广西科学2017，Vol.24Issue(6)：614-622,9.DOI:10.13656/j.cnki.gxkx.20171225.002
北部湾北部近岸全新世沉积环境变化及对8.2 ka小冷期的响应
The Coastal Sedimentary Environmental Changes and Their Response to Early 8.2 ka Cold Event along in the Northern Beibu Gulf since Holocene
摘要
Abstract
[Objective]The northern part of Beibu Gulf is not only in the area where East Asian summer monsoon meets Indian monsoon but also in the Mongolian cold high pressure zone.It is sensitive to climate changes.The distribution and variation of some indexes in the core sedi-ments from this area since Holocene reflect the characteristics of climate fluctuation and the factors controlling the coastal evolution.[Methods]In the northern Beibu Gulf,three cores were drilled from the area around Guangxi Province.The grain size,mineral and elemental compositions were determined,and paleontological identification and 14C dating were conduc-ted.The vertical distribution,variation of some indexes and their response characteristics to the climate event were compared and discussed.[Results ] In Holocene the sporopollen assemblage was characterized by the species of tropical and subtropical mountains.The fluctua-tion of the grain sizes along the cores represen-ted a sedimentary cycle,indicating the gradual change from the river bed deposits to the shal-low bay deposits.The sediments were of terrig-enous origin and the elemental compositions were almost synchronous with the fine compo-nents in the sedimentary cycle.Boreholes from the early Delta basin showed that the sediments deposited in the salt marsh environment.Compared with the late Pleistocene or the end of the Late Holocene,in the sediments deposited during the early Holocene the coarse particles re-duced and the fine particles increased,so the contents of organic matters increased by more than 700％.The types of detrital minerals also increased.The sporopollen and diatom fossils were abundant,and the number of diatom species also increased.The deposition rate was 1.36-1.85 times of the average rate in the whole Holocene.These features indicated the enhanced weathering,abundant sediment supplying,high deposition rates,and high biological produc-tivity in this period,which was accommodated to the climate conditions.Although the climate still fluctuated,the effect of the small cold event in 8.2 ka was remarkable and the Sr/Ba ratio was low.[Conclusion]As a land-sea interaction zone in the low altitude monsoon region of East Asia,the environmental changes of the study area were associated with the climate changes.关键词
北部湾北部/全新世/8.2/ka/小冷期/区域响应Key words
northern coast of Beibu Gulf/Holocene/8.2 ka cold event/regional response分类
天文与地球科学引用本文复制引用
黄向青,梁开,林进清,张顺枝,潘毅,霍振海,刘雄..北部湾北部近岸全新世沉积环境变化及对8.2 ka小冷期的响应[J].广西科学,2017,24(6):614-622,9.基金项目
中国地质调查局项目"我国重点海岸带滨海环境地质调查与评价"(1212010611403)资助. （1212010611403）
