Stratigraphic relations of the Bolsa Quartzite, Vekol Mountains, Pinal County, Arizona

A quartzite unit occurring between the rocks of the Precambrian Apache Group and those of the Cambrian Abrigo Formation in the Vekol Mountains, Final County, Ariz., has been called both Troy Quartzite (Precambrian) and Bolsa(?) Quartzite (Cambrian). Regional and local geologic relationships indicate that this intervening unit is definitely the Bolsa Quartzite. The Bolsa ranges in thickness from at least 200 ft at several localities in the Vekol Mountains to 0 ft over a positive area underlain by Precambrian diabase which has intruded the Apache Group. Previous observations that the diabase intruded the quartzite unit (thereby making this quartzite unit the Troy Quartzite) have been reinterpreted; all nonfaulted exposures of the basal contact of the quartzite unit show sedimentary relationships. No evidence was found to suggest that the Troy Quartzite was ever deposited in the Vekol Mountains.