158 APPENDIX D. GEOLOGY. 



Pursuing the same direction, twenty-five miles beyond is an outburst 

 of granite, wbich extends for the distance of twenty- six miles, with a 

 southerly bearing. This is the only example of rocks of igneous origin 

 to be met with between Fort Smith and Preston, and the rough and 

 rugged features of the country where it prevails, forms a striking con- 

 trast with the comparatively rounded outline of sandstone hills. The 

 rock is of a coarse texture, and varies in compactness in different portions 

 of the range; feldspar of the flesh colored varieties predominates over 

 the other ingredients. In places the rocks would form an excellent and 

 durable building material, but in other portions of the range it crumbles 

 readily when exposed to the action of the weather. 



We observed numerous veins of quartz traversing the granite in 

 various directions, and, at some points, dykes of compact greenstone 

 porphyry. Saline springs were found not unfrequently issuing from the 

 base of the range, and the waters in one or two instances were found 

 so strongly impregnated with saline matter, as to induce the belief that 

 they might be worked with profit. 



Passing this range the sandstone again reappears, and constitutes the 

 prevailing rock to within a short distance of Fort Washita, where it 

 disappears, and is succeeded by strata of the cretaceous period. 



From this point the cretaceous rocks were found to extend unin- 

 terruptedly until we reached the southwestern bound ry of the Cross- 

 Timbers, in Texas. From the best information I was able to procure, it 

 constitutes the prevailing formation from Fort Washita in the direction 

 of Fort Towson for upwards of a hundred miles, with an average 

 breadth of fifty miles. It forms part of that extensive belt of cretaceous 

 strata that extends from Georgia to Texas, and which, from the charac- 

 ter of its fossil fauna, is now regarded as the equivalent of the upper 

 chalk of England, and with that division of the cretaceous group to 

 which D'Orbigny gives the name of VEtage Seiionien, (Prodrome de 

 Palseontologie, tome II, page 669.) Wherever sections of the strata 

 were to be seen they presented the following characters : grayish yellow 

 sandstone, with intercalations of blue, yellow, and ash-colored clays, 

 and beds of white and bluish-white limestone. The limestone reposes 

 on the clays and sandstones. At some points it attains the thickness of 

 a hundred feet, while at others it is quite thin, and sometimes even 

 entirely wanting. It is usually soft and friable, and liable to disintegrate 

 rapidly when exposed to the action of the weather. These cretaceous 

 rocks are often full of fossils. At Fort Washita the layers are crowded 

 with Ananchytes, Hemiaster, Nucleolites, Ammonites, Ostrea, Pecten, <fec., 

 descriptions and figures of which will be found in Dr. B. F. Shumard's 



