Publication Name: Eastern Australian Basins Symposium 2001
Authors: G.C. Geary, A.E. Constantine and I.S.A. Reid
Date Published: November 2001
Number of Pages: 34
Reference Type: Magazine Article
Abstract:The recognition of syn-depositional NNE to NE trending folds within the Upper Cretaceous syn-rift Sherbrook Group of the eastern Otway Basin, led to the development of a new structural model for application to
seismic interpretation. Earlier recognition was impaired by poor seismic data quality and overprinting by Late Tertiary folds. It is suggested that Late Cretaceous folding and the formation of the prominent north-trending synclinorium represented by the Shipwreck Trough, resulted from sinistral transtension along a N-S wrench system related to Late Cretaceous rifting. The interpreted mechanism involves NE-SW directed crustal exten sion acting across pre-existing basement lineaments and zones of weakness. The structuring is syn-depositional and exerted major control on the stratigraphic development and distribution of Sherbrook Group sediments. Structural traps at the La Bella and Minerva gas fields and at the recent new gas discovery at Geographe-1 , di splay elements of this folding as do a significant number of other untested, faulted anticlinal structures seen on seismic across the region. Faulted anticline traps are more numerous, have a greater trap volume and lower trap risk than were interpreted previously, thereby enhancing the basin's exploration potential for hydrocarbons.