130 CRETACEOUS ROCKS OF TEXAS. 



rich dark red color, and covered with handsome timber growth, as seen at 

 the Pease mansion in West Austin. 



THE DENISON BEDS. 



This abrupt termination of the Lower Cretaceous, together with the Shoal 

 Creek limestone at Austin, is local, and, as will be shown later, due to the pe- 

 culiar igneous disturbances that prevailed in this vicinity. To the northward, 

 where these disturbing conditions were not present, the final termination of 

 the Comanche series is quite different, as at Denison, for instance, where the 

 Washita limestone, as seen one and one-fourth miles north of the city, is suc- 

 ceeded by shallowing alternations of clays and impure blue and yellow lime- 

 stones containing an abundant littoral fauna, characterized by Ostrea quad- 

 riplicata, Shumard. The details of these beds, although reconnoitered once 

 or twice, have not been accurately determined, but further field work will 

 soon be undertaken in that region. 



Dr. B. F. Shumard almost inextricably mixed his brother's results in his 

 generalized section of Texas rocks.* The Denison beds abound in massive 

 strata of an excellent, firm, semi-crystalline blue and yellow limestone, which 

 is extensively used throughout North Texas for building purposes. 



*B. F. Shumard: "Observations upon the Cretaceous Strata of Texas." Trans. Acad. 

 Science of St. Louis, Yol. I. 1856-60. 



