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The Sunda Shelf plays a key role in the sedimentation of the southern South China Sea (SCS). However, the impact of past climate changes on sediment transfer to the Sunda Shelf and the southern SCS is still unresolved. Here, we present new data on grain size, clay mineralogy, and Sr‐Nd isotopes of three marine cores, river sediments, and surface sediments of the Sunda Shelf. The results indicate that clay fractions of the central Sunda Shelf and the Gulf of Thailand derived mainly from the Mekong River and the rivers of northern Thailand since the last deglaciation. Significant changes in sediment sources are observed at 7.5 cal ka BP. From 13.3 to 7.5 cal ka BP, sediments in the Gulf of Thailand mainly originated from the rivers of northern Thailand, with contributions from the Mekong River increasing after 7.5 cal ka BP. An opposite shift is observed in the central Sunda Shelf. Such variations in the spatial distribution result from a combination of sea level and East Asian monsoon effects. After 7.5 cal ka BP, less Mekong River sediments were transported southeastwards into the southern SCS, and more sediments were gradually trapped within the delta and transported in a southwesterly direction into the Gulf of Thailand due to intense East Asian winter monsoon, which forced a strong southwestward coastal current. Our results demonstrate the important impact of East Asian winter monsoon strengthening and sea level rise in the mid‐Holocene, which can change sediment sources and transport processes on the Sunda Shelf. Plain Language Summary: Sea level and monsoon are two important factors controlling sediment transfer in the tropical and subtropical continental marginal seas. However, the impact of past sea level and monsoon changes on mineralogical composition and sediment transfer to the Sunda Shelf (the largest low‐latitude continental shelf) and the southern South China Sea (SCS) is unclear. This study provides new data on grain size, clay mineralogy, and Sr‐Nd isotopes of sediment from marine cores, river sediments, and surface sediments of the Sunda Shelf to constrain sediment sources and climatic control on sediments deposited on the Sunda Shelf since the last deglaciation. We find that the Mekong River and the rivers of northern Thailand are two major sediment sources to the Sunda Shelf. An opposite shift of sediment sources at 7.5 cal ka BP is observed between the Gulf of Thailand and the central Sunda Shelf, which results from the transfer of the Mekong River sediments between the southern SCS and the Sunda Shelf caused by sea‐level rise and East Asian winter monsoon strengthening in the mid‐Holocene. Our results highlight that sea level and East Asian winter monsoons can significantly change sediment sources and transport processes on the Asian low‐latitude continental shelf. Key Points: Clay minerals and Sr‐Nd isotopes identified sediment sources to the Sunda Shelf since the last deglaciation as Mekong and Thailand riversEstimation of the Mekong and Thailand river inputs to the sedimentation of the Sunda Shelf and the southern South China SeaSea‐level rise and East Asian winter monsoon strengthening drove major sediment‐source changes on the Sunda Shelf at 7.5 ka BP [ABSTRACT FROM AUTHOR]

Abstract Grain size, clay mineralogy, 87Sr/86Sr, εNd, and AMS14C analyses of deep-sea sediments cored in the central Bay of Bengal are used to reconstruct the evolution of provenances and climate control since the last glacial period. Clay minerals, 87Sr/86Sr ratios and εNd values indicate a mixture of sediment from the Himalaya source, Indian Peninsula and Indo-Burman Ranges/Irrawaddy River. These analyses show that the Himalaya Mountains and Indo-Burman Ranges/Irrawaddy River are the main suppliers before the Holocene period, while the inputs of erosion materials from the Indo-Gangetic floodplain and the Indian Peninsula increase during the Holocene period, accompanied by reduced inputs of the Indo-Burman Ranges and Irrawaddy sediments. The regional "source-sink" process is significantly controlled by the climate. Warm and wet climate conditions and enhanced Indian monsoon intensity during the Holocene period are responsible for the increase of sediment input from the Indo-Gangetic Plain and the Indian Peninsula by improving erosion in the source area, input from the floodplain to the river channel and the intensity of the southwest monsoon current. In contrast, due to the decrease of the northeast monsoon current during the Holocene period, sediment input from the Irrawaddy and Indo-Burman Ranges are constrained. Deposition center transition between the submarine fan and shelf during the last glacial period and the Holocene period occurs in response to the sea level change, which controls the sedimentary mode and thus significantly influences the transportation and deposition processes in the Bay of Bengal (BoB). [ABSTRACT FROM AUTHOR]

With sea level rise in the early Holocene, the warm and low-salinity sea water from the Java Sea was transported into the eastern Indian Ocean after the opening of the Sunda Strait. However, the impact of this process on sediment provenance and paleoproductivity is rarely known. In this study, we analyzed the grain size, Sr-Nd-Pb isotopic compositions and biogenic elements of core CJ01-185 (1538 m water depth) in the eastern Indian Ocean off the Sunda Strait. Our new results reveal a large volcanic eruption in the west of Java at 2.1 ka, and the Krakatau eruption at 1883 CE. On the basis of the Pb isotopic compositions, 87 Sr/ 86 Sr ratios, and ε Nd values, we infer that sediments from core CJ01-185 were derived primarily from Java Island. There is a distinct change in Sr-Nd-Pb isotopic compositions of the sediments from the last glacial period to the Holocene, indicating less radiogenic Nd isotopes from the Java Sea into the eastern Indian Ocean after the opening of the Sunda Strait at ∼10 ka. Moreover, the sedimentation rate increased significantly from 6.5 cm kyr −1 during the last glacial period to 20 cm kyr −1 in the Holocene. The input of additional terrigenous nutrients from the Java Sea induced paleoproductivity with higher TOC and TN concentrations after the opening of the Sunda Strait. Our results thus suggest that the paleoproductivity was mainly influenced by terrigenous materials input in the Holocene, other than southeast monsoon or upwelling in the last glacial period. [ABSTRACT FROM AUTHOR]

Submarine fan sediments are essential archives for understanding the interaction between continental weathering and climate change, but decoding multiple geological and environmental factors in such highly dynamic sedimentary environments is challenging. Here we present a high-resolution magnetic mineral record spanning the past ∼40 ka from the central Bengal Fan. Comprehensive rock magnetic and electron microscopic analyses are conducted to understand the origins of different magnetic mineral components in response to sedimentary and paleoclimate processes. Detrital magnetite and titanomagnetite are the dominant magnetic minerals in Bengal Fan sediments, whose abundance and grain size are primarily controlled by eustatic sea-level change. Increased Himalaya terrestrial input during Heinrich events is documented during sea-level low stand, but magnetic mineral variations and climate events are decoupled due to enhanced Indian hemipelagic sediment input since the last deglaciation sea-level rise. In addition, we identify an enriched biogenic magnetite layer near the Fe-redox boundary in the studied Bengal Fan sediment core, possibly related to relatively mild post-depositional diagenesis. Massive detrital inputs in the submarine fan sediments dilute the contribution of biogenic magnetite to the bulk magnetic record. Our results contribute to an integrated source-to-sink understanding of magnetic mineral components in continental margin submarine fans, which helps to construct multi-proxy Quaternary paleoclimate and paleogeography records in typical submarine fan deposits. • Direct recognition of detrital/biogenic magnetic minerals in Bengal Fan sediments. • Sea-level controls variations of detrital magnetic mineral component. • Stadial terrestrial input was enhanced during sea-level low stand. • Increased hemipelagic sediments at sea-level high stand reduce climate sensitivity. • Thriving biogenic magnetite near diagenetic Fe-redox boundary. [ABSTRACT FROM AUTHOR]