Orbital‐ and millennial‐scale paleoceanographic changes in the north‐eastern Japan Basin, East Sea/Japan Sea during the late Quaternary

Abstract

Two gravity sediment cores (GH99‐1239 and GH99‐1246) obtained from the north‐eastern Japan Basin in the East Sea/Japan Sea were analyzed for the orbital‐ and millennial‐scale paleoceanographic changes. Chronostratigraphically, core GH99‐1239 represents a continuous sedimentary record since 32 ka, based on correlation of distinct lithological markers (i.e. dark layer or TL layer) with those in core GH98‐1232 collected nearby. For core GH99‐1246, the age model is constructed through correlation of lightness (L*) values and tephra (Aso‐4 and Toya) layers with those in the well‐dated Oki Ridge core (MD01‐2407), indicating about 134 ka of sedimentation since the latest Marine Isotope Stage (MIS) 6. New geochemical data from both cores corroborate orbital‐scale paleoceanographic variation, such that surface‐water productivity, represented by biogenic opal and total organic carbon (TOC) contents, increased during MIS 1 and MIS 5; CaCO3 contents do not show such distinct glacial–interglacial cycles, but were influenced by dissolution and preservation rather than foraminiferal production. During the glacial periods when sea ice was prevalent, surface‐water productivity was low, and bottom‐water conditions became anoxic, as indicated by high total sulfur (TS) contents and high Mo concentrations. The geochemical data further document millennial‐scale paleoceanographic variability, corresponding to a series of thin TL layers in response to Dansgaard–Oeschger cycles but irrespective of the glacial or interglacial periods. In particular, thin TL layers formed during MIS 3 are characterized by less TOC (about 1%) and TS (about 0.4%) contents and lower Mo (about 5 p.p.m.) concentration, whereas those during MIS 4 and MIS 5 exhibit more TOC (up to 4%) and TS (up to 5%) contents and higher Mo (up to 120 p.p.m.) concentration. Such a discrepancy is attributed to different degree of surface‐water productivity and of bottom‐water oxygenation, which is closely related to the sea level position and extent of ventilation. Flux of the East China Sea Coastal Water controlled by millennial‐scale paleoclimatic events is the most critical factor in deciding the properties of TL layers in the north‐eastern Japan Basin. Our results strongly confirm that TL layers in the Japan Basin also validate the unique feature of basin‐wide paleoceanographic signals in the East Sea/Japan Sea. Copyright © 2011 John Wiley & Sons, Ltd.

Biological early diagenesis and insolation-paced paleoproductivity signified in deep core sediment organic matter

“…No hysteresis was observed here presumably due to the negligible time for organic matter from ocean surface settling down to the sediments compared to the 405-Kyr. Although the glacial-interglacial cyclic variations of density, biogenic opal, and total organic carbon have been previously reported in this region 1 , 40 , these shorter cycles could not be reflected in the data presented in this study since it needs higher resolution records. The estimated oscillations amplitude in PWDOM were 3.5 mM for DOC, 2.3 m −1 and 0.6 m −1 for a 254 and a 350 , and 0.4 RU, 0.2 RU, and 0.4 RU for C1p, C2p, and C3p (Table 2 ).…”

A paleoenvironmental reconstruction of the last 15 000 cal yr BP via Yellow Sea sediments using biomarkers and isotopic composition of organic matter

“…Recent applications of paleoclimatology to reconstruct Asian paleomonsoon variability have been well documented elsewhere (Ishiwatari et al, 2001;Ijiri et al, 2005;Zhao et al, 2006;Fujine et al, 2006;Yu et al, 2011;Khim et al, 2012). Oscillations in grain size and magnetic susceptibility between the late glacial and interglacial periods on the Chinese Loess Plateau over the last 179 kyr might have been caused by variability in the Asian paleomonsoon (Zhang et al, 2003).…”

Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current

“…Glacio-eustatic sea level fluctuations are critical key processes that bring about dramatic environmental shift between the glacial and interglacial periods of the East Sea, because all the straits connecting the East Sea with the neighboring seas are very Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current shallow (Gallagher et al, 2018;Itaki et al, 2004;Khim et al, 2007Khim et al, , 2008Khim et al, , 2009Khim et al, , 2012Kido et al, 2007;Oba et al, 1991;Tada et al, 1999). The East Sea was almost isolated during the last glacial maximum (LGM; 26.5-19 ka, Clark et al, 2009) when the global sea level was lowered by approximately 120-130 m (Fairbanks, 1989).…”

“…For example, such a physiographic constriction prevented the influx of the TWC, which subsequently caused a remarkable change in the sediment deposition due to the hydrographic alteration of seawater properties. As a result, in response to the low sea level position during the last glacial period, the dark laminated mud layers characterized by the high concentration of redox-sensitive elements were deposited on the seafloor at a water depth greater than at least 500 m (Bahk et al, 2000;Crusius et al, 1999;Ikehara et al, 1994;Khim et al, 2008Khim et al, , 2009Khim et al, , 2012.…”