120 CRETACEOUS ROCKS OF TEXAS. 



fountain of inestimable value to another region beneath which it lies con- 

 cealed and usually unappreciated. 



Wherever the surface outcrop of these sands has attained any areal extent, 

 they are covered with a comparatively abundant scrubby forest growth, as 

 conspicuously illustrated in the case of the Upper Cross Timbers. The 

 sandy soils resulting from their disintegration, however, are not as rich in fer- 

 tilizing ingredients as the overlying calcareous soils, but they can be greatly 

 improved by mixtures. The soils, as indicated by their natural vegetation, 

 are the best adapted to tree growth, and are becoming the seat of a fruit 

 growing industry. 



The lignites and occasional iron ores in the Trinity sands are worthless, and 

 the alleged gold discoveries existing in nearly every neighborhood invariably 

 turn out to be iron pyrites. 



NO. 2. THE FREDERICKSBURG DIVISION.* 



In the high bluffs of Cow Creek, in the western edge of Travis county, im- 

 mediately below Mr. Hensel's house, at Travis Peak postoffice, the Trinity 

 sands can be seen gradating upwards into this division, the lowest beds of 

 which are marked by the appearance of certain magnesian sandy marls and 

 rocks, accompanied by the presence of certain fossils, which we have called 

 the Caprotina Horizon No. 1. According to our classification in the general 

 section given beyond, this is the base of the Fredericksburg division, and 

 is principally composed of calcareous matter with apparently equal parts of 

 fine quartz sand ana magnesia, in bands or strata of alternating degrees of 

 consolidation. Although showing a deeper and more uniform sedimentation 

 than the Trinity sands, yet, as shown by the alternating sediments, the chalky, 

 deepest sea, conditions of the Comanche Peak beds have not yet been reached. 

 The alternation of harder and softer layers of arenaceous-calcareous strata 

 prevails, and the beds become thicker and more massive as the ocean's bottom 

 descended. Such is the beginning of the beds to which I have applied the 

 name of the Fredericksburg division, which may be divided into three litho- 

 logic subdivisions, to- wit: 



(c) The Caprina Chalky Limestone Beds. 



(b) The Comanche Peak Chalk Beds. 



(a) The Basal or Alternating Beds. 



* This division is named after the town of Fredericksburg, whose vicinity was visited by 

 Dr. Ferdinand Roemer, now Professor at Breslau, Germany, forty-five years ago (1845-1847). 

 This gentleman, who might be termed the pioneer of Texas geologic investigation, described 

 many of the unique fossil remains of the rocks which we now place in this division. 



