iNDENHALL,-, -, . 
and COPPER DEPOSITS OF MOUNT WRANGELL REGION. 14d 
nnRATlF.H J 
KENDENHALL 
AND 
SCHRADER. 
Chitistone limestone. A series of interbedded thin limestones and 
shales which carry Triassic fossils were next laid down, and these 
had accumulated to a thickness of several thousand feet before the 
era of sedimentation was brought to a close. Within the Chitina 
Basin the massive Chitistone limestone does not carry fossils, but it 
has been correlated with similar beds beyond the Scolai Range to the 
north, from which Permian shells have been taken. If we accept 
this evidence as determining the Permian age of the Chitistone, it 
becomes highly probable that the greenstone beneath it, with no 
srosional interval intervening, falls in the Carboniferous, and per- 
haps in the Upper Carboniferous. A more definite conclusion than 
Ibhis can not be reached with the evidence at present available. 
Following the outpouring of the Nicolai lavas and the deposition of 
]he succeeding calcareous terranes a period of stresses was inaugu- 
rated, during which these rocks were everywhere thrown into a suc- 
cession of open folds. Accompanying or following this folding the 
*ocks were brought within reach of subaerial erosional agencies, and 
phe folds were truncated; but the land was not, it is believed, reduced 
o a plain. On the contrary, a distinct relief remained, and when the 
jiext period of deposition began the sediments were laid down in local 
basins and unconformably upon the truncated edges of the folds in 
he older rocks. These deposits were gravels and muds, which have 
:>ince consolidated into the conglomerates and shales of the Kennicott 
formation. They were deposited during Jura-Cretaceous time. 
i After the deposition of these gravel beds the region was again ele- 
vated and folded slightly, and a period of erosion began which reduced 
|he land to a generally plane surface. This plain was elevated, dis- 
ected, and partly buried under the extra vasated igneous material 
|\ r hose accumulations have produced the peaks of the Wrangell 
•fountains. 
This, in brief, is the history, as at present understood, of the events 
jrhich have resulted in the accumulation, burial, folding, erosion, and 
iter partial reburial of the rocks which are economically important 
11 the region. Of these the chief is the Nicolai greenstone. As is 
ften true of greenstones in other parts of the world, this rock seems 
lo have contained originally minute quantities of copper dissemi- 
ated throughout its mass. During the operation of the processes to 
khich the formation has since been subjected some of this dissemi- 
nated copper has been concentrated at various points within the mass 
Iff the greenstone or the overlying limestone, and some of these 
iccumulations are of sufficient magnitude to constitute workable cop- 
er deposits. 
[ A plane which has seemed to be a favorite locus for these accumu- 
lations is the contact between the greenstone and the overlying 
limestone. Nearly all of the prominent ore bodies are on or near 
iris plane, sometimes in the greenstone just below it, sometimes, 
