Impact of the Indonesian Throughflow on northwestern Australian biochronology during the Pliocene (IDEAL).

国际海洋发现计划(IODP)第356次探险(2015年8月至9月)钻探了一条横跨西澳大利亚近海10°纬度七个陆架和上坡地点(地点U1458-U1464)的横断面，从珀斯盆地，穿过北卡纳冯盆地，到罗巴克盆地，采用RV Jodes决议。主要目标之一是记录自上新世早期以来印度尼西亚贯流的演变，这是全球温盐环流的一个重要组成部分，也是向南流动的勒温洋流的驱动力。这反过来又影响了澳大利亚干旱的发展和澳大利亚季风的爆发。尽管这些遗址具有现代浅水深度，但在中新世晚期，显著的下沉造成了半深海环境，因此在上新世期间，开阔的海洋条件占优势。这一环境直接位于ITF的流出处，允许积累独特的沉积物序列，构成自上新世早期以来ITF变化的高分辨率记录。先前来自海洋大陆和更远的西澳大利亚近海的研究表明，ITF在上新世发生了重大变化。然而，在356次远征之前，缺乏直接来自外流的高分辨率记录，这些记录有可能将这些变化与整个澳大利亚的干旱和季风的发展直接联系起来。该项目旨在通过检验以下假设来改善东印度洋的生物地层学：a)澳大利亚西北海岸的生物年代学在3.3 Ma之前一直与赤道太平洋相似；b)由于印度尼西亚Throughflow的限制，上新世浅层和深层浮游有孔虫的生物地理学发展是明显的。创建可靠的参考记录需要一个受良好约束的年龄模型。因此，计划创建一个具有轨道尺度分辨率的海底有孔虫稳定氧同位素记录，该记录将与全球海底d18O堆栈(LR04)相调谐。然后，这个年龄模型将被用来校准东印度洋的浮游有孔虫生物地层学。通常，上新世生物基准面要么来自大西洋，要么来自太平洋，它们之间的差异通常高达100 KYR。IODP地点U1463被选为该项目是因为它的位置非常理想，直接位于ITF流出的范围内，同时离岸足够远，受陆源冲击的影响最小，因此浮游有孔虫大量存在。

International Ocean Discovery Program (IODP) Expedition 356 (August-September 2015) drilled a transect across 10° latitude of seven shelf and upper slope sites (Sites U1458-U1464) off Western Australia from the Perth Basin, through the Northern Carnarvon Basin, to the Roebuck Basin with the RV Joides Resolution. One of the main objectives was documenting the evolution of the Indonesian Throughflow (ITF) since the early Pliocene, a critical component of global thermohaline circulation and a driver of the southward-flowing Leeuwin Current. This in turn has influenced the development of aridity in Australia and the onset of the Australian monsoon. Despite the modern shallow water depth of the sites, significant subsidence during the late Miocene created an upper-bathyal setting, so that open-marine conditions prevailed during the Pliocene. This setting, which is located directly in the outflow of the ITF, allowed accumulation of a unique sequence of sediments constituting a high-resolution record of ITF changes since the early Pliocene. Previous studies from the Maritime Continent and from further offshore western Australia have shown that significant changes in the ITF occurred during the Pliocene. However, high-resolution records from directly within the outflow, which have the potential to directly link these changes to development of aridity and the monsoon across Australia, were lacking prior to Expedition 356. This project aims to improve the biostratigraphy in the eastern Indian Ocean by testing the following hypotheses that: a) Biochronology off the northwest coast of Australia remained similar to the equatorial Pacific until 3.3 Ma; b) The Pliocene development of the biogeography of shallow- and deep-dwelling planktonic foraminifera was distinct due to restriction of the Indonesian Throughflow. Creating a reliable reference record requires a well-constrained age model. It is therefore planned to create a benthic foraminiferal stable oxygen isotope record with orbital-scale resolution that will be tuned to the global benthic d18O stack (LR04). This age model will then be used to calibrate the planktonic foraminiferal biostratigraphy in the eastern Indian Ocean. Typically, Pliocene bio-datums are either from the Atlantic or the Pacific and often have differences of up to several 100 kyr between them. IODP Site U1463 was selected for this project because its position is ideally located directly within the outflow of the ITF, and meanwhile far enough offshore to be minimally impacted by terrigenous impact so that planktonic foraminifera are abundantly present.