Early Pleistocene evolution of the Japan Sea Intermediate Water

Abstract

The Early Pleistocene fossil record of the Japan Sea reveals that the planktonic foraminifer Globorotalia inflata succeeded in expanding its range from the East China Sea to the Japan Sea during interglacial stages of the Early Pleistocene; however, the species is only found in surface sediment samples from the southwestern-most part of the sea. Based on the ecology of G. inflata and the water mass structure of the Japan Sea, it appears that its geographical distribution is mainly controlled by the low temperature of the intermediate water, which is caused by the cool-water mass of Japan Sea Proper Water. The temporal and spatial patterns of G. inflata occurrence indicate that the intermediate water at 200 m depth during interglacial stages between 1.46 and 1.3 Ma was warmest during the Quaternary. This warm intermediate water probably resulted from the influence of the low-salinity nature of the Tsushima Current due to the large inflow of East China Sea Coastal Water. After 1.3 Ma, the intermediate water at 200 m depth became cooler in a step-wise manner. This cooling can be explained by an intensification of thermohaline circulation in the Japan Sea associated with strengthening of the East Asian winter monsoon and an increase in salinity due to enlargement of the southern strait.

Transitional changes in microfossil assemblages in the Japan Sea from the Late Pliocene to Early Pleistocene related to global climatic and local tectonic events

“…3 Ma,according to the high occurrence of G. ruber and G. inflate, which was related to the TWC inflow (Kitamura 2009). During this period, the occurrence of warm-water ostracods in the Hamada Formation (ca.…”

“…Furthermore, the upper bathyal ostracod and deep-water radiolarian assemblages related to the cold JSPW are first observed near the Pliocene-Pleistocene boundary (Yamada et al 2005;Kamikuri and Motoyama 2007). A reduction in the planktonic foraminifera G. inflata indicates related cooling at intermediate depths (Kitamura 2009). After 2.8 Ma, an intensified winter monsoon and sea-ice expansion, indicated by the Chinese eolian loess (Xiong et al 2003) and IRD at ODP site 795 in the northern Japan Sea (Tada 1994), probably caused increased ventilation during the interglacial periods, as in the present day, as suggested by an increase in the JSPW-related radiolarian and ostracod fauna at that time.…”

Pleistocene biogeochemical record in the south‐west Pacific Ocean (images site MD97‐2114, Chatham Rise)

“…A shallow thermocline favors larger populations of these deep‐dwellers (e.g. West et al ., 2004; Kitamura, 2009), which has a preference for oligotrophic waters with a small but steady food supply (Giraudeau and Rogers, 1994; Northcote and Neil, 2005). N. incompta is another non‐symbiont species, shallow mixed‐layer dweller principally inhabiting transitional–subantarctic water.…”

The evolution of the Tsushima Current during the early Pleistocene in the Sea of Japan: An example from marine isotope stage (MIS) 47

“…The Yuhidera section can be correlated to the depositional sequences of the Okuwa section and was deposited in water a few tens of metres deeper . Kitamura (2009) compared the distribution of planktic foraminifera between deep-sea sediments in the Sea of Japan and the Omma Formation. It was found that the deep-sea sections had relatively poor carbonate preservation due to a shallower CCD (carbonate compensation depth) during interglacial periods after 1.7 Ma when compared with those from the Omma Formation.…”