Influence of Sea Level Change and Centennial East Asian Monsoon Variations on Northern South China Sea Sediments Over the Past 36 kyr

Abstract

South China Sea (SCS) sediments can provide important paleoclimate records because of their generally high deposition rates and strong regional influence of East Asian summer monsoon (EASM) variations. However, interpretation of sedimentary records from the northwestern SCS slope is complicated because sedimentation is sensitive to sea level and provenance variations. We seek to develop a paleoclimatic record of SCS sediments by analyzing sediment magnetic properties over the past ∼36 kyr from core PC338. The dominant magnetic minerals are magnetite and hematite in most parts of the core. The hematite concentration increased profoundly over the ∼15–32 kyr B.P. period when sea level was lower than −90 m below the present level. This suggests that Red River inputs were enhanced significantly in this period. Moreover, increased coarse magnetite contents were recorded in association with an enhanced East Asian winter monsoon (EAWM) during the Last Glacial Maximum and Heinrich event 1. Low‐field and frequency‐dependent magnetic susceptibility variations were coeval with EASM‐controlled climate change recorded in South China and the SCS over the past 15 kyr, probably because regional terrestrial weathering and erosion of iron‐bearing minerals, and their transportation are dominated by climate. Rhythmic coarsening of Holocene magnetic mineral concentrations coincided with global cooling events, which indicates that core PC338 also contains signals of enhanced EAWM variations. The study demonstrates that magnetic proxies are indicative of sediment supply and deposition variations on the SCS continental slope that are useful for understanding the effects of sea level and climate change on SCS sediments.

Interactions Between Depositional Regime and Climate Proxies in the Northern South China Sea Since the Last Glacial Maximum

“…Based on comparison to those fluvial sources, the relatively high values for χ lf , χ ARM , SIRM, and S‐ratio in cores F07 and S11 indicate a high abundance of fine‐grained magnetite from northern sources mixed with minor amounts of hematite, probably from Pearl River sources (Table S2 in Supporting Information ). Compared to the relatively high S‐ratio in both the studied cores, a significant decrease in S‐ratio occurred during the last glacial interval at other sites in the SCS, including Core PC338 in the northwestern SCS (M. Li et al., 2018b) and Core B9 in the southern SCS (Zhong et al., 2021) (Figure 4c). These lower S‐ratio in the northwestern and southern SCS indicate an increase in the relative proportion of hematite, which may have been supplied as aerosol dust (Q. Chen et al., 2017) or as strong weathering inputs (X. Yang et al., 2016).…”

Variability of indian monsoon and its forcing mechanisms since late quaternary

“…It is widely used to study large-scale climate and environmental processes. A lot of environmental magnetism works have been carried out in the inner Asia (Deng et al, 2006;Nie et al, 2017;Ao et al, 2021;Liu et al, 2021), the Pacific Ocean (Zhang et al, 2019), the Japan Sea (Chang et al, 2016), the South China Sea (Yang et al, 2016;Li et al, 2018). The periodic evolution of East Asian Monsoon on different scales and its teleconnection with ice sheets also have been studied.…”

High‐resolution upper Pliocene to Pleistocene calcareous nannofossil biostratigraphy in Ocean Drilling Program Hole 1146A in the South China Sea

“…The modern SCS is located in the monsoon regime. Winter monsoons from the north and northeast carry cold and dry winds across the marginal seas to the east of the Eurasian continent (Figure 1; M. Li et al, 2018). Cold, saline surface waters flow from the East China and Yellow seas southward into the SCS through the Taiwan Strait, forming a counterclockwise gyre in winter (Q.…”

“…In a previous study of calcareous nannofossil biostratigraphy at ODP Site 1146 (Su et al, 2004), the sampling resolution was relatively low (~1 m intervals), and some important datums were not detected. Li et al, 2018) successions in the SCS provide an ideal basis to construct a highresolution calcareous nannofossil biostratigraphic framework. The aim of this study was to improve the resolution of the calcareous nannofossil biostratigraphy for the SCS.…”