Data report: bulk sediment organic matter, carbonate, and stable isotope stratigraphy from IODP Expedition 346 Site U1427 (250–530 m CCSF-D_Patched)

Abstract

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Palaeoceanography of the Japan Sea Across the Mid‐Pleistocene Transition: Insights From IODP Exp. 346, Site U1427

“…sea-level of less than -30 m below present, the δ 18 O record is unaffected by the input of low saline/low δ 18 O waters due to unrestricted water mass exchange between the JS and the open ocean (mode 1 in Figure 5a). Palaeoceanographic mode 1 prevails during interglacials across MIS 39-17 and encompasses mode 4 in Tada et al (1999) 4d), indicating restricted inflow via the TSS and relatively high contributions of ECSCW to the TWC, as can also be inferred from high fluxes in marine productivity proxies as a result of the enhanced nutrient input by the ECSCW (Felder et al, 2021) and a relatively high precipitation on the Chinese Loess Plateau (Figure 4f). In contrast, during MIS 38 TSS sill levels were at times shallower than during MIS 23, dropping to as little as ∼60 m, but δ 18 O is consistently high, suggesting a relatively good water mass exchange with the open ocean and reduced contributions of ECSCW, as can also be inferred from relatively lower marine productivity (Felder et al, 2021) and much lower precipitation on the Chinese Loess Plateau (Figures 4a-4d, 4f).…”

“…MIS 36 begins and ends with relatively high δ 18 O and lower δ 18 O values in its mid‐section, while MIS 30 has overall low δ 18 O values (Figure 4a). During MIS 36, the reduced δ 18 O values are likely associated with a period of increased monsoon precipitation affecting the δ 18 O record and, although a direct proxy for freshwater input/monsoon variations (such as diatom assemblages) is not available, the enhanced contributions of nutrient‐rich ECSCW can also be inferred from enhanced marine productivity (Felder et al., 2021) and high precipitation over the Chinese Loess Plateau (Figure 4f). During MIS 30, the low δ 18 O values may be the result of a combination of enhanced monsoon precipitation (Figure 4f) and potentially a sea‐level/sill level that would have reduced the exchange of water masses with open ocean (Figure 4d, yellow area).…”

“…and lower δ 18 O values in its mid-section, while MIS 30 has overall low δ 18 O values (Figure 4a). During MIS 36, the reduced δ 18 O values are likely associated with a period of increased monsoon precipitation affecting the δ 18 O record and, although a direct proxy for freshwater input/monsoon variations (such as diatom assemblages) is not available, the enhanced contributions of nutrient-rich ECSCW can also be inferred from enhanced marine productivity (Felder et al, 2021) and high precipitation over the Chinese Loess Plateau (Figure 4f). 38, 36 and 34 (Hoiles et al, 2012;Kitamura et al, 2001).…”