GLACIAL WATERS IN BLACK AND MOHAWK VALLEYS 2/ 



below the Middleburg, while half that slope would still keep the 

 Middleburg plane superior. The second factor involves the ice 

 barrier. During the earher phases of the Schoharie lake history, 

 when the Middleburg pass might otherwise have been effective, the 

 Hudson valley ice tongue probably lay against the Catskill highland, 

 west of Catskill village, at so high a level as to block outflow of 

 the Schoharie-Mohawk waters by the Catskill valley. Later, when 

 the ice was removed from the Catskill scarp the Cedarville outlet 

 was probably open at an inferior level. Detailed study of the deltas 

 built in the Schoharie valley by side streams will probably show a 

 strong lake plane somewhat beneath the Middleburg pass, the latest 

 phase of the Herkimer lake. 



Professor Brigham has noted lake deposits in the Schoharie valley 

 above Esperance and in the tributary Cobleskill valley, which he 

 attributed to a morainal dam near Burtonsville, and he called the 

 waters the Schoharie lake. The present writing would make the 

 name include all the glacial waters which, extending through both 

 the Schoharie and Mohawk valleys, had their escape across the 

 east divide of the Schoharie basin. Local names may be desirable 

 for any distinct phases of these waters. 



Schoharie lake outlets. The first downdraining of the Herkimer 

 lake and the initiation of the Schoharie came when the Hudsonian 

 ice lobe, lying against the Helderberg scarp west of Albany, weak- 

 ened so as to permit outflow across the east divide of the Schoharie 

 valley. 



The earliest outflow of the Schoharie waters was probably along 

 the face of the Helderberg scarp, crowded between it and the 

 glacier. Plate 6 indicates the channels along the face of Country- 

 man hill and southward, specially under iioo feet. The writer has 

 not made close study of the district but sufficient to show that the 

 saliences of the great scarp west of New Salem up to about 1200 

 feet have been scraped by powerful water currents. The map shows 

 the southward continuation of these rivers, alongside the glacier, 

 and parallel to the wall of the Hudson valley. Apart from any 

 ponding of waters in the Mohawk basin such ice-border drainage 

 v/as a positive necessity ; but with the contribution of the Adiron- 

 dack-Mohawk drainage added to the copious waters from the glacier 

 melting there was a heavy concentration of flow along the margin 

 of the ice tongue, seeking southward escape. The continuation of 

 these channels far to the south is apparent on the topographic sheets. 



It must not be thought that the Wisconsin glacial drainage is 

 entirely responsible for these channels (transverse to the normal 



