Revleii' of Bee/' id Geological Literature. 31t> 
The metamorphic Mesozoic rocks belong to the Jurassic and Creta- 
ceous periods and comprise an apparently conformable series of sedi- 
ments and lavas several miles thick. The sedimentary rocks are princi- 
pally slates, often altered to ([uartzites, with some limestones. In the 
lower part of this series the principal eruptives are diabase and green- 
stone, products of alteration of moderately basic lavas; and in the up- 
per part, where the lavas were very basic, they are more or less com- 
pletely altered to serpentines. 
The prevailing strikes are parallel to the general trend of the range 
and of the coast; and the dips are mainly between GO and vertical. 
Mr. Mills has not observed curving folds,and therefore concludes that the 
strata at the time of their tilting experienced much shearing on approxi- 
mately horizontal planes of overthrust, and tliat the subsetiuent upheavals 
have been chielly by the faulting of mountain blocks. Neither has he 
found any unconformity of dip and strike between tbe pre-Mesozoic 
and Mesozoic groups of metamorphic strata: but they were doubtless 
separated by a long period of erosion and subsidence. Upper Cretaceous 
(Chico) and Tertiary beds at the western foot of the range dip westward 
at low angles, indicating that the greater part of the tilting and meta- 
morphism toot place during some stage of the Cretaceous period, which 
Becker, from his study of the few fossilifei-ous horizons, believes to have 
been at the close of the Gault epoch. The tilting was attended with 
much fissm-ing and the formation of veins of gold-bearing ((uartz and 
pyrite. 
T'he Oeology of the Gruxy Monniama, Montatid. By J. E. Wolff. Bul- 
letin, G. S. A., Vol. Ill, pp. 44r)-4r)2: August 8, 1S92. The Crazy moun- 
tains, an isolated range 40 miles long from south to north with a width 
of 15 to 20 miles, lie about oO miles east of the easterly border of the 
main range of the Rocky mountains, and attain an elevation of 11,000 
feet above the sea, the difference in level between their summit and base 
averaging perhaps 4,000 feet. They lie close north of the Yellowstone 
river, and are conspicuously seen from the Northern Pacific railroad 
for many miles eastward from Livingston. In structure they are com- 
paratively simple but unique, being probably, as noted by Upham, the 
best known example of the type of mountain ranges which have not 
been made by anj^ definite process of mountain-building but are simply 
remnants of extensive uplifted areas that have been deeply eroded. 
Nearly horizontal Cretaceous rocks form the principal mass of the 
range and reach far eastward in the great plains and westward to the 
frontal line of the Kocky mountains, where sharp uplifts expose the 
older rocks. The strata of the Crazy mountains consist of sandstones 
and occasional c(mglomerates, interstratified with shales, and appear t(v 
be wholly referable to the latest Cretaceous or F.aramie epoch. Erup- 
-tive dikes in wonderful profusion antl variety cut these strata: and in- 
trusive lava sheets and laccolites, up to a thickness of 305 feet, are in- 
terbedded with then\, but no evidence of surface Hows has been found. 
The more enduring igneous rocks preserved tliis range, while denuda- 
