4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



The Bell shales, because of their lithological unity, have been sepa- 

 rated as the basal Traverse group formation of the Lake Huron 

 section by Grabau.^ There is no good reason for the assignment of 

 this widespread lithologic member to a distinct formation, for the 

 contained fauna indicates continuous relationship with the succeed- 

 ing Long Lake beds which are, incidentally, but slightly more cal- 

 careous. Grabau® has more recently corrected this detail and 

 assigned the Bell shales their proper place as the basal member of the 

 Presque Isle series ^ which further includes the respectively higher 

 Grand Lake and Long Lake members. 



A study of the stratigraphic contacts between the Presque Isle, 

 Alpena,^ and Thunder Bay series has nowhere been given the slight- 

 est attention. Faunal distinction is, however, shown to be sharp 

 between the three series, and it is therefore provisionally proposed 

 to refer to them as stages, in conformity with the terminology of 

 similarly unestablished but probable formations. 



TRAVERSE BAY SEQUENCE 



" Complex " becomes but a mild term when applied to actual strati- 

 graphic, biologic, and structural conditions within the Traverse. For 

 a clear understanding of the subject as a whole it must therefore be 

 separated into its component parts and each discussed individually 

 with evidences for the present interpretation, finally by summary 

 comparison drawing similarities and variances between the separately 

 described portions. Stratigraphically, for present purposes, Traverse 

 rocks in Michigan may be studied independently in their eastern and 

 western occurrences, primarily because of the impossibility of direct 

 lithologic or faunal correlation between the two. Each area will be 

 seen to constitute an entity of sequential events in itself. Of the 

 western section we shall speak first. 



The development of geologic understanding of the Traverse group 

 has been until recently much hindered by the comparatively unex- 

 ploited condition of the country in which it occurs and further 

 through the lack of adequate natural outcroppings. The district 

 bordering Lake Huron has outstripped the Traverse Bay region in 

 industrial development, and as an indirect result of the greater ex- 

 ploitation of natural resources there is a fuller understanding of 

 stratigraphic conditions in the eastern portion of the Traverse belt. 

 In the past decade, however, the Traverse Bay district in Charlevoix 

 and Emmet counties has received greater industrial appreciation and 

 the opening of additional quarries in the vicinity of Petoskey has 



B Grabau, A. W. Mich. Geol. Surv. Ann. Kept, for 1901, p. 191, 1902. 



• Grabau, A. W. Unpublished manuscript, p. 290, 1915. 



'Grabau, A. W. Manuscript, pp. 290-308, 1915. 



9 Grabau, A. W. Mich. Geol. Surv. Ann. Kept, for 1901, p. 175, 1902. 



