SUMMARIES OF CURRENT NORTH AMERICAN PRE- 
CAMBRIAN LITERATURE. 
Van Hise,’ Bayley, and Smyth map and describe? the geology of 
the Marquette iron-bearing district of Michigan. The pre-Cambrian 
rocks of the district comprise three series, separated by unconformities. 
These are the Basement Complex or Archean, the Lower Marquette, 
and the Upper Marquette, the two latter constituting the Algonkian for 
this district. All of these are cut by basic intrusives. The pre-Cam- 
brian rocks are unconformably overlain by Cambrian sandstone. 
The Basement Complex occurs in two main areas, one north of the 
Marquette series, called the Northern Complex, and one south of the 
Marquette series, called the Southern Complex. There are also isolated 
areas within the Algonkian. ‘The oldest rocks of the Basement Com- 
plex are thoroughly crystalline, foliated schists and gneisses. A close 
field and laboratory study has failed to detect in them any evidence of 
sedimentary origin. These gneisses and schists have been cut by 
various igneous rocks at different epochs. The latter occur both in 
the form of great bosses and in dikes, sometimes cutting, sometimes 
parallel to, the foliation of the rocks. In the area of the Northern 
Complex there have been volcanic outbursts, and a vast series of lavas, 
agglomerates, greenstone-conglomerates, and tuffs have been piled up. 
By far the greater part of the volcanic material is of an intermediate or 
basic character. 
The Northern Complex is treated under the divisions of Mona 
schists, Kitchi schists, gneissoid granites, hornblende-syenites, basic 
dikes, acid dikes, peridotite, and ferruginous veins. The Mona and 
Kitchi schists are greenstone-schists, which are believed to be largely 
*Continued from page 541, Vol. VI., this JOURNAL. 
?The Marquette iron-bearing district of Michigan, by C. R. VAN HIsE and W. S. 
BAYLEY; with a chapter on the Republic Trough by H. L. SmytH: Mon. U.S. 
Geol. Surv. No. 28, 1896, pp. 1-607. With atlas of 39 plates. Preliminary report 
on same district, published in the 15th Ann. Report U. S. G. S., 1895, pp. 
477-650. 
3 The Algonkian rocks are described by VAN Hise; the Basement Complex and 
later igneous rocks are described by BAYLEY; the Republic Trough is described by 
SMYTH. 
739 
