Late Jurassic foraminifera, Wallaby Plateau, Offshore Western Australia

• Published in: The Journal of Foraminiferal Research
• Main Author: Quilty, PG
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cushman Foundation Foraminiferal Res 2011
• Subjects: Earth Sciences; Geology; Palaeontology (incl. Palynology); Indian; Antarc*; Antarctica
• Online Access: https://doi.org/10.2113/gsjfr.41.2.182; http://ecite.utas.edu.au/74912

Foraminifera are recorded from one sample dredged by RVSonne from 44384049 m water depths on the southwesternmargin of Wallaby Plateau, eastern Indian Ocean (25.5 S,108.5 E). An Oxfordian/Kimmeridgian age is estimatedbased on the foraminiferal fauna, but it conflicts with EarlyCretaceous zircon dates that suggest some recycling ormixing during dredging. The Jurassic age is significantlyolder than any previously known age in the region and predatesage estimates for the initiation of seafloor spreadingalong the Western Australian margin as India departed fromAustralia/Antarctica during the break-up of Gondwana. Thefauna is of low diversity possibly due in part to dissolution atdepth and thus probably does not accurately reflect theoriginal diversity. It is dominated by Conicospirillinawallabyensis n. sp. (Spirillinacea), Conorboides falveyi n.sp. and Lenticulina muensteri (Roemer, 1839). Diversity isgreatest among nodosariacean species; agglutinated forms arevery rare and planktonic and miliolid species are absent. Theforaminifera are accompanied by diverse fragmentary invertebrates.The sediment accumulated in shallow, fully marine,(warm-?) temperate conditions and the locality has subsidedsome 4000 m since deposition. Descriptions of taxa similar inform to Conicospirillina should be studied under crossedpolars to determine whether or not the skeleton has grown incrystallographic continuity. Marginulina suprajurassica Gordonis shown to be pre-occupied.