IODP SITE U1489 CARBONATE RECORDS FROM THE UPPERMOST MIOCENE TO RECENT

International Ocean Discovery Program (IODP) Expedition 363 cored a number of sites in the Western Pacific Warm Pool (WPWP). The WPWP’s high heat capacity impacts ocean currents, temperature, the atmosphere, and ultimately global climate. Site U1489 is located on the southern Eauripik Rise in the heart of the warm pool at 02°07.19’N, 141°01.67’E in 3421 m water depth, which is close to the modern calcite compensation depth (CCD). Therefore, this site should provide a record of changes in the CCD through time. The purpose of this study is to examine climate variability of this region by looking at changes in carbonate production, burial, and dissolution through time to better understand the carbon system and the forces that drive these changes. The studied interval primarily consists of nannofossil ooze with varying proportions of clay, and to a lesser extent foraminifers, and is dated to the latest Miocene to recent. The average sedimentation rate for most of the studied interval is ~2 cm/kyr; however, the uppermost Miocene to lower Pliocene interval is characterized by a higher sedimentation rate (~5 cm/kyr) and soft-sediment deformation. The climate of the last 5 Myr is of particular interest because it includes intervals when temperatures were warmer than today (such as the mid-Pliocene Warm Period and superinterglacials) that can be used as analogs for future climate change. For this study we collected core scanning X-ray fluorescence (XRF) measurements at 2 cm resolution to obtain a qualitative assessment of the chemical composition of the sediments. To calibrate the XRF data, we measured the calcium carbonate content of discrete samples using a coulometer. We also measured the major and trace element composition of a subset of the discrete samples by inductively coupled plasma mass spectrometry (ICP-MS). Our initial results indicate that the carbonate content varies between 50 wt% and 90 wt%. Barium and iron content also vary significantly over the studied interval and provide a proxy for primary productivity and terrigenous input, respectively. These results will allow us to examine changes in the global carbon cycle as recorded in the western Pacific over the last 5 Myr.