THICK PERMO-TRIASSIC REDBEDS AND EVAPORITES IN PANGEA: BUILDING CONCEPTUAL BRIDGES FROM NORTHERN IRELAND TO KANSAS

Three recent drill cores from County Antrim, Northern Ireland contain a thick package of halite, gypsum/anhydrite, and red mudstone. These cores contain the Permian Belfast Harbour Evaporite Formation, the Permo-Triassic Sherwood Sandstone Group, and the Triassic Mercia Mudstone Group. Our core descriptions and petrographic observations indicate a transition from clear, siliciclastic-poor bedded halite to orange bedded halite with associated anhydrite and redbeds to “dirty” red mud-rich evaporites.

Similar redbed and evaporite deposits are known from other subsurface Permo-Triassic locations, including those in Kansas. Cores contain, in stratigraphic order, the Permian Sumner, Nippewalla, and Quartermaster Groups. The Sumner Group includes the Hutchinson Salt, a clear, siliciclastic-poor salt associated with continental redbeds. The Nippewalla Group contains abundant red siliciclastics and mud-rich bedded and displacive halite and gypsum/anhydrite. The Quartermaster Group is composed of redbeds and bedded gypsum/anhydrite.

Extreme environments characterized by low pH, high salinity, arid conditions, strong winds, and high temperatures have been interpreted for some of these rocks. For example, estimated pH range of lake waters for the Mercia Mudstone Group range from ~2-3, and for the Nippewalla Group were as low as 1. Though these groups were located ~8,000 km apart from one another in Pangea and lasted for as much as ~30-40 million years, they have many similarities to one another. Were extreme environments common through the Permo-Triassic for Pangea? Does this stratigraphy indicate an evolution of these extreme environments and surface conditions? Ongoing research is focusing on refining the depositional environments and comparing trends in pH, water chemistry, and air temperatures of Permo-Triassic Northern Ireland and Kansas. Such trends could elucidate environmental factors that contributed to a greenhouse Earth and major mass extinction.