Distinguishing indicators and prospect significance of Cambrian dissolved gypseous breccias in southern Sichuan Basin
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摘要: 在四川盆地南缘寒武系地表露头上,发现了与雷波县火草坪、甘洛县黑马石膏岩密切共生的膏溶角砾岩;在寒武系实测剖面上,发现了抓抓岩剖面13层30余m、长坪剖面4层17.5m、范店剖面4层20余m以及三汇场剖面4层35m的膏溶角砾岩。膏溶角砾岩分为紫红色含石膏角砾状泥岩和灰黄色膏溶角砾状白云岩2类,局部保存较好的纹层状与条带状构造;角砾大小一般为大于2cm×3cm;成分为泥晶白云岩,胶结物为粘土与方解石;其原岩为韵律条带状白云质石膏岩,可以与丁山1井的中下寒武统的条带状石膏类岩层(26.9m/10层)很好地对比。推测从川东南往四川盆地内部具有更好的潟湖微相厚层石膏岩,从而改变了以往该区无膏盐岩的看法。Abstract: 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.
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Key words:
- gypsum /
- dissolved gypseous breccia /
- Cambrian /
- petroleum exploration /
- southern Sichuan Basin
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