470 B. T. Hill — Uppermost Cretaceous Beds of the 



The Lower, or Grand Prairie Formation (Comanche 



Series). 



[Grand Prairie and Upper Cross Timbers Formation.) 



This formation increases in thickness to the southward, and no 



general estimate of thickness is at present deemed advisable. 



Following is the section from Austin to Burnet : 



Thickness. 



9. Shoal creek or ( Vola) limestone 75 



8. Green clays (Exogyra arietina clays), bed of Shoal 



creek 100 



7. Washita limestone, railroad cut, west Pecan street 

 extension, Austin, and extending parallel to the 

 above, in a narrow line across the state, from Fort 

 Washita, 1. T., southward via Denison, Fort 

 Worth, Salado, San Marcos, Heliotes, and west to 

 Mexico 160 



6. The Austin marble, or Caprotina limestone, west of 



Austin + 20 



5. The paving flags, or lithographic horizon, west of city 



of Austin + 20 



4. Barton Creek, or Caprina limestone. Barton creek 

 above the ford ; the high bluffs of the Colorado at 

 and opposite Johnson's quarry, and the west bluff 

 of Mount Bonnel ... 1000 f 



3. The Nummulitic (Tinoporus) chalk, river bluffs near 



Bull creek 100 f 



2. Fredricksburg division, including all the limestones 

 and marls west of the above, which have not yet 

 been differentiated . +1000f 



1. The Upper Cross Timber, or Trinity, sands + 300 j 



Estimated Lower Cretaceous, Central Texas .. 2775 

 " Upper " " " .. 2100 



Total -. 4875 



The immediate objects of this paper are to call attention to 

 (1) the beds of the uppermost or glauconitic division of the 

 Upper Cretaceous, (2) to the important light they throw upon 

 the Cretaceous beds of the Gulf and Atlantic States east of the 

 Mississippi, and (3) to the complete nonconformity by erosion 

 and deposition that exists between them and the basal beds of 

 the Southern States Tertiary. 



* Artesian wells have penetrated these clays to this thickness at Corsicana, 

 Texas. 



f This thickness of these horizons is the most modest estimate that can be 

 given. Accurate measurements are now being made. 



\ My able assistant, Mr. J. A. Taff, who has recently made an accurate map 

 and sections of this horizon, finds ores a thousand feet of thickness. 



