THE DEEP KANSAN PONDINGS IN PENNSYLVANIA 

 AND THE DEPOSITS THEREIN. 



i 



PART ONE. 



By EDWARD H. WILLIAMS, Jr. 

 (Read November 5, 1919.) 



Introduction. 



As the name " Kansan " is given to the drift in Pennsylvania, 

 south of the moraine of Lewis & Wright, along the Allegheny River, 

 and as it extends across the Delaware River from New Jersey, the 

 intermediate drift in Pennsylvania south of the same will be so 

 called, though it differs almost entirely in petrographic character- 

 istics ; as drift everywhere tends to conform to the outcrops on which 

 it lies, and onfiy in moraine or overwash accumulations is there a 

 general and indiscriminate mixture. 



It is proposed to-night to examine the character and the origin of 

 the high-level gravels along Allegheny River, concerning which there 

 is a difference of opinion. Other gravels will be used as illustrative 

 material. 



Professor G. F. Wright expressed the opinion in 1894^ that some 

 of the Allegheny gravels' were remnants of a complete valley filling, 

 since excavated; but he abandoned this theory later. In 1902 F. 

 Leverett" expressed Wright's former opinion. Beginning in the 

 Lehigh Valley, in 1892, E. H. Williams, Jr.,-"* found that the sculp- 

 turing of the Kansan outwashes antedated the deposition of the 

 universal capping of iceberg silty clay. This is also the case in the 

 Susquehanna and Allegheny valleys and is applicable to all foreset- 

 bedded glacial outwashes deposited in deep pondings. 



Pondings are of two kinds : those against a watershed, with grad- 

 ually rising surface until a discharge over a col occurs and, if trench- 

 ing occurs, with gradually diminishing depth : those against per- 

 sistent or ephemeral ice-dams, with the depth varying with height 

 of the dam. The former class is characterized by a permanence 



PROC. AMER. PHIL. SOC, VOL. LIX, D, MAR. 22, I92O. 49 



