Professional Paper - United States Geological SurveyThe Survey, 1902 |
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abundant Alaska Range altered appear base basin beds bodies carry central character Chisna Chistochina Chitina Chugach claim clays collections continued Copper River course Creek deposits described diorite direction district drainage east evidence existed exposed extensive fault feet field flows Fork formation fossils Gakona geologic glacial Glacier gold gravel greater greenstone Gulch head indicate intrusives known later lavas less lignite limestone localities lower mass material middle miles Mineral Mount Mountains mouth nearly northern occur older origin outcrops Pass period Permian plain Pleistocene portion present probably proved quartz reached recent regarded region relations reported represented ridge River basin rocks sand schists Schrader sediments seems shales side silts similar Slate slope southern species Spencer stream surface Survey thickness Triassic tributaries upper usually Valdez Valley vein Wrangell zone
Beliebte Passagen
Seite 39 - FC A reconnaissance of a part of Prince William Sound and the Copper River district, Alaska, in 1898. In Twentieth Ann. Rept., pt. 7, 1900, pp. 341-423.
Seite 84 - FC, AND SPENCER, AC Geology and Mineral Resources of a Portion of the Copper River District, Alaska.
Seite 110 - In both of these regions bedrock had been reached on some of the claims at varying and usually not excessive depths, and wherever found It carried sufficient gold to enable the operators to wash the gravel at a profit. Throughout the intermediate portion of the river the bedrock lies at unknown depths beneath a mantle of glacial material. In one place, one-half mile above the mouth of Powell Gulch, a shaft was sunk from creek level through 21 feet of compact till into an underlying bed of sand, which...
Seite 110 - Oulch in general appearance, but is finer and somewhat more uniform in grain. Nuggets are rare, but flakes one-eighth inch or more in diameter are abundant. An assay value of $18.72 per ounce is reported. The developments have not yet determined fully the values to be won, but the gravels below the canyon are said to run from 1.7 to 5.5 cents per pan, with a maximum of $1 on bedrock. A small corner of Discovery claim, Just at the head of the canyon, is reported to have yielded $1,000 as the result...
Seite 110 - ... those on the upper, are erratic. • * * A narrow bench 10 or 15 feet above the level of the bed of Slate Creek, opposite the mouth of Miller Gulch, was one of the first areas in the district worked. Several thousand dollars were sluiced here from a space covering a few hundred square feet. The bench presumably represents a portion of the old Miller Gulch fan, and the gold is regarded as derived from the giilch.
Seite 110 - ... bedrock lies only from 4 to 8 feet below the surface of the flood plain for a considerable distance above the canyon, but since there are many coarse bowlders in the flood-plain material it can not be handled to advantage by ordinary sluicing methods. It is believed that hydraulic work at this point will prove profitable. The gravels contain a considerable variety of rock types, contrasting strongly In this respect with those of Slate Creek, Miller Gulch, and the upper Chisna. Such a contrast...
Seite 106 - ... occupied by Chistochina Glacier and the upper courses of Middle Fork, the Slana, and the Tok, and the various passes which connect these streams. North of this feature the peaks of the great range rise abruptly to elevations of 8,000 or 9,000 feet. South of it the nearest foothills are 6,000 or 6,500 feet in height, but decrease in altitude as their distance from the axis of the range Increases. These foothills are in detached groups, which, near the main range, occupy relatively large areas,...
Seite 110 - Chisna divide, thns reproducing a condition which has probably prevailed in the recent geologic past. Difficulty is also encountered in the attempt to reach bedrock on the claims immediately above the mouth of Miller Gulch. The difficulty here is probably due more to the filling from a tributary stream whose fan has spread out over the Slate Creek bottoms than to any extensive excavation because of glacial action. In that part of the upper Slate Creek channel where any sluicing has been done the...
Seite 41 - ... tuffaceous beds with included lava flows and intruded sheets. These beds were originally described as Permian, but should be correlated, on both structural and fossil evidence, with the beds along White River, and would now be called upper Carboniferous. The Mankomen formation, as described by Mendenhall, " falls naturally into two divisions — an upper, prevailingly calcareous division, which includes somewhat more than half the total thickness, and a -lower, prevailingly arenaceous and tuffaceous...
Seite 113 - July before the snow is melted from the upper portions of gulches, so that a working period of not more than three months is to be counted upon for this part of the district. Here again the lower Chisna is more favorably situated, since the fall freezing is delayed for two or three weeks and the snow melts away earlier in the spring. INDEX. Page. Acknowledgments to those aiding...