ART. 14 MICHIGAN TRAVERSE GROUP POHL. 5 



greatly facilitated the unraveling of the heretofore much misunder- 

 stood sequence of events and the measurement of strati graphic 

 thicknesses. 



Of former interpretations of the geology of the Traverse Bay 

 district the nearest approach to stratigraphic truth was gained by 

 Rominger.^ The very paucity of material from which this geologist 

 deduced his results attests his close observation and remarkable 

 acumen of mind. It is totally pardonable that his estimate of the 

 thickness of the exposed section was underrated by nearly 120 feet 

 when we remember that he was first to correct far grosser misinter- 

 pretations made by previous w^orkers in the same field. 



STRATIGRAPHIC UMTS 



Three new terms applying to as many distinct faunal and strati- 

 graphic units are here proposed. The defense for the introduction 

 of each will be treated separately. It has been found necessary to 

 separate the exposed section of the Traverse Bay region into a lower, 

 a middle, and an upper division ; and, since there is no way of recog- 

 nizing these divisions in comparable portions of the section in eastern 

 Michigan, to designate them by new geographical names as nearly 

 typical of their individual development as is possible. In ascending 

 order these divisions are — the Gravel Point stage, the Charlevoix 

 stage," and the Petoskey formation. ^^ 



Detailed! sections. — In the Traverse Bay district field locality 

 numbers have been applied to the many isolated outcrops of Trav- 

 erse rocks. These have been used in conformity with those em- 

 ployed by the 1926 Michigan Survey field party, although the original 

 number of observed and studied sections has been doubled in the 

 present investigation. The majority of localities investigated are of 

 secondary importance only, since they reveal in duplicate more lim- 

 ited representations of elsewhere more favorably developed sections. 

 A list of the " key localities " follows : 



Locations of sections from which the cmnplete sequence of Traverse teds in the 

 Traverse Bay district may he derived. 



Locality 7c. — Low bluff on shore of Grand Traverse Bay, 1 to 2 miles north- 

 west of Norwood, about a mile, in sees. 22 and 28, T. 33 N., R. 9 W., Charlevoix 

 County, Mich. 



Locality 8. — Ledges and bluffs on shore of Lake Michigan, 1% miles west of 

 Charlevoix, in sees. 28 and 29, T. 34 N., R. 8 W., Charlevoix County, Mich. 



Rominger, C. Mich. Geol. Surv., vol. 3, pt. 1, pp. 53-63, 1876. 



'" The physical evidence for the separation of the Gravel Point and the Charlevoix beds 

 has not been studied with sufficient intensity to warrant the establishment of the forma- 

 tional rank of these fauually distinct stages at the present time. 



11 This name was first applied by Grabau, (Rept. Geol. Surv. Mich., p. 201, 1901), to 

 beds largely equivalent to the formation herein proposed, but without proper delimitation. 

 Since the term is particularly applicable it has been here adapted to the usage pro^fosed. 



