| Paleoclimate and Paleoenvironment of Gonghe Basin, Qinghai-Tibet Plateau, During the Lastdeglacial: Weathering, Erosion and Vegetation Cover Affect Clay Mineral Formation |
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| 作者姓名： | SUN Qingfeng and Christophe COLIN |
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| 作者单位： | 1 Faculty of Geography, Northwest Normal University, Lanzhou 730070, Gansu, China
2 Laboratoire des Interactions et Dynamique des Environnements de Surface (IDES), UMR 8148, CNRS- Université de Paris-Sud, Batiment 504, 91405 Orsay Cedex, France |
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| 基金项目： | This work is financially supported by the Natural Science Foundation of China (Grant No. 41061022) and China Scholarship Council. |
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| 摘 要： | With the analysis of the sources and formation mechanism of the clay minerals in the sediment core from the Dalianhai lake in the Gonghe Basin,northeastern Tibet-Qinghai Plateau,clay mineral composition proxies,grain-size and carbonate contents have been employed for high-resolution study in order to reconstruct East Asian Summer Monsoon （EASM） over the northeastern Tibet-Qinghai Plateau during the lastdeglacial.The study also extended to establish a relationship between vegetation cover changes and erosion during the last 14.5 ka with pollen record and clay mineral proxies.Smectite/kaolinite and smectite/（illite＋chlorite） ratios allow us to assess hydrolysis conditions in lowlands and/or physical erosion process in highlands of the Gonghe Basin.Before 12.9 Cal ka BP,both mineralogical ratios show low values indicative of strong physical erosion in the basin with a dominant cold and dry phase.After 12.9 Cal ka BP,an increase in both mineralogical ratios indicates enhanced chemical weathering in the basin associated with a warm and humid climate.The beginning of Holocene is characterized by high smectite/（illite＋chlorite） and smectite/kaolinite ratios that is synchronous as with deposition of many peat laminae,implying the best warm and humid conditions specifically between 8.0 to 5.5 Cal ka BP.The time interval after 5.0 Cai ka BP is characterized by a return to high physical erosion and low chemical weathering with dry climate conditions in the basin.Comparing variations of clay mineral assemblages with previous pollen results,we observe a rapid response in terms of chemical weathering and physical erosion intensity to a modification of the vegetation cover in the basin.
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| 关 键 词： | 植被覆盖变化 共和盆地 物理风化 粘土矿物 侵蚀过程 青藏高原 矿物形成 古气候 |
| 收稿时间： | 2013/11/12 0:00:00 |
| 修稿时间： | 2014/1/24 0:00:00 |
Paleoclimate and Paleoenvironment of Gonghe Basin,Qinghai-Tibet Plateau,During the Lastdeglacial： Weathering,Erosion and Vegetation Cover Affect Clay Mineral Formation |
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| Authors: | SUN Qingfeng Christophe COLIN |
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| Abstract: | With the analysis of the sources and formation mechanism of the clay minerals in the sediment core from the Dalianhai lake in the Gonghe Basin, northeastern Tibet-Qinghai Plateau, clay mineral composition proxies, grain-size and carbonate contents have been employed for highresolution study in order to reconstruct East Asian Summer Monsoon(EASM) over the northeastern Tibet-Qinghai Plateau during the lastdeglacial. The study also extended to establish a relationship between vegetation cover changes and erosion during the last 14.5 ka with pollen record and clay mineral proxies. Smectite/kaolinite and smectite/(illite+chlorite) ratios allow us to assess hydrolysis conditions in lowlands and/or physical erosion process in highlands of the Gonghe Basin. Before 12.9 Cal ka BP, both mineralogical ratios show low values indicative of strong physical erosion in the basin with a dominant cold and dry phase. After 12.9 Cal ka BP, an increase in both mineralogical ratios indicates enhanced chemical weathering in the basin associated with a warm and humid climate. The beginning of Holocene is characterized by high smectite/(illite+chlorite) and smectite/kaolinite ratios that is synchronous as with deposition of many peat laminae, implying the best warm and humid conditions specifically between 8.0 to 5.5 Cal ka BP. The time interval after 5.0 Cal ka BP is characterized by a return to high physical erosion and low chemical weathering with dry climate conditions in the basin. Comparing variations of clay mineral assemblages with previous pollen results, we observe a rapid response in terms of chemical weathering and physical erosion intensity to a modification of the vegetation cover in the basin. |
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| Keywords: | clay minerals vegetation Gonghe Basin Tibet-Qinghai Plateau Asian monsoon Holocene |
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