2 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



Location wnd distribution. — The known areal occurrence of Tra- 

 verse rocks proper is unequally threefold. By good fortune these 

 three areas of outcrop combine toward a solution of two of the 

 greatest stratigraphic problems — sequence and correlation. No two 

 of these occurrences afford the necessary ties without the third, and 

 they are all therefore of equal importance in any consideration of 

 the Traverse problem. 



The area of greatest surface development of these rocks occurs 

 within the boundaries of the five northernmost counties of the Lower 

 Peninsula of Michigan — Charlevoix, Emmet, Cheboygan, Presque 

 Isle, and Alpena — forming thus the outer edge of one of the structural 

 " saucers " centering near Saginaw Bay. That this broad structure 

 is of post-Paleozoic origin will be shown under a later heading. 

 Numerous cement and alkali enterprises have resulted in the excava- 

 tion along the outcrop of some of the largest lime quarries in the 

 United States, which in conjunction with the shore exposures border- 

 ing Lakes Michigan and Huron give the line of sections a south- 

 wardly crescentic trend. Northward of this narrow line the surficial 

 distribution is abruptly broken by a thick covering of the ground 

 moraine, and to the southward the limestones of the Traverse dis- 

 appear beneath the succeeding black shales of Waverlian and possibly 

 Devonian age. 



The southernmost outcrop of undoubted Traverse beds is found in 

 the northwestern portion of Lucas County, Ohio. The details of 

 the sections obtained here and their peculiar significance will be 

 discussed with those of the third occurrence of Traverse rocks, a 

 portion of the Thunder Bay series on and near the east shore of 

 Lake Huron in Lambton, Huron, and Middlesex counties, Ontario. 



Nomenclature and former conceptions. — It is needless in a paper 

 of this character to recount the historical development of geological 

 knowledge of the Traverse beds of Michigan, especially in view of the 

 fact that the present investigation has shown remarkable incon- 

 gruities in all phases of the study. These are in most cases entirely 

 excusable, since they are partly due to formerly prevalent miscon- 

 ceptions and misunderstandings of conditions of deposition, partly to 

 the incompleteness of stratigraphic preservation, and partly to a lack 

 of necessary details, especially in the matter of authentic well records. 



The solutions of the problems here presented have been accom- 

 plished entirely independently under the auspices of the United 

 States National Museum with the assistance of Mr. G. O. Raasch 

 of the Milwaukee Public Museum, and there has been a purposeful 

 disregard of all previous work, published or otherwise, with the 

 exception of the results of the 1926 Michigan Survey field party, 

 in cooperation with the United States Geological Survey, represented 



