4 2 
ALASKA GEOLOGY 
(/) Ideally fresh small-porphyritic reddish-grey biotite-augite-an- 
desite 206), with the ground almost completely glassy. 
( u ) Dark grey fresh-looking gabbro-like diabase , coarsely ophitic, 
much calcified (208). 
(v) Dark aphanitic diabase with ophitic structure but idiomorphic 
pyroxene (216). 
(w) Olivine basalt . Hyalopilitic ground with distant squarish 
feldspars (275). 
( x ) (211) A fine-grained light grey diabase . The distant small 
phenocrysts lie in a hyalopilitic base. The augite is changed into a 
granular mass, mainly calcite. 
PLOVER BAY 
At Plover Bay (plate v and fig. 10) on the shore of 
Siberia the coast is mountainous, the bare cliffs rising 
sheer from the sea. On either side of the bay the cliffs 
seemed to be wholly made up of a light-colored granite. 
Coasting along the shore to the east, and after passing 
the first deep valley 
running up into the 
land, we saw rock of 
darker color, appar- 
FIG. IO. SKETCH OF THE SIBERIAN COAST. 7 r r 
ently a darker gran¬ 
ite, and this continues for a long way east. The Eskimo 
village in Plover Bay was placed as usual upon a long low 
spit, and this is made up of coarse cobbles. 
No soil or plant growth interrupts the view of the shore 
ledges. Only great streams of boulders occupy the steep 
gorges, and under the influence of the frost are slowly 
creeping downward. No sedimentary rocks or dikes 
were seen, to break the monotony of the bare granite. 
The following rocks were found as boulders on the spit. 
Hornblende-biotite-tonalite (174). A rather coarse, light grey, 
granitic rock, with small enclosures of fine grain and dark color. The 
plagioclase is subporphyritic, fresh, abundant, and markedly zonal; 
the orthoclase flesh-colored, in smaller and rarer anhedra; the biotite 
Light Granite 
Dark, Granite 
