18 
Relative age of the Red Sandstone and the volcanic 
sheets. — As already mentioned the greater part of the volcanic 
sheets rests upon the sandstone und is, consequently, younger 
than this. On the other hand, it does not seem improbable 
that the volcanic outbursts have commenced at a time when 
the deposition of the sandstone was still in progress. The 
question of the relative age is somewhat difficult, because we 
have not succeeded in finding a locality where the uppermost 
sandstone-beds are well exposed to view and, at the same time, 
readily accessible, and no decisive observations have been made. 
The facts which apparently indicate a partial contempora- 
neity of the sandstone formation and the volcanic activity are 
the following: (1) Although most of the volcanic sheets which 
occur intercalated between the sandstone-beds have the character 
of ordinary sills, Dr. Sreexsrru has observed a few sheets 
whose upper surfaces present the slaggy appearance of a lava- 
crust: thus, in several places near Igaliko and at Musartut on 
the north coast of Tunugdliarfik Fjord’. The horizon of the 
‘‘slaggy diabase” of Musartut is about 800 meters lower than 
the uppermost sandstone-bed. (2) While. most investigators 
have only found sandstone-pebbles in the conglomerate-beds of 
the sandstone Dr. Sreenstrur, after careful research, has found 
a conglomerate layer with numerous pebbles of diabase at an 
altitude of about 200 meters near Igaliko*. (3) At the head of 
Kangerdluarsuk, near the shore, an erratic is observed, about two 
cubic meters in size, which consists of red sandstone with a number 
of thin conglomerate beds; in these several pebbles of a porphyry, 
much like the porphyry of llimausak, and a few diabase pebbles 
are associated with the sandstone pebbles of the usual kind. 
Geological age of Igaliko Sandstone. — Different authors 
have expressed widely divergent opinions as to the geological age 
of the sandstone of Igaliko. Gizsecre (1818) classes this formation 
+ Meddelelser om Grønland, XXXIV, р. 127, Fig. 1 (1909). 
2 Ibidem, р. 130. 
