Sedimentary Evolution And Resource Significance Of The Lower Silurian Shiniulan Formation In Southern Sichuan

The Shiniulan Formation of the lower Silurian in southern Sichuan is rich in natural mineral resources,but its sedimentary pattern is controversial,and the storm deposition and limestone mineral resources are rarely mentioned.Therefore,the field profile measurement and laboratory identification of the lower Silurian series Shiniulan formation in southern Sichuan are carried out.Based on the petrological characteristics,the sedimentary environment and sedimentary evolution characteristics are divided,and the resource significance of the study area is analyzed in combination with the distribution law of sedimentary facies zones.Research shows:(1)The rocks of Shiniulan Formation are mostly carbonate rocks,and a small amount of clastic rocks and tempestite.There are five types of carbonates:sparite bioclast limestone,(Containing)bioclastic muddy to micritic limestone,Muddy micrite limestone,coral-reef limestone and lime dolostone;(2)Based on a summary of petrological characteristics and previous studies,it is concluded that the sedimentary environment of the lower Silurian series Shiniulan formation in southern Sichuan changed from carbonate gentle slope to carbonate platform environment.Among them,the carbonate rock gentle slope develops in the lower part of the Shiniulan formation,which contains two sedimentary subfacies,the outer gentle slope and the inner gentle slope.The carbonate platform is developed in the upper segment of the Shiniulan formation,which contains five sedimentary subfacies:restricted platform,open platform,shoal of platform margin,reef of platform margin and platform marginal slope.(3)Storm deposit was first observed in the lower Silurian series Shiniulian formation in the south of Sichuan Province.According to the analysis,it can be seen that:?We found many sedimentary structures,such as erosion surface,storm flow-generated gravelstones,graded bedding,hummocky and swaley cross-stratification,ripple bedding,and sediment interlayer formed by storm and calm weather.?From the old strata to the new strata,the storm deposits change from the distal storm deposits to the near storm deposits,and the storm intensity increases gradually.Upper and lower strata have some inheritance.?This paper analyzes the potential significance of storm sedimentary section and paleogeography,and the potential significance of oil and gas resources,and can be considered as a new way of resource evaluation.(4)Based on the characteristics of sedimentary evolution in the study area,the reef beach area is pre-determined as the favorable distribution area of decorative limestone stone,and the physicochemical characteristics of limestone in ore-forming strata are analyzed,which provides the basis for the exploitation of limestone mineral resources in southern Sichuan.