中生代中-西非裂谷系形成演化的应力来源与叠加机制OA

The West and Central African Rift System(WCARS)spans the Central African continent,whose stress regime of evolution remains unclear.We examine the characteristics of tectonic stress in the periphery of African continent during Mesozoic,and compare the response of tectonic stress within the rift system,revealing that 2 branches of WCARS inherit the Trans-Saharan mobile zone and the Central African shear zone respec-tively.Above the inherited weak zones,there are 4 kinds of tectonic stresses acting as key external factors for the development of WCARS,such as seafloor spreading related far field compression,hot spot related vertical compression,Neotethys rift related tension,and Africa-Eurasia collision related compression.Among them,the compressional stress generated by seafloor spreading came from the Atlantic Ocean on the west of Africa and the West Somali Basin on the east,and faster spreading rates usually cause greater compressional stresses.Mutations of spreading rate in geological history can directly lead to sedimentary unconformities in adjacent basins,showing a clear correspondence with the strike change of the oceanic fault zones.The Central African branch fully records two tensions and one tectonic inversion in Mesozoic,while the West African branch only records the second NE-SW tension and the tectonic inversion in Santonian.The spreading related compression of Western Somali Sea and the tensile stress of the Neotethys Rift affected West African branch and the east of Benue Trough in the Central African branch.The spreading related compression of South Atlantic affected the entire WCARS.The compressional stress in Santonian was concentrated in the West African branch and central-western part of the Central African branch,and the influence of hotspot was limited to Benue Trough.All tectonic stresses converged and superimposed in WCARS,whose morphology and scale were primarily deter-mined in Mesozoic.