REPORT OF THE STATE GEOLOGIST. liii 



ous sea. Towards the top of the beds the deposits become finer, and 

 where mixed with sufficient carbonate of lime to cement them, become 

 packsands. These sands form the soil on which the eastern portion of 

 the Upper Cross Timbers grow, and their line of outcrop forms the 

 western border of the eastern Cretaceous area. While the Trinity sands 

 do not furnish soils of great fertility, we are nevertheless indebted to 

 them for the great artesian water area which they have created and of 

 which they must always remain the source of supply. For this reason 

 their value is far greater than it could be as mere farming land. 



One curious fact which may be mentioned in connection with the 

 Trinity sands is that metallic iron is found in them in small quantities 

 in various localities. The origin of this iron, which has practically the 

 composition of meteoric iron, and shows lines similar to the Widman- 

 staetten when carefully etched, has not been determined. It occurs in 

 various forms, some of it appearing perfectly bright, as though just pol- 

 ished, but the greater part has a slight coating of clayey material and a 

 reddish appearance. Analyses of different specimens differ consider- 

 ably ; but it is principally metallic iron, with various percentages of 

 nickel, copper, platinum? and perhaps other metals. 



The beds also contain local deposits of lignite, which are, however, 

 not of any value, because of the quantity of sulphur they ordinarily 

 contain. 



In the Trans-Pecos region these sands are probably wanting, although 

 there are certain quartzites immediately underlying the Comanche Beds 

 which might be doubtfully referred to this division but for the imprac- 

 ticability of separating them from the other exactly similar quartzites 

 of seemingly earlier periods, such as the surface rocks of the mountains 

 of the Sierra Blanca group. If further investigation shows the entire 

 series to be of this age (which is considered very doubtful), it will give 

 it a very considerable thickness in this region. 



The Lower Cretaceous or Grand Prairie Series contains within its area 

 great quantities of very valuable building material — not only building 

 stones, but the very best materials for lime and Portland cement — which 

 must sooner or later meet with proper appreciation. While its soils are, 

 as a rule, not as rich as those of the Upper Series, it nevertheless com- 

 prises much valuable farming land and lands that can be made available 

 for farming purposes after a proper study of their character. 



Up to this point, if we except a part of the Lower Cretaceous, we 

 have been dealing with deposits, which, for the most part, were laid 



