Late Paleozoic brachiopod communities in the Qiligou section of the Western Mountains, Taiyuan, Shanxi, China, and their paleoenvironmental significance

Abundant Late Paleozoic brachiopod fossils are contained in the Qiligou section of the Western Mountains, Taiyuan, Shanxi, and 13 benthic communities have been recognized. According to a detailed study of the autoecology, ethology and community structure, combined with an analysis of the lithology and sedimentary facies, the ecological positions of these communities are located between BA1 and BA3. The main controlling factor of the distribution and mutual replacement of the brachiopod communities is relative sea-level change. Because of differences in velocity, amplitude and duration of sea-level changes, the mutual replacement of two adjacent benthic communities may be not only sudden but also gradual and can occur between two different sedimentary cycles or in the same cycle of marine transgression and regression. The water-depth changes indicated by the ecological positions of these benthic communities and analysis of the facies sequence structure of the section suggest that 11 marine transgression and regression cycles occurred from the Benxian to Shanxian stages, of which the Miaogouan stage witnessed the maximum sea transgression with an estimated maximum sea depth of 10-20 m. The lower Maoergou limestone and Miaogou limestone are both the product of this sedimentary cycle.