88 TWENTY-FIRST REPORT. 



between the beds of these formations. Because such a break seems to be 

 absent, Dr. Ulrich would not divide the formation designated Racine by Pro- 

 fessor Hall. It is the writer's belief that most stratigraphers will agree with 

 Dr. Ulrich that the division of the Racine of Wisconsin by Professors Cham- 

 berlain and Whitfield is unjustified. 



There seems to be no better reason for dividing the Racine formation of 

 the Northern Peninsula of Michigan than of Wisconsin. The strata through- 

 out the formation in the Northern Peninsula are very similar in lithologic 

 character and no evidence of a stratigraphic or paleontologic break seems to 

 be present. 



In the Northern Peninsula, the Racine formation is at or near the surface 

 of much of the region adjoining the north shores of Lakes Michigan and 

 Huron. It is exposed at many places on the shores of the Point Detour penin- 

 sula, Poverty and Big Summer Islands, Lake Michigan. The land adjacent to 

 Lake Michigan between the Point Detour and Seul Choix Point peninsulas is 

 probably underlain by older Niagaran strata of the Manistique formation, 

 although parts of this land, especially the extremities of the more lakewarQ 

 extended peninsulas, may be occupied by the Racine dolomite. A small outlier 

 of the Racine dolomite occurs at the village of Whitedale, which is situated 

 northwest of Seul Choix Point on the Minneapolis, St. Paul and Sault Ste. 

 Marie Railroad. Most of the Seul Choix peninsula is underlain by the Man- 

 istique strata, areas of Racine dolomite occurring only on its southwest and 

 northeast sides. This local areal distribution is due to the erosion of the latter 

 formation from the top of a low anticline, having a crest-line parallel to the 

 northwest-southeast axis of the peninsula. A continuous belt of Racine dolo- 

 mite, having an average width of six miles, extends from the Seul Choix Point 

 peninsula to the Detour Passage and borders the north shores of Lakes Michi- 

 gan and Huron except where it extends across the base of the large, triangu- 

 lar-shaped St. Ignace peninsula. The surface rocks of the St. Ignace penin- 

 sula and possibly the southern part of the St. Martin's Point peninsula belong 

 to the Monroe-Salina group. The southern portion of the Point St. Vital penin- 

 sula is apparently imderlain by the Manistique formation. A narrow strip of 

 land, adjoining the shore of Lake Huron between this peninsula and the vil- 

 lage of Detour on the Detour Passage, may also be underlain by the Manis- 

 tique, although it seems more probable that it is underlain by the Racine 

 dolomite. Outcrops of the latter formation are numerous along the south 

 shore of Drummond Island. The presence of a few exposures of the undei^ 

 lying Manistique formation along this shore is apparently due to the erosion 

 of the Racine dolomite from the tops of very low anticlines. 



The Racine formation consists of very thick beds of hard, highly crystal- 

 line dolomite of a predominant white color. Some beds are bluish-white or 

 very light-gray. Upon weathering, the color of the beds, especially the 



