Bedrock geology of the Ridgway area, northwestern flank, San Juan Mountains
— Paul Weimer

The Ridgway area is located on the northwestern flank of the San Juan mountain uplift in southwestern Colorado (fig. 1). The Uncompahgre River flows through the area, and the town of Ridgway is near the center. The local stratigraphic section consists of beds from Devonian through Late Jurassic in age in the subsurface. On the surface, the Upper Jurassic Morrison Formation, the Cretaceous Dakota Formation and Upper Cretaceous Mancos Group are exposed. Several wells have been drilled in the area and a small gas field is located in the eastern part. Regional high heat flow and structure resulting from Cenozoic uplift of the San Juan Mountains to the south have induced convective circulation of local ground water, resulting in several small hot springs.

 

The Ridgway area borders the southwestern margin of the late Paleozoic and early Mesozoic Uncompahgre Highland, which influenced the thickness and facies of late Paleozoic strata (fig. 2). The patterns of late Paleozoic and early Mesozoic tectonics and sedimentation are described here. The Dakota and Mancos Formations, which have not been previously studied in detail in this area, also are described. Finally, the origins of the Ridgway gas field and hot springs are explained.