IP UIBILILCATEIOINGS,. 
The Penokee lron-Bearing Series of Michigan and Wisconsin. By 
R.-D. Irvine and C. R. Van Hise. Monograph U. S. Geo- 
logical Survey No. XIX., 1892. Quarto, 534 pp.; with 37 
plates representing microscopic sections of the rocks of the 
district, and geological sections and maps of the region. 
The region discussed in this volume lies a few miles south of Lake 
Superior, partly in Michigan, partly in Wisconsin. It extends from 
Lake Gogebic in Michigan westward in a narrow strip from one to 
three miles wide, to Lake Numakagon in Wisconsin, a distance of 
about eighty miles. This area is covered by rocks of the Penokee 
series, which dip northward in a long and very regular monocline. 
The series is underlain by crystalline rocks designated the Southern 
Complex, though occasionally there intervenes between this and the 
Penokee series a formation designated the Cherty limestone. The 
Penokee series is overlain by the Keweenaw series, which in turn is 
overlain by the Eastern Sandstone. 
The Southern Complex is considered to be of Archean age and is 
discussed more fully in another part of this review by Professor 
Iddings. It was much eroded and reduced almost to base level before 
the deposition of the overlying formations. 
The cherty limestone is considered to belong to the Lower Huro- 
nian division of the Algonkian. It is composed of cherty, dolomitic 
limestone alternating with layers of chert, and averages about 300 feet 
in thickness. It is not continuous throughout the region, but is found 
intermittently between the Southern Complex and the Penokee series. 
A period of erosion of this formation occurred before the deposition 
of the overlying series, but it was of far less magnitude than the preced- 
ing period of erosion of the Southern Complex. 
The Penokee series is considered to be the equivalent of the 
Animikie, and belongs to the Upper Huronian division of the Algon- 
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