| 北部湾全新世海侵演进及其与气候、冰川关系分析 |
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| 关键词:Beibu Gulf transgression evolution climate glacier |
| 基金项目:中国地质调查局地质调查项目“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 Evolution of Beibu Gulf since Holocene Marine Progression and Its Relationship with Climatic and Glacial Change |
| The understanding of the evolution of Beibu Gulf since Holocene is necessary in protection, utilization and forecasting of Beibu Gulf’s environmental progress because it is an important large-scale continent shelf gulf and continent-marine transition zone which owns abundant marine resources under the background of global change. In this paper, the authors carried out laboratory analysis of geo-chemical elements, micro-paleontology and 14C age for samples from sediments core STAT22 in the southern basin of Beibu Gulf. Comprehensive data analysis shows that there were relatively abundant foraminifera and diatom fossils with dominant surface species Globigerinoides quadrilobatus, G.ruber, broad-temperature species Cyclotella striata and sub-dominant C.stylorum respectively and non-dominant species which fluctuate discontinuously. Sr/Ba ratio varies from 0.64 to 1.11, indicating quick sea level rise and marine progression from slope and then shelf of northern South China Sea during early Holocene and generally turned down together with foraminifera afterwards, but diatom increased instead for a growth of land input. Based on Sr/Ba ratio and the continuous variation features of main foraminifera and diatom species, 3 primary phrases of Beibu Gulf evolution corresponded to inter-glacial and glacial cycles with mean G.quadrilobatus and G.ruber 69.62%~93.50% and C.striata 39.39%~100.00% respectively. Molded palaeo-water depth’s linear slope was 3.091 m/ka and sedimentation rate also relatively rather slowly increased, revealing scouring and relatively stable hydro-dynamic equilibrium to maintain the gulf basin. Sr/Ba ratio and foraminifera abundance appeared maximally during 6.0~5.0 ka with amplitude 16.11%~344.74% but became lowered quickly from Late Holocene, i.e., from 5.0 ka to minimum in 4.0 ka, and regression started along near-shore and also exhibited high stands along near-shore which varied from 6.0~3.0 ka. The evolution of sea level could be comparable with Indo-Pacific fit output modes. The palaeo-Beibu Gulf stepped into new pattern from ~1.0 ka through general regression which could be further classified into 3 sub-phrases corresponding to pre-LIA, LIA, and warming period of modern time, and there were also active glacier advances from ~ 1.0 ka in Himalaya-Tibet orogenic belt, as shown by comparison with other study results. It could be concluded that Beibu Gulf was sensitive to global and regional climatic change, and there might had been mid-Holocene high sea level, mid-Holocene progression to near-shore and then palaeo-Mega Gulf; in addition, the main body of transgression was guided by the first-grade lowland system formed under tectonic background such as Red River Fault, meanwhile there was bottom scouring through palaeo-tide to keep the dynamically geomorphic balance, and transgression and high sea level in mid-Holocene were driven and maintained before mid-Holocene by tropical climatic system but its potential energy converted into second progressive energy to near-shore’s low-land complex for above climatic system’s southward shift from mid-Holocene. The above two ways of active and non-active marine progression constituted the foundation of of Beibu Gulf, and ~1.0 ka as an important new climatic phase from 2.0 ka was probably the modern Beibu Gulf’s starting time, and there was a tele-connection between Beibu Gulf and glacier advances in the Himalaya–Tibet orogenic belt. The combination effects of climatically driving and tectonically sunken stress-induced geomorphic lowland complex played fundamental role in the formation of Beibu Gulf. |
| HUANG Xiang-qing,LIANG Kai,XI Long,XIA Zhen,ZHANG Shun-zhi.2022.The Evolution of Beibu Gulf since Holocene Marine Progression and Its Relationship with Climatic and Glacial Change[J].Acta Geoscientica Sinica,43(1):49-64. |
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