CHA PTEREELE: 
LITHOLOGY OF THE KEWEENAW SERIES. 
SrcTIoNn I. Basic ORIGINAL ROCKS.—Pumpelly’s investigations on the basic rocks of Keweenaw Point; 
s ; 
of Northern Wisconsin.—Status of the subject at the close of the Wisconsin Survey.—Nomencla- 
ture.—General statement of results. —Classification. 
COARSE-GRAINED Basic RocKs.—Orthoclase-free diabase and gabbro, and olivine-gabbro: general macroscopic 
FINE 
description of; olivine of ; plagioclase of ; magnetite of; augite or diallage of; accessory ingre- 
dients of; appearance in the field of; typical localities of; tabulation of microscopic observa- 
tions on.—Orthoclase-bearing gabbro: distinctions from the non-orthoclastic gabbros; orthoclase 
of; plagioclase of; magnetite of; augite and diallage of; accessory ingredients of; occurrence in 
the field of; typical localities of; tabulation of microscopic observations on.—Hornblende-gabbro : 
distinctions of, from preceding kinds; tabulation of microscopic observations on.—Anorthite-rock : 
general description of; tabulation of microscopic observations on. 
-GRAINED BASIC ROCKS.—Quantitative relations.—Olivine-free diabase, of the ordinary type: Pumpelly’s 
study of; occurrence in the field of; amygdaloids and pseudamygdaloids of; alterations of; micro- 
scopic characters of; typical localities of; tabulation of microscopic observations on.—Olivin- 
itic fine-grained diabase anu melaphyr : Pumpelly’s descriptions of; occurrence in the field of; tab- 
ulation of observations on.—Ashbed-diabase and diabase-porphyrite: macroscopic characters of; 
microscopic description of: wide range in acidity of; typical localities of; tabulation of observa- 
tions on.—Amygdaloids: relations to the other basic rocks of ; microscopic characters of; macro- 
scopic characters of ; Pumpelly’s study of ; altered forms of; Pumpelly’s conclusions. 
SEcTION II. ACID ORIGINAL ROCKS: Quantitative relations of; classification of—Quarizless porphyry: 
relations of, to the diabase-porphyrites and quartziferous porphyries ; macroscopic characters of; 
microscopic characters of; porphyritic ingredients of; typical localities of; tabulation of micro- 
scopic observations on.—Quartziferous porphyry and felsite: quantitative relations and occurrence 
of; difficulties in the study of; Rosenbusch’s nomenclature; macroscopic characters of matrix 
of; microscopic characters of matrix of ; macroscopic and microscopic characters of porphyritic 
ingredients of; origin of; typical localities of; tabulation of observations on.—Augite-syenite and 
granitell or granitic porphyry : macroscopic characters of; microscopic characters of; gradation 
phases of, into other kinds; difficulty in finding a name for; relations of, to the modern 
trachytes; typical occurrences of; tabulation of microscopic observations on.—Granite: occur- 
rence of, in the Bad River country of Wisconsin; macroscopic and microscopic characters of; 
absence of, in the rest of the extent of the formation. 
SEcTION III. SUMMARY VIEW OF THE ORIGINAL ROCKS OF THE KEWEENAW SERIES. 
Srction IV. DETRITAL ROCKS.—Conglomerates.—Sandstones.—Basic sandstones.—Quartzose sandstones. 
—Secondary minerals in sandstones.—Tabulation of microscopic observations. 
The natural grouping of all of the rocks of the Keweenaw Series into 
the three classes of basic original, acid original, and detrital rocks has 
already been indicated.’ In what follows, each prominent variety is taken 
up in some detail. 
4See Chapter II. 
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