Abstract

The Carmel Formation in the Gunlock area of southwestern Utah documents a major Middle Jurassic marine transgression and regression. Most instructive sections are those in cut banks of the Santa Clara River, north of Gunlock, and in cuestas that extend northwestward from the shore of Gunlock Reservoir along Manganese Wash. Four lithogenetic limestone-siltstone units have been differentiated in the principally shallow marine Carmel beds, above the nonmarine gypsiferous red Temple Cap Formation. Basal Carmel Unit 1 is interbedded dolomite, limestone, and reddish mudstone 15–20 m thick. Unit 2 is micritic to fossiliferous limestone and dolomite approximately 40 m thick and is overlain by Unit 3 that is 25–30 m thick and composed of interbedded siltstone, oolitic limestone and stromatolitic limestone in eastern exposures but grades to massive micrite in western ones. Unit 4 is a siltstone with interbeds of oolitic to wackestone or packestone limestone that is 40–50 m thick. A redbed section, Unit 5, is exposed only along Limekiln Wash and is the youngest Carmel unit present. It and other younger Carmel members have been removed elsewhere near Gunlock by pre-Dakota Conglomerate erosion.