The Joana limestone (Mississippian) is a ridge-maker between two non-resistant shales and forms an easily mappable formation because of its habit of forming characteristic escarpments and cuestas. It is rather widely developed in eastern Nevada and western Utah. The distribution and lithologic attributes of this formation are presented in preliminary form.

Samples were taken from bottom to top of outcrops and analyzed for possible variation in the chemical composition. The chemical analyses indicate that the Ca/Mg ratio increases from bottom to top, with a higher rate of increase in the upper than the lower half of the outcrops. Inasmuch as the higher magnesium content is believed by the writers to be indicative of shallower and warmer waters, the increase in Ca/Mg ratios can be interpreted as due to the gradual subsidence and deepening of the Cordilleran miogeosyncline during Early Mississippian time.

The Ca/Mg ratio was successfully used for correlation purposes over short distances. An attempt was also made to correlate the Joana limestone with the Gardner formation of central Utah on the basis of Ca/Mg ratio. As variation of this type occurs at two levels in the Gardner formation, the Ca/Mg ratios appear to have only a limited value in correlation over long distances.