海南岛三亚湾全新世以来沉积特征与古环境演变

On the sedimentary environment change since Holocene in the Sanya Bay, Hainan Island

根据海南岛三亚湾SY01钻孔AMS14C测年建立沉积物年代框架,结合粒度、烧失量、色度和有孔虫等分析研究了三亚湾地区的海平面变化、沉积相和古环境演变过程。结果表明,SY01钻孔的沉积物呈现5个变化阶段:含砾粉砂层-含粗砂粉砂层-含中砂粉砂层-含细砂粉砂层-粉砂层;有孔虫和介形虫的分析结果显示出其主要出现在8.1~3.7calkaBP期间,且含量最丰富的层位在5.2~4.7calkaBP;烧失量的分析结果表明有机质和碳酸盐在5.2~4.7calkaBP期间的含量相对较高,揭示该时期陆地或海洋生物较为繁盛;色度值的结果也反映该阶段处于还原状态的沉积环境。因此,综合各个环境代用指标,研究区域的沉积过程划分为5个阶段:洪积相内侧-洪积相远端-滨岸相-海湾相-潟湖相;三亚湾地区从~9calkaBP开始沉积,全新世海侵高海平面期为~5calkaBP,之后进入晚全新世海退阶段,河流泥沙输送形成了三亚湾砂质海岸。

In order to study the sedimentary evolution and paleoenvironments change during the early Holocene, a 15.6 m core (SY01) was obtained from the Sanya basin. The age frame of core SY01 was established based on four AMS 14 C dating results. The paleoenvironmental analysis methods of grain size, loss on ignition (LOI), grayscale and foraminifera were used to reconstruct the sea level change, sedimentary facies and paleoenvironment evolution in this area. The results show that the SY01 sediments can be divided into five layers: gravel-silty fine sand layer, coarse-silty sand layer, medium-silty sand layer, fine-silty sand layer, and silty sand layer. The foraminifera mainly occurred in the period of 8.1-3.7 cal ka BP, with the highest abundance during 5.2-4.7 cal ka BP. The LOI analysis shows that the contents of organic matter and carbonate were relatively high during 5.2-4.7 cal ka BP, and the grayscale values also reflect the sedimentary environment with a reduction condition. Therefore, the depositional process of the study area can be divided into 5 stages: Inner pluvial facies-Lateral pluvial facies-Littoral facies-Estuarine facies-Lagoon facies. The deposition started from ~ 9 cal ka BP, and the highest sea level occurred at ~ 5 cal ka BP, and then the Sanya basin became the fresh water environment in the late Holocene.