BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, pp. 457-464, PL. 18 APRIL 27, 1891 



GLACIAL GROOVES AT THE SOUTHERN MARGIN OF THE 



DRIFT. 



BY P. MAX FOSHAY AND RICHARD R. HICE. 



[Read before the Society December 30, 1890.) 



CONTENTS. 



Page. 



Introductory Note 457 



Physiography of the Beaver Valley. 457 



The Glacial Phenomena _ 459 



Glacial Deposits 459 



Potholes 460 



Base-Level Kemnants 461 



Ice Markings 462 



Summary 463 



Introductory Note. 



lu a preliminary paper in the American Naturalist for September, 1890,* 

 there was a brief sketch of the phenomena herein described in greater detail 

 and illustrated by photographs reproduced mechanically (plate 18). These 

 phenomena, consisting of grooves, striae and potholes, were discovered by the 

 writers in the course of a survey of the Pleistocene formations of the valley 

 of the Beaver river. The description of the particular phenomena in which 

 we are interested is here prefaced by a short account of some of the features 

 and the geological history of this portion of western Pennsylvania. 



Physiography of the Beaver Valley. 



The Beaver river is formed at Lawrence Junction, on the Pittsburgh, 

 Youngstown and Azh tabula railroad, by the confluence of Mahoning and 

 Shenango rivers, and, after a course of about twenty-one miles in a southerly 



* Vol. XXIV, p. 816. 

 LXVII— Bull. Geol. Soc. Am., Vol. 2, 1891). (■!•->") 



