GLACIAL WATERS IN BLACK AND MOHAWK VALLEYS 39 



wasteweir or stream head at Rome. A little cutting would today 

 divert the flow of the Mohawk westward into Wood creek. 



SUMMARY OF THE MOHAWK DRAINAGE HISTORY 



Stage I. The axis of the valley was occupied by a strait of ice 

 connecting- the two ice bodies in the Hudson and Ontario valleys. 

 The v/aters of the Adirondacks escaped across the ice, the overflow 

 probably being into the Otsego-Susquehanna valley. Sand plains 

 through the Adirondacks with elevation 1450 and upward probably 

 correlate with this stage. See plate 12. 



Stage 2. The melting of the strait of ice in the valley left a 

 stretch of open water between the ice tongues, the Herkimer lake. 

 The water had two successive outlets, by Summit lake pass to the 

 Otsego-Susquehanna at 1360 feet, and by the Cedarville pass to 

 the Unadilla-Susquehanna, at 1220 feet. Correlating sand plains 

 of great expanse occur in the basins of the upper Mohawk, West 

 Canada and East Canada creeks at 1440 to 1280 feet. See plates 

 2) 5' 7» 13- The Black valley basin was flooded by the waters of 

 this stage, so far as relieved from the ice sheet. 



Stage 3. Waning of the Hudsonian ice lobe permitted escape of 

 the waters along the face of the Helderberg scarp, west of Albany, 

 the later flow being across the divide between the Schoharie and 

 Hudson valleys, at Delanson, 840 feet. Correlating sand plains 

 exist in many localities with elevation, according to latitude, from 

 1200 down to 820 feet. See plates 2, 7, 8, 14. The Black valley 

 waters were now tributary to the Schoharie lake, first through the 

 Remsen outlets and later by the Boonville outlet, as shown in plate 2. 



Stage 4. Amsterdam lake. Further recession of the Hudson 

 valley ice lobe permitted outflow of the waters about the Rotterdam 

 salient, west of Schenectady, at 800 down to 360 feet. See plate 6. 

 The correlating delta plains are widely distributed, having altitude 

 in the Rome district of 860 to 460 feet. See plates 2, 8, 15. The 

 Black valley waters were still tributary and two other tributary 

 lakes were the Lansing kill and the Sacandaga. See plate 8. 



Stage 5. Lake Albany, confined to the Hudson valley, with out- 

 let control southward. The Mohawk valley now had free drainage, 

 two phases being the Glaciomohawk, previous to Iroquois time, and 

 the Iromohawk, the overflow of Lake Iroquois. 



