_ &. D. Irving—Huronian Series of Northern Wisconsin. 395 
Format Average thickness, 
ae ‘Black feldspathic slate ; consisting of orthoclase 
grains imbedded in a paste of biotite, pyrite, limonite 
(Julien) and carbett 222-0 2 Ae 180 ft. 
VI. Unknown, always drift-covered......-.-.-----.. 880 ft. 
VIL Dark gray to black, aphanitic mica-slate, having a 
wholly crystalline base of quartz and orthoclase, with 
disseminated biotite scales... 52/2 2s6020.s Leics TO 
Vill. Unknown, but set in i part the same 
aa. VIL». 290 ft. 
IX. Chloritic, pyritiferous, massive diorite (J ulien) -. cece (SO 
X. Black, aphanitic mica-slate, like VIL....-.-.----- 25 ft. 
XI. Covered, but pro black mica-slate.. .....-- 280 ft 
XIl. Black micu-slate ; aphanitic; at times chiastolitic 
(Julien) - Lvebus dons eo ess cs ke ee ee 
XML. | Chloritic disrilaual. 35 ft. 
XIV. Black mica-slate, li . XII, often chiastolitic-... 375 ft. 
XV to XVIII. Alternations of black mica-slates, with 
quartzites and quartz-schists - 675 ft. 
xX Greenstone-schist ; aphanitic ; “the hornblende 
and plagioclase much aired 0 a 260 ft. 
XX. Covered; but oe like MX oose eee Se 525 ft. 
XXI. Mica schist » from aphanitic to medium-grained ; 
including bands of mi or os the mica 
becoming subordinate; all va s having a back- 
ground of quartz ; he mica wholly “biotite; penetrated 
by veins and masses 0 very coarse, Pang rick-red 
biotite granite; total seen on Bad Riv Se Discos ft. 
Total Noniogee of the Huronian in the Bad are 
se 10,300 ft. 
Add highs layers seen farther east ; same as XXII__ 2, OU 
TOG soo 12,800 ft. 
KEWEENAWAN. 
(Non-conformable with the Huronian.) 
Very coarse to fine-grained gabbro, including granite veins 
and mass 
The Bad River section does not show the entire thickness ~ 
the Laurentian gneiss, and Keweenawan gabbro, does not ex- 
ceed 2,500 fae, while at the same distance eastward it is over 
12,000 fee 
Rpuiialeneg of the Huronian systems of the Marquette and Pen- 
okee Districts.—There can be little doubt that the Huronian 
basin of rp: was once directly continuous with that in 
