Squier—Peculiar Deposits on the Mississippi Bluffs. 271 
This occurrence has in fact an important hearing on more 
than one point in local Pleistocene chronology. I alluded above 
to the fact that at one point the scarp rises directly from the 
water’s edge. This is at the mouth of Trempealeau Bay. For 
a few hundred feet eastward from that the river is forced 
some two or three hundred feet outward by the massive de- 
positional cone fronting the circ above, mentioned. East of 
the cone the shore line is again conspicuous, at the foot of the 
scarp but the river bed is occupied by a lagoon. The his¬ 
toric sequence thus shown was: First, a long period of 
erosion (possibly more than once interrupted, but if so the 
evidence of the interruptions has been lost) during which the 
river was encroaching on the foot hills. During this period, 
whatever detrital output may have been furnished by the circ 
the river was able to keep it cleared away. 1 
There then followed a period during which the output of 
the circ was able to build up its cone apparently in the very 
face of the river (the base of the cone is at a considerable 
though unknown distance below present river level.) In doing 
so it furnished a protection to the scarp against further erosion. 
There is indicated therefore a very close time relation if not 
synchronism between the forming of the deposits and the build¬ 
ing of the cones. 
While as already stated it is not my purpose to discuss this 
question directly from the glacial standpoint it seems desirable 
to indicate the relations which these deposits are supposed to 
have held to glaciers. The fact that they are so universally 
‘Composed of material from a certain horizon indicates that in 
some way the lower horizons were prevented from adding their 
contributions to them. 
It is believed that with bodies of ice, or even semi-com¬ 
pacted snow resting against the sides of the bluffs with the 
upper edges somewhere near the base of the Lower Magnesian, 
the material’ from that horizon must have been largely super¬ 
glacial, and that much of it would have moved across the 
steep upper surface by gravity aided by glacial drainage, and 
would have depended very little on the advance movement of 
Ihe glacier itself. 
