BONNIFIELD AND KANTISHNA REGIONS. 207 
and comprise highly metamorphosed rhyolitic rocks with probably 
some associated tuffs. 
The soft bed rock includes thick beds of slightly consolidated sands, 
clays, fine gravels, and many beds of lignite, all overlain by thick 
deposits of gravel. Some of these deposits, at least, are of Tertia^ age, 
and a more detailed description of them will be found in the section 
on the coal deposits (pp. 221-226). 
POlSKIFIEIiD PLACER REGION. 
GENERAL DESCRIPTION. 
The region known as the "Bonnifield country" is named for John E. 
Boiinifield, who was one of the first men to locate in this part of 
Alaska. The name referred originally to the region immediately west 
of Wood River, but as prospectors explored valleys farther west the 
name came to be used in a broader sense, and for the purposes of this 
report includes all areas of placer mining between Wood River and 
the Cant well, 50 miles farther west. 
The region is difficult of access in summer. The waterways are not 
easily navigable, even for small boats, yet supplies are sometimes 
brought in them about 40 miles upstream to points a dozen miles or 
more from the hills, whence they are transported overland by man or 
horse power about 20 miles to the creeks where they are to be used. 
Pack trains are occasionally taken over the flats along the west side 
of Wood River, but this method is expensive. Most of the supplies 
are transported during the winter, when streams afford good traveling 
for dog or horse sleds and the time consumed from Fairbanks to the 
creeks where mining is in progress is but a few days. 
The region is delimited on the south about 20 miles south of the flats 
by prominent eastward-trending ridges which overlook it. The area 
between these ridges and the flats contains several ridges approxi- 
mately parallel, with altitudes of 4,000 feet and intervening spaces a 
few miles in width at a level 2,000 feet below that of the ridges. Iso- 
lated prominences like Jumbo Dome form important landmarks and 
the area is one of diversity. 
THE CREEKS. 
The most striking characterHtic of the drainage and one that finds 
explanation in the different conditions that once prevailed is the fact 
that the streams in general have cut canyons in ridge after ridge in 
their northward progress toward the flats. These canyons are for the 
most part narrow, and talus from the overtowering cliffs obstructs the 
streams. The intervening parts of the valleys are in general open, and 
gravel plains up to 1,000 feet or more in width have been developed. 
