Reconstruction of early Paleogene landscapes and climate in the Jianghan Basin, central China: Evidence from evaporites and palynology

The early Paleogene environment and climate of East Asia are poorly understood. To improve knowledge, we investigated the palynological record of well ZK0303 in the southwest Jianghan Basin, Hubei Province (central China). The well lithology comprises three intervals whose lithofacies represent the deposits of a saline lake: anhydrite/silty mudstone, halite/mudstone, and dolomite/siltstone. Based on a study of 37 palynological samples, three assemblages were recognized. Assemblage A, which correlates with Paleocene, is dominated by Ephedripites and contains a high proportion of thermophilic and xerophytic taxa. Assemblage B, which correlates with the early Eocene, is dominated by Taxodiaceaepollenites and hygrophilous taxa while the proportion of xerophytes is generally low. Assemblage C, probably early Eocene too, is dominated by Ephedripites and contains higher numbers of xerophytic species while hygrophilous species decrease to nearly half of their earlier abundances. These palynological data show that the early Paleogene climate of the Jianghan Basin experienced a transition from hot and arid to warm and humid conditions, with the latter period interrupted by short arid intervals. Afterwards, hot-arid conditions prevailed again. The reconstructed desert shrub and mountain forest vegetation suggests that the regional Paleocene landscape resulted from basin and range tectonics. Under the influence of a hot and arid climate controlled by global circulation patterns and rain-shadow effects, desert landscape and evaporites were formed in central China during the early Paleogene, whilst humid climate and forest vegetation prevailed in central China under the influence of the Paleocene-Eocene Thermal Maximum (PETM).