BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 32, pp. 417-428 DECEMBER 1, 1921 



SOLITAEIO UPLIFT, PEESIDIO-BEEWSTEE COUNTIES, 



TEXAS 1 



BY SIDNEY POWERS 



{Read before the Society December 29, 1920) 



CONTP]NTS 



Page 



Introduction 417 



Summary 419 



Regional geology 421 



Detailed geology 422 



Stratigraphy 422 



Structure 425 



Origin 426 



Introduction 



The Solitario is a circular dome 5 miles in inside and 7 miles in out- 

 side diameter, situated GO miles south of Marfa, west Texas, in both 

 Presidio and Brewster counties (figure 1). It is in the trans-Pecos sec- 

 tion, 9 miles in a straight line from the Eio 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 Ter- 

 lingua quadrangle. United States Geological Survey (figure 1), and al- 

 though it has been visited by several geologists, including G. K. Gilbert, 

 J. A. Udden, and E. T. Hill, nothing has ever been written about it.- 



' Manuscript received by the Secretary of the Society May 17, 1921. 



-It is shown on the "Geological map of a portion of west Texas," by P>. F. Hill and 

 .1. A. I'dden, University of Texas Mineralogical Survey, 1904. References to the Big 

 Bend country are : .T. A. Udden, A sketch of the geology of the Chisos country, Brewster 



(417) 



