408 Geology of Johnson County. 
have partaken largely in 'the upward movement: That is, in view 
of the simplicity of the main portion of the Uinta fold, one might 
naturally expect that the uplifting force which was applied along 
its entire axis would have acted strongly and continuously, if not 
uniformly. But the foregoing statements show that neither of the 
upthrust axes coincide with such a line or with each other, and also 
that only a comparatively slight elevation of the strata has occurred 
along what I have designated as the inceptive portion of the Uinta 
fold. 
These upthrusts are so extraordinary in their character that one 
instinctively desires to know how they were produced. I freely 
admit my inability to reply to such an inquiry in a satisfactory 
manner ; and for the present I will offer only the following sug- 
gestion. Assuming—as the evidence seems to warrant us in doing 
—that the completion of the main Uinta fold and that of the Park 
Range were contemporaneous, or nearly so, they constituted ponder- 
ous buttresses at either end of the strongly-curved inceptive portion 
of the Uinta fold. It is not strange, therefore, that any elevating 
force that may have been applied along the axis of that. inceptive 
fold—which stretched across the intervening space—should have 
been diversely, if not abnormally, applied. , 
NOTES ON THE GEOLOGY OF JOHNSON COUNTY, 
IOWA. 
BY CLEMENT L. WEBSTER.! 
f hes superficial geology, or the study of the nature, origin, and 
distribution of the loose materials, or superficial detritus 
commonly denominated loess, drift, and aluvium, constitutes one of 
the most interesting as well as important fields for study that fall 
within the scope of investigation of the geologist. 3 
The interpretation of the phenomena of the glacial period, the 
cause of the advance and retreat of the ice sheets, the condition of 
the climate and of the fauna and flora of the surface (now cove 
by drift) during the interglacial time, the extent. and condition of 
1State University, Iowa. 
