Abstract
The oxygen isotopic composition of calcite from carbonate rocks of the lower unit of the Flagstaff formation (Paleocene) exposed along the western margin of the Wasatch Plateau, Utah, is about 7 per mil lower than that of coexisting dolomite, suggesting that isotopic equilibration of these two minerals can occur at relatively low temperatures. Unlike recent isotopic evidence presented by Degens and Epstein, the data do not preclude a primary chemical origin for the dolomite.