Sedimentologic and Petrologic Analysis of the Chinle Formation in Colorado

Abstract

The Permian-Triassic boundary denotes the largest mass extinction event on record, as well as a time with concurrent rises in temperatures and CO2 levels. This is similar to what the Earth is experiencing today. Outcrops located at South Canyon Creek near Glenwood Springs, Colorado, are part of the Eagle Basin, and are currently being researched with the intent of discovering conclusive information that can be utilized to infer about past environmental conditions during the Permian-Triassic extinction event. This area is home to a variety of rock formations, including the State Bridge and Chinle Formations. The State Bridge and Chinle Formations were likely deposited during and after the extinction event, respectively. Therefore, they offer an opportunity to study how climate changed during and after the largest mass extinction on record. Particular areas of these formations are home to fossilized soils, or paleosols, which serve as a proxy for past climate data. Field observations include vertic features such as wedge-shaped peds and slickensides, as well as carbonate and iron/manganese nodules, root traces, and burrow structures. Micromorphological investigation indicates differences in the style of root traces and burrow structures. The calcic and vertic features along with the nodules are interpreted for form as a result of seasonality. The occurrence of root traces and burrows likely indicates the presence of an abundance in early soil colonizers after the extinction evident. Further analysis of this information will lend to a greater understanding of modern-day climatic processes and events in analogous conditions.