Carboniferous and Permian integrative stratigraphy and timescale of North China Block

The Carboniferous-Permian strata in the North China Block (NCB) contain abundant fossils, coals and natural gases. Establishing a high-resolution timescale for the Carboniferous and Permian in the NCB is essential to understand the geologic events and explore the spatial and temporal distributions of the natural resources. The upper Carboniferous and the basal part of Permian are relatively well correlated because they yield marine conodont and fusuline fossils. However, the Permian terrestrial strata mostly rely on poorly constrained palynostratigraphy and phytostratigraphy and are short of the precise geochronologic constraints on the correlation with the marine strata. This study provides a critical review on the state-of-the-art of the latest Carboniferous and Permian chronostratigraphic and biostratigraphic frameworks and stratigraphic correlation in the NCB. The Penchi Formation ranges from lower Bashkirian to lower Gzhelian; the Taiyuan Formation is assigned to the upper Gzhelian to lower Asselian; the Shansi and Lower Shihhotse formations are from middle Asselian to lower Sakmarian; the Upper Shihhotse Formation is assigned to upper Artinskian to lower Kungurian, and the Sunjiagou Formation was assigned to Lopingian, respectively. A long hiatus up to ∼20 Myr between the Upper Shihhotse and Sunjiagou formations, mainly marked by a large-scale erosional surface at the base of a coarse conglomeratic sandstone unit and/or multiple paleosol layers as well as significant differences of floras between these two lithostratigraphic units, is present probably due to tectonic uplift in association with the closure of the Paleo Asian Ocean (PAO) during the Cisuralian and Guadalupian. The possible amplitude of sea-level changes from Carboniferous to Permian on the NCB is estimated from 0 to 40 m. The floral succession, depositional records and organic carbon isotope profiles suggest that the latest Carboniferous and earliest Permian was a favorable period for coal accumulation under an ever-wet and warm climate, followed by a prominent shift to dry climate from early-middle Cisuralian. This climatic shift during the Permian was mainly resulted from northward migration of the Pangea and the closure of the PAO, which is comparable with the Carboniferous and Permian trends in central Europe.