Record of Geology op Texas, 188V-1896. 
231 
S'TREERUWITZ, W. H. VON. 
“Ano'tlier source of complication arises from the greater erosion of the 
older mountains hy the Cretaceous sea, as well as from later erosions and 
intrusions, and the covering of these hy more recent materials after the 
Cretaceous deposits' were formed.” P. Ixxix. 
'Information derived from former reports meagre. Existing maps of 
doubtful value. Difficulties of running and measuring straight lines. 
Topographical map a necessity. This work undertaken. Start made at 
Sierra Blanca. Preliminary base measured. Instructions received to 
classify mineral lands. Camp at Sierra Blanca Junction. Topography of 
the Cretaceous Hills. Vertical Distance of Curves 100 feet. Camp at foot 
of Quitman Mountains. Camp at Eagle Flat. Camp six miles west of 
Torbert. Base line measured and monuments erected. 
368. ' 
Geology of Trans-Pecos Texas. Preliminary Statement. 
- First Ann. Kept, of the Geol. Snrv. of Texas, 1889, pp. 217- 
235; 2 ills. Austin, 1890. 
Contents: Character of country. Sierra Blanca Mountain. Quitman 
Mountain. Carrizo Mountain. Sierra Diablo. Mineral resources. Agri- 
culture and Irrigation. Development. Conclusions. Topographical notes. 
“As has been mentioned, the mountains and hills of Trans-Pecos Texas 
rise generally (seemingly, at least) in isolated ridges and groups from 
broad flats, abruptly in most cases, and either without foothills or sur- 
rounded only by those of limited extent and height. This is particularly 
the case with the eruptive mountains. 
“But even a superflcial examination shows that in spite of the great 
variety in rock material there exists an essential connection between all of 
the eruptive mountain ranges and groups, and that the flats and basins 
between these ranges and groups, however extensive they may be, are in 
fact deep valleys, having depths of even 1000 feet and more (as has been 
proved by borings), and filled in with Ihe debris not only of eruptive mate- 
rial, but also with that of Caibonic, Cretaceous, and possibly intermediate 
strata. This is often covered in turn with Quaternary detritus, which is 
in some cases more than- 100 feet thick. 
“In the Quitman Mountains, or at least in their northern part, we have 
to deal with eruptive rocks only; with granites of at least two ages, and 
'with porphyries, the latter evidently younger than the granites. 
“The Sierra Blanca group of mountains rises north of the first ridge 
of the Quitmans, and is separated from them by a valley two miles in 
width, which sloipes gently from the mountains on either side, and west 
towards the river. The group consists of four isolated, moderately cone- 
shaped mountains, the highest of which, the Sierra Blanca Peak, has a 
height of nearly 7200 feet above the sea level, or 2000 feet above the sur- 
rounding flat. lUp to the present time no granites similar to those of the 
Quitman range have been detected in the Sierra Blanca group, and out- 
crops of dioritic rocks exist 'which have not been observed in the Quitman 
Mountains, so far as they hare been examined, Porphyritic rocks are 
