Climatic and tectonic constraints on the Plio-Pleistocene evolution of the Indonesian Throughflow intermediate water recorded by benthic 318O from IODP site U1482

The Indonesian Throughflow (ITF) is the unique low-latitude connector between the Pacific and Indian oceans. During the Plio-Pleistocene, the ITF may have played a significant role in the global climate associated with the tectonic constriction of the Indonesian gateway, which was possibly one of the factors spurring the Northern Hemisphere glaciation. Persistent constriction of the gateway would have restricted the ITF intermediate water (ITF-IW) with a high priority over the ITF upper waters. Due to limited availability of sediment archives, however, no investigations have been carried out on the Plio-Pleistocene evolution of the ITF-IW. In this study, we present our work on a total of 1368 sediment samples spanning the past-3.17-1.07 Ma from Site U1482, which was drilled during the International Ocean Discovery Program Expedition 363 in the Timor Passage, the main exit of the ITF to the Indian Ocean. Site U1482 is bathed by the ITF-IW, the evolution of which could thus be monitored by benthic foraminiferal shells preserved in the sediments of the site. Based on establishment of the first high-resolution (-1.53 kyr) Plio-Pleistocene benthic 318O stratigraphy within the ITF region, we recognized that, superimposed over the prominent 41-kyr glacial-interglacial cycles, the long-term change of Site U1482 benthic 318O was punctuated at-2.51-2.43 Ma (Marine oxygen isotope stage (MIS)100/99-96/ 95) and at-1.6 Ma (MIS 56/55), followed by an interval of decreased glacial-interglacial amplitudes in the duration of-1.6-1.2 Ma. We propose that Site U1482 benthic 318O was mainly driven by the global ice-sheet growth prior to-1.6 Ma, in addition to possibly influenced by the tectonic constriction of the Indonesian gateway. In contrast, the decreased glacial-interglacial amplitudes in the benthic 318O during the interval of-1.6-1.2 Ma more likely indicate the regional signal carried by the ITF-IW, which is attributed to a freshening of the ITF surface waters that was subsequently transmitted to the interme-diate depths via vertical mixing in the Banda Sea, caused by enhanced regional precipitation related to monsoonal and western Pacific warm pool conditions. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The Indonesian Throughflow (ITF) plays a significant role in global climate and may have contributed to the Northern Hemisphere glaciation. This study investigates the evolution of the ITF intermediate water (ITF-IW) and upper water through sediment analysis.