Identifier: annualreportofu2021geol_2 (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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yielded clastic material of which a basal conglom-erate is formed. The granite would make a good building stone, and is free from ironP3?rites or other minerals which might be expected to decomposereadily and cause stains. It is not traversed by mineral veins andholds out no inducements to the prospector. In a few places, as nearLeavenworth, it is cut by narrow basic dikes, similar and probablybelonging to a series of basaltic dikes which traverses a neighboringarea of Tertiary sandstone. The granitic core of the Wenache Moun-tains now stands in bold relief on account of the removal to a greatextent of the softer rocks with which it was formerly surrounded,and is one of the most striking and picturesque groups of sharp peaksto be found in the entire Cascade region. A notable fact in connec-tion with the erosion of the mountain mass is the manner in which itis trenched by the canyon of Icicle Creek, a tributary of WenacheRiver. This creek has its source to the west of Mount Stuart and
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UNIVERSITY «f ILLINOIS. RUSSELL.) GRANITE. 107 flows eastward directly throughthe granite area, in a canyon that isfrom 2,000 to 3,500 feet deep. This behavior of Icicle Creek indi-cates that its course was established before the Wenache Mountainshad their present prominence. In this same connection I may notethat the Wenache River leaves a region of comparatively low reliefcomposed of soft sandstone and makes an excursion into the graniticarea or 6 miles in length, flowing in this portion of its course througha canyon fully 3,000 feet deep, and then returns to the sandstone oncemore. These interesting facts have a hearing on the origin of thepresent topography and will he discussed later. The next area of granite met with by the writer along the route ofexploration followed in 1898 has its southern border about 12 milesnorthwest of Lake Wenache, where the two forks of White Creekunite. The drainage basin of the North Fork of White Creek, withthe exception of an area of a few square

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