GEOLOGY AND PALEONTOLOGY 
21 
The larger dikes are of a coarse-grained diorite, varying 
to a hornblende-gabbro (74) in some of its phases, show¬ 
ing large hornblende crystals in a matrix of basic plagio- 
clase and colorless augite. These larger dikes branch and 
send off fine-grained dikes of compact diorite (73) and 
quartz-diorite-porphyry (75). 
All these dikes have narrow contact zones where they 
cut the limestones, which contain brownish garnet, pale 
green pyroxene and needles of tremolite in confused ag¬ 
gregates. 
The same limestones make magnificent cliffs on the 
west side of the bay, near the Indian village in Queen 
Inlet; the white rock is everywhere most intricately cut 
by the dark diorite dikes. 
On the western point of Reid Glacier the country rock 
is granite, a rock not before reported from this region. 
It is coarse-grained (61), with large pinkish orthoclase 
crystals and sugary quartz grains, the original hornblende 
being largely altered to chlorite. Plagioclase feldspar is 
very subordinate. There is some titanite and a small 
amount of zircon. 
The granite is cut by a succession of dike rocks, the 
earliest of which appears to be a greenish aphanitic quartz- 
porphyry (59) of almost flinty appearance. Of later date 
are a succession of intrusions of rocks similar to those 
described from the eastern point; fine-grained compact 
diorites and diorite-porphyries in mostly narrow dikes; 
and last of all, an intrusion of quartz diorite, similar in 
appearance to the tonalite so abundant farther down the 
bay, which has invaded the whole series and often brec- 
ciated the black dikes so that the whole mass looks like a 
mosaic. 
One of the most striking rocks collected in Glacier Bay 
is a very coarsely porphyritic diorite found only as a 
boulder on the shore in Hugh Miller Inlet, near the 
