62 FAIRBANKS AND RAMPART QUADRANGLES. 
During 1907 there was much activity on the southern side of the 
divide and the discoveries on Patterson Creek indicate the possibility 
of another productive, area. 
BED ROCK. 
Most of the gold-producing creeks tributary to Minook Creek from 
the east head in areas composed of slates, quartzites, feldspathic 
quartzites, chert, and sheared chert derivatives, and flow in the lower 
parts of their valleys through areas of greenstone, which are largely 
tuffaceous. The schistose, fine-grained fragmentals, alternating with 
the slates and quartzites, form the greater part of the bed rock in the 
valleys of the streams tributary to Baker Creek. The same rocks 
strike northeastward and occupy large areas in the valleys of the 
headwaters of the Tolovana, which were traversed by the Brooks 
party in 1902, and still farther in the same direction are found in 
the White Mountain section. There is no essential difference in the 
bed rock of the northern and southern sides of the divide in the 
Rampart region, except that the greenstones are confined mostly to 
the northern side in the lower part of Minook Valley below Florida 
Creek. 
ALLUVIAL DEPOSITS. 
The alluvial deposits of the Rampart region are in general much 
shallower than those of the Fairbanks region. They include muck and 
underlying gravels. The gravels reflect the variety of the bed rock 
and are present as both stream gravels and bench gravels. The 
stream gravels are composed of both angular and subangular mate- 
rial from the bed rock and well-rounded material from the benches. 
Bowlders at some localities are rather common. Bench gravels are 
of common occurrence, and much of the mining at present is confined 
to them. In this respect the region differs from the Fairbanks region, 
where bench gravels are the exception. The bench gravels lie at 
various levels up to 600 feet or more above the streams, and the great- 
est thickness that has been determined is about 100 feet. The 
material is both fine and coarse and includes a large proportion of 
quartzite pebbles. The pay streak of the pay gravels is next to bed 
rock, or partly within it when this is blocky, or in the lowermost few 
feet of gravel. Prospects have been found at several localities in the 
high bench gravels of Minook Creek, but the distribution of gold in 
these gravels has not been determined. In the Baker area the pay 
of a part of the bench gravels at least occurs as a streak similar to 
that of the creeks. The gold is mostly well worn and on some creeks 
is associated with nuggets of silver. 
