Benthic foraminiferal assemblage of Seogwipo Formation in Jeju Island, South Sea of Korea: Implication for late Pliocene to early Pleistocene cold episode in the northwestern Pacific margin

摘要

Foraminiferal faunal records of the Seogwipo Formation (SGF), old marine sedimentary strata of Jeju Island in the South Sea of Korea, strongly influenced by Kuroshio, were investigated to study mid-latitude northwestern Pacific Ocean response to Northern Hemisphere deglaciation during the Plio-Pleistocene transition period. The variation of benthic foraminiferal assemblage clearly indicates that the SGF, especially the early to middle stage of the formation (ca. 1.7-0.85 Ma), was deposited during the cold phase of the climate, corresponding to the global early Pleistocene cold episode. This cooling phase recorded in the SGF is a possible indication of extended influence of oceanic front in northwestern Pacific marginal seas due to 1) strengthened subarctic water mass by polar cooling from high northern latitude ice sheet expansion during the late Pliocene/early Pleistocene, and/or 2) decrease of the Kuroshio Current in response to changes in thermal contrast between subarctic and subtropical water masses during that period. The result suggests a strong teleconnection between high northern latitude climate and mid-latitude oceanographic conditions, implying the existence of important feedback between these distant regions.