Half-graben basin filling models: new constraints on continental extensional basin development |
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| Authors: | Roy W Schlische |
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| Institution: | Department of Geological Sciences, Rutgers - The State University of New Jersey, New Brunswick, New Jersey 08903, USA |
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| Abstract: | Three end-member models of half-graben development (detachment fault, domino-style, and fault growth) evolve differently through time and produce different basin-filling patterns. The detachment fault model incorporates a basin-bounding fault that soles into a subhorizontal detachment fault; the change in the rate of increase in the volume of the basin during uniform fault displacement is zero. Younger strata consistently pinch out against older synrift strata rather than pre-rift rocks. Both basin-bounding faults and the intervening fault blocks rotate during extension in the domino fault block model; a consequence of this rotation is that the change in the rate of increase of the volume of the basin is negative during uniform extension. Basin fill commonly forms a fanning wedge during fluvial sedimentation, whereas lacustrine strata tend to pinch out against older synrift strata. In the fault growth models, basins grow both wider and longer through time as the basin-bounding faults lengthen and displacement accumulates; the change in the rate of increase in basin volume is positive. Fluvial strata progressively onlap pre-rift rocks of the hanging wall block, whereas lacustrine strata pinch out against older fluvial strata at the centre of the basin but onlap pre-rift rocks along the lateral edges. These fundamental differences may be useful in discriminating among the three end-member models. The transition from fluvial to lacustrine deposition and hanging wall onlap relationships observed in numerous continental extensional basins are best explained by the fault growth models. |
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