GEOLOGY OF TSE PORT LEYDEN QUADRANGLE 5 1 



and limestone are also present in great abundance in the till and 

 other drift of the Remsen quadrangle. However, much of the shale 

 must have been ground up and carried away by glacial waters. 



Glacial sand plains or terraces 



A remarkable development of glacial sand plains or terraces is 

 to be found within the Port Leyden quadrangle. Here, on the east 

 side of the river, most of the region is occupied by these terraces, 

 which taken together may be looked upon as a single great terrace 

 with steep front facing Black river [see fig. 5]. On the Port Ley- 

 den sheet alone they cover fully 75 square miles and continue both 

 northward and southward from this area. They are clearly shown 

 upon the topographic map. The sands and gravels of these terraces 

 show a depth of from 200 to 250 feet along the western edge, and 

 there is a gradual thinning out to disappearance several miles east- 

 ward. 



Except in a few cases the flat-topped surfaces are practically desti- 

 tute of large boulders. A characteristic feature is the presence of 

 pitlike or kettlelike depressions over the surfaces [see map]. These 

 depressions are of various sizes and shapes and are sometimes occu- 

 pied by lakes or ponds, as for example Brantingham, Little Otter 

 and Catspaw lakes and Sand pond. They are often very steep- 

 sided and range in depth from a few feet to 50 or 60 feet. The 

 terraces are dissected by many streams so that enough good sections 

 are exposed to make it certain that the materials are crudely strati- 

 fied and cross-bedded, and occasionally interstratified with clay, thus 

 proving that they were water laid. The western margin of this 

 great terrace is distinctly lobate in character and is strongly sug- 

 gestive of delta origin as for example in the southeastern part of 

 the quadrangle. Another very notable feature is the concordance 

 of altitudes at about the same distance back from the margin. The 

 altitudes vary from about 11 50 to 1260 feet, the higher altitude^ 

 being on the east, thus giving a gradual slope of the terrace surface 

 toward Black river. 



A study of the character and distribution of these terraces as well 

 as their relation to the other drift deposits, leaves no doubt as to 

 their origin as delta deposits in a marginal lake along the waning ice 

 tongue during its retreat from the Black river valley. The im- 

 mense amount of material thus deposited was readily obtained by 

 the streams, especially Black and Moose rivers and Otter creek, as 

 they emerged from the newly drift-strewn Adirondack highlands. 



