HR: 1330h
AN: OS52A-0894    [PDF]
TI: Three-dimensional modelling of thrust-controlled foreland basin stratigraphy
AU: * Clevis, Q
EM: quintus.clevis@geog.ox.ac.uk
AF: School of Geography and the Environment, University of Oxford, Mansfield Road, Oxford, OX1 3TB United Kingdom
AU: Nijman, W
EM: w.nijman@geo.uu.nk
AF: Sedimentology Group, Faculteit Aardwetenschappen, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD Netherlands
AU: de Boer, P
EM: pdeboer@geo.uu.nl
AF: Sedimentology Group, Faculteit Aardwetenschappen, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD Netherlands
AB: In this study we present a 3D forward stratigraphic model, which aids in the interpretation of alluvial successions in foreland basins filled by axial-deltaic and alluvial fan systems, under conditions of variable tectonism and eustatic sea-level change. The first set of model experiments indicate that the onset of tectonic activity is reflected by rapid retrogradation of both depositional systems, widespread flooding and onlap of marine sediments. Syntectonic fluvial patterns on the axial-delta plain are dominated by bifurcating channels, swiftly relocating in response to the general rise of relative sea level induced by flexural subsidence. The resulting surface morphology of the axial delta is conical. Syntectonic eustatic sea-level fluctuations result in parasequence-scale packages of retrograding and prograding fan and deltaic sediments bounded by minor flooding surfaces and Type-2 unconformities. Incised channels are rare within the syntectonic parasequences and are formed only during phases of tectonic quiescence when eustatic falls are not longer compensated by the subsidence component in the rise of relative sea level. Suites of amalgamating axial channels corresponding to multiple eustatic falls delineate the resulting Type-1 unconformities. Coarse-grained, incised channel fills are found in the zone between the alluvial fan fringes and the conical body of the axial delta, as the axial streams tend to migrate towards this zone of maximum accommodation. Similar suites of amalgamating axial channel belts are created when the foreland basin is detached from its substratum by a hinterland-dipping sole thrust and transformed into a thrust-sheet top basin. This is shown in the second set of experiments. Here, the competition between rates of regional flexural subsidence, and local detachment-induced uplift controls the accommodation space evolution and the stratigraphic patterns in the marine-influenced thrust-sheet top basin. Model experiments show that displacement over low-angle faults (2~6 degr.) with moderate rates (~5.0 m/kyr) results in a vertical uplift component sufficient to counteract the background flexural subsidence rate. Consequently, the basin-wide accommodation space is reduced, fluvio-deltaic systems carried by the thrust sheet prograde and part of the sediment supply is spilled over towards adjacent basins. The intensity of the forced regression and the interconnectedness of fluvial sheet sandstones increases with the dip angle of the detachment fault.
UR: http://www.library.uu.nl/digiarchief/dip/diss/2003-0708-104559/inhoud.htm
DE: 3025 Marine seismics (0935)
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
DE: 4558 Sediment transport
DE: 4863 Sedimentation
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting