Analogue models of delta systems above ductile substrates
Published:January 01, 2003
Ken McClay, Tim Dooley, Gonzalo Zamora, 2003. "Analogue models of delta systems above ductile substrates", Subsurface Sediment Mobilization, P. Van Rensbergen, R. R. Hillis, A. J. Maltman, C. K. Morley
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Delta systems developed above ductile substrates such as overpressured shales and salt have been modelled using layered sand-packs above ductile silicone polymer layers. Gravity spreading of progradational sedimentary wedges produces delta-top and upper delta-slope grabens linked to delta-toe contractional fold–thrust and diapir zones. The delta-top grabens are bound by both regional and counter-regional listric growth faults. A basinward-stepping sequence of regional, counter-regional followed by regional faulting is commonly developed. Polymer pillows and ridges commonly develop in the footwalls of the major listric extensional faults and may evolve into reactive diapirs. Successive progradational loads generate new delta-top or upper delta-slope graben systems on top of older contractional belts where the ductile polymer layer has been thickened significantly. The analogue model results in cross-section show many similarities to examples of natural deltas and differential sedimentary load systems such as offshore Angola, the Niger and Nile Deltas, Kutai Basin, Kalimantan, the Baram delta, Brunei and the Orinoco delta, Columbus basin and offshore Trinidad.
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Subsurface Sediment Mobilization
Sedimentary facies in the subsurface are usually interpreted from a epositional/stratigraphical perspective: the depositional layering is generally considered to remain undisturbed, except in a few settings. But, there is growing evidence that subsurface sediment mobilization (SSM) is more widespread than previously thought, as new observations arise from the ever-increasing resolution of subsurface data. Many examples are from hydrocarbon provinces but studies elsewhere, for example in preparation for the underground storage of hazardous waste, have yielded unexpected examples. Although until now the different aspects of SSM, including soft sediment deformations, sand injections, shale diapirs, mud volcanoes, etc, have been separated, the new discoveries emphasize their inter-connection, regardless of scale, depth, location, grain size or trigger mechanism. This volume integrates the different aspects of sediment mobilization in the subsurface and their structural consequences, allowing a more generaland a more coherent view of the subject.