Beds of fairly pure to impure dolomite, varying in thickness from 1 mm to 1 ft., occur widely throughout a large part of the Salt Flats of the Great Salt Lake Desert in Western Utah. Most of the sediments studied evidently formed within the past few tens of thousands of years (as dated by C14 methods), during late Lake Bonneville and Recent time. Alternating dark and light layers of dolomite, carbonate-bearing clays, and clays make up the upper few feet of sediment that was sampled. Dark layers however, are significantly higher in silicates plus SiO2, content and have approximately twice as much Mg2+ as the light layers. The writers suggest that the process of dolomite-formation was hastened by elevated temperatures, occasioned by solar absorption through a saltcrust “window” over the salt pans. Results of this study indicate that the dolomite is possibly of secondary origin (replacement type). Enough information is not available at this time in order to determine the duration of diagenetic dolomitization in terms of days, weeks or years, nor is it known if the diagenetic alteration of calcite to dolomite occurred at the sediment-water interface or after burial (or both at different times).