A Geological Reconnaissance in Northern Idaho and Northwestern Montana

A Geological Reconnaissance in Northern Idaho and Northwestern Montana

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 edition. Excerpt: ...The gneissic banding also that is developed in the granite or quartz monzonite at Bonners Ferry and to the south may be due to shearing in a zone of faulting. Again, although along the western base of the Purcell and Cabinet mountains the strata dip eastward and belong to the lowermost division of the series, farther south the structural trend makes a considerable angle with the line of the Purcell trench, and areas of strata so high in the series as the Newland formation extend to the western limit of the Algonkian belt. The lack of concordance in this vicinity between the course of the dominant topographic feature and that of the structural axes and faults to the east of it might have been produced" by faulting. FOLDS. In the northern part of the region the strike of the rocks is notably uniform and is, on the average, a little west of north. In the southern part, and especially in the Coeur d'Alene district, it is far more variable, but is most commonly near west-northwest. As has already been mentioned, few extensive unbroken folds can be traced. The greatest one recognized is an anticline that runs along the northeastern side of the Cabinet Range. Its course is about northnorthwest, and it makes an oblique angle with the Snowshoe fault, which cuts off a part of its western limb, so that in the vicinity of the Snowshoe mine only its eastern limb is seen. At the head of Fisher River, however, a fine section across the crest of the arch is exposed. Here in the axial portion typical Prichard slate appears, and this is flanked on either side by quartzite of the Burke formation. A clearly synclinal structure is exhibited along the international boundary between Yaak River and the crest of the Kootenai-Yaak divide, but this...
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Product details

  • Paperback | 48 pages
  • 189 x 246 x 3mm | 104g
  • United States
  • English
  • black & white illustrations
  • 1236785622
  • 9781236785626