Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 169

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race meets the erosional slope of Hatta (512 m), and in a
narrow rim around the remarkable lake Heiðarvatn there are
heights of 315, 330, 329, 367, and 398 m. This lake, whose
level is at 72 m, is possibly a late erosional feature but there
are also some indications that it might be either of tectonic
or volcanic origin.
Reynisfjall is a 5 km long and about 1 km broad ridge
with a flat surface mostly above 200 m and rising a little
above 300 m (324, 333 m) in two hilltops only. It fits well
with the 300 m base level.
Lágaheiði and Dalaheiði (4X4 km2) is an extensive ero-
sion plane reaching a maximmn height of 270 m (Neskamb-
ur) while it lies mostly a little above 200 m. In the north the
terrace meets the steep slopes of Sauðafell where the level
rises suddenly to over 450 m. This is not a fault but a very
clear erosional scarp: the layers forming Sauðafell rest on the
rocks that form the terrace.
Finally, it may be mentioned that the isolated Pétursey
with its flat surface (summits at 275,284 m) fits well as a
part of the high terraces, and its isolation may be taken as
an indication of the great amount of erosion carried out at
lower base levels.
In the southem scarp of Lágaheiði, the so-called Skamma-
dalskambar, is a remarkable occurrence of fossil shells which
have been studied by J. Áskelsson and E. Einarsson (Áskels-
son 1960). The rock is largely volcanic breccia which appears
to have been empted at this place but incorporated in this
are lumps of clay and sand containing the shells. The vol-
canic material has obviously broken its way through marine
sediments which probable had already acquired considerable
hardness, but they are perhaps not much older than the vol-
canic rocks.
Among the 30 species found here a number indicate Plio-
cene age, and Áskelsson compares them with the Tjömes
fauna. He thinks that they may be of the same age as the