Wed 3rd December

12 – 1 pm

Rm 312.222

Stephen Gallagher

Department of Earth and Atmospheric Sciences, Univer

International Ocean Discovery Program Expedition 356, August-September 2015

Reefs, Oceans, and Climate: A 5 million year history of the Indonesian Throughflow, Australian monsoon, and subsidence on the Northwest Shelf of Australia

Stephen J Gallagher, Craig Fulthorpe and Kara Bogus

Abstract

The Indonesian Throughflow (ITF) is a critical part of the global thermohaline conveyor. It plays a key role in transporting heat from the equatorial Pacific (the Indo-Pacific Warm Pool) to the Indian Ocean and exerts a major control on global climate. Because of the continued northward motion and impingement of the Australasian plate into the southeast Asian part of the Eurasian plate, the complex tectonic history of the Indonesian archipelago makes it difficult to reconstruct long-term (million year) ITF history from sites within the archipelago. The best areas to investigate ITF history are downstream in the Indian Ocean, in regions directly under the influence of the ITF. International Ocean Discovery Program Expedition 356 will drill a transect of cores over 10° latitude on the northwest shelf (NWS) of Australia to obtain a 5 m.y. record of ITF, Indo-Pacific Warm Pool, and climate evolution that has the potential to match orbital-scale deep-sea records in its resolution. Coring will reveal a detailed shallow-water history of ITF variability and its relationship to climate. It will allow us to understand the history of the Australian monsoon and its variability, a system whose genesis is thought to be related to the initiation of the East Asian monsoon. It also will lead to a better understanding of the nature and timing of the development of aridity on the Australian continent.  Paleobathymetric and stratigraphic data from the transect will also allow subsidence curves to be constructed to constrain the spatial and temporal patterns of vertical motions caused by the interaction between plate motion and convection within the Earth’s mantle, known as dynamic topography. The NWS is an ideal location to study this phenomenon because it is positioned on the fastest moving continent since the Eocene, on the edge of the degree two geoid anomaly. Accurate subsidence analyses over 10° of latitude can resolve whether northern Australia is moving with/over a time transient or long-term stationary downwelling within the mantle, thereby vastly improving our understanding of deep-Earth dynamics and their impact on surficial processes.

Biography

Stephen Gallagher is an Associate Professor at the University of Melbourne. He has had diverse research experience in Carboniferous to Recent microfossils, sedimentology and stratigraphy globally.  He uses applied stratigraphy & micropalaeontology to solve stratigraphic problems and to interpret (palaeo) environments, bathymetry and oceanography.