Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation |
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| Authors: | Masaki Inagaki Masanobu Yamamoto Yaeko Igarashi Ken Ikehara |
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| Institution: | (1) CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, No. 511 Kehua St., Tianhe District, Guangzhou, 510640, China;(2) The First Institute of Oceanography, SOA, Qingdao, 266061, China;(3) Graduate School of Chinese Academy of Sciences, Beijing, 100039, China; |
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| Abstract: | We investigated marine and terrestrial environmental changes at the northern Japan margin in the northwestern Pacific during
the last 23,000 years by analyzing biomarkers (alkenones, long-chain n-alkanes, long-chain n-fatty acids, and lignin-derived materials) in Core GH02-1030. The U
37K′-derived temperature in the last glacial maximum (LGM) centered at 21 ka was ∼10°C, which was 2°C lower than the core-top
temperature (∼12°C). This small temperature drop does not agree with pollen evidence of a large air temperature drop (more
than 4°C) in the Tokachi area. This disagreement might be attributed to a bias of U
37K′-derived temperature within 2.5°C by a seasonal shift in alkenone production. The U
37K′-derived temperature was significantly low during the last deglaciation. Because this cooling was significant in the Kuroshio-Oyashio
transition zone, the temperature drops are attributable to the southward displacement of the Kuroshio-Oyashio boundary. Abundant
lignin-derived materials, long-chain n-alkanes and long-chain n-fatty acids indicate a higher contribution of terrigenous organic matter from 17 to 12 ka. This phenomenon might have resulted
from an enhanced coastal erosion of terrestrial soils due to marine transgression and/or an efficient inflow of higher plant
debris to river waters from 17 to 12 ka. |
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