Magnetic signals in deep‐sea sediments have the potential to unravel past continental environmental changes, via changes in primary terrigenous magnetic supply, but also record past marine environmental conditions, via in situ formation of secondary magnetic minerals, particularly when complemented by independent proxies. By combining environmagnetic, geochemical, and siliciclastic grain size data, we investigated marine sediment core GL‐1090 (24.92°S, 42.51°W, 2,225 m water depth) aiming to unravel changes in terrigenous sediment input and bottom water conditions during the last ∼184 ka at the western South Atlantic middepth. The Al/Si, Fe/κ and siliciclastic grain size data show that terrigenous sediments at this core location derived from the Plata River (southeastern South America). This material was transported northwards by the Brazilian Coastal Current and their delivery to our core site was modulated by sea‐level oscillations. Periods of low sea‐level were characterized by the input of coarser and more abundant terrigenous sediments. Environmagnetic parameters indicate significant downcore variations in the magnetic domain state, which we interpret as changes in the content of biogenic magnetite following glacial‐interglacial cycles. Coeval negative excursions in magnetic grain size and benthic δ¹³C suggests that concentrations of single domain magnetite (possibly magnetotactic bacterial magnetite) vary in response to middepth water ventilation. We suggest that reduced ventilation in the middepth western South Atlantic bottom waters during peak glaciations triggered a decrease in the production of biogenic magnetite. Peak glaciations were, in turn, linked with increases in the residence time of North Atlantic Deep Water (or its glacial counterpart).

中文翻译：

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多代理方法揭示南大西洋西部西部晚更新世沉积物通量和底水状况

深海沉积物中的磁信号有可能通过原始陆源磁性供应的变化来揭示过去的大陆环境变化，但也可能通过原位形成次生磁性矿物来记录过去的海洋环境状况，特别是在独立代理的辅助下。通过结合环境磁，地球化学和硅质碎屑的粒度数据，我们研究了海洋沉积物核心GL-1090（24.92°S，42.51°W，2,225 m水深），旨在揭示最后一个时期陆源性沉积物输入量和底水状况的变化。 184 ka位于南大西洋中西部。Al / Si，Fe /κ和硅质碎屑粒度数据表明，该核心位置的陆源沉积物来自普拉塔河（南美东南部）。这种物质是由巴西沿海海流向北运输的，由于海平面的振荡，它们向我们核心地点的交付受到了调节。低海平面时期的特征是输入了较粗，更丰富的陆源沉积物。环境磁参数表明磁畴状态存在明显的下核变化，我们将其解释为冰川-冰川间周期后生物磁铁矿含量的变化。磁性颗粒尺寸和底栖δ的同期负偏移 我们将其解释为冰川-冰川间周期后生物磁铁矿含量的变化。磁性颗粒尺寸和底栖δ的同期负偏移 我们将其解释为冰川-冰川间周期后生物磁铁矿含量的变化。磁性颗粒大小和底栖δ的同期负偏移¹³ C表明，单畴磁铁矿（可能是趋磁细菌磁铁矿）的浓度会随着中深度水的通风而变化。我们建议，在高峰冰川期，南大西洋西部中部深水底部的通风减少会触发生物磁铁矿的产量减少。反过来，高峰冰川与北大西洋深水（或其冰川对应）的停留时间增加有关。