Geological studies of the Guadalupe Mountains area, New Mexico and West Texas, to 1928
— Barry S. Kues

This paper traces observations and studies of the classic Permian sequence of the Guadalupe Mountains area through 1928. Early American expeditions in 1849 and 1850 provided the first descriptions of the southern Guadalupes, including a sketch of the southern end of the range by John R. Bartlett. Pope’s 1854 32nd parallel Pacific Railroad expedition passed through Guadalupe Pass; geological reports by Blake (1856) and Hall (1857) included simple geological maps of the Guadalupe region. George Shumard, the first geologist to visit the range (1855), reported four stratigraphic units, including an “upper white limestone” that yielded fossils identified as Permian by B. F. Shumard (1858). Opinion shifted to a Carboniferous age based on reconnaissance surveys in the 1890s by Tarr, Cummins, and Hill. George Girty collected and studied Guadalupian fossils, which he originally considered Late Permian (1902), but by the time of publication of his monograph (1908) he had retreated from that view and by 1909 thought they were of late Carboniferous age. G. B. Richardson (1904) provided a moderately detailed geologic map, considered the Guadalupe Mountains an eastward dipping monocline with little faulting, and named the Capitan and Delaware Mountain formations, as well as the probably younger Castile and Rustler formations to the east. Later work by Girty and Richardson ascertained that Guadalupian strata passed northward into red beds and evaporites but precise correlations were not possible. Beede (1910) thought it likely that Guadalupian strata were an isolated equivalent of Lower Permian strata in the Midcontinent, but gave an age range of mid-Pennsylvanian to Late Permian for the Capitan and Delaware Mountain formations. Baker (1920) clarified aspects of the stratigraphy, by which time the age was again thought to be Permian. Studies by Darton and Reeside (1926) and Darton (1928) concluded that Permian Chupadera Formation (=Yeso and San Andres) strata graded into the Capitan and Delaware Mountains, while recognizing that the Castile and Rustler were of younger Permian age. Recognition of the reef complex nature of Guadalupian strata in 1929 provided a new paradigm for stratigraphic interpretation, one that has continued to be refined to the present.