USING MINERALOGY TO ADDRESS THE HYPERSALINE MARINE VERSUS SALINE LAKE DILEMMA OF THE PERMIAN HUTCHINSON SALT MEMBER OF KANSAS

Evaporite mineralogy is used to decipher between hypersaline marine and saline lake depositional environments. However, in both environments, halite and gypsum are the most common minerals. Other minerals must be considered to distinguish ancient evaporite environments. Trace amounts of evaporite minerals may be found in efflorescent crusts, solid inclusions, and within fluid inclusions in bedded halite. These trace minerals may not be present or detectable. This study uses mineralogy, along with supplemental sedimentology, to address the marine verse continental dilemma of the Permian Hutchinson Salt Member of Kansas.

The Hutchinson Salt Member is well known for its industrial uses. Although many industries rely on this salt, few detailed mineralogical and sedimentological studies have been completed on this member. The most recent sedimentological studies were completed in the 1960s and inferred this salt to have had a marine origin based mainly on the presence of halite and gypsum. However, these observations are not sufficient. Therefore, we challenge this marine interpretation.

This research project presents a sedimentological study of the 110-m-thick Hutchinson Salt Member in the Atomic Energy Commission Test Hole 2 core drilled in Rice County, Kansas. The Hutchinson Salt Member is composed of bedded halite, siliciclastic mudstone, displacive halite, bedded gypsum/anhydrite, and displacive gypsum/anhydrite. These lithologies are found in both hypersaline marine and saline lake environments. Therefore, we must rely on presence or absence of other mineralogies. We have observed a paucity of carbonates, an absence of characteristic marine minerals and lithologies, and a lack of marine-diagnostic fossils. In addition, the stratigraphic context of the Permian of Kansas associates these rocks with continental environments. Utilizing this data, we interpret that the Hutchinson Salt Member formed in continental shallow surface brines, wet mudflats, and dry mudflats that underwent flooding, evapoconcentration, and desiccation. This continental depositional environment interpretation has significant implications for Pangean shorelines. Future geochemical analyses are needed to further investigate climatic and biological proxies to better understand the Permian of Kansas.