292 R. T. Hill — Texas Section of American Cretaceous. 



locally called "White Rock," or "rotten limestone." It dips 

 at a visible angle to the eastward, disappearing beneath the 

 Marine Eocene about twenty-five miles east of the escarpment 

 line. Along the east bank of Shoal Creek, in the western 

 part of the city of Austin, and in the banks of two unnamed 

 creeks, emptying into the south side of the Colorado, opposite 

 Shoal Creek, these limestones are seen to abruptly terminate, 

 and in several places to rest usually upon blue calcareous shales 

 (I>), containing an entirely different fauna. These shales, 

 which are only visible when protected by the above-mentioned 

 limestones, owing to rapid disintegration, in turn are seen to 

 rest upon the hard, eroded surface of another limestone forma- 

 tion (C) which composes the beds of the creeks, and, dipping 

 from the northwest at an angle of fully fifteen degrees, also 

 forms the whole face of the escarpment and plateau. In places 

 the soft, rotten limestone of the Black Prairie is seen to rest 

 directly upon the disturbed harder limestone without interven- 

 tion of the shales. The characteristic strata and fauna of the 

 first-mentioned formation invariably terminates at the foot of 

 this escarpment, so that it is not found west of these contacts, 

 nor that of the harder limestones of the escarpment and plateau 

 east of them, as shown in the following diagram: 



Fig. 1. — The Austin Xew-Braunfels 

 Non-conformity as it is. — Contact seen 

 on both sides of the Colorado River at 

 Austin. A, Rotten limestone of Black 

 Prairie region; B, shales; 0. Lower Creta- 

 ceous limestone of escarpment and plateau. 



There is a clear non-conformity between each of these 

 divisions at Austin, both stratigraphically and faunally, not a 

 single species extending from one division to the other, and 

 the well-marked lithologic features of each terminating very 

 abruptly. This non-conformity is clearly and unmistakably 

 visible in and near Austin, San Marcos, Heliotes and New 

 Braunfels; and this relation of the strata, which is the same 

 along the face of the escarpment from Austin to Rio Grande, 

 is diametrically opposite to that originally announced by 

 Roemer (and accepted by Shumard and other writers down to 

 the present day),* who made the Cretaceous of the plain at the 



* But one author has ever published an opposite view to this relation of the 

 strata. Professor E. D. Cope, in Bulletin No. 17 of the TJ. S, National Museum, 

 makes the following statement, which, excepting its correlations, is true, but has 

 apparently passed unnoticed. He says : 



" An abrupt elevation commences somewhere to the southwest of Fort "Worth 

 and continues southward and westward, passing close to Austin, the State capi- 

 tal, and within twenty miles of the city of San Antonio, extending westward 'to 

 the Rio Grande. The position of the limestone thus elevated is said to be older 

 than that which occupies the adjoining lowlands, being correlated by some geolo- 



