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

Abstract

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

Structural evolution of a gravitationally detached normal fault array: analysis of 3D seismic data from the Ceduna Sub‐Basin, Great Australian Bight

“…The Bight Basin contains four other major depocentres, the Eyre, Recherche, Duntroon and Bremer sub‐basins, though the sedimentary thickness in the Ceduna sub‐basin far exceeds that in the other depocentres. The Ceduna Sub‐basin formed following the rifting of Australia and Antarctica during the break‐up of eastern Gondwana from the Late Jurassic onwards (Fraser & Tilbury, ; Bein & Taylor, ; Stagg et al ., ; Willcox & Stagg, ; Totterdell et al ., ; Holford et al ., ). The inboard, south‐southwest‐striking, steeply dipping Jurassic to Lower Cretaceous Pademelon and Potoroo rift systems, provide evidence for this mechanical extension (Totterdell & Bradshaw, ; see fig.…”

Cenozoic deformation in the Otway Basin, southern Australian margin: implications for the origin and nature of post‐breakup compression at rifted margins

“…The Otway Basin is one of several depocentres that formed during Cretaceous‐Palaeogene continental breakup between Antarctica and Australia (Norvick & Smith, ). Along this margin, compressional structures have been most commonly identified within the post‐rift Cenozoic successions of the Otway, Gippsland and Bass basins (Hill et al ., ; Perincek & Cockshell, ; Dickinson et al ., ; Hillis et al ., ), and many significant oil and gas producing fields in these basins are hosted within Cenozoic anticlines (Bernecker et al ., ; Holford et al ., ). Similar Cenozoic anticlines occur within the Torquay sub‐basin (Holford et al ., ) but drilling has shown that they do not contain significant quantities of hydrocarbons (Trupp et al ., ), implying that the relative timing of compressional deformation with respect to hydrocarbon generation and charge is a key factor in defining prospectivity along the margin (Duddy, ; Holford et al ., ).…”

Elevated, passive continental margins: Not rift shoulders, but expressions of episodic, post-rift burial and exhumation

“…Gaina et al, 2009;Green and Duddy, (2010); Japsen et al, 2010). Holford et al (2009Holford et al ( , 2010 also suggested that episodes of regional exhumation of the British Isles and of southern Australia were caused by far-field, compressional stresses. Geodynamic modelling of lithospheric folding along EPCMs and documentation of the changes in plate movements that are needed to produce the necessary forces for the episodic, vertical movements along these margins are important subjects for future studies.…”