Study On Sedimentary Systems Of Mesozoic In Dongying Depression

Dongying depression is the Cenozoic rift basin,With the exploration turning to the deep strata,the potential of oil and gas exploration in the Mesozoic strata has received more attention,but its not deep enough for the basic geological research in this area,and not clear enough for the understanding of depositional system spatial characteristics.In this paper,according to the distribution of the Mesozoic strata,the isographic stratigraphic framework is established,and the characteristics of the residual strata are clarified.Based on the analysis of the data such as outcrops,cores,logging and seismic.The main results achieved are the following aspects:(1)The contact relationship and stratigraphic structure of the study area are determined.The Jurassic and Cretaceous strata are developed in the Dongying Depression,which are in contact with the Cenozoic and Paleozoic,and the Jurassic and Cretaceous strata are not integrated contact,formed Mz/Pz,E/Mz,K/J three regional unconformity.The residual Mesozoic strata are thin in the north and tilted northward,the thickness zone is developing close to the northwest basin.(2)Source characteristics has mixed source characteristics,the Jurassic source is the main result of the reversion of the orogenic belt,and the source of the Cretaceous material is mainly magmatic arc source area.The Jurassic strata are highly correlated with the Precambrian and Late Paleozoic strata,and the Cretaceous strata are highly correlated with the Early Paleozoic strata.The Mesozoic provenance comes mainly from the Paleozoic,it indicated that the sediments of the Dongying depression mainly from the denudation of the raised Paleozoic strata.(3)The sedimentary facies of Mesozoic in Dongying depression are fan delta,river,delta and lake.Fangzi group of Jurassic is mainly composed of fluvial,delta and shore shallow lake.Santai group of the Jurassic is mainly composed of fluvial and delta facies.The range of lake is smaller.Mengyin group of the Jurassic is mainly composed of river,delta,fan delta,lake.The Cretaceous Xiba Formation is mainly composed of igneous rocks and volcanic clastic sediments.(4)The sedimentary evolution of the Mesozoic under the influence of tectonics in Dongying Depression.The Jurassic Dongying Depression is a depression basin,the Shicun fault and the Chennan fault are characterized by a low activity abnormal fault,and the sedimentation center is close to the northward fault.The sedimentary system of alluvial fan-river-delta-shore shallow lake are developed.Due to the negative failure of the Shicun fault and the Chen-Nan fault,the sedimentary center of the Cretaceous is close to the upper plate of the north-west fault,the gentle slope zone developed the alluvial fan-river-deltashallow lake sedimentary system,the steep slope developed fan delta-lake sedimentary system.