论四川盆地白垩纪地质发展史

    THE CRETACEOUS GEOLOGICAL HISTORY OF THE SICHUAN BASIN

    • 摘要: 四川盆地在白垩纪(距今74~135Ma)的地史变迁,说法不一。原因在于对这个时期保留下来的地史资料(岩石、地层和古生物等)的掌握和研究程度的不同,特别是由于对地层的岩相特征、接触关系和化石意义认识的差异,导至地层划分、对比的不同方案,从而引出地壳运动、湖泊河流与陆地沙漠转换等方面的不同结论。本文据笔者十年来对四川盆地白垩系的研究提出一些新的认识。一、地层划分与对比

       

      Abstract: On the basis of the division and correlation the strata and the character- istics of deposits and fossils, the author advances a different view on the the Cretaceous geologic history in Sichuan. The Ghengoiangyan Group and its cor- relatire strata are of latest Jurassic age, and the Jiading Group and its cor- relative strata are late Early Cretaceous to early Tertialy in age, the base of the latter being youunger than the top of the former. The latter is found to overlie the former in two drill holes in Guanghan and at a section of Long Q- uan, Chengdu. There is a lake basin in the Guanghan-Deyang-Zhongjiang area, while the other areas of Sichuan were denuded areas in the earliest Creta- ceous. From the late Early Cretaceous to middle Cretaceous, the sedimentary basin shifted towards the southwest, and a lot of eolian sandstone was deposited in the south but the fluvio-lacustrine deposition occurred in the west. In the Late Cretaceous, the sediments were of fluvio-eolian origin in the south but mainly of lacustrine origin in the west, intercalated with some salt deposits. As the Sichuan basin was affected by the first phase of the Yanshan- lan subcycle from the Late Jurassic to Early Cretaceous, its southeastern part rose owing to southeast-directed compression and the lake retreated to- wards the northwest. Owing to the effect of the second phase of the Yanshan- lan subcycle in the late Early Cretaceous to Late Cretaceous, the southwestern part of the basin sank, while the northeastern part rose. Therefore, a discon- formity was formed between the Jiading Group and the ChengQiangyan Group.

       

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