HR: 0830h
AN: H51D-1115    [PDF]
TI: Numerical modelling of drainage basin evolution and alluvial fan stratigraphy
AU: Wachter, M
EM: Maarten.Wachter@Wintershall.com
AF: Sedimentology Group, Faculty of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD Netherlands
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: de Boer, P L
EM: pdeboer@geo.uu.nl
AF: Sedimentology Group, Faculty of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD Netherlands
AB: A 3D forward numerical model is presented to study the effects of bedrock erodability, thrust displacement rate, pulsating tectonic activity and sea-level fluctuations on drainage basin morphology and stratigraphy of large alluvial fan systems. A low value of the bedrock erodability coefficient (Kb = 0.5 x 10-4 yr-2/3) versus thrust rate (Rthrust = 2.0 m/kyr) is associated with a time lag between cessation of tectonic activity and maximum sedimentation rates observed on the alluvial fans. Applying higher Kb values, ranging between 1.0 and 8.0 x 10-4 yr-2/3, results in higher sediment yields due to more rapid headward catchment erosion and elaborate sideways branching of drainage networks. Pulsating tectonic activity is reflected in a stratigraphic alternation of prograding and retrograding alluvial fan gravels. During tectonic activity fan gravel fronts and coastlines retreat because catchment yields are insufficient to fill the accommodation space created by the flexural response due to thrust loading. Phases of tectonic quiescence and cessation of flexural subsidence are indicated by progradation of the gravel front. Depending on the position in the basin, the lag time for arrival of the gravel associated with tectonic cessation is several tens to hundred kyrs. A combination of pulsed tectonic activity with sinuous sea-level fluctuation leads to a more complex stratigraphic pattern. In that case stratigraphic response to tectonic pulses is masked by a similar but higher-order frequency-stacking pattern, especially in the more distal parts.
UR: http://www.library.uu.nl/digiarchief/dip/diss/2003-0708-104559/inhoud.htm
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 8005 Folds and folding
DE: 8102 Continental contractional orogenic belts
SC: Hydrology [H]
MN: 2003 Fall Meeting