Early Cretaceous sedimentary environment and filling in the Eastern Subbasin, North Yellow Sea

The Lower Cretaceous strata constitute the most important oil and gas exploration horizon at present in the Eastern Subbasin of the North Yellow Sea. Accurate understanding of the Lower Cretaceous sedimentary characteristics is very important for the further strategic exploration and optimization of exploration deployment. According to drilling, well logging and seismic data and by means of paleontology, geochemistry and geophysics, the sedimentary facies types in the study area were analyzed. The sedimentary environments of paleoclimate, paleo-salinity, paleo-hydrodynamic force and provenance were studied. Finally, the sedimentary filling and evolution characteristics of the Lower Cretaceous period were discussed under the third sequences stratigraphic framework. The results show that the fan deltas and lucustrine facies were developed in the Lower Cretaceous. This period was dominated by subtropical hot and semi-arid climate, characterized by shortage of warm and humid climate. The ancient water bodies were fresh and brackish. The provenance was from north, east, southwest and some other directions. The early stratigraphic distribution of Lower Crataceous was limited, and the sedimentary facies were dominated by shore shallow lake and fan delta interbedding. After that, the lake water bodies expanded, and the sedimentary sequence of fan delta plain, fan delta front and shore shallow lake developed vertically. In the middle and late stage, influenced by the regional uplift and denudation, the strata remained only in the northwestern part of the basin, and the sedimentary facies were dominated by shore shallow lake.