NUNATAK MORAINES 225 



tion. Frequently they cap the hilltops, making nunatak moraine caps, 

 formed apparently when the hilltops barely rose above the ice. Some 

 of these caps are single ridges, some sag and swell moraine, some merely 

 thickened drift of slightly irregular topography. 



Where the nunataks rose well above the ice sheet, moraine collars 

 were built on the hill slopes. These nunatak moraine collars are not 

 developed with uniform intensity throughout, but, as a general rule, 

 thicken toward the lee side of the hill, where they form great masses, 

 sometimes of irregular till and clay, sometimes of gravel, with kamey 

 topography. 



Morainic Complex in the upper Cayuga and Seneca Valleys 



In both the Cayuga and Seneca valleys, beginning at a point 2 or 3 

 miles south of the lake, and extending thence southward about to the 

 present divide, a distance of 10 or 12 miles, is a massive valley-bottom 

 moraine whose striking development exceeds that of any other areas in 

 the quadrangle. Since the valleys in each case slope northward and 

 the moraines over a large part of the area are not higher than the divides 

 to the south, it is evident that in each of the valleys the moraines were 

 built in the standing water of a marginal lake dammed up by the valley 

 ice tongue. Leading down to this morainic complex are a series of 

 moraine terraces and ridges, well developed on the moderate slopes, but 

 absent on the steeper slopes. These moraines, which are directly con- 

 tinuous with the lateral moraine bands previously described, are pre- 

 vailingly of gravel, and often have the form of perfect moraine terraces 

 with moderate slope, ending in abruptly descending ridges which ex- 

 tend out into the valley, where they become lost in the general morainic 

 complex. These rapidly descending ridges are evidently the correlative 

 in the main valley of the frayed moraine strands of the smaller lateral 

 valleys. 



The freer movement of the ice in these main valleys, doubtless in- 

 cluding slight advances as well as retreats, accounts for the greater length 

 and more striking development of moraine there. Each of the ice stands 

 made a series of moraine deposits at its terminal portion, and even where 

 halts were not of sufficient duration for the accumulation of lateral mo- 

 raines on the valley sides, terminal deposits were undoubtedly accumu- 

 lated in these major valleys. It is only on this basis that the marked 

 continuity of the valley-bottom moraines is to be accounted for. The 

 same explanation is advanced to account for the fact that in both valleys 

 the valley-bottom moraine extends farther north than the point where 

 the lowest lateral moraine descends into the valle}'; for on the valley sides 

 there are no lateral moraine bands which can be correlated with the 



