336 Richardson — Stratigraphy of the upper Carboniferous 



instance, locally gives way to or is replaced by thinner bedded 

 limestone and intercalated beds of sandstone, so that it is diffi- 

 cult to distinguish the northward continuation of the formation 

 from the overlying and underlying beds. Considered as a 

 whole the rocks of the Guadalupe Mountains constitute a 

 group which in detailed work will be separated into units 

 similar to the Delaware Mountain formation and the Capitan 

 limestone. A red bed phase is developed in the upper part of 

 the Guadalupe Mountain section 25 miles southwest of Carls- 

 bad, where, as stated above, deposits of red sandstone and 

 shale are present in the prevailing limestone and gray sand- 

 stone. To the east the red sediments become more abundant, 

 and in Pecos Valley the strata of the Guadalupe Mountains 

 are overlain by the red beds of Pecos Valley. 



Followed along the strike to the northern termination of 

 the Guadalupe Mountains in the vicinity of Penasco Eiver, a 

 distance of fifty miles north of the Texas-New Mexico bound- 

 ary, the Guadalupian series are found to overlie the limestones 

 and sandstones, which have just been described, on the eastern 

 flanks of the Sacramento Mountains. No evidence of any dis- 

 turbance which would alter the apparent simple relations of 

 the rocks was observed. The zone of faulting developed along 

 the western base of the Guadalupe Mountains near the state 

 boundary fades away northward, and is represented in Panasco 

 Valley, if at all, by a belt of gently undulating dips. The 

 strata of the Guadalupe Mountains, therefore, overlie the 

 Hueco formation conformably, and in turn are overlain 

 by the red beds of Pecos Valley into which they tend to 

 merge. 



Comparatively few fossils have been obtained from the 

 rocks in the New Mexico portion of the Guadalupe Mountains, 

 and these Dr. Girty states show but little relationship to the 

 typical Guadalupian fauna from the Texas portion of the 

 mountains.* It is not within the province of this paper to 

 consider the Guadalupian fauna or its relation to others which 

 is discussed by Dr. Girty. It seems probable, however, that 

 the difference in the fauna in the same group of rocks in the 

 Texas and the New Mexican portions of the Guadalupe 

 Mountains is due to changed environment, which is indicated 

 by the varied stratigraphy. 



Summary. 



The following is a summary of the chief facts, which I wish 

 to emphasize in this review of the upper Carboniferous strati- 

 graphy of southeast New Mexico and west Texas : 



* Girty, George H., The Guadalupian Fauna and New Stratigraphic Evi- 

 dence : Annals N. Y. Acad, of Sciences, vol. xix, pp. 135-147, 1909. 



