Stratigraphy of the Guadalupian (Permian) siliceous deposits from central Guizhou of South China: Regional correlations with implications for carbonate productivity during the Middle Permian biocrisis

Abstract

In comparison with the amount of study undertaken on the end-Permian mass extinction, the preceding Guadalupian mass extinction has received little investigation, even though it marks a significant biotic turnover associated with global environmental changes. During the earlier event, reef carbonate production shut down and was replaced by siliceous, mud-rich deposits (SRDs) in South China. However, changes in carbonate platform productivity during this epoch remain to be clarified. This paper presents sedimentological and conodont biostratigraphic investigations on the Guadalupian SRDs developed on the Yangtze Carbonate Platform (YCP) in central Guizhou. The findings are viewed in the context of Guadalupian sequence correlation of South China successions, which shows that the integrity of the YCP failed to match the platform tectonic evolution. The platform evolution saw the onset of major intra-platform depressions and the gradual onlap by SRDs along the platform margin. Stratigraphic correlation reveals that the platform experienced three phases of onlap by SRDs during the early Roadian, the late Wordian and the late Capitanian upwards. Platform carbonates re-expanded their extent following the first two phases, but not during the final phase. An evolutionary model is proposed for the Guadalupian carbonate platform, which follows the contemporaneous eustatic sea-level fluctuations. The partial drowning observed within the platform interior and increasing retreat along the platform margin could suggest an insufficient carbonate sediment supply shedding from the platform top during the Guadalupian. The variation in carbonate productivity raises our attention to the change in shallow-water carbonate factories, which is closely related to the fortunes of carbonate-secreting biota and environmental factors impacting the carbonate platform producers during the Guadalupian.