REPORT OF THE STATE GEOLOGIST. li 



Texas, and they are only known by a few scattered fossils in the 

 Trans-Pecos region. 



The lower part of the division is composed of limestones. In the 

 eastern part these limestones are chalky and show by their fossil re- 

 mains a condition of deep and gradually shallowing water during their 

 formation. They are of such character as to furnish excellent building 

 material. In the Trans-Pecos region the upper limestone, known dis- 

 tinctively as the Washita limestone, has a far greater development than 

 the thickness of the entire division, as it is known in the area north of 

 the Colorado. In the range of hills between Sierra Blanca junction 

 and the river it can not be less than one thousand feet in thickness. 

 The limestones at this locality do not appear to have been affected by the 

 porphyritic intrusions to such an extent as some of the underlying and 

 overlying beds — probably on account of the more massive character of 

 the strata of which they are composed. While they vary somewhat in 

 color on the inside, they weather to a uniform greyish-blue, and to a 

 casual observer present nothing different from the limestone of the un- 

 derlying Cretaceous and Carboniferous. A careful examination, how- 

 ever, reveals a difference in the manner of weathering, which, while hard 

 to describe, is nevertheless plainly apparent after a few observations on 

 the different strata in the field. The limestones contain some sand and 

 also more or less iron. When freshly broken they are often of a pur- 

 plish color with numerous yellow clayey or ochreous spots scattered 

 through them. There are also numerous bands of conglomerate or 

 breccia interstratified among them. The distribution of these lime- 

 stones is wide. They have been observed in the hills southwest of 

 Finlay ; in small detached areas in the Sierra Blanca group and Quit- 

 man Mountains (resting here directly upon the granites and porphy- 

 ries) ; in the hills around Sierra Blanca Junction ; and eastward from 

 that point they form the Devil's Ridge, and occur well developed in 

 the Eagle Mountains, on the west of the entrance to the spring. North 

 of Eagle Flat they form two small buttes in the flat, and are seen again 

 underlying the Lower Cross Timber sands to the north. 



The fossils of these beds are very numerous and some of them ex- 

 ceedingly well preserved. 



THE FREDERICKSBURG DIVISION. 



This middle division of the Grand Prairie Series consists of chalky 

 limestones underlaid by beds of limestones containing more or less 



