REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1902 r37 



Drainage history 



The continental glacier did not uncover this upper Mohawk 

 valley all at once, but the ice front slowly receded up the valley. 

 In other words, the valley was slowly opened from Little Falls 

 successively westward. The primitive waters, held between the 

 barrier at Little Falls on the east and the retreating ice lobe 

 on the west, lengthened out after the ice. At the same time 

 the open part of the valley was filling with stream detritus and 

 the outlet was being lowered by the down cutting of the rock 

 barrier. In addition to the broader delta plains described above, 

 the evidences of standing water in the valley up to 500 feet 

 and over are abundant to the eye of the trained observer in 

 the almost continuous terraces and benches of wave-washed 

 accumulation along the sides of the valley which are now gullied 

 by the modern stream drainage. 



The earliest lake level was probably about 600 feet, the alti- 

 tude of the bare crystalline rock on the north side of the 

 Little Falls channel. But this higher level would hold only for 

 the lower section of the valley. Up the valley, toward Utica 

 and Rome, the highest level of standing water would be less 

 than 600 feet, by whatever amount the Little Falls outlet had 

 been lowered by down cutting while the valley was opening 

 by ice recession. 



In the narrow Herkimer-Frankfort section of the valley the 

 open waters may have been only temporary, as the detrital 

 inwash from side streams and the ice drainage possibly kept 

 this part of the valley filled with gravels, specially at the lower 

 water levels. Above Frankfort the valley was wider and prob- 

 ably deeper and held lake waters up to Iroquois time. In the 

 section from Utica to Oriskany the lake plains are about 540 

 feet in altitude. Further up the valley, at Ninemile creek, they 

 are somewhat less, being given only the 520 contour on the Oris- 

 kany sheet. And, when the ice sheet had withdrawn from the 

 ground south of Rome, the Utica lake had still lower level; for 

 the latest pre-lroquois cuttings at Stanwix are 460 feet and lower 

 [see 21st annual report, pi. 10]. Soon after the Stanwix stream- 

 cut banks were made, the flood of the Iroquois overflow took pos- 



