지난 35만년 동안 북서태평양에 퇴적된 풍성기원입자의 기원지 변화 연구

Abstract

Eolian dust, emitted from dry areas of the Asia, are transported to China, Korea, Japan, and the northwestern Pacific via the westerlies jet (WJ) and East Asian Winter Monsoon (EAWM), of which role as a transport agent in a specific site varies in importance depending on relative position to trajectories of these two wind systems. The Shatsky Rise, the mid-latitude oceanic plateau located in remote northwest Pacific, is under the minimal influence of the EAWM in dust transport and is thus a plausible place to trace changes in trajectory of the WJ in the geologic past. We investigated chemical and physical characteristics of inorganic silicate fractions deposited by eolian process for the last 350 kyrs in a core from the South High of the Shatsky Rise (32°16&#697 N, 158°13&#697 W, 2514m). Sr and Nd isotope compositions and crystallinity and electron spin resonance signal intensity of quartz grain indicated unanimously the increased supply of Mongolian Gobi (MG) dust during the glacial periods. In contrast, Taklimakan dust prevailed during the interglacials. Such a systematic variation is attributed to changes in timing of the seasonal northward movement of the WJ main axis to the north of the Himalaya-Tibetan Plateau (HTP) over the glacial-interglacial cycles. The WJ main axis had likely stayed south of the HTP throughout year or most of the year during glacial periods. This process enhances the long-range transportries in importance depending on relative position to trajectories of these two wind systems. The Shatsky Rise, the mid-latitude oceanic plateau located in remote northwest Pacific, is under the minimal influence of the EAWM in dust transport and is thus a plausible place to trace changes in trajectory of the WJ in the geologic past. We investigated chemical and physical characteristics of inorganic silicate fractions deposited by eolian process for the last 350 kyrs in a core from the South High of the Shatsky Rise (32°16&#697 N, 158°13&#697 W, 2514m). Sr and Nd isotope compositions and crystallinity and electron spin resonance signal intensity of quartz grain indicated unanimously the increased supply of Mongolian Gobi (MG) dust during the glacial periods. In contrast, Taklimakan dust prevailed during the interglacials. Such a systematic variation is attributed to changes in timing of the seasonal northward movement of the WJ main axis to the north of the Himalaya-Tibetan Plateau (HTP) over the glacial-interglacial cycles. The WJ main axis had likely stayed south of the HTP throughout year or most of the year during glacial periods. This process enhances the long-range transport