File:Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900-Twenty-First Annual Report of the United States Geological Society (1901) (14782151354).jpg

Identifier: annualreportsofd003unit (find matches)
Title: Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society
Year: 1901 (1900s)
Authors: United States Department of the Interior
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Contributing Library: Clemson University Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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ments are made at right angles to the longside of the block (N. ± 5^ W.), the distance along the shorter side(N. ± 54° E.) would be almost exactly 50 paces, or 150 feet. Confirma-tions of these values and of the fault directions are obtained by trav-ersing the cliffs which form the margin of this and the eastern hills,as well as by measuring the peculiar pedestal-like blocks upthrown inthe area of Cannon Hill. The orographic blocks within this districtare thus found to be rhomboidal prisms formed of two rhombic prismsin contact along one of their vertical faces. They measure ± 300 feetalong the longer side and ±150 feet along the shorter side. The dis-locations of a lower order which were frequently observed at 50-paceintervals in the cliffs of the intermontane valley would indicate thatthe area is really broken into rhombic prisms, and that the rhom-boidal prisms formed by faults of the same order of displacement aredouble rhombic blocks. Such rhomboidal blocks may be designated
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HOHBS.) SHAPE AND SIZE OF BLOCKS. 109 tho unit l)locks of the district, althougli it must not hv assumed thatthe) are the smallest of their kind. The. dislocations which trend N.±o^ W. and N.±o-i- E. seemtherefore to be here the predominant ones, not only in number l>ut inthrow, and therefore the ones which determine the shape and size ofthe unit orographic blocks. With them, however, occur dislocationstrending N.±34° W. and N.dzl5° E., and in a few instances alsofaults have been observed which bear N. ± 90° E., and one N. ± 65° W.Careful search on a cliff angle formed at the junction of faults of thetwo prevailing series of this district will generally reveal one or theother of the two remaining and prevalent series of faults by a 1)evel-ment of the angle for a short distance or by a division of it. Forconsiderable distances, however, as will be seen by an examination ofthe map, the N.±15° E. series, and less frequently the N.db3-J:° W.series, forms the boundary wall o

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