Exploring the coupling between plate tectonic and climate evolution: Eocene–Oligocene chronology of the southwest Pacific
Geophysics
Final Report Abstract
The results obtained during the DFG project represent a step forward in the knowledge of the southwest Pacific area, in terms of both tectonic dynamic and climate history. The early Eocene–early Miocene magnetic polarity chronology of the sediments recovered during IODP Exp. 371 played a fundamental role in constraining the timing of the vertical motion (uplift and subsidence) of the different part of Northern Zealandia. These movements are modulated by the convergence of the Australian and Pacific plates, which resulted in a “subduction resurrection” event and eventually in the self-sustained Tonga-Kermadec subduction. The lithospheric failure propagated horizontally for up to 1000 km away from the evolving plate margin, as revealed by seismic and borehole data. Paleomagnetic data from the Exp. 371 also contribute significantly to the very scarce Cenozoic data inventory of the Australian plate, and the results helped refining the absolute paleolatitude evolution of Zealandia and the connected plates for the whole middle Eocene–early Miocene. In terms of paleoclimate-paleoceanography new carbon isotope and calcareous micronannofossil data have been generated from the lower Eocene carbonate sediments of Site U1510. Results shed new light on the coupling between surface and bottom Ocean water during hyperthermal events, which is a fundamental topic to understand the response and dynamic of the oceanic ecosystems in the (very likely significantly warmer) near future. Paleomagnetic data generated in a late phase of the project also significantly improved the chronologic control on the recovered sediments across the Eocene-Oligocene transition and during the Miocene climate optimum, two significant events of the Cenozoic that were not adequately represented and studied in this part of the Planet. One of the objectives of the proposal was also to investigate the intensity of the chemical weathering on the Australian continent by studying the clay record deposited onto the Tasman abyssal plain and recovered in Site U1511. Preliminary results indicate a clear increase of iron oxides during the early Eocene climate optimum but detailed analyses budgeting the Fe-oxides influx are currently undergoing.
