CLINTON FORMATION NEAR DUBUQUE 123 



hill. But as weathering has continued inward from the sides 

 of the hill the iron ore has softened and slumped with the soft 

 shales underlying: it. The slumping undoubtedly is aided by the 

 pressure of the dolomites above. Considerable mingling of the 

 two layers has taken place, and the division line between shale 

 and iron band is not always definite. 



CORRELATION. 



The stratigraphic position of the oolitic band at Lore is practi- 

 cally identical with that of the so-called Clinton iron ore at May- 

 ville and other points in eastern Wisconsin, as described by 

 Chamberlin. 3 The Wisconsin ore rests on the eroded surface of 

 the Cincinnati (Maquoketa) shale, and it too contains fossils 

 of Maquoketa age which Chamberlin considers to have been mixed 

 with the ore by the action of the glacial ice. Here also there is 

 more or less mingling with the underlying clay shale, although 

 the division in general is definite. 



Thwaites 4 has described the ''Clinton" ores of eastern Wis- 

 consin as follows : 



-an essentially unaltered sedimentary deposit which oc- 



curs in broad lenses in eastern Wisconsin, between the overlying 

 Niagara dolomite (Silurian) and the underlying Maquoketa 

 ("Cincinnati") shale (Ordovician). The lenses vary greatly 

 in thickness, one of 55 feet being the thickest known. On 

 the other hand their extent is so meager that by far the greatest 

 portion of the beds at the ore horizon show not even a trace of 

 the "Clinton" ore. 



Crane 5 speaks of the presence of a layer of red, oolitic iron 

 ore in the Silurian of Holt county, Missouri, and suggests that 

 it probably is of Clinton age (op. cit., p. 48) . The member, how- 

 ever, was studied only in the material from a deep drill hole* and 

 the description is very incomplete. 



Savage and Koss G have recently studied the "Clinton" de- 

 posits of eastern Wisconsin, and have found in the ore numerous 

 fossils which indicate a closer relationship to the Ordovician than 

 to the Silurian. They consider the ore to have been deposited in 

 late Maquoketa time in local basins formed after the withdrawal 

 of the main Maquoketa sea. The name "Neda Iron Ore" is pro- 

 posed as a substitute for the apparent misnomer ••(Mint mi Ore." 



3 Chamberlin, T. C, Geology of Wisconsin, Vol. II, 1S77, p. 331. 

 4 Thwaites, F. T., Bull. U. S. Geol. Survey No. 540, p. 338. 

 5 Crane, G. W., Missouri Bur. Geol. & Mines, 2d Series. Vol. X, pp. 148-149. 

 «Savage, T. E., and Ross, C. S., Am. Jour. Sci., Vol. XLI, 1916, pp. 18.-193. 



