24 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



THICKNESS OF THE TRAVERSE GROUP IN WESTERN MICHIGAN 



So far as is known from the combined well records and exposures 

 in the western portion of Michigan there is no great thickness of 

 continuous shale deposition above that at the base of the Traverse. 

 This bed of shale, to which the term " Bell Shale " has been applied 

 in well records in conformity with the occurrence in eastern Michigan 

 of a similar stratum resting on the Dundee, varies according to re- 

 ports from 40 to 100 feet in thickness. In later and more reliable 

 records this " Bell Shale " is seen to maintain an average thickness 

 of nearly 70 feet, its lower -boundary being drawn at the contact, with 

 great lithologic change, with the " Dundee." 



Paradoxically enough the most useful of the numerous well records 

 is one of the earliest and least detailed reports, but its location is 

 accurately described and it was begun in beds having a determined 

 position in the stratigraphic sequence. Fortunately this early record 

 gives sufficient information, having penetrated to the Bell Shale, to 

 make possible an estimate of the complete thickness of Traverse 

 rocks deposited in western Michigan. This record has been already 

 published ,^^ but for convenience of reference it is again cited. 



Location : Sec. 33, T. 35 N., R. 5 W., Bear Creek Township. 120 paces northwest 

 from door of G. R. & I. R. R. station and 40 feet from shore of Bay. " Bay- 

 View well." 

 Elevation : 585 feet above sea level. 

 Completed July, 1895. 



Thickness, Depth, 

 feet feet 



Pleistocene: Shingle 4 4 



Devonian : 



Traverse group — 



Cream limestone 260 264 



Medium grey limestone 198 462 



Dark limestone lli^ 473^^ 



Cellular blue clay (Bell Shale) 25 4981/2 



The mouth of this well is situated at or about the contact between 

 tlie Gravel Point and the Charlevoix stages. The tools are recorded 

 as encountering the " Bell Shales " at about 470 feet. If to this we 

 add the average 70 feet of the Bell and the minimum known thick- 

 ness of rocks above the mouth of the well (130 feet), the entire 

 thickness of the Traverse is here shown to have a minimum of ap- 

 proximately 660 feet, proving the existence of more than 400 feet 

 of unexposed Traverse beds underlying the region. 



Computations from the records of other wells at various localities 

 in Charlevoix and Emmet Counties substantiate the estimate of the 

 thickness of the western Traverse beds derived from the Bay View 



"Grabau, A. W. Mich. Geol. Survey Ann. Rept. for 1901, p. 197, 1902. 



