Geologic map that depicts the surface geology of Montague, Cooke, Grayson, Wise, Denton, and Collin Counties and parts of Jack, Fannin, Hunt, and Clay Counties, Texas. The 16-page booklet indicates geologic formations, abbreviations, and ages. The Sherman Sheet honors the late Walter Scott Adkins, distinguished Texas geologist, who was on the Bureau of Economic Geology staff from 1919 to 1921 and from 1926 to 1934. Mr. Adkins specialized in Cretaceous stratigraphy and paleontology and was internationally known for his contributions in these subjects.

Since production of fluorspar began in northern Coahuila, Mexico, in 1950-51, thousands of tons of high-grade ore have been mined from numerous deposits situated 5 to 75 miles south of the Rio Grande. A large part of the fluorspar mined from these deposits has moved northward through Boquillas, Stillwell Crossing, and Heath Crossing to the railhead at Marathon, Texas. Consequently, Marathon has become one of the principal fluorspar shipping points in the world.

Geologic map that depicts surface geology of Crosby, Dickens, and King Counties and parts of Hale, Floyd, Motley, Cottle, King, Lubbock, Lynn, Garza, Kent, and Stonewall Counties. The Lubbock Sheet honors the late Dr. Halbert Pleasant Bybee, distinguished Texas geologist, professor at The University of Texas at Austin from 1914 to 1925 and 1936 to 1957, and the man who organized, and for many years directed, the University Lands Office in Midland, Texas. Dr.