DESCRIPTIVE GEOLOGY. 15 
The low ridges forming the eastern side of Beaver Valley east of the 
White Mountains present in places the appearance of a well-timbered 
country, but on closer view are found to be covered with only a thick 
growth of small spruce. The upper valley of Hess Creek and the val- 
leys of its tributaries contain also abundant small spruce, with some 
larger timber near the streams. The valley of Minook Creek has con- 
tained considerable timber of sufficient size for mining purposes, but 
only a small amount of such timber is left. The valleys of the south- 
ern slope facing the Baker flats contain but little timber of large size, 
but some good timber is reported to be present in the valleys of Hut- 
aid Baker creeks. On the hillsides near the Baker Hot Springs 
is a luxurious growth of birch and poplar. Timber for fuel purposes 
is abundant in most of the valleys and lower slopes throughout the 
region. 
Feed for horses can be found on the sunward-facing slopes of most 
of the main valleys and there are large grass-covered areas in the Tol- 
ovana flats. Blueberries are almost everywhere to be found in abun- 
dance on the open hillsides and valleys, and locally currants, cran- 
berries, and red raspberries are sufficiently abundant to be of practi- 
cal importance. Most of the hr.jdy vegetables can be grown success 
fully, and at Hot Springs they are produced in large quantities and 
sold to the miners of the Fairbanks and Rampart regions. 
DESCRIPTIVE GEOLOGY. 
GENERAL STATEMENT. 
The area covered by the maps is composed essentially of two rock 
groups, for the most part widely different in characteristics. (Sec 
PI. I.) The members of the one are highly schistose and are pre- 
dominantly quartzite schists and quartz-mica schists, with some crys- 
talline limestone and greenstone. The members of the other are 
predominantly carbonaceous slate and coarser fragmentals, chert, 
greenstone, and limestone. The older group is the schists, which 
are characteristically developed in the Fairbanks, Birch Creek, and 
Fortymile regions and are the oldest rocks known in the Yukon- 
Tanana region. Their age has not been definitely determined, but 
they are probably older Paleozoic or pre-Paleozoic. The younger 
group is characteristically developed in the Rampart region and in 
areas farther east, including the White Mountains. Rocks pro- 
visionally correlated with them occur also south of the Tanana. 
Their age is Paleozoic, for fossils determined as possibly Silurian, 
as Devonian, and as Carboniferous have been found in them. The 
main line of demarcation between the two groups extends uortheast 
and southwest in the area between the AVhite Mountains and the 
