Late Cretaceous paleoclimate reconstruction from halite in an evaporite deposit on the Khorat Plateau, Laos

Abstract

Cretaceous was a warm climate interval in the world, however, the climate was arid or desert in some places, such as at the Khorat Plateau (KP) in Thailand and in central Laos where giant Cretaceous evaporite deposits have been found. We know little about the Cretaceous paleotemperature in this area. The homogenization temperatures of primary inclusions in halite (Th-halite inclusions) can provide direct and quantitative paleotemperature data for the brine and air. In this study, we present the Th-halite inclusions and the iodine contents and the I/Cl molar ratios of halite extracted from Core ZK2893 in Laos. Most of the Th-halite inclusions ranged from 25 °C to 40 °C, which is consistent with the paleo-temperature based on the δ18O of foraminifera. The halite inclusions with Th values of more than 40 °C mainly formed at 92－85 Ma, while those with of Th values of less than 25 °C mainly formed at 80－72 Ma. The climate was dry and warm, but showed a cooling trend during the Late Cretaceous in the study area. Most of the iodine was present as I− in halite. The total organic carbon was too low to be detected. There was a positive correlation coefficient between the I and Br contents, suggesting that evaporation significantly influences the I content of halite formed in arid climates. The very low iodine contents of 0.07–0.57 ppm suggest that there was not a significant supply of seawater into the basin in the Late Cretaceous.