316 CENTRAL MINERAL REGION OF TEXAS. 



able to agree with him as regards the area familiar to me, which he has not 

 yet visited ; but his cogent reasons for adopting this view for the area north- 

 ward, which he has examined, are not subjects of this discussion. From the 

 best judgment I can make, after the kindly aid of Messrs. Hill, Dumble, Cum- 

 mins, and Tarr, in view of my own limited observations north of the San Saba 

 River, it would appear that the violent disturbances which have made the 

 Central Mineral Region a veritable piece of " crazy patchwork " expended 

 their energy largely before reaching the valley of the Colorado River upon 

 the north. In our area, prior to the Cretaceous period, there was, as it were, 

 a struggle for the supremacy in orographic expression of the forces acting 

 along meridianal and longitudinal lines. While it is certain that some of the 

 uplifts at least were but small parts of important continental elevations, it 

 ought not to be forgotten that this was practically a centering point for them 

 all, though not necessarily the initial point. On this account, and by reason 

 of the badly broken condition of the strata, the portion of the region which 

 had all along been an area of shallow water or of dry land, was in good shape 

 for elevation, while the surrounding region was being depressed. Mr. Hill 

 has well shown in his writings the fact of this long continued subsidence in 

 Cretaceous times. We have seen how the Central Mineral Region was in 

 earlier times a changing, but permanent bulwark between the inner and outer 

 seas. The latitudinal uplift at the close of the Paleozoic Era left a new topog- 

 raphy, and one which went far towards preventing what would otherwise 

 have been a covering of our district by the Cretaceous sea. At the same 

 time the Lower Silurian anticline trending northward (north 25 degrees east) 

 presented a barrier in a part of our district which has never since been sub- 

 merged. 



Reference has been made to the difference of present level between the 

 Silurian (Hoover) beds in Kimble and Gillespie counties and the same geo- 

 logic horizon in Burnet and San Saba counties. The relations of these beds 

 and the subsequent Silurian and Carboniferous deposition go to show that the 

 Post-Paleozoic, Pre-Cretaceous orographic movement was foreshadowed late 

 in the Silurian period, and culminated at the close of the Carboniferous pe- 

 riod, when subsidence ensued. 



But as was previously noted, the irruption of the Capitol granite at this 

 juncture was most active over the eastern half of the district and practically 

 over the southeastern quarter. The subsidence in the north and the elevation 

 in the south resulted in the deposition of several hundred feet of Post-Hoover 

 deposits in the former area, none of which are found in the latter, although 

 they do occur in part upon the east. 



Now it happens that the summit of the Trinity (Cretaceous) Series upon tha 

 southeast at the border of our district is nearly on a level with the base of the 



