Comparative Study On The Difference Of Hydrate-bearing Turbidites In The Shenhu Sea Area

In this paper,the high-resolution seismic data and core grain size data collected in Shenhu area of Guangzhou Marine Geological Survey Bureau were used.Focusing on the turbidite of the mouth of the canyon group and the downstream part of the canyon in Shenhu area,the identification of the hydrated turbidity sediments and the fine descriptions were carried out.Using macroscopic seismic reflection data,there are two sets of sedimentary units with different characteristics above the bottom simulating reflectors(BSR)identified in blocks GMGS01 and GMGS03.Above the GMGS01 block BSR,the lower unit 1 is a thin layer disorderly lenticular strong-amplitude reflection unit,and the upper unit 2 is a reflection unit with the characteristics of wave fluctuation in the thick layer of continuous medium and strong amplitude.Above the GMGS03 block BSR,the lower unit 1 is a thin layer lenticular high-amplitude reflection unit,and the upper unit 2 is a medium-weak amplitude reflection unit with a thick layer continuously parallel to the seafloor.Using the core particle size data and comprehensive analysis of sedimentary processes,it was determined that the grain size of GMGS03 blocks was slightly coarser than that of GMGS01 blocks.The samples identified in the microscopic grain CM plots for the two blocks of hydrated zones all showed a baseline with C=M.The approximately parallel features,combined with seismic reflection characteristics and deposition process analysis,show that the lower thin layer disorderly lenticular strong amplitude reflection unit 1 corresponds to the sample in the hydrate section of the CM diagram of the grain size,and is tnterpreted as an aqueous hydrate cloud.Flow deposits,and proved that the turbidity sediments have a certain coupling relationship with hydrate production.Based on the comprehensive analysis of the site data of the two block hydrates,three types of turbidites were identified.(1)The turbidite in the GMGS01 block was related to the waterway.The waterway eroded the underlying stratum,transports the sediment along the landslide,and is deposited again in the valley ridge.This is called fine turbidite.(2)As the submarine canyon destroys and reconstructs the previous strata,the eroded sediments are transported along the direction of the canyon axis,and the restricted turbidite is deposited at the middle and lower reaches of the canyon,the mouth.(3)Located in the mouth of canyon is no longer affected by the canyon terrain and the limitations are called turbidity leaflets.The distribution range of turbidites in the Shenhu drilling area is preliminarily dibided,and the mechanism and pattern of occurrence of hydrates in this area are discussed.