Rit (Vísindafélag Íslendinga) - 01.07.1962, Side 119

117
Fig. 59. Hestfjall; northem end, looking east.
Explanation in the text.
fluviatile, formed in shallow moving water. Finally there is
a thick primary breccia (7) and a light grey lava flow (8),
and these are most probably the equivalent of the Vatnsheiði
section, 225 m lower.
The dolerite cover of Hestfjall most likely corresponds to
remnants of dolerites on the lowland farther north (Hvera-
kot, Brjánsstaðir) and more generally to the extensive sheet
already described as extending from Laugardalsfjöll to Ing-
ólsfjall-Grafningur. The uplift of Hestfjall has gone a step
further than that of Lyngdalsheiði.
It is remarkable that Plateau basalts form much of the
lowlands west and north of Hestfjall while they are not found
in the socle of the uplifted blocks. This shows that the frag-
mental rocks were formed and preserved within depressions.
Hengill and the mountain chain on the Reykjanes
peninsula.
We have already pointed out that the Grafningsfjöll are
cut by a smooth mature erosion surface. Towards the west
this surface extends to the valleys Sauðárdalur and Laxár-
dalur where it comes to a sudden end. On the west side is a
10 km broad zone, enclosing the mountain Hengill, of much
younger, rough topography. This is formed by numerous