INVESTIGATION OF THE DOLORES SALT ANTICLINE AND POTENTIAL EVAPORITE DISSOLUTION

The Dolores Salt Anticline is the most southeastern salt feature in the Paradox Basin, a province of salt anticline and syncline structures in southwestern Colorado and eastern Utah. Unlike, other Paradox Formation salt features, the Dolores Salt Anticline is not breached or collapsed and therefore is far less studied. However, analysis of the Dolores River water chemistry may reveal that the core of the Dolores Salt Anticline is also dissolving at this moment. The Dolores River has eroded through several hundred feet of the Cutler Formation which overlies the Paradox evaporites. Additionally, the crest of the anticline is cut by multiple normal faults at the Glade Graben and Dolores Fault Zone, which may provide conduits for groundwater circulation. At Paradox Valley, one of the collapsed salt anticlines in the region, groundwater flows across the top of the Paradox evaporites and discharges directly into the Dolores River, contributing approximately 200,000 tons of salt annually. If groundwater discharge is similar at the Dolores Salt Anticline, the conductivity is expected to be notably high at base flows. Water samples and conductivity measurements will be collected from the Dolores River along a downstream transect through the Dolores Salt Anticline. While the Paradox Formation salt is the major evaporite source in the region, Mancos Shale also produces secondary gypsum. To differentiate Paradox Formation from Mancos Shale contributions, samples will be further characterized by Sulphur isotopes and major ion concentrations. Results of conductivity, Sulphur isotope, and major ion concentration analyses of the water samples will be reported. Results will give insight to the salt tectonics and groundwater-surface water interactions in the region.