254 CENTRAL MINERAL REGION OF TEXAS. 



STRATIGRAPHIC GEOLOGY. 



The preceding pages indicate clearly the nature of the problems which lay 

 before the writer when he first entered the field in 1889. A cursory view of 

 the area made it apparent that nothing but a very accurate survey of the 

 region, topographic and geologic, could enable one to unravel the intricate 

 and confused structure, complicated as it is by faults, cross-foldings, contor- 

 tions, and irregular erosion. A very little study of the region proved that 

 any attempt to trace the course of the mineral belts, to define the outcrops, 

 and to determine the extent and character of the resources, must be based 

 upon such detailed and connected observations as can only be made by care- 

 ful instrumental work. However important and desirable in less disturbed 

 regions, this method of procedure is absolutely essential in our area to a pro- 

 per understanding of the situation. 



No fact is more strongly apparent in the structure of Central Texas than 

 the widespread character of the geology. One can not diligently note and 

 plot dips, strikes, and faults over this tract without becoming firmly convinced 

 that the salient structural features are not merely local phenomena, but that 

 without doubt the foldings, plications, faultings, and unconformities here 

 visible are but partial relics of geologic events of considerable magnitude, af- 

 fecting extensive adjacent areas. Observations reported by Messrs. Dumble 

 and Streeruwitz in Southwest Texas tend to confirm this judgment, and the 

 trends of the uplifts are such as harmonize well with the great continental 

 ribs of which these may possibly be the extensions. But it is not possible at 

 present to bridge over the gaps, and to trace the buried axes very far beyond 

 the limits of the field in hand. Owing to inequalities of erosion in part, but 

 much more to the complications induced by successive upheavals, and the 

 confusion arising from intrusions and infiltrations, even the relations of 

 one part of the district to others at a distance can only be understood by ac- 

 curately plotting all the structural features upon a good topographic map. 

 None of the maps heretofore published have been accurate enough for this 

 purpose, and it has therefore been necessary to devote much time and labor 

 to such work, which is even now only partially completed. For this reason 

 it has not been possible in a single season to cover the whole area in such 

 manner as to completely close every hiatus in the geologic history, nor has it 

 yet been feasible to determine all the conclusions which may be eventually 

 drawn from the observations. But some of the questions left unsettled by 

 previous workers have been, it is believed, fully solved, while upon many 

 points which are still doubtful the experience already had will direct how and 



