Entrada Sandstone - Age and History of Investigation

Age and History of Investigation

This formation has been dated to the early to middle Callovian stage of the latest Middle Jurassic. The type locality and place for which the unit is named is Entrada Point, located in the northern part the San Rafael Swell in Emery County, Utah.

Entrada Sandstone was named as one of the four formations of the San Rafael Group by Gilluly and Reeside in 1928. Gregory and Moore worked out the geographic extent of the formation and gave an overview of it in 1931. The extent was revised several times afterwards (most recently in 1992 by Condon). It was divided into Gunsight Butte, Cannonville, and Escalante members by Thompson and Stokes in 1970. The principal reference for the formation was written in 1988 by Peterson.