Climatically Driven Changes in the Supply of Terrigenous Sediment to the East China Sea

Abstract

We examine the paleoceanographic record over the last ∼400 kyr derived from major, trace, and rare earth elements in bulk sediment from two sites in the East China Sea drilled during Integrated Ocean Drilling Program Expedition 346. We use multivariate statistical partitioning techniques (Q‐mode factor analysis, multiple linear regression) to identify and quantify five crustal source components (Upper Continental Crust (UCC), Luochuan Loess, Xiashu Loess, Southern Japanese Islands, Kyushu Volcanics), and model their mass accumulation rates (MARs). UCC (35–79% of terrigenous contribution) and Luochuan Loess (16–55% contribution) are the most abundant end‐members through time, while Xiashu Loess, Southern Japanese Islands, and Kyushu Volcanics (1–22% contribution) are the lowest in abundance when present. Cycles in UCC and Luochuan Loess MARs may indicate continental and loess‐like material transported by major rivers into the Okinawa Trough. Increases in sea level and grain size proxy (e.g., SiO2/Al2O3) are coincident with increased flux of Southern Japanese Islands, indicating localized sediment supply from Japan. Increases in total terrigenous MAR precede minimum relative sea levels by several thousand years and may indicate remobilization of continental shelf material. Changes in the relative contribution of these end‐members are decoupled from total MAR, indicating compositional changes in the sediment are distinct from accumulation rate changes but may be linked to variations in sea level, riverine and eolian fluxes, and shelf‐bypass processes over glacial‐interglacials, complicating accurate monsoon reconstructions from fluvial dominated sediment.

Aeolian delivery to Ulleung Basin, Korea (Japan Sea), during development of the East Asian Monsoon through the last 12 Ma

“…This element suite has proved useful in other NW Pacific studies to discriminate between terrigenous and volcanic sources (e.g. Ziegler et al 2007;Scudder et al 2009Scudder et al , 2014Anderson et al 2018), and our use of them here also facilitates comparison to these other relevant studies. Other refractory elements (e.g.…”

“…With continued progress in determination of aeolian provenance, we can also improve reconstructions and interpretations of continental margin deposits over shorter time frames (e.g. Anderson et al 2018).…”

“…Homogenized representative subsamples were freeze-dried and hand powdered with an agate mortar and pestle for each discrete sample prior to digestion. Samples were dissolved using flux fusion and acid digestion, and were analysed for a total of 50 elements as described most recently by Anderson et al (2018).…”

“…The implementation and interpretation of these techniques are guided by downhole profiles of elemental ratios and ternary plots to ensure the statistical results are consistent with the basic geochemical characteristics of the dataset. These statistical techniques have been used in a variety of marine settings by our research group and are discussed at length in Anderson et al (2018) and references therein. QFA determines the minimum number of components necessary to explain a given fraction of total variance in a dataset by identifying groups, or 'factors', of co-varying elements (Pisias et al 2013).…”

Stable Isotope Analysis of Japan Sea and East China Sea Sediments: Late Pleistocene Paleoceanographic Reconstructions

“…The sea is surrounded by China, Taiwan, the Japanese archipelago, and the Korean peninsula and has an open exchange with the Bohai Sea, Yellow Sea, South China Sea, and Pacific Ocean and a limited exchange with the Japan Sea. The Yangtze and Yellow Rivers discharge significant amounts of freshwater, nutrients, and sediment to the East China Sea with increased discharge during East Asian Summer Monsoon (EASM) conditions (Anderson et al, 2018;).…”