GLACIAL GRAVEL IN LIMESTONE, RIPON, WISCONSIN 61 
The direction of the movement which caused the fold is not in 
harmony with slumping of the St. Peter on the inclined surface 
of the underlying Lower Magnesian. The hypothesis of slumping 
might, however, explain the eastward-dipping vee and gashes in 
the St. Peter sandstone. 
-The forcing up by glacial pressure of a eee of St. Peter upon 
the shaly surface of the underlying Lower Magnesian is a satis- 
factory hypothesis. The strike of the fold is N. 5° W., that of the 
glacial striae on top of the quarry S. 65-75° W., making an angle of 
70 to 80 degrees. Somewhat similar phenomena are described by 
Chamberlin near Burlington, Wisconsin, and by Alden.* 
Folds are known in the Paleozoic rocks of the region, as at the 
abandoned quarry in Fond du Lac, while faults are by no means 
uncommon. In many instances it can be definitely proved that 
these features far antedate the glacial period and are not due to 
ice work. It is therefore necessary to have more evidence than is 
now at hand to prove that these particular joints and folds at 
Ripon are different in age from those of the Driftless Area. The 
localization of the fold by the wedging out of the sandstone will fit 
with this hypothesis as well as that of glacial pressure. 
The writer has therefore concluded that the fold is probably 
only in part due to glacial action but was principally caused by 
earth movements. 
The following hypotheses may be considered in connection 
with the origin of the gravel seam between the dolomite layers: 
t. Deposition of gravel in Ordovician times between layers of 
dolomite. 
2. Glacial transportation of a slab of dolomite on to a previously 
planed-off surface, covering a small thickness of gravel. 
3. Raising of frozen-together upper layers, possibly during the 
formation of the fold, followed by filling of the crack with gravel 
and subsequent settling back of the overlying rocks. 
4. Entry of glacial or post-glacial gravel-bearing waters along 
a bedding plane. 
=T. C. Chamberlin, Geology of Wisconsin, Vol. II (1877), p. 203; Wm. C. Alden, 
“Quaternary Geology of Southeastern Wisconsin,” U.S. Geol. Survey, Prof. Paper 106 
(1918), pp. 206-8. 
