Pennsylvanian–early Permian palaeokarst development on the Yangtze Platform, South China, and implications for the regional sea-level history

The Pennsylvanian to lower Permian succession at Madiyi, South China, represents a nearshore mixed siliciclastic-carbonate system characterized by cyclic sedimentation patterns along a depth gradient from continental siliciclastics to marine open platform carbonates. Various palaeokarst features related to subaerial exposure are widely distributed. Additionally, pedogenesis was pervasive. The identification of twenty-eight sedimentary cycles grouped into five sequences allows the reconstruction of a relative sea-level curve. The cycles represent higher frequency changes superimposed on the long-term evolution. After the initial transgression, the sea level remained relatively low in the late Bashkirian to early Moscovian. Then, it rose stepwise until a major drop occurred in the late Moscovian. Afterwards, the sea level rose again, but marine sedimentation ceased during at least the early Kasimovian. The area was flooded in the late Kasimovian, and the sea level rose until a late Gzhelian sea-level drop. The subsequent marine sequence contains uppermost Gzhelian to upper Asselian deposits, which are capped by lower Permian continental facies associated with a major regional regression. Shallow to deeper marine sedimentary settings recorded high-frequency sea-level changes throughout South China during the late Bashkirian to Asselian. The main transgression–regression cycles are clearly associated with different depositional settings during several time intervals. Furthermore, the good correlations among South China, Ukraine, and the U.S. Mid-continent are rooted in the impact of Gondwanan glaciations on the global sedimentation patterns. However, not all changes at Madiyi are the result of glacio-eustatic sea-level fluctuations; some are related to the local subsidence history and the rise of the Xuefeng Uplift.