A Michio;an Preliminary Section. — Grabait. i8i 
Strata 15 to 17 are provisionally considered the equivalent 
of the New York Marcellus, though there is no evidence at 
present to indicate that the faunal characteristics, on which 
the separation of the Marcellus beds alone rests, are found in 
this region. For this reason it is perhaps better to speak of 
these beds as the lowest Ti^averse shales, regarding the five- 
foot stratum of limestone (No. 16) as an integral part of the 
series. The total thickness of this lowest shale series is there- 
« 
fore 81 feet. 
Strata 18 and 19 are provisionally referred to the Dundee 
limestone, which is considered the equivalent (approximately) 
of the Onondaga limestone series of New York. The com- 
bined thickness of the two strata referred to this formation, is 
102 feet. 
Stratum 21 probably represents the Mackinaw limestone, a 
formation which is believed to be the time equivalent of the 
Manlius limestone of New York. It undoubtedly is of upper 
Siluric age, but the determination of its exact equival- 
ency must be deferred until paleontological investigations are 
made. 
Whether the shale of stratum 20 belongs to the overlying or 
underlying fomiation is likewise an unanswered question. 
If the above correlations are correct, the well record gives 
us the following thicknesses of Devonic formations. 
Traverse upper shales not represented 
Traverse middle limestone 25 
Traverse lower shales and limestones 378 
Total middle and lower Traverse 403 
Dundee limestones 102 
Total 505 
The strike of the strata of this region is approximately 
northwest and southeast. The dip is 42 feet to the mile toward 
the southwest. This is equivalent to 30 feet to the mile along 
the line of the section. 
A. Traverse Middle Limestone. 
This limestone underlies a considerable area to the north 
and northeast of Alpena. It aj^pears on the surface in 
the northeastern portion of the town where sev- 
eral quarries arc opened in it ( Loc. i ) . It is also quarried in 
