Quantitative temperature records of mid Cretaceous hothouse: Evidence from halite fluid inclusions

摘要

Quantitative temperature reconstructions for the mid Cretaceous are still rare although its typical greenhouse climate is regarded as one of the best analogues for future global warming. For the first time, mid Cretaceous temperatures were quantitatively reconstructed based on homogenization temperatures (Th) of halite fluid inclusions from the Lower Member of the Nong Bok Formation in the Thakhek mining area, Laos. Petrological features and primary textures of halite indicate a shallow water setting during halite formation that allows the use of homogenization temperatures as air temperature proxy. Obtained homogenization temperatures mainly range from 30 to 50 degrees C, probably representing local air temperature conditions of Laos during the mid Cretaceous. The determined temperatures are relatively similar to temperatures in many modern and ancient evaporative settings. The maximum homogenization temperature (Th-Max) for the Nong Bok Formation of 62.1 degrees C is significantly higher than existing mid Cretaceous paleotemperature records from both continental and marine sediments and comparable with the temperature records from the contemporaneous Mengyejing Formation of Yunnan, Southern China. The correspondence of the temperature records from Laos and Yunnan implies that very high temperature conditions prevailed in the region. Our results and other reconstructed very high temperatures from potash deposits (e.g., 59 degrees C for the Silurian Michigan Basin and 58 degrees C for the Quaternary Lop Nur region) suggest that extremely high temperatures probably had an important impact on the formation of the large potash deposits of the world. However, more studies are needed to improve our understanding of the detailed and quantitative relationships between temperature conditions and potash formation. (C) 2015 Elsevier B.V. All rights reserved.