南海南部陆坡晚第四纪沉积环境变化

The Changes of the Depositional Environment of the Southern South China Sea Continental Slope during Late Quaternary

主要依据沉积柱状样的颜色、粒度、矿物分布及其地球化学等特征,结合微体古生物记录等对南海南部陆坡末次冰期以来的沉积环境进行分析。结果表明,冰期-间冰期气候变化引起的海-陆变迁、通道启闭和上升流活动等造成了南海南部陆坡区的古沉积环境曾一度发生明显改变。其中在末次冰期期间,由于海平面降低,搬运入海的陆源物质增加,造成海洋生态环境相对较差;同时由于该区域水体相对较为封闭,水体交换减弱,陆坡区海底的沉积环境基本上为还原状态。冰后期全球气候变暖,海平面上升,海洋生态环境趋好,特别以全新世早期为最佳;并且由于水体的流通状况改善,该海区深层水的氧气补给量也增加。

According to the characteristics of the sediment color, grain size and mineral compositions, as well as the records of paleomicrofossils in 86GC core, the change of the depositional environment of the southern South China Sea （SCS） continental slope since the last glacial period are analyzed. The results indicate that the paleo-depositional environment of the southern SCS continental slope experienced obvious changes due to the marine-terrestrial transition, the open and close of strait thoroughfare and the upwelling activities caused by climate changes in the glacial and interglacial periods. During the last glacial period, the sea level was low and the terrestrial matters transported into the southern SCS increased and the ecologic environment in the studied sea area deteriorated. Owing to the relatively close condition of the sea area, water mass exchange was weakened, which caused the reduction condition of deep water. However, since the postglacial period, the global climate warmed up, the sea level began to rise, and the intensified southwest monsoon caused upwelling in the southwest part of SCS. All those factors consequentially resulted in the active water mass exchange and enhanced the oxygen supply to the sea floor, then the ecologic environment tend to melioration in the sea area, especially during the early Holocene.