上扬子地区寒武系风暴岩特征及其构造-古环境约束OA

Storm deposits(tempestites)serve as sensitive indicators for reconstructing tectono-paleogeography and paleoenvironmental conditions.Consequently,analyzing storm depositional patterns through geological time represents a crucial approach for understanding basin evolution from both tectonic and environmental perspectives.The Upper Yangtze region preserves abundant Cambrian tempestite records,making it an ideal area for investigating storm-generated deposits and their formative mechanisms.By integrating extensive field sections,core data,and thin-section observations,this study systematically classifies Cambrian tempestites and proposes the concept of"storm-induced mixed deposits."We establish a refined storm depositional sequence model while exploring the intrinsic relationships between storm deposition in the Upper Yangtze and global/regional tectono-paleoenvironmental evolution during the Cambrian.The main results are as follows:① Cambrian tempestites can be classified into hybrid(mixed)and non-hybrid types,further subdivided into 5 categories,10 subcategories,and 20 minor types.Mixing intensity is primarily controlled by tectonic activity and climate at the macroscale,while being influenced by sea-level fluctuations and depositional environments at the microscale.The Canglangpu and Xixiangchi formations,deposited during tectonically and climatically active periods,show significantly higher mixing intensity compared to the relatively stable Longwangmiao and Gaotai formations.Vertically,the mixing intensity gradually decreases along a proximal-to-distal gradient from tidal flat to slope environments.②The ideal Cambrian storm depositional sequence consists of five vertical divisions(A,B,C,D,and E[including E1 and E2]),each exhibiting distinctive sedimentary structures and assemblages that vary with storm energy and transport mechanisms.The sequence shows facies-dependent variations:tidal flat environments are dominated by divisions A,B with rare C～E;platform interiors contain more C,D divisions in addition to A,B;platform margins are mainly composed of A,B divisions,while slope environments are characterized by the A,C,and E divisions.③ The development of Cambrian tempestites was collectively controlled by paleoenvironmental,tectonic,and paleogeographic factors.The greenhouse effect induced by elevated atmospheric CO2 levels during the Cambrian promoted widespread tempestite formation across various blocks,as evidenced by abundant storm deposits in the Upper Yangtze since the early Cambrian(～521 Ma).Moreover,the Yangtze block,although experiencing southward drift,remained within the tropical storm belt(15°N～30°N)throughout the Cambrian,corresponding to the latitudinal zone(10°～30°)most prone to storm activity.