Sedimentary modulation of magnetic mineral records in the Central Bengal Fan

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 postdepositional 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 multiproxy Quaternary paleoclimate and paleogeography records in typical submarine fan deposits.

Automated summary

Submarine fan sediments in the central Bengal Fan provide a high-resolution magnetic mineral record spanning the past 40 ka. The abundance and grain size of detrital magnetite and titanomagnetite are primarily controlled by sea-level change. Magnetic mineral variations and climate events are decoupled due to increased Indian hemipelagic sediment input since the last deglaciation sea-level rise. Additionally, an enriched biogenic magnetite layer near the Fe-redox boundary suggests mild postdepositional diagenesis.