Cenozoic post-breakup compressional deformation and exhumation of the southern Australian margin

摘要

We present results from a margin-wide analysis of the history of post-breakup Cenozoic compressional deformation and relatedudexhumation along the passive southern margin of Australia based on a regional synthesis of seismic, stratigraphic andudthermochronological data. The Cenozoic sedimentary record of the southern margin contains regional unconformities of intra-udLutetian and late Miocene-Pliocene age, which coincide with reconfigurations of the boundaries of the Indo-Australian Plate.udSeismic data show that post-breakup compressional deformation and sedimentary basin inversion, characterised by reactivation ofudsyn-rift faults and folding of post-rift sediments, is pervasive from the Gulf St Vincent to Gippsland basins, and occurred almostudcontinually since the early-to-mid Eocene. Inversion structures are absent from the Bight Basin which we interpret to be the resultudof both the unsuitable orientation of faults for reactivation with respect to post-breakup stress fields, and the colder, strongerudlithosphere that underlies that part of the margin. Compressional deformation along the southeastern margin has mainly beenudaccommodated by reactivation of syn-rift faults resulting in folds with varying ages and amplitudes within the post-rift Cenozoicudsuccession. Many hydrocarbon fields in the Otway and Gippsland basins are located within these folds, the largest of which areudoften associated with substantial localised exhumation. Our results emphasise the importance of constraining the timing ofudCenozoic compression and exhumation in defining hydrocarbon prospectivity of the southern margin.