3D Seismic Analysis of the Structural Evolution of the Ceduna Sub-Basin, Great Australian Bight

Abstract

We use three-dimensional (3D) seismic reflection data to determine a suitable growth model of four hard-linked normal fault assemblages, at the extensional top of a gravitationally driven delta system in the central Ceduna Sub-basin, Australia. The fault array we present soles out at a detachment surface at the base of a marine mud of late Albian age. Strike linked fault assemblages are oriented NW-SE, with all faults dip-linked through the Santonian interval, joining upper post-Santonian normal fault segments to lower Cenomanian-Santonian listric fault segments. Kilometre-scale Cenomanian-Santonian displacement of listric fault segments defines an underlying structural grain, which has likely reactivated, nucleating the post-Santonian fault segments, which mimic the underlying fault plane geometry. Through simplistic depth conversion a fault plane model has been created from fault plane dip measurements, which calculates fault plane dip slip displacement from vertical throw measurements. This is necessary to measure Cenomanian nucleation and growth at the base of a listric fault plane decreasing in dip angle with depth. To examine normal fault growth, we have used displacement-distance, displacement-depth and expansion index analysis to identify synkinematic strata. Our analysis shows that Cenomanian-Santonian fault growth is in accordance with the isolated fault model and that post-Santonian fault growth is in accordance with both the isolated fault model and the segmented coherent fault model. This indicates that these fault growth models need not be mutually exclusive to the growth of vertically and laterally segmented fault systems.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015