Re-evaluation of Mentelle Basin, a polyphase rifted margin basin, offshore southwest Australia: new insights from integrated regional seismic datasets

• Published in: Solid Earth
• Main Authors: Maloney, D, Sargent, C, Direen, N, Hobbs, RW, Grocke, DR
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2011
• Subjects: Earth Sciences; Geology; Structural geology and tectonics; Kerguelen; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/se-2-107-2011; http://ecite.utas.edu.au/74911

Vintage 2-D (two-dimensional) seismic reflectionsurveys from the sparsely explored Mentelle Basin (westernAustralian margin) have been reprocessed and integratedwith a recent high-quality 2-D seismic survey and stratigraphicborehole data. Interpretation of these data sets allowsthe internal geometry of the Mentelle Basin fill anddepositional history to be reanalysed and new insights intoits formation revealed. Basin stratigraphy can be subdividedinto several seismically defined megasequences separated bymajor unconformities related to both breakup between India-Madagascar and Australia-Antarctica in the Valanginian-Late Hauterivian and tectonically-driven switches in depositionthrough the Albian.Resting on the Valanginian-Late Hauterivian breakup unconformityare several kilometre-scale mounded structuresthat formed during Late Jurassic to Early Cretaceous extension.These have previously been interpreted as volcanic edificesalthough direct evidence of volcanic feeder systems islacking. An alternative interpretation is that these featuresmay be carbonate build-ups. The latter interpretation carriessignificant climatic ramifications since carbonate build-upswould have formed at high palaeolatitude, ~60degree S.Soon after breakup, initial subsidence resulted in a shallowmarine environment and deposition of Barremian-Aptiansilty-sandy mudstones. As subsidence continued, thick successionsof Albian ferruginous black clays were deposited.Internally, seismic megasequences composed of successionsof black clays show previously unresolved unconformities,onlapping and downlapping packages, which reflect a com-plex depositional, rifting and subsidence history at odds withtheir previous interpretation as open marine sediments.Southwestwards migration of the Kerguelen hotspot led tothermal contraction and subsidence to the present day waterdepth (~3000 m). This was accompanied by Turonian-Santonian deposition of massive chalk beds, which are unconformablyoverlain by pelagic Palaeocene-Holocene sediments.This substantial ...