BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 17, pp. 251-256, PL. 6 JUNE 6, 1907 



CAVE-SANDSTOKE DEPOSITS OP THE SOUTHERN OZARKS* 



BT A. H. PURDUE 



(Read before the Society December 28, 1906) 



CONTENTS 



Page 



Stratigraphy of the southern Ozarkt. 251 



Unconformity at the top of the Everton limestone 252 



Sandstone masses at the horizon of the unconformity 252 



Sandstone masses in the manganesian limestone 253 



Shape and size of sandstone masses 254 



Character of the sandstone 254 



Reasons for considering the sand masses cave deposits 254 



Source and manner of introduction of the sand 255 



Features of the sandstone accounted for 255 



Age of the deposits 256 



Age of the caverns 256 



Stratigraphy of the southern Ozarks 



The surface rocks of the southern Ozarks are of Ordovician, Silurian, 

 Devonian, and Carboniferous ages. Those of Silurian age are absent over 

 a large portion of the region, as a result of unconformities, and those of 

 Carboniferous age are locally absent, as a result of erosion during the 

 present erosion cycle. 



In southern Missouri and northern Arkansas the streams have in many 

 places cut far below the Carboniferous rocks, leaving the older rocks ex- 

 posed on the hillsides. The rocks of Devonian age consist of a thin 

 stratum of sandstone, or of sandstone and shale, and as those of Silurian 

 age are usually absent, practically all the rocks exposed below those of 

 Carboniferous age belong to the Ordovician. 



Near the Arkansas-Missouri line the Ordovician rocks exposed along 

 the sides of the rather deep ravines consist of manganesian limestone 

 containing several beds that are more or less cherty and locally thin beds 

 of ripple-marked sandstone. A few miles south of the Arkansas-Missouri 

 line there appear at the top of the manganesian limestone two beds of 

 sandstone with an intervening bed of limestone. These sandstones are 



* Received by the Secretary of the Society March 29, 1907. 



XXII — Bull. Gbol. Soc. Am., Vol. 18, 1906 (251) 



