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

国际海洋发现计划（IODP）第356考察队（2015年8月至9月）在澳大利亚西部的7个大陆架和上斜坡地点（地点U1458-U1464）进行了横断面钻探，从珀斯盆地开始，穿过北卡那封盆地，到Roebuck盆地，使用RV Joides Resolution。其中一个主要目标是记录上新世早期以来印度尼西亚通流（ITF）的演变，这是全球热盐环流的关键组成部分，也是向南流动的Leeuwin洋流的驱动因素。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开始。尽管这些遗址的现代水深较浅，但中新世晚期的显著沉降创造了上深海环境，因此在上新世期间，开阔的海洋环境占主导地位。这种环境直接位于ITF的流出处，形成了独特的沉积物序列，构成了上新世早期以来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在上新世期间发生了重大变化。然而，在356号考察队之前，缺乏直接从流出物内部获得的高分辨率记录，这些记录有可能直接将这些变化与澳大利亚各地的干旱和季风的发展联系起来。该项目旨在通过测试以下假设来改善东印度洋的生物地层学：a)在3.3 Ma之前，澳大利亚西北海岸的生物年代学与赤道太平洋相似；b)受印尼通流的限制，上新世浅栖和深栖浮游有孔虫生物地理发育明显。创建可靠的参考记录需要一个约束良好的年龄模型。因此，计划建立一个具有轨道尺度分辨率的底栖有孔虫稳定氧同位素记录，该记录将调整为全球底栖d18O堆栈（LR04）。该年龄模型将用于校正东印度洋浮游有孔虫生物地层。通常，上新世的生物基准面要么来自大西洋，要么来自太平洋，两者之间的差异往往高达100千米。IODP站点U1463被选为本项目，因为它的位置非常理想，直接位于ITF的出口内，同时离海岸足够远，受陆源影响最小，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.