Palaeoceanography of the Japan Sea Across the Mid‐Pleistocene Transition: Insights From IODP Exp. 346, Site U1427
Palaeoceanography of the Japan Sea Across the Mid‐Pleistocene Transition: Insights From IODP Exp. 346, Site U1427
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DOI：
10.1029/2021pa004236
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发表时间：
2021-12
影响因子：
3.5
通讯作者：
Sonja Felder;T. Sagawa;M. Greaves;M. Leng;K. Ikehara;K. Kimoto;Siro Hasegawa;T. Wagner;A. Henderson
中科院分区：
文献类型：
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作者：
Sonja Felder;T. Sagawa;M. Greaves;M. Leng;K. Ikehara;K. Kimoto;Siro Hasegawa;T. Wagner;A. Henderson
大尺度大气环流模式，如东亚季风，被认为是中更新世过渡（MPT）的可能反馈。日本海（JS）的海洋沉积物记录了东亚季风在长时间尺度上的变化，可能是理解MPT的关键。要正确解释这些沉积物，必须了解JS古海洋学。到目前为止，JS古海洋学已经从最近的冰川-间冰期循环的研究中推断出了MPT。这表明在间冰期海平面高位期间与开阔海洋有良好的连接和不受限制的水团交换，而在冰期海平面低位期间，JS几乎是孤立的。冰川隔离通常导致碳酸盐保存较差，并且盆地中低盐/低δ 18 O沃茨积累的氧同位素（δ 18 O）比值异常低。利用综合大洋钻探计划（IODP）U1427站点（位于JS南部的一个浅水站点）的沉积物，我们提供了一个包括MPT的连续有孔虫δ 18 O记录。这一记录显示，在海洋同位素阶段（MIS）24 - 17的MPT晚期，JS-典型的低冰川δ 18 O值，而在MIS 39 - 25的早期MPT冰川，其特征是高δ 18 O值。我们认为，高的冰川δ 18 O值是在早期MPT冰川期间，南部JS和邻近海洋之间的联系改善的结果。这种古海洋学模式的影响，如果继续到深水站点，将使黑暗/光明的沉积层作为冰川/间冰期沉积物的解释不确定。
Large‐scale atmospheric circulation patterns, such as the East Asian monsoon, have been proposed as possible feedbacks of the mid‐Pleistocene transition (MPT). Marine sediments of the Japan Sea (JS) record variations in the East Asian monsoon over long timescales and may be crucial for understanding of the MPT. To interpret these sediments correctly an understanding of the JS palaeoceanography is necessary. So far, the JS palaeoceanography has been extrapolated across the MPT from studies of the most recent glacial‐interglacial cycles. These suggest a good connection and unrestricted water‐mass exchange with the open ocean during interglacial sea‐level highstands, while during glacial sea‐level lowstands the JS is nearly isolated. Glacial isolation often results in poor carbonate preservation and unusually low oxygen isotope (δ18O) ratios from low‐saline/low‐δ18O waters accumulating in the basin. Using the sediments of Integrated Ocean Drilling Program (IODP) Site U1427, a shallow‐water site in the southern JS, we present a continuous foraminiferal δ18O record encompassing the MPT. This record shows the JS‐typical low glacial δ18O values in the late phase of the MPT, across Marine Isotope Stages (MIS) 24‐17, while earlier MPT glacials, across MIS 39‐25, are characterized by high δ18O values. We propose that high glacial δ18O values are the result of an improved connection between the shallow, southern JS and adjacent ocean during early MPT glacials. The impact of this palaeoceanographic mode, if continued to deep‐water sites, would make the interpretation of dark/light sediment layers as glacial/interglacial deposits uncertain.