536 G. SHERBURNE ROGERS 
shale, with some sandstone, belonging to the Lance formation and 
overlain (see upper right-hand portion of Fig. 1) by alluvium. 
Fig. 2 is a nearer view of the coal bed, which is 16 inches thick, 
and contains a white clay parting which forms an excellent indicator 
of the exact character of the deformation. The total displacement 
is 29 inches. 
The fault plane strikes north 15 degrees west. The nearest 
exposures along this line in either direction are about half a mile 
away and no trace of the fault can be found except at the locality 
described. 
The thrust seems to have been from the northeast, 1.e., toward 
the Bighorn Mountains. As stated above, it would seem that this 
fault is connected with the Bighorn uplift, but since there are very 
few, if any, thrust faults on the eastern slope of these mountains, 
and since comparatively little is known of the geology between the 
two localities, it is perhaps unwise to speculate on the tectonic 
relations of this small overthrust. A feature of greater interest is 
its occurrence in nearly flat strata, since overthrusting is commonly 
believed to be a characteristic of, and practically confined to, 
steeply dipping rocks. In most of the few published descriptions 
of apparent overthrust faults in flat-lying rocks the writers appear 
inclined to regard the dislocation as due in some cases to mere local 
squeezing, probably incident to the settling and adjustment of clay 
or other soft rock, or in other cases to the slight tilting of a normally 
faulted block.t In the present instance, however, the fault zone 
may be traced to the top of the cliff, a distance of about 35 feet 
across the strata, which include several thin sandstones. There 
seems little doubt as to its true overthrust character. 
t The case noted by T. E. Savage in ‘‘The Geology of the Herrin Quadrangle,” 
Bull. Illinois State Survey, No. 16, 1900, p. 279, may, however, be a true overthrust. 
