Lower Silurian sandstones in the Shizhu synclinorium and its periphery, Chongqing:Compositional variations and tectonic significance

According to the thin section examination of the field outcrops and drilled holes, the present paper focuses on the statistical analysis of the detrital compositions, source area types and plate tectonic settings of the Lower Silurian sandstones in the Shizhu synclinorium and its periphery, Chongqing. Tectonically, the Silurian sandstones are mainly derived from the passive continental margins. The high maturity and stability of the Silurian sandstones suggest a very long distance of the study area from the source areas. The absence of typical volcanic arcs and subduction zones as source areas shows that no volcanic arcs and subduction zones were formed during the amalgamation of the Cathaysian land and Yangtze plate. The provenances include the stable craton and recycled orogen for the Longmaxi Formation sandstones;stable craton for the Xiaoheba Formation sandstones, and recycled orogen for the Hanjiadian Formation sandstones. The amalgamation of the Cathaysian land and Yangtze plate displayed characteristic episodic and creep patterns during the Early Silurian.