MICHIGAN ACADEMY OF SCIENCE. 89 



bluish-white ones, changes to a light-buff or brown. Some strata are also 

 characterized by many cavities, which are more or less completely lined with 

 crystals of dolomite. The beds generally show a very poorly developed and 

 irregular jointing. In the unweathered condition, the dolomite is usually 

 massive, but upon weathering, it often shows numerous, more or less closely 

 spaced and uneven planes of bedding. 



The Racine formation in the Northern Peninsula is probably 275 to 300 

 feet thick and has a general dip southward of 40 to 60 feet per mile. 



The Racine dolomite lies conformably upon the strata of the Manistique 

 formation. The uppermost Manistique strata consist of thin, uneven-bedded, 

 siliceous dolomites of a buff to brown color. They are also characterized by 

 relatively few silicfied corals, such as Favosites favosus, Halysites catenulat-ia, 

 Alveolites undosus and Cladopora laqueata, which become very abundant in 

 lower strata of the formation. At some localities, the contact between the 

 two formations is well-defined ; at others, it is more or less obscured by a few 

 feet of transitional strata, which, in the writer's opinion, should be included in 

 the Racine formation, because they are more nearly related in lithologic 

 character to the Racine than to the Manistique strata. 



So far as known, the contact between the Racine dolomite and the over- 

 lying strata of the Monroe-Salina group is not exposed. The lowest, observ- 

 able strata of the Monroe-Saline group, which apparently are very near to this 

 contact, outcrop on the bottom and sides of the Carp River in the S. E. 1,4 Sec. 

 12, T. 42 N., R. 4 W., Mackinac County. These strata are composed of thin- 

 bedded, fine-crystalline dolomites of light pinkish-gray and brownish-gray 

 color. 



The correlation of the Racine formation of Michigan with the Racine 

 formation of Wisconsin is based chiefly upon the lithologic similarity and 

 apparent continuity of the strata. This correlation is supported by the fact 

 that the Racine formation occupies the same stratigraphic position in both 

 states. In northeastern Wisconsin, the formation rests upon the Upper Coral 

 Beds. In Michigan, it rests upon the same strata, which are included in the 

 Manistique formation. The Racine formation, in both states, is overlain by 

 Cayugan strata of similar lithologic character. Whether these beds are of 

 exactly the same age in the two states is, however, not known. 



The lowermost strata of the Racine formation of Michigan and north- 

 eastern Wisconsin and the massive, sparingly-fossiliferous beds of dolomite 

 at the top of the Lockport formation of Cockburn and Manitoulin Islands, 

 Ontario are lithologically similar and with little doubt continuous. The upper- 

 most beds of the Lockport of the Ontario region southeast of Manitoulin 

 Island may represent a further extension eastward of these same beds. 



Certain information, communicated to the writer by Dr. M. Y. Williams of 

 the Canadian Geological Survey, indicates that the uppermost strata of the 

 Lockport of Dawson Point, Lake Timiskaming are lithologically similar to the 



