BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 10, pp. 121-130 March 23, 1899 



GLACIAL SCULPTURE IN WESTERN NEW YORK* 



BY GROVE KARL GILBERT 



{Presented before the Society December 30, 1898) 

 CONTENTS 



Page 



Introduction 121 



Sculpture of the Niagara limestone 122 



Sculpture of the Clinton and Medina ledges . 125 



Sculpture of the Medina shale 1 26 



Summary 129 



Introduction 



The question whether the Pleistocene ice-sheets accomplished a large 

 amount of rock erosion has been a fruitful subject of discussion. The 

 most diverse views have been expressed, and there are probably still 

 some geologists who think that the ice executed only a slight superficial 

 scraping and polishing, as well as others who ascribe to it works of such 

 magnitude as the excavation of the basins of the Laurentian lakes. The 

 most important recent contribution is by Goodchild, who shows that the 

 topograph}^ of a large district in Scotland, a district largely occupied b}^ 

 sandstones, breccias, and other resistant rocks, was remodeled by Pleis- 

 tocene ice. Its topography is rugged in detail, comprising many hills 

 and valleys, and these features, instead of conforming in trend to the 

 strike of the rocks, conform to the direction of ice motion, which makes 

 wide angles with the strike.f 



In line with his conclusions are the phenomena of the Finger Lakes 

 region in western New York. Many of the more striking features of that 

 region have been ascribed by various writers to ice sculpture, | and my 

 own observation, which has been somewhat extensive, supports that 

 conclusion. It ap})ears to me that the peculiar topographic facies of the 

 great body of Devonian shales underlying that district owes more to ice 

 work than to antecedent water work, and that the face of the country is 



*The observations set forth in this and the two following papers were made by the autlior as a 

 member of the U. S. Geological Survey, and are here published with permission of the Director of 

 the Survey. 



t J. G. Goodchild : Glaeialist Magazine, vol. iv, 1896, pp. 1-7. 



X See Bull. Geol. Soc. Am., vol. 5, pp. a39-356. 



XVIII— Bull. Geol. Soc. Am., Vol. 10, 1898 (121) 



