BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 5, pp. 191-198, PLS. 5-7 FEBRUARY 9, 1894 



PALEOZOIC INTRA-FORMATIONAL CONGLOMERATES * 



BY CHARLES D. WALCOTT 



{Presented before the Society December 28, 1893) 

 CONTENTS, 



Page 



Introduction 191 



Intra-formational Conglomerates 192 



Definition of Term and Illustration , 192 



Canadian Localities 192 



Vermont and New York Localities 193 



Pennsylvania Localities 194 



Virginia Localities 195 



Tennessee Localities 195 



Origin 197 



Introduction. 



Usually the presence of a conglomerate in a stratigraphic series of 

 rocks is a matter of considerable importance to the geologist. He natur- 

 ally infers the presence of a break in the continuity of sedimentation; 

 an orographic movement of greater or less extent ; erosion of a preexist- 

 ing formation. He sees, in his mental review, the waves sorting and 

 depositing sand, pebbles and bowlders derived from the uplifted land. 

 The idea of the lapse of a period of time of considerable and often long 

 duration is formed as he recalls orographic movement, erosion and un- 

 conformity of deposition. If the conglomerate is near the base of some 

 formation or series of formations, he views it as almost conclusive evi- 

 dence of the marked change that introduced the new deposits. This is 

 all fair induction from observed facts, and it is the general and approved 

 experience of geologists. When I ventured to describe to a veteran 

 geologist the peculiarities of a formation of conglomerate that occurs in 

 the Lower Cambrian rocks of the eastern United States he advised my 

 reviewing my field work and opinions, as the latter were unusual. This 



* Printed by permission of the Director of the U. S. Geoh^gical Survey. 

 XXVr— Bui.T,. Geoi-. Soc. Am., Vor,. 5, 1893. (191) 



