on a length scale of 10–20 km, comparable to that of the largest fault segments.
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Architecture and sedimentary facies evolution of a marine, expanding outer‐arc half‐graben (Crete, late Miocene)
Authors GEORGE Postma and HARA DriniaAbstractVertical trends in architecture and facies of delta systems are preserved in a clastic wedge of an expanding marine half‐graben in which tectonics, eustatic sea‐level change and climatic change are roughly known from independent evidence. The studied half‐graben is situated on Crete (Greece) and part of a larger, E‐W‐trending extensional domain situated north of the Hellenic subduction zone. The extension seems to be related to the southward migration of the trench (roll‐back) in early Late Miocene times. The infill pattern is discussed in the light of theoretical fault‐growth models for expanding half‐grabens.
The geometry of the half‐graben fill is typically wedge shaped, with a thickness of nearly 1000 m near the fault scarp thinning to c. 50 m about 20 km away from the scarp. The lower part of the wedge (Stratified Prina Series) contains coarsening‐upward units representing progradational, shallow‐marine deltas. At the base of the wedge these units are thin and retrogradationally stacked. Upwards in the succession, the units become composite (coarsening‐upward subunits), thicker and finer grained. The composite structure, the thickening and the fining trend is related to progressive increase in accommodation space inherent in fault growth.
Rapid deepening of the basin from the photic zone (evidenced by intercalated coral and stromatolite beds) up to a depth of 900 m started at the top of the Stratified Prina Series. The deepening continued over some tens of metres of marly sediments of the base of the Kalamavka Formation and may be related to structural collapse of the fault block. After the structural collapse, basin depth remained more or less constant and basin infilling occurred by progradation of deep‐water delta systems. These systems are characterized by a muddy delta slope with channelized conglomerates, and by mainly aggradation of prodelta turbidites deposited in small lobes at the base of slope.
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The timing and extent of illite formation in Ordovician K‐bentonites at the Cincinnati Arch, the Nashville Dome and north‐eastern Illinois basin
Authors W. CRAWFORD Elliott and JAMES L. AronsonAbstractThe K/Ar ages of illite/smectite (I/S) were measured from Middle Ordovician K‐bentonites both west and east of the present crest of the Cincinnati Arch and the Nashville dome to test a previous hypothesis that I/S formed by reaction with migrated saline solutions during the Alleghanian Orogeny. The K/Ar ages of I/S at the distal margin of the southern Appalachian basin and from central Indiana range from 251 to 277 Ma. However, the ages of I/S from west of the crest of the Cincinnati Arch are slightly older (286–301 Ma) and the ages of I/S from north‐eastern Indiana, on the northern edge of the Kankakee Arch and in effect in the Michigan basin, are the oldest measured in this study (315–325 Ma).
The westward decrease in the K/Ar ages of I/S from Late Pennsylvanian ages in the proximal basin (286–303 Ma) to Permian (251–277 Ma) at the distal margin suggest that I/S was formed by the westward migration of fluids during the Alleghanian Orogeny as opposed to being formed by projected deep burial by Permian sediments. Moreover, the available thermal maturation data suggest the Cincinnati Arch was not buried deeply. The ages of I/S west of the Cincinnati Arch are an enigma as they are older than the ages in the distal Appalachian basin. The ages of I/S from central Indiana within the Illinois basin suggest the possibility that I/S was formed by reaction with fluids that migrated from the Ouachita orogenic belt in Mississippi. The oldest ages of I/S from north‐eastern Indiana suggest the formation of I/S might have been influenced by the presence of potassic brines from the Michigan basin.
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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)