458 J. M. BOUTWELL 
of Empire Canyon, opposite Daly shaft No. 2. The limestone 
cliffs forming that wall of the canyon terminate abruptly on the north, 
and the same beds (Thaynes limestone) reappear 5,000 feet to the 
west in Crescent Ridge, on the north side of a strongly defined east- 
west fault. 
A significant fault structure has also been brought out in the course 
of this work to the east of the Ontario fracture zone, on the extreme 
eastern slope of the range. A block (or wedge) averaging 2 miles in 
width north and south, and made up of the regular sedimentary suc- 
cession, including the Weber to Thaynes formations and intruded 
andesite porphyries, has moved bodily to the east at least 2 miles. 
Its northern limit is a strong east-west fault, followed by McHenry 
Canyon. Its southern wall is a companion fault which crosses Cot- 
tonwood Canyon near its mouth about a mile southeast of the Valeo 
Mine. The economic significance of this discovery is that the desir- 
able ore-bearing limestones should not be sought in their normal 
strike and position, and that within the extent of this block they le 
at least 2 miles beyond to the east at an unknown depth beneath thick 
andesite extrusives. The scientific bearing of this structure, however, 
is of deeper interest, in view of the present eager search for evidence 
on the manner of intrusion, especially as to the disposition of the rock 
which previous to intrusion occupied the space subsequently taken by 
the igneous mass. The general aspects of this occurrence are most 
suggestive. 
From the foregoing statements regarding intrusives and structure, 
it is to be noted that a series of intrusives lie in a narrow east-west belt 
extending across the range; that these appear on other distinct evidence 
to have invaded this area from the west, breaking upward and east- 
ward; that the intrusives in this area are thus the highest and eastern- 
most members; that in the path and ahead of this chain of intruded 
igneous masses occurred the maximum deformation and dislocation; 
that slightly to one side on the north sediments were broken and driven . 
eastward over geologically higher members; and that directly ahead 
of the invading wedge of intrusives the country gave way and moved 
eastward at least 2 miles. 
