South Tasman Rise subsidence and its role in the onset of the Antarctic Circumpolar Current

Supervisory Team:

Jo Whittaker

Taryn Noble

Brief project description:

This project addresses the Cenozoic evolution of the Tasmanian Gateway, which formed during the tectonic separation of Australia and Antarctica. The opening of the Tasman Gateway has been implicated in the initiation of the Antarctic Circumpolar Current, and possibly played a role in glaciation of Antarctica 34 million years ago.

Recent high-resolution ocean model simulations by our team demonstrate that only small changes in the depth of the gateway, from 300m to 450m, cause a fundamental reorganization of the Southern Ocean circulation patterns and dramatic surface water cooling (by >4°C) along the entire Antarctic coast. Although the broader plate tectonic motion between Australia and Antarctica is well constrained, uncertainties remain around the detailed plate tectonic evolution of the Tasman Gateway and its evolving paleodepth, particularly through this crucial 300-450m transition. Additionally, controversies exist around when ‘shallow water’ ocean current flows commenced through the gateway, their directions, strengths, possible linkage to glauconite formations and climatic consequences.

In this project, you will constrain the exact timing of Tasman Gateway subsidence and bottom current flow directions and strengths through the Tasman Gateway. You will perform authigenic Rare Earth Element (REE), Neodymium (Nd) and Strontium (Sr) isotopic composition analysis, on Eocene and early Oligocene samples taken from drill sites ODP 1170 & 1171 on the South Tasman Rise.

The key objectives of this project are to:

1. build a well-constrained subsidence curve for the Eocene and early Oligocene:
2. constrain bottom water flow direction and strength

Skills students will develop during this research project:

• Sediment lab skills
• Critical analysis
• Linking results to regional and global context
• Writing skills