Carbonate microfacies characteristics and sedimentary environment of Karaqi Formation and Kangkelin Formation in Akqi area, Xinjiang

Using the microfacies analysis method, the authors studied microfacies types and depositional environment of carbonate rocks during Late Carboniferous-Early Permian Karaqi Formation and Kangkelin Formation from Akqi, Xinjiang. The two stratigraphic units have many differences in rock textures, granular components and fossil assemblages. The Karaqi Formation sediments have finer granularity, higher content of argillaceous materials and less bioclast matter, and can be divided into five microfacies types and five secondary microfacies types. The sediments of Kangkelin Formation have abundant organic species, complete individuals and lower content of argillaceous materials, and its grains contain lots of oolites, oncolites etc. This formation can be divided into six microfacies and eight secondary microfacies. According to the field sedimentary structure and assemblage characteristics of microfacies types, Karaqi Formation carbonate rocks are considered to have been mainly formed in basin margin and platform slope, followed by platform margin shoal and open platform, suggesting a deep water environment. The Kangkelin Formation carbonate rocks were mainly formed in platform margin shoal, open platform and restricted platform, implying a relatively shallow sedimentary environment.