Abstract

A seismic-derived acoustic impedance volume was used to image the locations and shapes of water-saturated sands deposited within the producing interval of a continental half graben. Wire-line log crossplots showed that high values of impedance relate to sand lithology. Constrained sparse spike inversion resulted in good comparisons between the derived impedance traces and band-filtered wire-line impedances. Maximum impedance extractions in map view and three-dimensional (3-D) displays revealed two styles of sand distribution: axial deposits comprising delta lobes and boundary fault-induced deposits comprising fan deltas and sand-filled feeder canyons. Coarse-grained sedimentation was dictated by the structural configuration of the basin. Axial sedimentation prograded from south to north, plunging into the basin. Boundary-fault influence on sedimentation was controlled by a transfer zone and relay ramp geometry between en echelon fault segments and showed two component pathways: fan deltas were transported perpendicular to the fault, whereas feeder canyons transported sediment downslope to interfinger with the rift-floor deposits. These styles of structure and sedimentation support previously published models of structural-sedimentation interactions in rifts.

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