PLEISTOCENE DEPOSITS, GROUND-ICE FORMATION AND KOWAK CLAY. 91 



glacier ice (save the single instance cited on John River) has disappeared. To the 

 east, however, as noted under "Previous explorations," prospectors and whalers 

 who have crossed the range in the vicinity of the one hundred and forty-ninth 

 meridian report the presence of valley glaciers of considerable size. 



The glacial phenomena that have been described tend to show that, although the 

 Endicott Mountains (PI. VII) do not on the whole seem to have been overridden 

 en masse by a moving ice sheet, they were doubtless, especially in their northern 

 part, largely occupied by an ice cap or perennial neve, constituting a breeding ground 

 for glaciers. The zone of maximum snowfall, and consequently of maximum ice 

 accumulation, trending in an east- west direction, was apparently in the northern part 

 of the range at least somewhat north of its median line. From this zone the ice 

 moved off to the north and to the south, respectively, into the Colville and Koyukuk 

 basins. Its flowage, especially during the latter part of the Ice age, was confined 

 mainly to the valleys and drainage ways in the form of alpine glaciers, of which there 

 is ample evidence. But there is also good reason to believe, as shown by the till 

 sheet north of the mountains, that during the zenith of the Ice age the northern 

 edge of the range was occupied by a more or less extensive ice sheet, which, as a 

 small regional or piedmont glacier, thinning out toward the north, extended north- 

 ward over a considerable portion of the Anaktuvuk Plateau, its occurrence at that 

 time being, perhaps, similar to that of the Bering or Malaspina glaciers of to-day. 



GROUND-ICE FORMATION AND KOWAK CLAY. 



At some localities along the Arctic coast there are stretches of low bluff's or 

 banks of ground ice overlain by a deposit of dark muck and moss several feet in 

 thickness. Deposits of light-colored cla} r also are occasionally seen. The occurrence 

 and distribution of these deposits appear, in a measure, to be as represented by 

 Doctor Dall on his map of the "Known distribution of the Neocene formations in 

 Alaska." 3 



The ground-ice formation was hitherto supposed to be of very widespread occur- 

 rence in this Arctic region. To give an idea of the evidence on which this supposi- 

 tion rests I shall here freely quote from Doctor Dall's report.* 



"From information gathered from several masters of vessels in the whaling 

 fleet, and derived from experience gained in the effort to dig graves for seamen who 

 had died aboard vessels on this shore from time to time during the last twenty j^ears, 

 it would appear that somewhat north of Cape Beaufort the land between the low hills 

 and the sea is low and the soil chiefly a sort of gravel. ' At a depth of 2 feet is a 

 stratum of pure ice (not frozen soil) of unknown depth. This formation extends, 

 with occasional gaps, north to Point Barrow, and thence east to Return Reef, where 



"Dall, W. H., Correlation papers, Neocene: Bull. IJ. S. Geol. Survey No. 84, 1892, opposite p. 268. Becker, G. F., Recon- 

 naissance of the gold fields of southern Alaska: Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 3, 1898, pi. i. 

 6 0p. cit., p. 264. 



