Biostratigraphy and lithofacies of the Permian System in the Laibin-Heshan area of Guangxi, South China

The Laibin-Heshan area is probably a unique area containing a suitable marine reference for the entire Permian system. Various fossils, sedimentary characteristics, lithofacies and palaeoenvironments including near shore, distal shelf, slope, and basin are developed. The Permian system in the Laibin-Heshan area is composed of the Maping, the Chihsia, the Maokou, the Heshan/Wuchiaping and the Talung formations in ascending order. The Maping Formation is characterized by restricted shoal or intertidal facies and ranges from the Late Carboniferous Kasimovian to Early Permian Artinskian. The Chihsia Formation (Artinskian-Kungurian) and the Maokou Formation (Roadian-Capitanian) represent a slope carbonate environment and a transgressive interval. By the end of the Guadalupian, the Permian sea was reduced to the confines of the Laibin area in South China and nearshore massive crinoid limestone was deposited, representing the most continuous marine deposits across the Guadalupian-Lopingian boundary. The Lopingian sequence in the Laibin-Heshan area reflects an independent transgression-regression system. During the Wuchiapingian basinal or slope phase, siliceous siltstone and chert and carbonates were deposited. During the Changhsingian, the Laibin-Heshan area subsided rapidly, accumulating about 600 m of limestone, tuffaceous sandstone, shale, siltstone before the basin was drained and terrestrial clastics with coal-seams developed. The end of the Changhsingian reflected the initial stage of the rapid transgression of the Triassic forthcoming supercycle. Limestone with latest Permian benthic faunas developed during the last stage of the Permian, which were immediately replaced by the nektic ammonoid and bivalve-dominated faunas in the earliest Triassic.