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Modern and past processes of ocean-atmosphere-climate interactions in the low-latitude western Pacific and Indian Ocean
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Regional paleoenvironment record of dinocycts in the Beibu Gulf: evidence from sedimentary core SO31
P-G2-02
Chao Li* , Xiamen University
Jinpeng Zhang, Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 510760, China
Yilin Cai, Xiamen University
Tingting Weng, Xiamen University
Xiulin Feng, Xiamen University
Zhichao Zhao, Xiamen University
Jianfei Mao* , Xiamen University
Guangshan Liu, Xiamen University
Pengfei Zhan* , Xiamen University
Presenter Email: lichao@xmu.edu.cn |
| Dinoflagellates are eukaryotic, single-celled plankton, important primary productivities in the sea, and some species could produce resting cysts during their life cycle. Dinocysts indicator related to productivity, temperature and the eutrophication situation of seawater etc. In order to understand paleoenvrionment in the Holocene and Last Deglaciation in the Beibu Gulf, NW of the South China Sea, a sedimentary core SO31 (716 cm length, since ca. 13 cal. kyr. BP) from the middle of Beibu Gulf was processed and focused on the dinoflagellate cysts. 14 genus 37 species of dinocycts are identified from 178 samples, including the dominated species, Gonyaulax scrippsae, Gonyaulax spinifera, Gonyaulax sp., Lingulodinium polyedra, Posoniella tricarinelloide, Protoceratium reticulatum, Protoperidinium sp. and Scrippsiella trochoidea. According to dinocysts abundance and species assemblages, four dinocyst assemblage zones could be divided in this core.
The first dinocyst assemblage zone, in the 0 - 285 cm interval ( ca. 2700 cal. yr. BP to present), was characterized by not continuous disappearance of dinocysts, with poor abundance in general. These reflected dinoflagellates productivity was lower level under low nutrients condition. The dinocysts lack intervals, in term of unfavorable preservation conditions probably was influenced by strong hydrodynamics. More high average percentage of warm water species (e.g. G. scrippsae, G. spinifera, P. sp. Scippsiella trochoidea ). indicated a warm seawater environment.
The second dinocyst assemblage zone, in 285-485 cm interval (ca.2 700 - 7 500 cal. yr. BP) is characterized by higher abundances in general, with higher percentage of G. scrippsae, S. trohoides, L. polyedra. In addition, P. tricarinelloides and P. reticulatum with peak percentage were 30.5% and 76.5% respectively. These indicated relative stable hydrodynamic status with higher nutrients condition.
The third zone, in 485-615 cm interval, (ca.7 500 - 11 700 cal. yr. BP) is characterized by dinocycts abundance changes greatly, with higher percentage of G. scrippsae, G. sp., L. polyedra and S. trohoides, the extreme abundance in this core occurred at ca.9 300-?9 500 cal. yr. BP, that means algal blooms might had outbroken with terrigenous nutrients input increased during the early Holocene.
The forth dinocyst assemblage zone, in 615 - 715cm interval (ca. 11700 - ca. 13 000 cal. yr. BP), was characterized by lower abundances with less taxa, and just Gonyaulax spp., Protoperidinium sp. had relatively high percentage. This zone was set in the rising sea level process with relative strong hydrodynamic environment after the last Glacial Maximum. The autotrophic type a little more than heterotrophic type with means of the mix water happened.
Key words: dinocycts, paleoenvironment record, Beibu Gulf |
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