Micropalaeontological evidence for Late Quaternary sea-level changes in Bonaparte Gulf, Australia

• Published in: Global and planetary change 2009-03, Vol.66 (1), p.85-92
• Main Authors: De Deckker, Patrick, Yokoyama, Yusuke
• Format: Article
• Language: English
• Subjects: Brackish; Foraminifera; Last Glacial Maximum; Marine; microfossils; northern Australia; ostracod; Ostracoda; pteropods; sea level change; taphonomy
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2008.03.012

The shallow seas surrounding Northern Australia, far away from former ice sheets and on a tectonically stable margin, is ideally suited for sea-level reconstructions as hydro-isostatic effects there are minimal. Detailed examination of ostracod and foraminifer remains, recovered from gravity core RS176/GC 5 from Bonaparte Gulf, and which is located at 118 m water depth, provides a detailed history of sea-level transgression coinciding with the end of Last Glacial Maximum [LGM]. For the period spanning ~ 30,000 to 20,100 cal years BP, the paucity of sediment may represent some erosion, but there is no sign of pedogenesis for that interval in the core. After 20,100 cal years BP, estuarine conditions prevailed at the site, followed by an obvious sea level rise at 19,400 years BP that is well constrained by 14C dates and high sedimentation. The evidence of a sea-level rise after 19,400 cal years BP of the order of 10 m is based on observations made on microfossil remains. Higher in the core, the presence of aragonitic pteropods is a clear indication of open marine conditions because they could not have been reworked, due to their fragility.