ABSTRACT
The evaporites of the Paradox Member of the Hermosa Formation of Pennsylvanian age in southeast Utah and southwest Colorado are direct precipitates from marine brines and have been changed only slightly by subsequent events. Geophysical logs of deep wells indicate that the Paradox Member is composed of 29 evaporite cycles. Lithologies that make up the cycles, in order of increasing salinity, are: black calcareous shale, dolomite, anhydrite, and halite (with or without potash). Studies of cores from two wells in the central part of the basin show that some of the cycles in the upper part of the Paradox Member are remarkably symmetrical above and below the black shale, indicating regular changes in salinity. Lithic texture, crystal morphology, and bromine distribution are suggestive of primary sedimentation with only minor early diagenesis related to burial dehydration.
