CAKBONIFEROUS UNDIVIDED. 359 



with only subordinate beds and lenses of sandstone. The sandstone is a massive to thin bedded 

 buff to brownish quartzose rock and the limestone likewise is both thick and thin bedded, of a 

 prevailing gray color, and contains little chert. * * * 



In the Guadalupe Mountains, 60 miles north of Van Horn, about 2,200 feet of the Delaware 

 Mountain formation is conformably overlain, in a magnificently exposed section, by 1 ,800 feet 

 of limestone named the Capitan limestone. The name is taken from El Capitan Peak, which, 

 having an elevation of 8,690 feet, is the highest point in Texas. The Capitan is a light-colored, 

 usually white limestone which, although possessing minor variations, is homogeneous in general 

 appearance. Bedding planes in many places are not apparent and the rock is characteristi- 

 cally massive. Chemically it is of variable composition, some analyses showing the presence 

 of considerable magnesium while others indicate its almost complete absence. Besides its 

 main occurrence in the Guadalupe Mountains the Capitan limestone was determined in 1907 

 to be present in the southern end of the Delaware Mountains, where it has been faulted down 

 and adjoins the limestone of the Delaware Mountain formation. E. S. Tarr reports," in the 

 paper cited above, the presence of 1,000 feet or more of sandstone lying above the Capitan 

 formation, but these rocks have not been studied, so that neither the base nor the top of the 

 strata bearing the Guadalupian fauna has yet been determined. It is expected that these 

 relations can be determined in the northward continuation of the formations in the Sacramento 

 Mountains of New Mexico. 



The age of the Guadalupian fauna has been much discussed. Girty tenta- 

 tively regarded the Guadalupe group as younger than the lower portion of the 

 Kansas Permian, from which alone invertebrate fossils were known. This view 

 was based on the close faunal relationship of the Kansas Permian with the Kansas 

 Pennsylvanian, on the general resemblance to the Pennsylvanian shown by the 

 fauna of the Hueco limestone, which underlies the Guadalupe group, and on the 

 great unlikeness of the Guadalupian fauna both to the fauna of the Hueco lime- 

 'stone and to that of the Pennsylvanian and Permian of Kansas. Subsequent 

 investigations, however, have seemed to indicate, as noted below, that the 

 striking peculiarity of the Guadalupian fauna is only regional. Furthermore, J. W. 

 Beede has reached the conclusion, on stratigraphic and paleontologic evidence not 

 altogether satisfactory, that the lower part of the Capitan limestone, which is the 

 upper formation of the Guadalupe group, is equivalent to the lower part of the 

 Kansas Permian; that the upper part of the Capitan is equivalent to the middle 

 part of the Kansas Permian; and that the upper part of the Kansas Permian (equiva- 

 lent to the Greer and Quartermaster formations of Oklahoma and Texas) overlies 

 the Capitan limestone. The lower formation of the Guadalupe group (the Delaware 

 Mountain) he correlates with the Pennsylvanian of Kansas, while the still older 

 Hueco limestone is inferentially of early Pennsylvanian (PottsviUe?) age. 



In 1909 Richardson ^''°^ traced the Guadalupe group from the type locality 

 in Texas northward in New Mexico for 50 miles and found that the stratigraphy 

 is varied and that both the Delaware Mountain formation and the Capitan lime- 

 stone lose their individuality when traced far along the strike. The northward 

 continuation of the group hes between the Pennsylvanian Hueco formation, as 

 developed in the Sacramento Mountains, and the Permian red beds of Pecos Valley. 

 The fossUs in the northward continuation of the Guadalupe group, according to 

 Dr. Girty, ^"^ show but little relationship to the typical Guadalupian fauna but 



<» Tarr, R S., Reconnaissance of the Guadalupe Mountains: Bull. Texas Geol. Survey No. 3, 1892. 



