1895. | NEW YORK ACADEMY OF SCIENCES. 31 
desolate belt of mountain ranges some thirty to forty miles in 
width. That this is occupied in large part by the Coast range 
granite seems quite probable; at least this is likely to be the 
case if the aparent similarity between the different sections 
holds good. It is quite likely that the intrusive diorite of 
Glacier Bay is merely an unusually large sample of the diorite 
reported by Dawson as intruding into the granite. But nothing 
like the great quartz-diorite mass of Glacier Bay has been de- 
seribed elsewhere in Alaska. It may represent a phase of the 
granite, or an intrusion of later date analogous to the diorite. 
It is more basic than the former, more acidic than than the latter. 
Dr. Dawson further reports that the Carboniferous limestone 
in his Stikine section is followed apparently in ascending order, 
“by a series of altered volcanic rocks * * * * apparently 
chiefly diabases, but including also porphyrite like rocks.”* 
These are stated to be bedded, are regarded provisionally as of 
Carboniferous age, and are likened to rocks forming part of the 
Cache Creek group, in the southern interior of British Columbia. 
Rocks of similar character occur on the mountains enclosing 
the northeast portion of the Muir glacier amphitheatre, which 
are at least older than the quartz-diorite, being cut by a dike of 
that rock, one of the apophysz mentioned on a previous page. 
They have not been sufficiently studied to bring out their rela- 
tions to the Palaeozoic clastics, but as far as observed they are 
in contact with the argillites instead of lying above the limestone. 
The more recent dike rocks, which are of possible Tertiary 
age, seem widespread throughout the whole extent of the Coast 
range and are mentioned by every observer. 
PETROGRAPHICAL NOTES. 
The Quartz-diorite.—This rock has been briefly described by 
Dr. Williams, but in view of its extent and importance in the 
region a somewhat fuller description seems advisable, though 
the rock is a quite normal one. Unfortunately the material at 
hand has not been sufficient to permit of chemical study in con- 
junction with that under the microscope. 
In thin section the quartz-diorite is seen to consist of a 
coarsely hypidiomorphic granular aggregate of plagioclase, 
hornblende, quartz and orthoclase (?), with accessory biotite, 
magnetite, ilmenite, titanite and apatite. The order of crystal- 
lization is the usual one, apatite followed by the iron oxides, 
then titanite, hornblende and biotite, plagioclase, orthoclase (?) 
and quartz in the order named. 
*G. F. Dawson. Geol. Sury. Can, An. Rep., 1887-8, p. 55 B. 
