482 G. B. Richardson— Paleozoic Formations. 



the rocks in the two mountains. As lias been stated, the 

 Sierra Diablo is made up of the Hneco limestone, the strati- 

 graphic top of which has not been observed. And the Guada- 

 lupe-Delaware Mountains are composed of Paleozoic strata, 

 younger than the Pennsylvania!!, which contain a fauna not 

 elsewhere known in North America, that Girty has named 

 Guadalupian. This fauna, which has Permian affiliations, is 

 described by Dr. Girty in a paper now in press, and it is 

 intended here only to outline the stratigraphy of these rocks, 

 which complete the long Paleozoic sequence of trans-Pecos 

 Texas. 



Delaware Mountain Formation. 



The Delaware Mountain formation includes a varying mass 

 of sandstone and limestone having a maximum thickness of 

 at least 2300 feet, but the base of the formation is not exposed 

 in Texas and has not been determined. In the northern part 

 of the Guadalupe-Delaware Mountain uplift, the formation is 

 prevailingly sandy and contains only thin beds and lenses of 

 limestone. Southward the sandstone decreases and the lime- 

 stone increases in amount until, in the southern part of the 

 main Delaware Mountains, the formation consists of gray 

 limestone 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. The following fossils, determined by Dr. Girty, are 

 characteristic of the Delaware Mountain formation : 



List of fossils from the Delaware Mountain formation. 



Fasulina elongata. Astartella nasuto. 



Productus Guadalupensis. Pleurophorous Delawarensis. 



Productus Meekanus. Pleurotomar ia englyphia. 



Productus Walcottianus. Pleurotomar ia arenaria. 



Richthofenia Permiana. Warthia Americana. 



Myoconcha costulata var. Gastrioceras serratum. 



Capitan Limestone. 



In the Guadalupe Mountains, 60 miles north of Van Horn, 

 about 2200 feet of the Delaware Mountain formation is 

 conformably overlain, in a magnificently exposed section, by 

 1800 feet of limestone named the Capitan limestone. The 

 name is taken from El Capitan Peak, which, having an 

 elevation of 8690 feet,* is the highest point in Texas. "The 

 Capitan is a light colored, usually white limestone which, 

 although possessing minor variations, is homogeneous in gen- 

 eral appearance. Bedding planes in many places are not appa- 

 * Recently determined by Arthur Stiles. 



