Stratigraphic division and correlation and sedimentary characteristics of the Cambrian in central-southern Sichuan Basin

摘要

Under the guidance of sequence stratigraphy and through analyses of large amounts of well and outcrop data, the correspondence of all formations in the Cambrian of southern and central Sichuan Basin is defined and a new scheme of stratigraphic division and correlation for the Cambrian in central-southern Sichuan Basin is proposed based on the characteristics of lithology, logging curves and fossils. The Jiulaodong Formation in southern Sichuan Basin is corresponding roughly to the Qiongzhusi Formation in central Sichuan Basin, the Yuxiansi Formation in southern Sichuan roughly to the Canglangpu, Longwangmiao and Gaotai formations in central Sichuan Basin, the Xixiangchi Group in southern Sichuan roughly to the same group in central Sichuan. The Cambrian in central-southern Sichuan Basin is divided into the Qiongzhusi Formation, Canglangpu Formation, Longwangmiao Formation, Douposi Formation and Xixiangchi Group from bottom to top. On the basis of that, sedimentary facies of the Cambrian was studied. Controlled and impacted by the paleo-uplifts formed by Caledonian Orogeny, the deposition of the Cambrian experienced three evolutionary stages: shore–continental shelf, restricted platform–evaporation flat–shelf lagoon, restricted platform. The sandy, oolitic and carst dolomites in the Longwangmiao Formation and the Xixiangchi Group are the targets of oil and gas exploration.