COPPER DEPOSITS OF THE REDDING REGION CALIFORNIA. 
By J. S. Diller. 
SITUATION AND DISTRICTS. 
The copper deposits of the Redding region of California lie among 
the foothills and mountains about the northern end of the Sacramento 
Valley, within the Redding quadrangle. This quadrangle was sur- 
veyed geologically in 1901-2, with a view to discovering the general 
relations of the ore deposits, and only such results can be announced 
at the present time, as detailed surveys have not yet been made. 
Four copper districts occur, more or less completely isolated, in which 
there lias been extensive prospecting, but only the two largest, Bully 
Hill and Iron Mountain, have thus far yielded paying mines. 
ROCKS OF THE COPPER REGION. 
Sedimentary rocks. — The copper region contains an extensive series 
of sedimentary rocks, ranging from the Devonian into the Miocene, 
associated with igneous masses of various ages, shaj^es, ami kinds, 
which have been intercalated or intruded into the sediments. The 
general abundance of fossils in the Cretaceous, Jurassic, Triassic, 
Carboniferous, and Devonian sediments, from all of which large col- 
lections have been made, has rendered it i>ossible to work out the 
structure in detail with a high degree of probability. 
Unconformities. — The great succession of sediments is wholly of 
marine origin; but their relation to one another, whether conformable 
or unconformable, is not easily determined, for in most cases igneous 
rocks lie between them. Thus the relation in succession between the 
Devonian, Carboniferous, Triassic, and Jurassic is much obscured by 
igneous rocks, but between the Jurassic and Cretaceous there is a 
conspicuous unconformity which represents not only a long interval 
of time, but a great epoch of mountain building followed Iry erosion. 
The mountain-building epoch at the close of the Jurassic was a time 
of rock folding, faulting, and crushing, as well as igneous intrusion, 
which greatly modified the rocks and prepared the way for the asso- 
ciated ore deposits. 
Relation of ores to sedimentary' rocks. — Disseminated ores occur at 
many points in all the sediments of the copper region older than the 
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