The coupling relationship between biogenic deposits and productivity may vary across different stages or regions. To explore the responses of biogenic deposits to productivity since the last glacial period, we analyzed multiproxy biogenic deposit data from Core YDY09 in the Bay of Bengal (BoB) spanning the past 30 ka. We first observed that the trends of biogenic depositional records (radiolarians, BSi, and CaCO) were in antiphase to that of the productivity of siliceous organisms in the overlying waters during the Last Glacial Maximum (LGM), Heinrich Stadial 1 (HS1) and late deglacial period (LdGp; 15–10 ka) in the northeastern Indian Ocean. We suggest that productivity variations were influenced mainly by the Indian summer monsoon (ISM) during the last deglaciation to glaciation. The decoupling between high productivity and low biogenic deposition during the LGM and LdGp was attributable to significant dilution by large-scale terrigenous inputs. Unlike the substantial inputs of terrestrial materials caused by low sea levels during the LGM period, the sea level rose rapidly during the LdGp period, suggesting that the intense ISM may have played a crucial role at that time. Conversely, the high amount of biogenic deposition during HS1 could be attributed to weak terrigenous dilution resulting from diminished rainfall in the Intertropical Convergence Zone (ITCZ). The strong terrigenous dilution observed during the LGM and weak terrigenous dilution during the HS1 in the BoB were consistent with findings in the northern South China Sea (SCS), except the unique LdGp period. Our findings will enhance the understanding of the decoupling mechanisms between biogenic deposits and productivity in global marginal seas.

中文翻译：

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末次冰消期到冰川作用期间，显着的陆源稀释影响了孟加拉湾的生物沉积物


生物沉积物与生产力之间的耦合关系在不同阶段或地区可能有所不同。为了探索自末次冰期以来生物沉积物对生产力的响应，我们分析了过去 30 ka 孟加拉湾 (BoB) 岩心 YDY09 的多代理生物沉积物数据。我们首先观察到，在末次盛冰期（LGM）、Heinrich Stadial 1（HS1）和晚期，生物沉积记录（放射虫、BSi和CaCO）的趋势与上覆水域中硅质生物生产力的趋势相反。印度洋东北部的冰消期（LdGp；15–10ka）。我们认为生产力变化主要受到末次冰消期至冰期期间印度夏季风（ISM）的影响。末次盛冰期和末次冰川期期间高生产力与低生物沉积之间的脱钩可归因于大规模陆源输入的显着稀​​释。与LGM时期低海平面造成的陆地物质大量输入不同，LdGp时期海平面迅速上升，表明强烈的ISM可能在当时发挥了至关重要的作用。相反，HS1期间的大量生物沉积可归因于热带辐合带（ITCZ）降雨量减少导致的陆源稀释作用较弱。除了独特的 LdGp 时期外，BoB 中末次盛冰期期间观测到的强陆源稀释和 HS1 期间观测到的弱陆源稀释与南海北部的发现一致。我们的研究结果将增进对全球边缘海生物沉积物与生产力之间脱钩机制的理解。