THE PLAINS PROVINCE 



105 



contains considerable chert in irregular form. In the uppermost part we find 

 one or two beds of reddish-brown sandstone about 4 feet thick. The entire 

 thickness of this formation is about 2,000 feet. 



"GILLIAM FORMATION. 



"This series is composed of gray, light-colored, and reddish limestone and 

 dolomite; both are frequently brecciated. In the upper part the rock is nearly 

 massive, or, at least, bedding planes are very dim. In the middle the limestone 

 shows thick lenticular beds, while in the lower part it is decidedly thin-bedded. 

 At the base we find thicker layers of reddish dolomite alternating with thinly 

 laminated layers of the same rock and with thin strata of yellowish marly sand- 

 stone. The thickness of this enormous mass is 2,500 feet, in Gilliam Canyon." 



The Permo-Carboniferous appears in other localities near Ord Mountain, 

 but the general character of the deposits are the same as those already 

 described. (See page 53 of Udden's report.) 



Correlation table of the Texas Permian. 

 From Udden's Report, page 56. 



Shafter region. 



Ord Mountain and 

 vicinity. 



Glass Mountains. 



Delaware-Guadalupe 

 Mountains. 



Yellow limestone. 



I. Vidrio formation. 



Gilliam formation. 

 Vidrio formation. 



Rustler 

 limestone. 



/ limestone. 

 Castile / 

 gypsum. / Delaware 



/ formation. 



Hueco formation. 



2. Sandstones and lime- 

 stones. 



Word formation. 



Thin-bedded zone. 

 Zone of sponge spicules. 

 Lower brecciated zone. 

 Transition beds. 



3. Shales, sandstones 

 and limestones. 



Leonard formation. 



4. Limestone conglomer- 

 ate and thin-bedded 

 or flaggy limestone. 



Pennsylvanian (Alta and 

 and Cieneguita beds). 



Pennsylvanian. 



Gaptank formation. 



Two papers in the University of Texas Bulletin^ give additional informa- 

 tion concerning the late Paleozoic deposits of the western part of Texas. 

 Udden adds three formations to the list quoted above. His series in the 

 Glass Mountains is as follows: 



Permian {?) Permo-Carbotdferous: 



Tessey 1,400 



Gilliam 740 



Vidrio 1,700 



Word (?) 1,400 



Leonard 1,800 



Hess 2,100 



Wolfcamp 500 



Pennsylvanian: 



Gaptank 2,000 



^ Udden, J. A., Notes on the geology of the Glass Mountains, Univ. Texas Bull., No. 1753, 

 1917. 

 Baker, C. L., and W. F. Bowman, Geologic exploration of the southeastern Front Range 

 of Trans-Pecos Texas. Idem. 



