90 
TENTH REPORT. 
PLEISTOCENE BEACHES OF SAGINAW COUNTY. 
BY 
W. F. Cooper, 
Michigan Geological Survey. 
CONTENTS. 
Introduction. 
Centers of Ice Radiation. 
Glacial Epochs. 
Lake History. 
Beach Formations. 
702-715 foot beach. 
680 foot beach. 
651-665 foot beach. 
647-654 foot beach. 
633-645 foot beach. 
618-635, 639 foot beach. 
Algonquin and transition beaches. 
Nipissing beach. 
Introduction. 
For an account of the Glacial Geology of the “Southern Peninsula of 
Michigan,” the reader is referred to an article by F. Leverett in the Sixth 
Report of the Michigan Academy of Science, 1904, page 100. During the 
present year the same author has -prepared the report on the Glacial Geology 
of the Ann Arbor Folio, No. 155 of the U. S. Geological Survey publications, 
in which will be found a general summary of the glacial geology of the Lower 
Peninsula. Prof. James W. Goldthwait of Northwestern University, Evan- 
ston, 111., has prepared Bulletin 17 for the Wisconsin Geological Survey in 
which will be found an excellent historical and geological review of the 
Pleistocene Lake History down to 1906. For a general account of glacial 
geology those interested in this subject would do well to read Chapter XIX 
on the Pleistocene in Volume III of Chamberlin & Salisbury’s Geology, 
printed in 1906. 
[ ^Centers of Ice Radiation .*J '! 
As far as the geology of Michigan is concerned we only have two centers 
of ice accumulation and dispersal to deal with, namely the Keewatin ice 
sheet in central Canada and west of Hudson Bay, and the Labradorean 
which takes its name from the peninsula of that name in eastern Canada. 
During the advances and retreats of these great continental glaciers there 
have been separated six epochs of glaciation beginning at the bottom as 
follows: Jerseyan, Kansan, Illinoian, Iowan, early and late Wisconsin. In 
the intervals of deglaciation are found early indications of soil deposits be- 
