THE PERMIAN-TRIASSIC BOUNDARY IN THE HOGUP MOUNTAINS, NORTHWESTERN UTAH: AN INTEGRATED STRATIGRAPHIC STUDY

The Permian-Triassic boundary in the western United States miogeocline has long been considered a regional unconformity. An integrated study of the lithostratigraphy, biostratigraphy, chemostratigraphy and sequence stratigraphy of a locality containing the contact between the Upper Permian Gerster Limestone and the Lower Triassic Dinwoody Formation in the Hogup Mountains of Utah indicates that this section is likely complete. This would represent one of the first documented Permian-Triassic boundary sections from the western United States. The combined evidence suggests the formational boundary is a unconformity and sequence boundary, the lowest part of the Dinwoody formation is uppermost Permian in age, and the Permian-Triassic boundary is located near the low point of the large negative carbon isotope excursion found in the first few meters of the Dinwoody. Examination of the basal beds of other formations previously regarded as exclusively Triassic may reveal complete sections in other localities worldwide. Although diagenetic concerns cannot be discounted, there is no increase in redox-sensitive trace metals across the boundary, and no geochemical evidence for dysoxic or anoxic deposition throughout the section.