THE PENOKEE HURONIAN, 391 
THE PENOKEE HURONIAN, 
In the third volume of the Geology of Wisconsin, I have described 
in some detail the rocks of the Penokee region, which extends from the 
vicinity of Lake Agogebic in Michigan to Lake Numakagon in Wisconsin. 
The following is the succession of strata as I have given it in that volume: 
Feet. 
ieeireamotie crystalline temestoné .-....-c.-...-. o+2-++se+ss-sseececee 90 
II. (A) Arenaceous white quartzite, often brecciated, 35 feet; (B) magnetitic 
TUaMe-SCRIST, OMLCOD 222 /= lei =~. sistas wcin simiSGhaeie = eet eee eeminns Bee ree 40 
III. Siliceous slaty schists; including quartzite, “ argillitie” mica-schist, and 
novaculite; all having much quartz, and none ever showing any 
amorphous material ...... ae : 410 
IV. Magnetic belt; including: (a) banded meaemente ade to. red 
quartzite, free from or lean in iron oxides, banded with seams, from 
a fraction of an inch to several inches in width, of pure black gran- 
ular magnetite, only rarely mingled with the specular oxide; (b) mag- 
netitic quartzite, the magnetite in varying proportions, pretty well 
scattered throughout, and mingled with the specular oxide in pro- 
portions varying from nothing to a predominating quantity; (c) mag- 
netitic quartz-slate, the magnetite pervading the whole, and mingled 
with the specular oxide as before; (d) slate like (c), but largely 
charged with tremolite or actinolite; (e) arenaceous to compact and 
flaky quartzite, free, or nearly so, from iron oxides; (f) thin lami- 
nated, soft, black magnetitic slate; (g) hematitic quartzite, the iron 
oxide the red variety ; (h) garnetiferous actinolite schist, or eclogite; 
(4) greenstone, which is restricted to the western end of the Huro- 
nian belt. Kinds (a) to (ad) all carry much pyrolusite or other man- 
ganese oxide. These varieties have no persistent stratigraphical 
arrangement, and are named here in order of relative abundance. 
otal ChiCknesss 2OOUW be cle see = eee =) ance eles) sinleleye ale eliatelmteel che nt atm etal 780 
V. Black feldspathic slate; consisting of orthoclase grains imbedded in a 
paste of biotite, pyrite, limonite and carbon....-. --..--..------. 180 
VI. Unknown, always drift covered ......--.--.--- +. -++-+---------+ + 880 
VII. Dark-gray to black, aphanitic mica-slate, having a wholly crystalline 
base of quartz and orthoclase, with disseminated biotite scales... . 120 
VIII. Unknown, but probably in large part the same as SVGILL Sie eyeisaerteyetora 290 
IX. Chloritic, pyritiferous, massive greenstone. .-....----- ++ +--+ ++++++++- 150 
X. Black, aphanitic mica-slate like VIL ..-....+--+---+--+-+2++ +5 RUSE 25 
XI. Covered, but probably mica-slate.--. --..---- +--+ eee eee ee ee recess 280 
XII. Black mica-slate; aphanitic, at times chiastolitic...-....-.-.--------- 225 
XIU. Chloritic greenstone. . - - - PEE A BER Een SAR SG Dae DOCS COUR A SSE 35 
XIV. Black mica-slate, like X11, often chiastolitie REG Gen RAB OG Ate cnacormaeoe 375 
XV. To XVIII, alterations of black mica-slates, with quartzites and quartz- 
