Stratigraphic relationships across the Triassic-Jurassic Boundary, Northwest Bighorn Basin; Park County, Wyoming

Abstract

Early Mesozoic stratigraphy in the foreland Rocky Mountains of Wyoming records deposition in a variety of depositional environments and tectonic settings which have led to contrasting interpretations of the stratal relationships of these units. In particular, the boundary between the Triassic and Jurassic represents a complex relationship consisting of multiple unconformities, formations, and lithologies. Since the 1970s, regional studies have relied on laterally extensive erosional surfaces or unconformities across the Western Interior as time constraining correlation tools. However, since the formal establishment of these unconformities, the recognition and proper placement of these surfaces within local areas has come under increasing scrutiny. This study was undertaken to demonstrate the complexities of the Triassic-Jurassic boundary and to clarify simplifications and generalizations made during previous research. This study will allow future researchers to take into account the complexities of the Triassic-Jurassic boundary and avoid previous generalizations.