| 北部湾全新世气候与古生态环境演进特征及其驱动因素 |
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| 关键词:Beibu Gulf Holocene palaeo-ecology palaeo-productivity |
| 基金项目:中国地质调查局“海南岛东北部沿海地区综合地质调查”(编号: DD20190308);地质科研项目“南海北部湾全新世环境演变及人类活动影响研究”(编号: 1212010914027) |
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| The Driving Factors on Climatic and Palaeo-ecological Evolution of Beibu Gulf since Holocene |
| Located on northwestern South China Sea and the transition zone between continent and marine, less understanding on Beibu Gulf’s background of Holocene palaeo-climatic & ecological evolution needs to further improve. We acquired Holocene sediments drilling cores in its southern basin and made the lab analysis on high resolution samples’ sporopollen fossil, granularity, macro-& micro-geochemical elements, detrital mineral and δ18O and G.ruber 14C aging. Comprehensive analysis and comparison showed that composition of Pinus sp.,Castanopsis sp., Quercus sp., and Microlepia sp., Polypodaceae revealed historic tropical and sub-tropical climatic background, and fern spices’ general growth trend from 6.2 ka and also indicated fluctuations from their distribution. From above time point, silt sand and clay also generally increased and the sorting improved. Indicating continent provenance, Al2O3, Fe2O3, MgO etc increased and SiO2, CaO, MnO, Sr decreased instead, and main minerals were Quartz, Feldspar and weathering mineral. δ18O temporal distritution could primarily corresponded to Chinese Holocece temperature demonstrating a cooling trend from HTO with mean relative difference –21.20% in δ18O, and the basic climatic phrases were classified based on 9.0 ka, 6.2 ka, 4.0 ka, 2.0 ka timing points displayed in regional and also North Atlantic fluctuations. It also showed that Beibu Gulf had become the interaction zone of summer monsoon systems and cold mass frontier after westerly southward shift enhancing the regional precipitation and chemical weathering, which demonstrated in hydro-genesis of heavy mineral Hematite too. Regional litho-surface process included coupled heat expand & extraction and de-silicon & –calcitication to speed up weathering and geochemical elements’s release forming soil horizon further. There were dramatic oscillations of above granularity and other elements during the end part of HTO also called deteriorating period showing a cooling as well as HTO termination trend in China. “4.2 ka Event” exerted significant impacts on sedimentation and since then the chemical weathering continued intensifying. Also the bio-diversity index of sporopollen fossil indicating the palaeo-vegetation’s structure and optimization displayed an overall increase based on above cycling time nodes and thus marine palaeo-produtivity benefited from climatically driving growth of runoff input. The summary could be reached that Beibu Gulf was sensitive to climatic change, westerly southward shift acted a positive effect on precipitation mechanism through climatic mode’s evolution constituting a transiton zone between warm as well as humid and cold air masses, and the litho-surface processes were under the almost orderly regulation of solar radiation forcing and climatic change and there was a close relationship between regional continent and marine forming a complex and had become the fundamental of modern ecosystem and an important marine ecological component of northern SCS. |
| HUANG Xiang-qing,CUI Zhen-ang,LIN Hai,XIA Zhen,ZHANG Shun-zhi.2022.The Driving Factors on Climatic and Palaeo-ecological Evolution of Beibu Gulf since Holocene[J].Acta Geoscientica Sinica,43(2):129-143. |
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