A multiproxy study of past environmental changes in the Sea of Okhotsk during the last 1.5 Ma. (June 2019)

• Record Type: Journal Article
• Authors: Lattaud, Julie; Lo, Li; Zeeden, Christian; Liu, Ya-Jun; Song, Sheng-Rong; van der Meer, Marcel T.J.; Sinninghe Damsté, Jaap S.; Schouten, Stefan
• Is Part Of: Organic geochemistry. Volume 132(2019)
• Page Start: 50
• Page End: 61
• Publication Date: 2019-06
• Subjects: Sea of Okhotsk -- Mid-Pleistocene Transition -- LDI -- TEX86 -- Uk′37 -- Biogenic opal -- Long-chain diols; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2019.04.003
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: LDI-reconstructed sea water temperature is impacted by seasonality. FC32 1, 15 is influenced by sea-level changes in the Sea of Okhotsk. 1, 14-diols and opal suggest that primary productivity is controlled by sea-ice cover. TEX L 86 -temperatures shows a 100-kyr cyclicity after 1100 ka. Abstract: Long-chain diols have been detected in a wide range of environments and have been used to reconstruct past environmental changes, however only a few long-term records exist to date. Here we reconstructed past environmental changes in the central Sea of Okhotsk over the last 1.5 million years, covering the Mid-Pleistocene Transition (MPT). Sea surface temperatures (SST) reconstructed using the Long-Chain Diol Index (LDI) reflects glacial/interglacial changes. However, when compared with other organic paleothermometers (U k′ 37 and TEX L 86 ) the LDI-SST is lower during interglacials and similar or higher during glacials, possibly suggesting a shift of diol production season during interglacials. The LDI-SST does not change in periodicity around the MPT as observed for the TEX L 86, likely due to this seasonal shift. Diatom productivity, as recorded by 1, 14-diols and biogenic opal content, increased during the main deglaciations with a succession from Proboscia diatoms to diatoms with a more heavily silicified shell, confirming that primary productivity in the central Sea of Okhotsk is driven by sea-ice progress and retreat. In contrast to the LDI-SST, the 1, 14-diols record shows a change in periodicity around the MPT from 41- to 100-kyr cycle, suggesting an influence of orbital parameters on diatom productivity. In the central Sea of Okhotsk, the relative amount of C32 1, 15-diol (FC32 1, 15 ), a proxy for riverine input, correlates with sea-level change with more riverine-derived material reaching the core site when the Amur River mouth is closer at lower sea-levels. In agreement, FC32 1, 15 shows a change in periodicity during the MPT, with the appearance of a 100-kyr cycle. Our results show that the long chain diols can provide important paleoceanographic information in subpolar environments over long time scales, but that temperature reconstructions can be severely impacted by changes in seasonality.