Tectonic Evolution and Continental Fragmentation of the Southern West Australian Margin

• Main Authors: Whittaker, J, Halpin, JA, Williams, SE, Hall, LS, Gardner, R, Kobler, ME, Daczko, NR, Muller, RD
• Format: Conference Object
• Language: English
• Published: RE Solutions Resource & Energy Services P/L 2013
• Subjects: Earth Sciences; Geology; Tectonics; Bruce Rise; Antarc*; Antarctica
• Online Access: https://www.aime.com.au/__novadocuments/44419?v=635258742235770000; http://ecite.utas.edu.au/86218

Continental rocks dredged in 2011 show that the BataviaKnoll and Gulden Draak Knoll, two prominent bathymetricfeatures located ~1600 km offshore Perth, are micro-continents.Plate tectonic modeling reconstructs the pre-rift position ofthese knolls to the north and south of the Naturaliste Plateau,respectively. The Batavia Knoll was conjugate to part of thenorthern Naturaliste Plateau, while the Gulden Draak Knollwas conjugate to the western Bruce Rise, Antarctica. Here,we compare basement rocks, patterns of sedimentation,volcanism and structure on the better studied NaturalistePlateau, Mentelle Basin and Bruce Rise with newly collecteddata from the knolls. Significant volumes of metamorphic andgranitic basement rocks were dredged from both the Bataviaand Gulden Draak knolls. Preliminary geochronological andgeochemical analyses show that these rocks are continental innature and include protolith granitoids that were emplacedduring the Archaean (~2850 Ma) and the Mesoproterozoic(~12901200 Ma) (Gulden Draak Knoll), and during the EarlyPalaeozoic (~540530 Ma) (Batavia Knoll). All metamorphicrocks were invariably reworked during the Kuunga Orogeny(~550500 Ma) during the final assembly of Gondwana.Sediment accumulations are generally relatively thin (upto a few hundred meters) on all the continental fragments,with the exception of NNE to NE oriented rift basins withup to ~2 km of sediments. Sedimentary rocks, predominantlysandstones were dredged from adjacent to the interpretedrift basin locations on both the Batavia and Gulden Draakknolls. Volcanic/intrusive material has been interpreted on thenorthern flank of the Naturaliste Plateau from seismic profiles,but no basalts were found in either of the Batavia Knolldredges. Extensive volcanism has also been interpreted onboth the Naturaliste Plateau and Bruce Rise. Volcanic materialwas dredged in one of two sites on the Gulden Draak Knoll,and geophysical data may support the presence of an igneousdomain. The structural, volcanic and sedimentary nature ofthe knolls will be tested in late-2014 with the collection ofnew magnetic, gravity, seismic reflection and dredge data.