The Late Paleozoic-Early Triassic sedimentary characteristics in southwestern Fujian indicate that the Late Paleozoic-Early Triassic sedimentary construction is a typical passive continental margin sedimentary, and its continental slope faces to south, the line of Datian-Zhangping is equivalent to the low part of the slope at that time. The centre of the sedimentary basin lies at the line of Datian-Longyan-Yongding, with the source materials from the north and south. There are Tethys domain genetic elements in the Late Paleozoic paleontology of southwestern Fujian. The Early Triassic Xikou Group is the last marine sediment of the passive continental margin; its tectonic evolution is similar to that of the ancient Tethys in time and geological features etc.. It may be a branch of the ancient Tethys Ocean in southwestern Fujian sea area, and its tectonic evolution reflects that of the ancient Tethys.
