Study On Shelf-slope Evolution And Sedimentary System Of Neogene In North South China Sea

The continental Shelf Margin Delta and Central Canyon are developed in the Huangliu Formation in Lingshui Depression of the Qiongdongnan basin.The Central Canyo is a potential area for oil and gas exploration and development in the north of the south China sea.By studying the relationship between shelf margin delta and central canyon,we can better understand the sedimentary environment of shelf margin and the influence of Shelf Margin Delta on the development of Central Canyon.Based on 2-D and 3-D seismic data,drilling and logging,and related research results in the research area,this paper conducts research on the delta deposition at the continental shelf edge and the deposition in the Central Canyon of the continental slope and their control factors,and further explores the coupling relationship between the two.In addition,the evolution law of the slope trajectory is summarized by quantitative analysis of the characteristics of the slope trajectory at the edge of continental shelf on the north slope.The main understanding and conclusions are as follows:1)The continental shelf margin delta is developed in section I of the Huangliu Formation on the north slope of the study area,with internal reflection in the shape of "S" type foreproduct or imbration,distributed in the front edge of the delta,and its provenance is derived from the uplift of Hainan island.The main controlling factors are relative sea-level change,provenance supply,tectonic activity and paleotopography.2)The inner shape of the Central Canyon can be divided into three types: "V" type,"U" type and "W" type.The overall trend of the canyon is basically parallel to the continental shelf slope break track.The canyon is composed of several channels and lobes,and the width of the canyon gradually widens from west to east.The main controlling factors for the development of the central canyon include fracture zone,abundant source supply,tectonic activity,paleotopography and relative sea-level change.The evolution of canyon development can be divided into three stages: ancient depression leveling,traceable downward cutting erosion and canyon interior filling.3)According to the trajectory accretion distance,shelf slope break into the product such as quantitative analysis,distance and trajectory Angle slope break trajectory can be divided into flat type,low Angle slowly rising,rising high Angle and complex four.The main provenance of the study area is central and northern Vietnam,and the provenance of Hainan island is the secondary provenance.So affected by the different direction of the source,the west shelf slope break into product distance significantly greater than the east.4)The abundant supply of provenance is the basis of the connection between Shelf Margin Delta-Central Canyon-Deep Water Fan.The development of the deltas at the continental shelf margin provides sufficient provenance for the Deep-water Fan and is a favorable indicator of the Deep-water Fan body potential,forming the Delta-deep-water Fan sedimentary system.Due to the "interception" effect of the Central Canyon,the sediment transport direction was forced to be changed and deposited in the interior of the Canyon.The Deep-sea Fan no longer developed in the basin floor perpendicular to the Canyon,forming the Delta-central Canyon sedimentary system.