NOTES ON THE GEOLOGICAL SECTION OF MICHIGAN 
PART I. THE PRE-ORDOVICIAN 
A. C. LANE and A. E. SEAMAN 
Houghton, Mich. 
INTRODUCTION 
It is not as easy to summarize the section of Michigan as, for 
instance, a compact state like Iowa. For one thing the state is so 
spread out that, turned around by its southeast corner on the map, 
it would reach beyond New York into the Atlantic Ocean, and turned 
around by its northwest corner, would extend to Hudson’s Bay and 
into the Dakotas. Again it includes within its borders representa- 
tives of probably the oldest land masses, which have been frequently, 
if not continuously, above sea level ever since they were first elevated. 
The geological succession may therefore be expected to be inter- 
spersed with beds laid down on land and in lakes fresh and salt, and 
seas like the Caspian and Black, by stream and wind, as well as 
wave. 
Part I includes the pre-Trenton rocks which even the drill has 
not reached in the Lower Peninsula. 
In preparing these notes the state geologist had assistance from 
Professor Seaman of the College of Mines as to the older rocks to 
such an extent that it may be best expressed by joint authorship. 
Indeed what he knows of the Upper Peninsula is so interwoven with 
what he has learned from and with Professor Seaman that anything 
he could write would be essentially of that nature. 
With regard to the Paleozoic series he has had the advantage of 
the constant assistance of Mr. W. F. Cooper, and of unpublished 
reports by A. W. Grabau and N. H. Winchell to examine. Since, 
however, he differs quite materially from Dr. Grabau, and Dr. 
Grabau has recently given elsewhere? the essential features of his 
interpretation, no detailed reference to these unpublished reports will 
t Bulletin Geological Society of America, Vol. XVII, p. 567. 
680 
