Palaeoenvironmental changes from pollen record in deep sea core PC-1 from northern Okinawa Trough, East China Sea during the past 24 ka |
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Authors: | HongYan Xu FengMing Chang YunLi Luo and XiangJun Sun |
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Institution: | 1 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
2 Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;
3 State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;
4 Graduate University of Chinese Academy of Sciences, Beijing 100049, China |
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Abstract: | A pollen record of core PC-1 from the northern Okinawa Trough, East China Sea (ECS), provides information on vegetation and
climate changes since 24 cal. kaBP. A total of 103 samples were palynologically analyzed at 8 cm intervals with a time resolution
of 230 a. Four pollen zones are recognized: zone I (812–715 cm, 24.2–21.1 cal. kaBP), zone II (715–451 cm, 21.1–15.2 cal.
kaBP), zone III (451–251 cm, 15.2–10.8 cal. kaBP), zone IV (251–0 cm, 10.8–0.3 cal. kaBP), corresponding to Late MIS 3, Last
Glacial Maximum (LGM), deglaciation and Holocene, respectively. The LGM is characterized by the dominance of herbs, mainly
Artemisia, and high pollen influx, implying an open vegetation on the exposed continental shelf and a cool and dry climate. The deglaciation
is a climate warming stage with Pinus percentage increased and Artemisia percentage decreased and a rapid sea-level rise. The Holocene is characterized by predominance of tree pollen with rapid
increase in Castanea-Castanopsis indicating the development of mixed evergreen and deciduous broad-leaved forest and a warm, humid climate. Low pollen influx
during the Holocene probably implies submergence of the continental shelf and retreat of the pollen source area. The vegetation
indicated by pollen assemblage found in this upper zone is consistent with the present vegetation found in Kyushu, Japan.
Originating from the humid mountain area of North Luzon of the Philippines, Tasmania and New Zealand, Phyllocladus with sporadic occurrence throughout PC-1 core probably suggests the influence of Palaeo-Kuroshio Current or intense summer
monsoon. The observed changes in Pinus and Herbs percentage indicate fluctuations of the sea level, and high Pinus percentage corresponds to high sea level. Spectrum analysis of the pollen percentage record reveals many millennial-scale
periodicities, such as periodicities of 6.8, 3.8, 2.2, 1.6 ka. |
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Keywords: | East China Sea Okinawa Trough palynology Kuroshio palaeoenvironment MIS |
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