Ulrich—Paleozoic Systems in Wisconsin. 
105 
gorge at Ableman-—at its base and at various higher positions in 
the formation beds of almost perfectly rounded quartzite pebbles. 
These range in size from less than an inch in diameter to masses 
three or four feet across. The typical outcrop of the Devils Lake 
sandstone occurring^ as they do, on the flanks of old quartzite 
ridges, were deposited under conditions admirabily adapted to the 
production of such coarse clastic material. 
Conglomerate of similar kind and probably derived from the 
same or similar sources occurs in southern Wisconsin somewhat 
rarely at the bases of preceding Cambrian formations. But the 
volume of such material in these older occurrences is far inferior 
to that found in the Devils Lake sandstone. This disparity in 
quantity suggests not only intervening diastrophic movements that 
made more of such material available but also the lapse of consid¬ 
erable time during which such large quantities might be produced. 
Eeally, in view of the demonstrable fact that the Devils Lake sand¬ 
stone is of quite early Ozarkian age and the deposits beneath it 
very late Cambrian, the abundance and character of the conglom¬ 
erates in the former prove to be the best objective evidence we have 
in establishing the verity of the break between the Cambrian and 
the Ozarkian. 
That warping of the surface did occur in the Upper Mississippi 
Valley during the otherwise unrecorded interval between the Cam¬ 
brian and Ozarkian is further clearly proven by the altogether dif¬ 
ferent distribution of the Cambrian and early Ozarkian marine 
sediments. Thus, whereas the Cambrian formations are for the 
most part common to both the east and west sides of Wisconsin the 
first two of the Lower Ozarkian formations are confined to small 
areas in the eastern half of the State. The succeeding Madison 
sandstone seems to extend from the most southern of these areas 
across the State to the Mississippi, but even this appears to be con¬ 
fined to much narrower limits in north and south directions than 
were the Cambrian formations. 
Another interesting and in this connection important fact is that 
whereas the organic remains in the Cambrian formations, except¬ 
ing perhaps those of the Mazomanie, become fewer and finally dis¬ 
appear entirely when the formations are traced toward the east 
and especially the northeast angle of the State, the Lower Ozarkian 
formations, on the contrary, become barren in a westerly direction. 
This fact suggests at once that the seas in which the more impor¬ 
tant of the Cambrian formations were deposited terminated on the 
