Distinguishing indicators and prospect significance of Cambrian dissolved gypseous breccias in southern Sichuan Basin

Dissolved gypseous breccias were discovered with gypseous rocks in the Cambrian surface outcrops in Huocaoping region of Leibo County and Heima region of Ganluo County in the southern Sichuan Basin.According to profile analyses of the Cambrian,several dissolved gypseous breccias were found in Zhuazhuayan(13 layers,over 30 m thick),Changping(4 layers,17.5 m thick),Fandian(4 layers,over 20 m thick)and Sanhuichang(4 layers,35 m thick).The dissolved gypseous breccias were divided into 2 types,including amaranth gypsum-bearing breccia mudstones and lark gypsum-dissolved breccia dolostones,with locally well preserved lamellar and flaser deposit structures.The breccias were gene-rally 3 cm long and 2 cm wide.The compositions were micrite dolostones and the cements included clays and calcites.Initial rocks of the dissolved gypseous breccias were rhythmically banding dolomitic gypseous rocks,which could be compared with the Middle and Lower Cambrian gypseous rocks(10 lay-ers,26.9 m)from Well Dingshan 1.It is predicted that,from the southeast to the center of the basin,there exist thick gypseous rocks of lagoon facies.