32 FAIRBANKS AND RAMPART QUADRANGLES. 
iially toward the* base of the hills. The bed-rock surface, so far as 
known (1905), is in general nearly flat, or has a very gentle grade 
hillward from the creek. The deposits are in most places separable 
into three divisions, which, from surface to bed rock, are referred to 
by the miners as muck, barren gravels, and pay gravel. 
The muck ranges in thickness from a few feet to a maximum of 
about TO feet, the line of separation between it and the underlying- 
gravels being fairly sharp. It is a black deposit containing a large 
amount of material derived from the decomposition of moss and 
other vegetation, a considerable percentage of clay and sand being 
either intermingled with the organic matter or distributed as layers 
and thin lenses irregularly through the mass. Horizontal, and occa- 
sionally vertical, sheets of ice several feet thick occur in this deposit. 
The underlying gravels, ranging in thickness from 10 to over GO 
feet, are derived from the rock occurring within the areas drained 
by each particular stream. As quartzite schist is the most common 
bed rock and also the most resistant to the processes of wearing and 
weathering, the largest proportion of the coarse material in the 
gravels is composed of it. The gravels also include quartz-mica and 
carbonaceous schist, vein quartz, and some igneous material, mostly 
granite. Teeth of the mammoth and bones of other animals now 
extinct are occasionally found. The coarse material being mostly 
schistose occurs as more or less flattened angular pieces, only slightly 
waterworn. Few of them exceed a foot in diameter and the pro- 
portion of bowlders is therefore small. The fine material is com- 
posed partly of smaller pieces of the more resistant rocks and 
partly of clay derived from the decomposition of the micaceous and 
carbonaceous schists. These gravels contain also a small percentage 
of individual minerals released by the process of weathering. The 
proportion of clay in the barren gravels is small, but that in the 
underlying pay gravels is large. All the material, both coarse and 
fine, is irregularly intermingled, the larger pieces being usually 
nearly horizontal. 
The pay gravels resemble those above them, but contain a consid- 
erable amount of clay, which adheres tightly to the gravel and to 
the surface of the blocky fragments of bed *ock. This clay is pre- 
vailingly of a yellowish color in the more shallow diggings and of a 
bluish color in the deeper gravels. The proportion of clay varies, 
but in most places there is enough present to render the pay gravels 
easily distinguishable in the drifts from the barren ground above 
them. The thickness of the pay gravels ranges from a few inches 
to 12 or more feet, a range which is rather uniformly maintained. 
The under surface of the gravels not only rests upon the bed rock, 
but where the latter is blocky the fine material is found within it to 
a depth of from 1 to 3 or more feet, The pay gravels vary in width 
