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- Volume 9, Issue 2, 1997
Basin Research - Volume 9, Issue 2, 1997
Volume 9, Issue 2, 1997
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Impact of sediment transport efficiency on large‐scale sequence architecture: results from stratigraphic computer simulation
More LessOur understanding of the formation of the wide range of sequence architectures we observe in the rock record is still somewhat limited. The sedimentary response to the complex interaction of various time‐variable basin‐scale processes such as subsidence, eustasy and sediment supply is difficult to understand without numerical models. The computer simulation model presented here, DEMOSTRAT, is a powerful tool to investigate the sequence development scenarios in a 2‐D dip section. The model includes tectonic subsidence, eustasy, two‐component (sand and mud) nonlinear diffusional sediment transport, compaction and isostasy. The transport coefficients in the diffusion equations express the system’s ability to transport sand and mud, and are mainly dependent on climate and subaquatic processes. Keeping other model input parameters constant, the magnitude of transport coefficients seems to have an important impact on sequence development. With high transport coefficients, extensive erosion during sea‐level fall and lack of sediment buildup above sea‐level during rise may reduce the preservation potential for nonmarine sediments. In addition, the former slope break will be eroded during transgression, forming sand‐rich slope or basin floor sediments that may be misinterpreted as lowstand fans. Moreover, the magnitude of transport coefficients has an impact on unconformity timing and development (shown in Wheeler plots).
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New palaeogeographic and lake‐level reconstructions of Lake Tanganyika: implications for tectonic, climatic and biological evolution in a rift lake
Authors A. S. Cohen, K.‐E. Lezzar, J.‐J. Tiercelin and M. SoreghanPalaeogeographic and lake‐level reconstructions provide powerful tools for evaluating competing scenarios of biotic, climatic and geological evolution within a lake basin. Here we present new reconstructions for the northern Lake Tanganyika subbasins, based on reflection seismic, core and outcrop data. Reflection seismic radiocarbon method (RSRM) age estimates provide a chronological model for these reconstructions, against which yet to be obtained age dates based on core samples can be compared. A complex history of hydrological connections and changes in shoreline configuration in northern Lake Tanganyika has resulted from a combination of volcanic doming, border fault evolution and climatically induced lake‐level fluctuations. The stratigraphic expression of lake‐level highstands and lowstands in Lake Tanganyika is predictable and cyclic (referred to here as Capart Cycles), but in a pattern that differs profoundly from the classic Van Houten cycles of some Newark Supergroup rift basins. This difference results from the extraordinary topographic relief of the Western Rift lakes, coupled with the rapidity of large‐scale lake‐level fluctuations. Major unconformity surfaces associated with Lake Tanganyika lowstands may have corresponded with high‐latitude glacial maxima throughout much of the mid‐ to late Pleistocene.
Rocky shorelines along the eastern side of the present‐day Ubwari Peninsula (Zaire) appear to have had a much more continuous existence as littoral rock habitats than similar areas along the north‐western coastline of the lake (adjacent to the Uvira Border Fault System), which in turn are older than the rocky shorelines of the north‐east coast of Burundi. This model of palaeogeographic history will be of great help to biologists trying to clarify the evolution of endemic invertebrates and fish in the northern basin of Lake Tanganyika.
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Tectonic modelling of the Middle Jurassic synrift stratigraphy in the Oseberg–Brage area, northern Viking Graben
Authors M. Ter Voorde, R. Ravnås, R. Færseth and S. CloetinghA finite difference model, allowing for episodic movements along different faults, is used to examine the effect of tectonics on the stratigraphic signature in the Oseberg–Brage area in the northern Viking Graben. Constraints are provided by local exploration and production well data and 3‐D seismic coverage, and a regional depth‐converted seismic line.
In the modelling, we focus on the influence of varying rates of fault movement on stratigraphic signatures such as upflank unconformities and changes in layer thickness. We couple the basinwide features of the northern Viking Graben with the fault‐block‐scale features of the Oseberg–Brage area by using parameter constraints derived by large‐scale modelling as input for the local‐scale model. In addition, subsidence patterns resulting from the basinwide model were used as background subsidence for the fault block model of the Oseberg–Brage area.
The model results indicate that the alternating activation of different faults with varying extension rates can cause stratigraphic features such as unconformities, condensation and onlap/offlap patterns. Onlap occurs during periods of low extension rates. An increase in extension rate along a fault causes footwall uplift, resulting in condensation or upflank erosion yielding unconformities. This influence can also affect sub‐basins further away from the fault. Downdip layer thickening reflects the local tilting of fault blocks.
The coupling of the local and regional scales turns out to be essential in explaining the stratigraphy of the Oseberg–Brage area: basinward and, notably, updip layer thickening as observed on some of the fault blocks can only be explained by activity of the boundary fault on the opposing, western margin of the northern Viking Graben.
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Thermal effects of intrusion below the Taranaki Basin (New Zealand): evidence from combined apatite fission track age and vitrinite reflectance data
Authors P. A. Armstrong, P. J. J. Kamp, R. G. Allis and D. S. ChapmanA high surface heat‐flow anomaly on the northern Taranaki Peninsula in the Taranaki Basin (New Zealand) coincides spatially with Quaternary volcanic edifices, but the temporal aspects of heating of the sedimentary column associated with volcanism and any related plutonism have been unclear. A combined analysis of fission track age and vitrinite reflectance data, in particular comparing data from within the high heat‐flow anomaly to calibration wells elsewhere in the Taranaki Basin, provides important new constraints. Within the high heat‐flow region, apatite fission track (AFT) ages are older and vitrinite reflectance (Ro) values are lower than in samples from elsewhere in the basin that have undergone similar burial histories. Modelled AFT ages and Ro values suggest gradual heating to within about 20 °C of maximum temperature followed by rapid heating of sedimentary strata in the last 1 Myr, perhaps as recently as the last 0.1 Myr. The inferred age of this heating event is younger than the age of the volcanic edifice on which it is centred, suggesting that volcanism precedes heating that may be related to plutonism under the northern peninsula. These results suggest that, if the heating is caused by intrusion, then the intrusion is probably in the upper crust.
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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)