A
BRIEF DESCRIPTION
OF THE
CRETACEOUS ROCKS OF TEXAS AND THEIR ECONOMIC USES.
ROBT. T. HILL, F. G. S. A.
SYNOPSIS.
The Cretaceous Areas of Texas Briefly Defined.—General Statement of the Importance of the Underlying Rock Structure—Broadly Subdivided into the Black and Grand Prairie Regions.
The Upper Cretaceous, or Black Praries, Series.—The Black Prairie and its Subdivisions—Its Underlying Rock Sheets—The Lower Cross Timber Sands—The Eagle Ford Clays—The "White Rock," or Austin—Dallas Chalk—The Exogyra Ponderosa Marls, or Main Black Prairie Beds—The Uppermost, or Sandy Glauconitic Beds.
The Lower Cretaceous, or COmanche, Series.—The Grand, or Fort Worth, Prairie—Compared with the Black Prairie—The Trinity Sands, or Upper Cross Timber Beds—The Fredericksburg Division—The Basal Alternating, or Magnesian Beds—The Comanche Peak Chalk, and the Caprotina Limestone—The Occurrence of Flints in the Latter Beds— The Leander Beds—The Washita Division, or Fort Worth Limestone—The Exogyra Arietina Clays—The Shoal Creek Limestone and the Denison Beds.
Tabular Review of the Creatceous System of Texas.—Economic Features of the Cretaceous System—The Agricultural Soils and Natural Fertilizers—The Building Material— Peculiar Adaptability for the Manufacture of Portland and Hydraulic Cements— Important Water Conditions—Mineral Products—Lines of Investigation for the Future.
The two series of rocks comprising the Cretaceous System occupy the area of the State known as the Black Prairie, the Grand Prairie, and the two Cross Timbers, and unstudied areas in the eastern and trans-Pecos regions of the State.
"Most of the scientific facts contained in this paper have been published from time to time in various publications by the author, lists of which, with other references to the literature, fossils, and more technical points, have been published in Bulletin No. 4 of this Survey.