New Views on the Lithofacies Palaeogeography of Northern Sichuan Basin and Qinling Area during the Sinian-Cambrian

Key words: 
• the northern Sichuan Basin /
• Qinling /
• Sinian-Cambrian /
•   /
• palaeogeography /
• dolomite of tidal flat /
• swamp and lagoon

Abstract: Most previous studies suggest that the lithofacies palaeogeography of northern Sichuan Basin and Qinling area is the deep-sea slopes or slopes of platform margin during the Sinian-Cambrian. However, in the process of paleogeographic mapping in this area, it was discovered that the Carbonaceous mudstone and the stone coal are deposited in the surface water or near shore shallow water, such as swamps and lagoons, rather than in the deep water or the deep sea. Therefore, based on the detailed observation , the measurement of outcrop profiles and the profound analysis of the well datas, and combined with the interpretation ofseismic profiles in the northern Sichuan Basin, the comprehensive analysisof the single section facies, cross section facies and facies mapping were made; meanwhile, by referring to the tectonic palaeogeography, quantitative palaeogeography and production palaeogeography in the area, the paleogeographic maps were drew optimally  from the Sinian to Cambrian.It was concluded that the palaeogeographic framework in the area of northern Sichuan Basin to Qinling area mainly consists of tidal flats, lagoons, peat swamps, shores and restricted platform facies, rather than the facies of the deep-sea basin, slopes or margin slopes of platform during the Sinian-Cambrian.