The Mesozoic Sedimentary Systems In The Southern East China Sea Shelf Basin

The east China sea shelf basin is a Mesozoic-Cenozoic superimposed basin on acratonic basement. The southern part of the east China sea shelf basin neighboredFujian and Zhejiang uplift area to the west and Diaoyu Island fold belt to the east. Therecent discovery of oil and gas and well petroleum geological conditions indicate thatMesozoic has good oil and gas exploration prospects in study area. However, the lowlevel of basic geological research Is not able to give an accurate prediction ofMesozoic oil and gas resources potential evaluation in the region. Guided by theprinciple of Sequence Stratigraphy and Sedimentology, this paper has usedoutcrop, seismic, drilling, paleontology and related test to comprehensively study theMesozoic sedimentary system. Also in this paper, tectonic setting, magmatic activityand sediment source system of Mesozoic Era in East China Sea shelf basin ispreliminarily explored and a sedimentary model is established.Continental lacustrine facies is considered as the dominant facies in Cretaceousin the southern part of the east China sea shelf basin by previous study. Based on theanalysis of the cores, thin section, field emission electron microscopy, electronmicroprobe and other test results, types of sedimentary facies of target layers in thestudy area is identified and some new ideas different from previous views areproposed. Typical wave-generated wavy bedding and asymmetric tidal rhythmicbedding, abundant glauconite and marine fossils Tintinnid developed in the core ofCretaceous Minjiang Formation of FZ13-2-1well indicate that the sedimentaryenvironment of Mesozoic Upper Cretaceous Minjiang Formation in the southern partof the east China sea shelf basin is intertidal and subtidal zone of Shallow marine.Marine fossils coccolithophores and sponge spicules are found in Jurassic FuzhouFormation of FZ10-1-1well and the organic geochemical analysis of these fossils’source of organic materials are from lower marine plankton, both points out thedepositional environment in Mid-Lower Jurassic Fuzhou Formation in study area areshallow marine. Provenance analysis of Mesozoic core by mineralogical andgeochemical methods indicates that Mesozoic sedimentary-tectonic setting of thesouthern part of the East China Sea shelf basin is littoral-neritic sediments under thebackground of the island arc and continental arc.Within the sequence stratigraphic framework, seismic and sedimentary facies interpretation of2D seismic sections is conducted. Due to less drilling in study area,2D seismic attributes, regional paleoclimate, tectonics, depositional setting,transgression direction, source direction and other factors are fully taken into accountto analyze the distribution characteristics of the types of sedimentary facies in theplane. From west to east, Mesozoic deposits in study area are divided into eightsedimentary systems: Zhejiang and Fujian onshore volcanic belt, typeAAA pyroclastic-alluvial system, Yandang ancient uplift, typeWWW pyroclastic-littoral system, Taipei underwater volcanic belt, slope fan system,bathyal-turbidite system and Diaoyu Islands uplift belt. Furthermore, sedimentarymodel of Mesozoic Era in the study area is established.The study of Mesozoic sedimentary system in the southern part ofthe east China sea shelf basin provides basic geological data for the next step to oiland gas resources exploration in the East China Sea.