Site U1514

Abstract

International Ocean Discovery Program (IODP) Site U1514 is the northernmost (33°7.2327′S, 113°5.4672′E) and deepest (3850 m water depth) site cored during Expedition 369. The greater paleodepth of the site relative to other sites cored in the Mentelle Basin provides the opportunity to characterize the evolution of deep water masses and deep ocean circulation during the final phase of breakup of the Gondwana continents. Because Site U1514 is located at a high paleolatitude (~60°S), the sediments preserve a paleoclimate record that serves as a sensitive monitor of global climatic changes. Coring at this site sampled Cenozoic and Late Cretaceous deposits that enable new insights into the early and later phases of the opening of the Tasman Gateway and the restriction of the Indonesian Gateway. The Cretaceous sedimentary basin is probably underlain by synrift Permian to Jurassic sediments that are part of an earlier rifting event extending along the western margin of Australia. Following the separation of India from Australia/Antarctica in the Early Cretaceous, the basin underwent a period of rapid thermal subsidence with deposition of deltaic sediments, shale and claystone sequences, and then deep-water chalks and limestones. The current seabed is composed of Paleogene/Neogene/Quaternary oozes that sit unconformably on the Cretaceous. The primary objectives for coring Site U1514 were as follows: 1. Obtain a continuous Cenozoic sediment record in the Mentelle Basin to characterize how oceanographic conditions changed during the Cenozoic opening of the Tasman Gateway and the restriction of the Indonesian Gateway; 2. Reconstruct middle through Late Cretaceous paleotemperature changes to document when the Cretaceous hot greenhouse climate initiated, how long the extreme warmth persisted, and when a switch to a cooler climate occurred; and 3. Obtain a complete and well-preserved sediment record across mid-Cretaceous oceanic anoxic events (OAEs) to better understand their cause and accompanying changes in the climate-ocean system and in the marine biota. The Site U1514 sequence will be compared with coeval Expedition 369 sections cored elsewhere in the Mentelle Basin and Site U1512 from the Great Australian Bight. Other IODP and industry data from the Western Australia margin and the Great Australian Bight will be used to identify any regional differences in the geochemical and/or biological responses to the OAEs and Cretaceous and Neogene ocean circulation history.