The Solitario is a circular dome 5 miles in inside and 7 miles in outside diameter, situated 60 miles south of Marfa, west Texas, in both Presidio and Brewster counties (figure 1). It is in the trans-Pecos section, 9 miles in a straight line from the Rio Grande, on the western side of the “Big Bend” in the river and 25 miles east of Presidio. Occasional ranches are scattered through this barren mesquite desert, but few are near the highways. Military roads have been constructed from Marfa to Lajitas past the Solitario and to other outposts. There is a wagon road from the Lajitas road past McMahon’s ranch into the north end of the uplift.
Although the Solitario is shown on the topographic sheet of the Terlingua quadrangle, United States Geological Survey (figure 1), and although it has been visited by several geologists, including G. K. Gilbert, J. A. . . .