Savage and Ross— Age of Iron Ore. 189 



In connection with the study of the early Silurian strata in 

 eastern Wisconsin during the summer of 1914, additional in- 

 formation was obtained bearing directly on the age of the iron 

 ore formation in that region. The relations of this bed to the 

 underlying Maquoketa shale, and to the overlying Silurian 

 limestone, so well described by Chamberlin, are well exposed 

 in an abandoned ore pit near the station of Neda, as shown in 

 figure 1. A detailed section of the strata at this place is given 

 below : 



Section of strata exposed in an old ore pit near Neda. 



Mayville limestone Feet 



4. Dolomite, gray, crystalline, somewhat vesicular, 



in layers 1 to 4 feet thick _ . 36 



A break in deposition. 

 Iron ore bed 



3. Iron ore band, hard, non-oolitic 2/3 to 1-1/3 



2. Iron ore, oolitic, reddish-brown, in rather even 

 layers, with a thin band of iron coated frag- 

 ments of shaly material, and iron pebbles near 

 the bottom.. 25-32 



A break in sedimentation. 



Maquoketa shale 



1. Shale, calcareous, bluish-gray, hard, in layers 3 to 

 8 inches thick ^containing shells of Hebertella 

 occidentalis, JPlatystrophia acutilirata and 

 Mhynchotrema capax 8-10 



In the vicinity of Green Bay, about 60 miles north of the 

 locality last described, the iron ore bed is well exposed in the 

 gorge near the foot of Cascade Falls, about 5 miles east of 

 DePere. The succession of strata exposed at this place is 

 shown in fig. 2, and described in the following section : 



Section of strata exposed at Cascade Falls. 

 Mayville limestone p eet 



3. Dolomitic limestone, yellowish-gray, in layers 6 to 



1 8 inches thick ^ 30 



A break in sedimentation. 



Iron ore bed 



2. Iron ore, oolitic, in places somewhat conglomeratic 

 in appearance, with a shale band about 10 

 inches above the base, and much iron pyrites 

 near the top _ 4-1/2 to 5 



