706 R. W. RICHARDS AND G. R. MANSFIELD 
Between the Absaroka and Bannock thrusts there appears to 
be at least one extensive parallel thrust zone. The Crawford 
thrust (24g) or the parallel fault (10h) immediately to the west 
may represent the southern end, while the faults reported in the 
vicinity of Cokeville (101), Afton (18b), and observed by the senior 
author and A. R. Schultz in the Snake River region, represent the 
northward continuation. 
These overthrusts are held by Veatch (24) and Schultz (20) to 
have occurred near the close of the Cretaceous period. 
Ogden, Utah.—In the vicinity of Ogden, Blackwelder (1) has 
recently described several overthrusts. The major of these, the 
Williard thrust, causes lower Algonkian slates and graywackes to 
overlie Cambrian and Carboniferous sediments. The thrust plane 
has an average easterly dip of 15° but locally is as high as 50°. 
Blackwelder holds that subsequent deformation of the plane has 
been slight and that the apparent distortion is mainly due to 
original undulation. The maximum exposed horizontal displace- 
ment of 4 miles is probably only a small fraction of the total heave. 
The direction of movement is naturally inferred to be westward 
from the inclination of the thrust plane. The writers suggest that — 
broader regional studies are necessary before a westward direction 
of movement can be regarded as proved. It may well be that the 
present eastward inclination of the fault plane is the result of 
deformation, as is clearly the case in many lees along the trace 
of the Bannock thrust. 
Blackwelder described two other anne 3 in the Ogden region, 
one which produces discordant relations within the Cambrian, and 
another which causes Carboniferous limestone to overlie Cambrian 
shales and quartzites. 
Blackwelder concludes that the Ogden thrusts ‘‘are of Cretaceo- 
Eocene age.” 
RELATION OF BANNOCK THRUST TO PARALLEL THRUSTS 
The fact that the several portions of the Bannock thrust as 
described have been isolated by erosion and disguised by subsequent 
deformation makes it possible that future study will show that 
outliers of the overthrust block lie to the east of the margin of the 
Bannock thrust as at present defined. 
