239 
The two main faults bound a sunken area which has its 
greatest length from У. $. W. to E. N. E., and the sandstone, 
the volcanic sheets, and the newer Plutonic rocks are only pre- 
served within this sunken area. 
That the sandstone formerly extended far beyond its pre- 
sent boundaries is evident from the distribution of the erratics, 
and from the phenomena seen along the great fault south and 
southwest of Igaliko (p. 260). The volcanic sheets must also 
once have extended over a large area; their feeder dykes occur 
abundantly, not only within the sunken area, but also in the 
areas adjoining, and everywhere maintain the same general char- 
acter and have the same main direction from N.E. to S. W. or 
from Е. N. Е. to W. S. W. 
Apart from minor irregularities, the sandstone strata in the 
larger northeastern part of the sunken area show a slight dip 
towards southwest or south, while the strata in the southwestern 
part of the area are inclined northeastward. If the original 
surface of the sunken area is reconstructed parallel to the 
stratification of the sandstone, this surface, though broken irre- 
gularly, will on the whole be trough-like, and its lowermost 
portion will lie in the south or southeast of the Ilimausak 
Mountains, over the central part of the Ilimausak batholite 
(Fig. 26). 
Since the sandstone outside the sunken area has been 
entirely removed by erosion, the full extent of the vertical dis- 
placement cannot be acertained. At Nulup Kaka, south of 
Igaliko, where the southern main fault is well exposed, the 
minimum amount of the down-throw must be 800 meters. At the 
southwestern end of Nunasarnak Mountain the uppermost sand- 
stone beds outcrop about 300 meters above sea level, and as 
the sandstone has a fairly uniform thickness of about 1200 meters, 
and the old granite only seven kilometers south of this place 
attains an altitude of 1260 meters, the vertical displacement 
here must be at least 2000 meters. In that part of the area 
XXXVIII. 19 
