Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 162

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the many great rivers that have had to cross it, and that it
was formed during the strandplane stage.
The peneplane stage is well preserved at a height of about
400 m on the many ridges separating the valleys of the east-
ern hinterland. Here the peneplane has been essentially sta-
tionary when the mountains to the north and south of the
area were uplifted. This most probably also means that the
area of the present lowland remained stationary at that time,
that it was very low during the Older and Younger 300 m
stages, and that therefore such a wide plain was created at
the strandplane stage.
Several valleys in the northern highlands have been well
graded to the strandplane level. This applies e.g. to Hítar-
dalur. After this valley had developed a flat broad floor at
the strandplane level volcanic activity took place here, and
several mounds of tuff-breccia were formed. The material is
mostly of normal magnetization and thus falls into the higher
part of the Pleistocene. But there was also an older phase
whose products were considerably eroded when the normal
ones were produced. In several bombs in the older member
I found reverse magnetization and it is very probable that
this phase belonged to the reverse lower Pleistocene, and this
would give the same result as Skagi: That the strandplane
was fully developed before the end of the reverse period.
However, as there is only fragmental material we cannot con-
sider the reverse polarity as absolutely certain.
The strandplane of Borgarf jörður continues west and south-
west of Hafnarfjall and surrounds Akrafjall, which must have
been an island at the strandplane time.
Within Hvalfjörður, only rather insignificant remnants of
the strandplane are left, which is referable to glacial erosion.
The area Kjós together with Hálsnes is the main remnant,
but we may also mention Thyrilsnes and Hvammshólar, and
the floor of Brynjudalur. But at the mouth of the fjord the
plane reappears with great extension in the approximately