碳酸盐缓坡区的露头层序地层研究

Outcrop Sequence Stratigraphy in Carbonate Ramp

碳酸盐缓坡区沉积相带宽 ,缺乏直观的物理层序界面标志 ,但区域上受气候海平面控制的多级岩性旋回发育 ,可对比性强 ,生物丰富 ,因而可借助于旋回地层学和生态地层学方法进行区域露头层序地层研究 .通过岩性旋回叠加型式和生境型迁移过程研究 ,较好地进行了下扬子区下三叠统露头层序划分 ,建立了层序地层格架 。

The carbonate ramp, characterized by the wide sedimentary facies, is short of visual physical markers of the sequence surface. But the multi scale lithological cycles caused by the fluctuation of regional climate sea level are well developed, which are strong in regional correlation and abundant in fossils. Therefore, the regional outcrop sequence stratigraphy can be well studied in the light of the application of cyclostratigraphy and ecostratigraphy. The stacking patterns of the lithological cycles, i.e. parasequences, and the migration of the habitat types show that the Lower Triassic sequences are properly identified, on the outcrops in the Lower Yangtze region, for the establishment of the sequence stratigraphic framework. In addition, the transgressive surface can be used to define the third order sequences in the outcrop sequence stratigraphy on carbonate ramp, which are more understandable and practical.