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Caprina limestone is no doubt the continuation and culmination of the great subsidence of the ocean's bottom in Lower Cretaceous time, and will be of service in future interpretation and final correlation. It is very uniform, and covers large areas of the Grand Prairie plateau in southwest Texas, especially in the region adjacent to the lower Pecos. It also caps the mesas of the remnantal areas in the Abilene country, and as far east as Comanche Peak in Hood County. The railroad from Brueggerhoff to McNeil along the Williamson-Travis County line crosses a typical portion of its strike.
Economics of the Caprina Limestone.—The Caprina limestone is also productive of many rare building stones and other structural material, while the immense flint deposits will no doubt be ultimately utilized.
The Caprina limestone is the material used in the manufacture of the Austin lime, which has a wide celebrity for its purity. This stone also makes a good material for macadamizing roads, and is now being extensively used for that purpose by the city of Waco.
The residue of the Caprina limestone and certain marly beds at the top make the richest and most productive agricultural soil of the Grand Prairie region. It is readily distinguished by its dark red, sometimes nearly black, color, as seen in the country between Florence, Williamson County, and Leander, and in the Jollyville neighborhood of Travis County. It also occurs in Bell, Coryell, Hamilton, Bosque, and Hood Counties. This soil has not yet been mapped or classified.
No. 3. THE WASHITA DIVISION.
The Caprina chalky limestones which mark the culmination of subsidence in the Comanche series are succeeded by deposits of a lithologic and stratigraphic character which indicate that the ocean's bottom had reached the culmination of the long subsidence which it had been undergoing since the beginning of the Trinity beds, and had commenced the gradual elevation which finally terminated in the Mid-Cretaceous land. This shallowing is well illustrated in the thin stratification of the rocks above the Caprina limestone, to which the name Washita Division has been given, after the region where its rocks were first seen by early explorers near Fort Washita, I. T.
"The Caprina limestone was given its name by Dr. B. F. Shumard from the abundance of the peculiar aberrant fossils of the genus Rudistes (which have been described as Requienia, Caprina, Monopleura, Ichthyosarcolithes, etc.) occurring in it. These peculiar forms are found occasionally in great masses. Accompanying these beds are also many new and undescribed species.
These beds are characterized by the peculiar smooth-ribbed Ammonite Schloenbachia peruvianus, De Buch (A. acuto-carinatus, Rœmer). They have not been satisfactorily studied in the Colorado section as yet.