New Understanding of the Contact Relationship between Shihtzupu Formation and Pagoda Formation in Sichuan Basin
详细信息
- 责任者：Fan Ru (Research Institute of Petroleum Exploration & Development ; Beijing 100083 ; China) ; Lu Yuanzheng
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(3)
- 关键词：奥陶纪 ; Ordovician ; 不整合 ; unconformities ; 四川盆地 ; Sichuan Basin
- 页码：p.321-329
- 图表：illus., 20 refs.
- 分类号：1200
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Since nomenclature in the 1920s, Shihtzupu and Pagoda Formations of the Ordovician System in Sichuan Basin have long been considered to be conformable contact in the stratigraphic circle. This study analyzed the conodont biostratigraphy and carbon isotopic stratigraphy in the Liangcun and Huangcao sections of the middle-upper Ordovician around the Sichuan Basin. The biostratigraphic and chemostratigraphic results indicate a sedimentary gap between the Shihtzupu and Pagoda formations, suggesting an unconformity contact between two formations. The discontinuity can be contrasted with the M4/M5 sequence boundary which is prominent unconformity in North America. Both of them probably resulted from the regression of sea level in early and late Sandbian. The unconformity occurring at this time can also be found in the Bachu area and Tarim Basin. Due to the fact that the Shizhpu Formation is widely distributed in Sichuan basin and dominated by carbonatic rock, discovery of disconformity between the Shihtzupu Formation and Pagoda Formation has great significance for us to acquire new understanding of exploration potential for oil and gas in the Sichuan Basin.
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