Characteristics and environmental significance of upper carboniferous rugose corals in the Qijiagou section, southern margin of the Junggar Basin

The Upper Carboniferous sediments are widely exposed in the southern margin of the Junggar Basin, including Liushugou Formation (C-2l), Qijiagou Formation (C-2qj) and Ortu Formation (C-2a) from bottom-to-top, all of which are shallow marine sedimentary strata. The Qijiagou formation is rich in marine fossils, mostly represented by tetragonal corals. Here, we focused on Carboniferous corals with a cone-shaped channel (qitaitai subspecies) found in the Qijiagou Formation (Qijiagou section), southern margin of the Junggar Basin. Considering the corals' structure and external morphology, we can infer that they lived in a low-energy, shallow-water environment, above the wave base surface (at the transition between turbulent and stable environments). These corals' environmental niche corresponded to the lower part of BA2 and to the upper part of BA3: . Based also on the study of the carbonate microfacies and of the coral burial characteristics, we can infer that the rugose corals were buried in a low-energy, still water environment, in the lower part of a platform margin slope. Notably, the corals were well preserved and could also be found in other locations. To sum up, both the burial and living environment of these studied corals corresponded to a shallow lagoon on an open platform.