Developing a consistent sequence stratigraphy for the Wilkes Land and Great Australian Bight margins

• Main Authors: Lane, H, Muller, RD, Totterdell, JM, Whittaker, J
• Format: Conference Object
• Language: English
• Published: Petroleum Exploration Society of Australia 2012
• Subjects: Earth Sciences; Geology; Marine Geoscience; Wilkes Land; Antarc*; Antarctica
• Online Access: http://www.earthbyte.org/publications.html; http://ecite.utas.edu.au/84450

The conjugate margins of Wilkes Land, Antarctica, and theGreat Australian Bight (GAB) are amongst the least understoodcontinental margins. Breakup along the GABWilkes Land part ofthe AustralianAntarctic margin commenced at approximately 83Ma. Using recent stratigraphic interpretations developed for theGAB, we have established a sequence stratigraphy for the WilkesLand margin that will, for the first time, allow for a unified study ofthe conjugate margins. By reconstructing the two margins to theirpositions prior to breakup, we were able to identify comparablepackages on the Wilkes Land margin to those recognised on theGAB margin. Excluding the glacial sediments on the Antarcticmargin, the sedimentary sequence along the Wilkes Land marginis very thin compared to the GAB margin, which has substantiallymore syn- and post-rift sediments. Despite the differences inthickness, the syn-rift sedimentary package on the Wilkes Landmargin exhibits a similar style of extensional faulting and seismiccharacter to its GAB margin counterpart. In comparison, post-riftsequences on the Wilkes Land margin are markedly different ingeometry and seismic character from those found on the GABmargin. Isopach mapping shows substantial differences in thethickness of the post-breakup sediments, suggesting differentsediment sources for the two margins. The Late Cretaceousinterval termed the Hammerhead Supersequence provides muchof the post-rift thickness for the GAB margin as a result of largesediment influx into the basin. This supersequence is characterisedby a thick progradational succession and was deposited in fluviodeltaicand marine environments. The equivalent succession onthe Wilkes Land margin has a different seismic character. It isthinner and aggradational, which is interpreted to represent a distalmarine environment of deposition.