ART. 14 MICHIGAN TRAVERSE GROUP POHLi 3 



by Dr. E. O. Ulrich, who has very generously allowed full access 

 to all his field notes and collections. Since that time I have been 

 favored with the complete confidence of the officers of the Geological 

 Survey of Michigan, who have made available to me all the informa- 

 tion at their disposal. 



Since early in the nineteenth century accounts of the Devonian 

 rocks of the Southern Peninsula have commanded a prominent 

 place in geologic literature. The earliest local name reference to 

 these beds was made in 1841 by C. C. Douglass/ who referred to 

 them in their Lake Michigan occurrences as the " Little Traverse Bay 

 limestones," while those bordering Lake Huron were called the 

 " Thunder Bay limestones." A. C. Lane ^ indirectly grouped all 

 strata between the Dundee and the black shales under the term 

 Traverse, dropping the, according to his conception, useless prefix 

 " Little," and omitting reference to the Thunder Bay. Actual strati- 

 graphic conditions, however, would have been better served by a 

 retention of the original nomenclature. 



An attempt to rectify the nomenclature must take into considera- 

 tion the fact that the two original names applied by Douglass were 

 adequately described according to our more recently accepted nomen- 

 clatorial system. As regards the " Thunder Bay limestone," the 

 term has already been properly restricted to the upper third of the 

 Lake Huron section by Grabau.^ This will be hereinafter referred 

 to as the Thunder Bay stage (faunal delimitation). Douglass's 

 loosely defined locality of outcrop of his " Little Traverse Bay lime- 

 stone " is now known to exhibit several distinct stratigraphic units, 

 and since he unquestionably applied this term to all beds occurring 

 on the shores of Little Traverse Bay, as is seen in his indefinite 

 geologic section for the region, it is here suggested that the term be 

 dropped. This disposition will further relieve possible confusion 

 were two terms as closely similar as " Little Traverse " and 

 "Traverse " retained, even though they be of different stratigraphic 

 value. 



The first use of the abbreviated title " Traverse " was made by 

 Lane.^ His usage of the term to include all beds lying between the 

 limestones of Onondaga age and the black shales of Upper Devonian 

 and Waverlian deposition is here retained. It is, however, proposed 

 to extend the rank of the term to the position of a group, for as we 

 shall see the area designated in Douglass's and Lane's descriptions 

 represents the development of several distinct faunal and strati- 

 graphic units. 



> Douglass, C. C. Michigan Senate Document No. 16, 1841. 



a Lane, A. C. Geol. Surv. Mich., vol. 5, pt. 2, p. 24, 1893. 



8 Grabau, A. W. Mich. Geol. Surv. Ann. Rept. for 1901, p. 192, 1902. 



* Lane, A. C. Geol. Surv. Mich., vol. 5, pt. 2, p. 24, 1893. 



