Evolution of extreme continental saline environments: a sedimentological investigation of Permo-Triassic redbeds and evaporites in Northern Ireland and Kansas

The Permo-Triassic was a time of extreme environments, unusually warm and arid climates, and biotic crises. This study investigates Pangean environments and climate leading to extreme acid saline lake systems represented by the Permian Nippewalla Group of Kansas and the Triassic Mercia Mudstone Group of Northern Ireland. Sedimentological observations of the underlying rocks, the Permian Hutchinson Salt Member of Kansas and the Permian Belfast Harbour Evaporite Formation of Northern Ireland, help to understand trends in environmental and climatic conditions leading to these extreme environments. This dissertation also refines the geographic extent of extreme acid saline lake and groundwater systems through the study of the Triassic Mercia Mudstone Group of Northern Ireland. The second chapter, entitled “Using sedimentology to address the marine or continental origin of the Permian Hutchinson Salt Member of Kansas”, was published in the journal Sedimentology. This paper addressed the controversy about whether the Hutchinson Salt Member was deposited by a marine or continental environment and is the first comprehensive sedimentological study of the Hutchinson Salt Member. The Hutchinson Salt Member is composed of bedded halite, siliciclastic mudstone, displacive halite, bedded gypsum/anhydrite, and displacive gypsum/anhydrite. It formed in ephemeral saline lakes and adjacent wet and dry mudflats. The third chapter, “A missing link in mid-late Permian record of northeastern Pangea: a sedimentological evaluation of the Permian Belfast Harbour Evaporite Formation of County Antrim, Northern Ireland”, will be submitted to the journal Palaeogeography, Palaeoclimatology, Palaeoecology. This is the first publication to document the sedimentology of the Permian Belfast Harbour Evaporite Formation, with the goal of interpreting depositional environment and climate. The Belfast Harbour Evaporite Formation is dominated by bedded halite, with some siliciclastic mudstone and bedded anhydrite, and formed in a neutral ephemeral saline lake system in an arid climate. The fourth chapter is entitled “Is detailed correlation feasible in continental evaporite systems? An example from the Triassic Mercia Mudstone Group of County Antrim, Northern Ireland” and will be submitted to the Journal of Sedimentary Research. This manuscript is the first publication that compares detailed stratigraphic relationships of evaporite and red beds from two nearby, high-recovery cores. It suggests localized and abundant acid saline lakes existed in equatorial – subequatorial Pangea. Collectively, these chapters refine Permo-Triassic depositional environments and climates. There is a trend of shallow neutral saline lake systems, represented by the Permian Hutchinson Salt Member and the Permian Belfast Harbour Evaporite Formation, preceding extreme acid saline lake systems, represented by the Permian Nippewalla Group and the Triassic Mercia Mudstone Group. This dissertation provides evidence that extreme acid saline lakes systems of Pangea formed after a long period of continental weathering and erosion in an increasingly arid climate