Saline lake deposition and complex diagenesis in the Permian Cloud Chief Formation, Texas Panhandle, U.S.A.

ABSTRACT Gypsum and its many forms are common in modern sediment and the ancient rock record. In particular, Permo-Triassic bedded gypsum and associated red beds from Pangea represent continental environments that persisted during a time of extraordinary climate change and mass extinction. Despite this significance, there is a paucity of work investigating textures of ancient gypsum, and in particular, diagenetic gypsum textures. Here, we describe gypsum textures from the Permian Cloud Chief Formation of the Palo Duro Basin in Texas, midcontinental United States. We interpret the Cloud Chief Formation gypsum to represent continental saline lakes and mudflats, based on their depositional textures and association with red-bed protosols. Additionally, we document, for the first time, the diagenetic features of the Cloud Chief Formation. Diagenesis is extensive, complex, and remarkably heterogeneous, with distinct textures of gypsum interlocking-crystal mosaics varying at a cm-scale and a mm-scale. The diagenetic history of the Cloud Chief Formation gypsum includes partial replacement by dolomite and subsequent gypsum replacement of the replacement dolomite rhombs, a process we name “gypsum dedolomitization.” This work advances our understanding of the depositional and diagenetic histories of ancient gypsum and expands the known geographic extent of Permo-Triassic continental saline-lake systems.