海南岛福山凹陷古近系流沙港组沉积相

Sedimentary facies of the Liushagang Formation of Paleogene in Fushan Sag of Hainan Island

古近系流沙港组沉积时期是海南岛福山凹陷的主要成盆期,沉陷幅度较大,地势较陡,由此导致流沙港组深水湖泊沉积和辫状河三角洲沉积相当发育。通过对岩心、测井和地震等资料的综合分析,分别对流沙港组3个岩性段的沉积相进行了研究。单井沉积相和平面沉积相分析表明流沙港组主要发育辫状河三角洲相和湖泊相,并可进一步划分出7种亚相和13种微相。流三段沉积时期辫状河三角洲沉积最为发育,约占研究区总面积的一半,仅在研究区北部为半深湖亚相—深湖亚相分布区。流二段沉积时期是福山凹陷最大湖侵期,深水湖泊相最为发育,研究区北半部几乎全为深湖亚相—半深湖亚相分布区。流二段沉积之后,凹陷周缘发生较大范围隆升,因此,流一段沉积时期的沉积范围比流二段沉积时期小得多,但其沉积相展布格局与流二段沉积时期仍比较相似。通过对ZTR指数(代表锆石、金红石、电气石三种重矿物在透明重矿物中所占的比例)等值线图、砂(砾)岩百分含量等值线图及沉积相展布格局等分析认为,流沙港组沉积时期的物源主要来自南方的海南隆起,东、西方向还存在2个次要物源。

The deposition of the Liushagang Formation of Paleogene coincided with the main basin forming period of the Fushan Sag. During this period, the subsidence was rather significant and the surface relief was rather steep. As a result, the deposits of deep lacustrine and braided delta were well developed. Based on the comprehensive analyses of the core and the well logs and seismic data, the sedimentary facies of the Liushagang Formation have been studied. The individual well sedimentary facies and the plane sedimentary facies analyses indicate that the braided delta and lacustrine facies are two major sedimentary facies in the Liushagang Formation, which can be further sub-divided into seven sub-facies and thirteen microfacies. During the deposition of the member 3 of the formation, the braided delta deposit was most developed, and it covered half of the study area. The semi-deep and deep lacustrine sub-facies were restricted to the northern part of the study area. During the deposition of the member 2 , the maximum lake transgression occurred in the Fushan Sag. The deep lacustrine facies was most developed so that the semi-deep and deep lacustrine sub-facies nearly occupied the entire northern half of the study area. After this stage, the areas surrounding the sag uplifted greatly. Thus the sedimentary area of the member 1 of Liushagang Formation was much smaller than that of the member 2, but its pattern of sedimentary facies distribution was similar to that of the member 2. Based on the analyses of the isoline maps of ZTR index, the percentage of sandstones （and conglomerates） ,and the distribution pattern of sedimentary facies, we conclude that the source of sediments are mainly from the Hainan Uplift, south part of the Fushan Sag. In addition, there are two secondary source areas that are located in the east and west.