Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 67

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son 1959b) representing river erosion after sea level had fal-
len below the Early Pleistocene 80—lOOm stage. Further
the valley floor and the walls of the channel had been scour-
ed by a glacier before Hvalfell was formed. From this, com-
bined with the normal magnetic polarity of the volcanic pro-
ducts, it is found that Hvalfell is of Middle or Upper Pleisto-
cene age.
Hvalvatn found an outlet along the north side of Hvalfell,
and here the Botnsá river dug a deep, 1 km long, extremely
narrow canyon, Glymsgil, into the 350 m high basalt slope
of the original valley.
Fig. 27. N-S section of Hvalfell.
g = upper limit of glaciation.
The contact of the young volcanic masses and the sides and
floor of the valley is seen at Glymsgil and at Hvalskarðsá
river, along the southwest slope of the volcano. Some 200 m
up the Hvalskarðsá (from its confluence with Botnsá) is
seen a steep valley slope, cut into basalts, against which leans
brown volcanic tuff and fresh kubbaberg. Farther up, at 110
m elevation, the brown tuff rests on striated older basalt (di-
rection of striae due west in accordance with the trend of the
old valley). The tuff is covered by kubbaberg on whose
striated surface rests a hard moraine. The direction of these
striae is W 39°N, which is the local trend of the valley after
formation of Hvalfell.
At 180 m we have still the brown tuff, 6—8 m thick, on a
striated basalt floor with the direction due west, and then the
kubbaberg and a coarse volcanic breccia, which are seen to
have settled in a slope on the tuff.
At 310 m the tuff has become coarser and is clearly a pri-