The Gunlock Member: Description of a Proposed New Member of the Carmel Formation (Middle Jurassic) of Southwestern Utah — The Independent Study project of Lucie Fiala (’23)

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Lucie Fiala was advised by Mark Wilson (me!) and was on Team Utah 2022. The following is her thesis abstract —

This Independent Study investigates the paleoecology and stratigraphy of the lower Carmel Formation in southwestern Utah. The Co-op Creek Member and the here proposed Gunlock Member of the Carmel Formation are mostly limestone units formed during the Bajocian (Middle Jurassic). During the Middle Jurassic, much of western North America was covered by an epicontinental seaway called the Sundance Sea, which stretched from southern British Colombia to Utah. In this study there are four principle locations (Eagle Mountain Ranch, Manganese Wash, Dammeron Valley, and Jackson Peak) of study. The proposed Gunlock Member was formed in a low energy, intertidal environment. It is characterized by stromatolite and thrombolite layers, trace fossils, and bivalves. The overlying Co-op Creek Member was formed after a transgression in a high energy, subtidal environment and is characterized by its ooid-rich limestones, shales, and abundant fossils.

The boundary between the Co-op Creek and proposed Gunlock divides these members into the underlying stromatolitic member and the overlying ooid-rich member, and indicates a significant transgression. The Bajocian saw a few notable global transgressions that roughly coincide with that of the Sundance Sea; while there are several theories as to the cause of these rises in sea level, tectonic and glacial activity are the most likely.