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• The main provenances of surface sediments in the lower Bengal Fan are the Himalayas and the Indian river systems. • The average contribution of the Himalayas is 55% and that of the Indian river system is 45%. • Contributions from the Himalayas gradually decreases from southeast to northwest, while the opposite trend occurred for the Indian river systems. • The material supply from the two provenances is dominated by different monsoonal currents. The Bengal Fan, the largest submarine fan in the world, receives a large amount of terrestrial material from the Himalayas and the Indian Peninsula, making it an ideal area for studying land-sea interactions in different time scales. Using the major and trace element compositions of 98 surface sediment samples from the lower Bengal Fan, we identified the provenances of the sediments, calculated the relative contributions of each provenance, and further assessed their controlling factors. The statistic results of the major and trace elements confirm that terrigenous materials comprise the majority on the sediment and that the study area can be divided into three depositional provinces. The main sources of sediments are the Himalayas and Indian river systems, which can be distinguished in the Fe/Al-K/Al scatter diagram. Based on calculation results of a two end-member mixing model, the relative contributions of the Himalayas and the Indian rivers are 55% and 45%, respectively. However, the spatial distributions of sediments from these two sources in the three provinces exhibit a large variation. The Himalayan contributions decrease from 63% in province I (southeast part of the study area) to 53% in province II (central part of the study area) and 45% in province III (northwest part of the study area). Correspondingly, the contributions of Indian rivers increase from province I through province III. During the high sea levels of modern time, seasonal monsoonal currents play a key role in controlling the sediments transport from South Asia continent to the lower fan. [ABSTRACT FROM AUTHOR]

The long-term evolution of deep-sea turbidity current activity is closely related to climate and sea level changes; however, the impact of abrupt climate change (e.g. millennial-scale events in high northern latitudes) is poorly known. In this paper, deep-sea turbidite records in the western part of the lower Bengal Fan were identified since the Last Glacial Maximum (LGM) to investigate the effects of abrupt climate change on the development of the Earth's largest deep-sea fan. Our records show a termination of turbidite activity in the western lower fan at 16.6 ka–15.4 ka almost contemporaneous with Heinrich 1 event (a cooling stadial in high northern latitudes). The trigger of this termination in turbidite activity may have been a sharp decrease in erosion rates during a time of relatively stable sea level and rapid source-sink processes. The subsequent episodes of the Bolling/Allerod warm interstadial and Younger Dryas cold stadial and the rapid sea level rise event that followed possibly induced adjustment of turbidity current activities in the Bengal Fan, as indicated by other published records. In summary, we show that close links exist between abrupt climate changes in the high-latitude Northern Hemisphere and deep-sea turbidity current activity in the low-latitude South Asia. • Deep-sea turbidite records in the Bengal Fan since LGM were recovered. • Termination of turbidite in the western lower fan was triggered by HS1 event. • Links between high latitudes climate and low latitudes sedimentation were revealed. [ABSTRACT FROM AUTHOR]

The Bengal Fan is world famous for its developed turbiditic system. This study identified turbidite records in a gravity core (BoB-104) taken from near a currently inactive channel (E4) based on lithology, geochemical and mineralogical parameters. This core contained turbidite and hemipelagic layers in this core. This study identified 21 turbidite layers which exhibited consistent provenance with the hemipelagic layers, showing a two end-member mixing pattern and indicating consistent sources since the last glacial period. Typical turbidite layer analysis was used to study the possible turbidite deposition mechanism. Features such as the lithology break interface, normal graded sequence, a consistent pattern of a sharp increase and gradual decrease in the variation of the mean grain size (Mz), and median grain size (D50) and Si/Al ratios commonly implied a continuous deposition in accordance with variations in densities and particle sizes. This study identified long-term evolution of turbidite deposition in the eastern middle Bengal Fan that appears to be the last and indispensable part of the systematic response of the "Bengal depositional system" to the climate. Four stages were identified from the turbidite records and all the identified intervals showed synchronous changes with the entire system. The Indian summer monsoon (ISM) played a dominant role in the system interactions. The sea level affects the turbidity system by regulating the transition of the deposition center between the deep-sea and the shelf, whereas the migration of the main channel to the "Active Valley (AV)" between 14.5 ka to 10.4 ka almost halted the deposition of turbidites along the E4 channel. Thus, turbidity activity in the eastern middle Bengal Fan is not an isolated incident but part of a comprehensive system resuling from global and regional changes at different scales. • 21 turbidite layers have been identified in a core near a currently inactive channel on the eastern middle Bengal Fan. • Effective identification index system, including lithology and multiple proxies has been established and applied. • Turbidite were deposited in accordance to differences in density and particle size forming a normal graded sequence. • Long-term evolution of turbidite appears to be the last and indispensable part of the systematic response to the climate. [ABSTRACT FROM AUTHOR]

Abstract Major and trace elements of sediments from two gravity cores (10YDY09 and 12I712) in the northeastern Indian Ocean have been analyzed for sediment provenance and the relationship of the sediments with climate change since 50 ka. The rare earth element (REE) compositions were analyzed, and the sediment contributions were estimated for the major potential sources, including the Ganges-Brahmaputra (G-B), Godavari-Krishna (G-K) and Mahanadi Rivers. Our results showed that the sediments in the study area were a mixture of sediments discharged from the above three rivers. The sediment contribution of the G-K Rivers increased notably during the Holocene when the rainfall increased, which may be caused by the strengthening of the East Indian Coastal Current (EICC) and the resulting large amounts of sediments supplied by the G-K Rivers. The higher sediment contribution from the G-B Rivers demonstrated the role of the Active Channel in transporting sediments to the distal Bengal Fan. During the last glacial maximum (LGM), especially in the late period, the Indian summer monsoon weakened, but the winter monsoon strengthened, resulting in a decrease in chemical weathering and elemental enrichment in the northeastern Indian Ocean. Conversely, when the rainfall was low, the chemical weathering strengthened and K 2 O/TiO 2 ratios were lowered due to the longer weathering time and resulting sediment potassium loss. However, when the sea level reached a certain height during the Holocene, the fluvial sediments could not easily enter deep-water environments through submarine channels, which were well developed in the Bengal Fan. Highlights • The major and trace elements of two cores were analyzed for sediment provenance. • The role of the Active Channel in the formation of the Bengal Fan was discussed. • The influence of the sea level fluctuations and rainfall changes over the past 50 ka was evaluated. • Coastal currents driven by the monsoon winds are key forces in sediment transport. [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]