LIBJRARY 
THE 
AMERICAN GEOLOGIST 
Vol. VII. 
FEBRUARY, 1891. 
N<>. 2. 
REMARKS ON THE GEOLOGY OF THE CONCHO 
COUNTRY, STATE OF TEXAS. 
By Otto Lbrch, M. A.. Ph. D., San Augelo, Texas. 
Since a joint publication by Prof . A. T. Cummins and myself 
entitled "A geological survey of the Concho country,"* I Have 
studied the beds between fine Lower Cretacic, Hie Trinity sands of 
Kobt, T. Hill, and the Permian, which are well exposed a few 
miles west of San Angelo, near the center of that section of 
Texas. I am now inclined to think that this group of strata are 
of Triassic age, and may lie a southward continuation and thinning 
out of the strata three hundred mill's northward called Jura- 
Trias by Jules Marcou, the occurrence of which belowthe -staked 
plains " was announced many years ago by him. 
Great denudation has laid hare several hundred feet of strata 
in vertical hi<>lit around the town of San Angelo. The waters of 
the Concho rivers follow the southeasterly dip of the Lower C re 
tacic formation and have cut through the chalky deposits of the 
Comanche series: their valleys gradually widen and after a com- 
paratively short course of from forty to eighty miles, a numberof 
these rivers and creeks unite a few miles wesl of San Angelo, where 
they cut down to sandy and clayey deposits with a north-westerly 
dip. This unconformity of the Red .beds with the overlying sili- 
ceous strata below the Lower Cretacic, and the Red beds offering a 
stronger resistance have caused the waters to spread, and thc\ Lave 
formed a beautiful and fertile valley from twenty to thirty miles in 
♦Americas Geologist, June 1890. No. 6. 
