LOW-ANGLE FAULTING 5 
by great overthrusts whose planes dip in under the mountains at 
low angles. McConnell has estimated that on the South Fork of 
the Short River in Alberta the horizontal displacement of the 
Cambrian strata—which here rest upon the Cretaceous—has been 
about 7 miles, while the vertical displacement amounts approxi- 
mately to 15,000 feet." 
In the Glacier National Park of Montana, Willis found the 
Proterozoic strata which make up the outermost range (here called 
the Lewis Range) overthrust at least 7 miles upon the Cretaceous 
of the foothills. The dip of the thrust plane, as determined by 
Willis by graphic construction, ranges from 3° to 7° 45’.2. More 
recently Campbell has been able to show that where the Great 
Northern Railroad crosses the range this great mass of strata has 
been shoved at least 15 miles northeastward along the Lewis thrust 
plane, and were the original position of the mountain mass known 
the distance might prove to be much greater. 
At the International Boundary the northward continuation of 
the Lewis thrust has been termed the Waterton Lake thrust by 
Daly. The known extent of the bodily movement here represented 
is about 8 miles, as measured on the perpendicular to the line 
tangent to Chief Mountain and the outermost mountains of the 
Clarke Range. But the actual movement, according to Daly, has 
probably been ro miles or more, and may be as much as 4o miles, 
for “it is not impossible that the entire Clarke Range (the equiva- 
lent of the Livingston Range of Willis) in this region represents a 
gigantic block loosened from its ancient foundations, like the Mount 
Wilson or Chief Mountain massifs, and bodily forced over the 
Cretaceous or Carboniferous formations.’’4 
The Willard thrust discovered by Blackwelder in the Wasatch 
Mountains of Utah has a displacement, so far as exposed, of about 
4 miles, though this is probably but a small fraction of its total 
R. G. McConnell, Geol. Surv. Can., II (1886), Part D, p. 33. 
2 Bailey Willis, ‘‘Stratigraphy and Structure, Lewis and Livingston Ranges, 
Montana,” Bull. Geol. Soc. Amer., XIII (1902), 331-43. 
3M. R. Campbell, ‘‘The Glacier National Park,’ Bull. 600, U.S. Geol. Surv., 
IQI4, p. 12. ° 
4R. A. Daly, “Geology of the North American Cordillera at the Forty-Ninth 
Parallel,” Mem. 38, Geol. Surv. Can., Part I (1912), p. ot. 
