What is the basis of stratigraphic correlation among Zigui, Yichang and Zhang Xia in Figure 1 1-2? Brief introduction of Zhang Xia

The basis of stratigraphic correlation among Zigui, Yichang and Zhang Xia in Figure 1 1-2 is as follows:

The strata in these three areas are mainly limestone, which contains marine fossils such as corals, brachiopods and sea lilies. In addition, these strata all contain ancient river sediments, such as marl and sandy shale. Therefore, these similarities can be used as the basis of stratigraphic correlation in these three areas.