Early Permian Mudrock Deposits and Deep-time Land Surface Temperature Reconstruction, Southern North China

Abstract

Earth has experienced multiple greenhouse and icehouse periods and their inter-transformations， and extreme climatic events （e.g.， ‘snowball’ Earth， hyperthermal hothouse） in its geological past. The Permian was a critical period for the evolution from the late Paleozoic ice age to the Mesozoic greenhouse. One of the main challenges to understanding climate evolution in the Permian has been the acquisition of high-precision age-constrained quantitative data regarding successive paleoclimate changes. This work reviews geochronological and geochemical weathering data reported in recent studies of Permo-Carboniferous coal-bearing successions in southern North China. From this data， a high-precision chronostratigraphic framework is established for strata from the Benxi Formation through to the Taiyuan and Shanxi to Xiashihezi Formations， tracking chemical weathering trends in mudrock-source regions in southern North China. The weathering trends correlate very well with the glacial-deglacial sequence in high-latitude Gondwana continents. The proposed land surface MAT （mean temperature） - τNa （sodium depletion index） transfer function reconstructs the MAT variations for southern North China in the time interval ~300-286 Ma. The MAT curve reflects climate warming during the earliest Asselian and late Sakmarian deglaciations， and indicates climate cooling with the initiation of the Asselian and subsequent Artinskian glaciations.