NEOCENE DEPOSITS OF CALIFORNIA 381 
Mountain is a ridge of gravel transverse to the course of the chan- 
nel. Close by on the north, Stewart’s Fork River has cut a 
valley across the old channel to the depth of 1,600 feet, without 
reaching the bottom of the gravel. On the southwest, a well in 
Weaverville is said to have penetrated over 600 feet of gravel 
and sand before reaching the metamorphic rocks. Atleast 1,000 
feet in thickness of the deposit was removed in the erosion of 
Weaver basin. A thickness of the old channel deposit of 1,600 
feet is a very conservative estimate. On Oregon Mountain the 
La Grange mine exposes 500 feet in depth of these gravels. 
North from Stewart’s Fork several streams, Stope Creek and the 
East Fork of Stewart’s Fork, have cut transverse valleys through 
the old channel to a depth exceeding 500 feet, and have not 
reached its bottom. That its thickness is abnormally great for 
an alluvial deposit needs no further evidence. 
Lithologically, the formation is just an ordinary river gravel, 
irregularly stratified in the manner common to such deposits. 
The pebbles, cobbles, and small bowlders are very plentiful, and 
have been derived from the metamorphic rocks of the neighbor- 
hood. The predominating species in any section is that of the 
bordering terrane. Below the zone of oxidation the color is a 
deep blue, but higher, yellow and buff predominate, and at 
the surface there is a deep staining of bright red. There is 
much clay among the gravel, in places gathered into separate 
layers. 
At the mouths of certain valleys which issue from the high 
mountains on the west, as, for instance, Stope Creek and the 
East Fork of Stewart’s Fork, northwest of Minersville, after the 
completion of the main deposit, it was covered by alluvial fans 
remarkable for the immense bowlders, largely of granodiorite, 
which are thickly packed in them. So old are these deposits 
that all the bowlders are decayed, and a ditch or a fresh natural 
section, as a recent landslide, shows merely their outlines, and 
never a projecting rock —that is, the bank is smooth, like a clay 
or sand bank. On the main channel deposit near its original 
surface, there are no bowlders or cobbles scattered about, all 
