156 APPENDIX D. GEOLOGY. 



REMARKS UPON THE GENERAL GEOLOGY OF THE COUNTRY 

 PASSED OVER BY THE EXPLORING EXPEDITION TO THE 

 SOURCES OF RED RIVER, UNDER COMMAND OF CAPTAIN R. 

 B. MARCY, U. S. A.: BY GEO. G. SHUMARD, M. D. 



It is to be regretted that the main objects contemplated by the 

 expedition were of such a character as to allow of merely a partial 

 geological exploration. It was found necessary to traverse a large extent 

 of country in a limited period of time, so that not as many opportunities 

 were allowed for making minute and detailed sections of the strata as 

 could have been desired. However, it is believed that something has 

 been done towards elucidating the geology of a valuable and interesting 

 district of our country, which hitherto has received but little attention 

 from geologists. 



We will first submit a brief account of the geological features of a 

 portion of Northwestern Arkansas, which will enable us to understand 

 more clearly the character of the deposites observed on the route 

 travelled by the party, and exhibit more satisfactorily the connection of 

 the cretaceous group with the older or palaeozoic rocks. In Washing- 

 ton county we have a fine development of rocks belonging to the 

 carboniferous period, rising sometimes several hundred feet above the 

 water-level of Arkansas river. They consist of beds of dark-gray and 

 bluish-gray limestone, surmounted by heavy-bedded coarse and fine- 

 grained quartzose sandstone. The ridges of highest elevation run nearly 

 north and south through the centre of the country, forming a geological 

 back-bone; the waters from one side flowing eastwardly into White 

 river, and on the other westwardly into Illinois river, both streams being 

 tributaries of the Arkansas. 



Wherever the limestone forms the surface-rock, the soil is of excellent ' 

 character, and for productiveness is unsurpassed by any in the State ; 

 but where the sandstone reaches the surface, the soil becomes too arena- 

 ceous, and is of inferior quality for agricultural purposes. The lime- 

 stone is generally highly charged with fossils, and, in many places, beds 

 of considerable thickness are almost entirely composed of the remains 

 of Crinoidea. 



In the lithological and palseontological characters it corresponds very 

 closely to the rocks of the superior division of the carboniferous system 

 of Indiana, Kentucky, Illinois, and Missouri. The fossils are usually 

 remarkably well preserved. The following are the most abundant and 



