摘要:
四川盆地白垩系的划分,虽有若干方案,但都缺乏足够的佐证,尤其是生物地层资料较少。1977～1980年,盆地开展了20幅1∶20万区调联测工作,在中国科学院南京地质古生物研究所及古脊椎动物与古人类研究所、地质部地质科学院成都地质矿产研究所、四川地矿局研究所等单位的配合下,在白垩系中发现了大量多门类化石,从而提供了四川盆地白垩系划分的可靠依据。
Abstract:
The Cretaceous of the Sichuan basin is represented by non-marine red clastic rocks, up to 3000 m in thickness. Vertically it shows distinct tripartite characteristics. It overlies the Upper Jurassic disconformably and underlies the Lower Tertiary conformably. In recent years, through biostratigraphical work, abundant fossils have been collected; they include ostracods,bivalves, conchostracans,charophytes, spores and pollen. These fossils can be divided into four fossil assemblages. Most of them belong to the fresh-water type and a part belong to the brackish-water type. These fossils exhibit three development stages. They are of major significance in the division and correlation of the Cretaceous of China. According to three sequences of rocks, biotic successions and sedimentary cycles,the Cretaceous of the Sichuan basin may be divided into three series; i.e. the Lower Cretaceous: the Chengqiangyan Group and the Tianmashan Formation; the Middle Cretaceous: the Jiaguan Formation and the lower and middle parts of the Jiading Group （the Wotoushan and Daerdang Formations）; and the Upper Cretaceous:the Guankou Formation and.the middle and upper parts of the Jiading Group （the Sanhe and Gaokanba Formations）.
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