GEOLOGY OF LITTLE ROCKY MOUNTAINS 403 
porphyry intrusion to the nucleus of crystalline schists and the 
overarching sedimentary beds. It is a miniature representation 
of the geological structure of the Black Hills of Dakota. 
(BRA 
S7 PAU Sq 
MISSION 
i 
( 
i 
) 
i 
Wi 
SS 
Fs 
SS 
NOK 
PWN 
N+ 
ie 
Mi 
vy, 
ty 
ft 
Mi 
SS 
oe 
ue 
+t 
+ At i+ 
l 
id 
ert 
+ 
= 
Dy 
fe 
b 
bes, 
— 
{hy 
+++ a 
Al 
Nya liliinngesit3 
PNM, 
ZEON == ye 
% fp 2) oH ys " Fe 4 & 
atl 
Sevarap en 
76 
aa 
—<— =< 
—— HS ttt+ = MK 
SSS ++ F 4+ TAASIA 
IAA tet POZE 
a b aNG a e Wa 
Fic. 2.—a =Jurassic; 6 = Carboniferous; c—Siluro Devonian; @= Cambrian; 
e = Porphyry ; f= Crystalline Schists. 
In the brief time spent in the region no attempt was made 
to trace out geological boundaries nor to measure detailed sec- 
tions, it being necessary to ascertain the character and age of 
