琼东南盆地北部新近系三亚组遗迹组构特征及其沉积环境OA北大核心CSTPCD

The trace fossils are well developed in the Neogene strata with the huge thickness in northern Qiongdongnan Basin.Based on detailed observation of the cores from seven drilling wells,combi-ning with the thin section analysis,imaging logging and related experiments,the ichnofabric characteris-tics and sedimentary environment of the Neogene Sanya Formation were studied in detail.The results show that a total of 14 genera of trace fossils have been identified in the Neogene Sanya Formation in northern part of the Qiongdongnan Basin.Based on the types,occurrence,abundance and diversity of trace fos-sils,biodisturbance degree,and symbiotic relationship between biological burrows,five ichnofabrics can be classified.Among them,the Ophiomorpha-Thalassinoides ichnofabric was mainly developed in the up-per shoreface,the Palaeophycus ichnofabric was mainly developed in the middle shoreface,the Planol-ites-Talassionides ichnofabric was mainly developed in the lower shoreface,the Phycosiphon-Planolites ich-nofabric is mainly developed in the upper shallow sea,and the Phycosiphon-Chondrites ichnofabric was mainly developed in the lower shallow sea.Based on analysis of the ichnofabrics and logging facies,it is believed that the coastal and offshore sedimentary environment was mainly dominated in the Neogene Sanya Formation in the study area.The first section of Sanya Formation transited from coast to shallow marine,while the second section of Sanya Formation was mainly dominated by shallow sea deposition.Based on the analysis of lithofacies,fossils,ichnofabric characteristics,logging facies and sedimentary microfacies of Sanya Formation,the sedimentary model of Neogene Sanya Formation in the northern part of the Qiong-dongnan Basin has been established.It has an important guidance for the hydrocarbon exploration of the Neogene in the northern South China Sea.