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Reconstruction of Holocene Optimum paleoclimatic variations using long-chain n-alkanes and alkenones in sediments from Dabusu Lake, northeastern China
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| Title: | Reconstruction of Holocene Optimum paleoclimatic variations using long-chain n-alkanes and alkenones in sediments from Dabusu Lake, northeastern China |
| Authors: | Sawada, Ken Browse this author →KAKEN DB | | Ono, Makiko Browse this author | | Nakamura, Hideto Browse this author | | Tareq, Shafi Mohammad Browse this author |
| Keywords: | Alkenone-based temperature | | n-alkane proxy | | Holocene Optimum | | P | | aleoclimatic variation | | Chinese saline lake | | Asian Monsoon events |
| Issue Date: | 10-Jun-2020 |
| Publisher: | Elsevier |
| Journal Title: | Quaternary international |
| Volume: | 550 |
| Start Page: | 27 |
| End Page: | 38 |
| Publisher DOI: | 10.1016/j.quaint.2020.03.011 |
| Abstract: | Long-chain n-alkanes and alkenones were analyzed in sediments from Dabusu Lake, northeastern China, from ca. 7.2-4.5 kyr BP (the Holocene Optimum) and the present. Long-chain n-alkanes are derived from leaf waxes of terrestrial vascular plants and aquatic macrophytes. Using n-alkane proxies such as Paq and average chain length (ACL) indices, variations in paleovegetation were reconstructed. The Paq values were generally low, indicating that aquatic macrophytes were a minor floral component in Dabusu Lake. The ACL data indicated that forest/ grassland mixed vegetation occurred around the lake. From the alkenone distribution patterns (C-37/C-38, C-40/C-37, and %C-37: 4 ratios), the main alkenone producers were inferred to be Group II producers, especially Ruttnera lamellosa. We estimated water temperatures based on alkenone unsaturation indices (U-37(K) and UK37K") using the temperature calibrations obtained from culture strains of R. lamellosa. The variation pattern of the U-37(K")-based water temperatures was almost similar to that of the U-37(K)-based pattern, although some spikes differed between the temperatures based on the two indices. The U-37(K')'-based water temperatures were lower from 7.2 to 6.2 kyr BP, and subsequently increased after 6.2 kyr BP. The alkenone-based temperatures were highest from 5.5 to 5.3 kyr BP, indicating that this maximal stage was the Holocene Thermal Maximum in the Dabusu region. The markedly decreasing spikes of UK''37-based water temperatures in our study likely corresponded to the cooling events during the Holocene Optimum, as previously reported, especially Asian monsoon events (AM) 1 and Bond event 4 (BE4). Also, the increasing spike (7.2 kyr BP) in temperatures was possibly associated with the warming regime just after AM2. Moreover, the rapid increasing spikes of alkenone-based temperatures corresponded to those of Paq at 7.2 kyr BP (just after AM2) and 6.4 kyr BP. These results imply that the rapid warming reconstructed using alkenone-based temperatures might have resulted in increased precipitation around the lake at these ages, especially just after the AM2 cooling. |
| Rights: | ©2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ | | http://creativecommons.org/licenses/by-nc-nd/4.0/ |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/85811 |
| Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 沢田 健
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