The Botany of Iceland - 01.12.1914, Page 29

PHYSICAL GEOGRAPHY
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ness (20—50 metres) in the north-western peninsula and was origi-
nally deposited at one ievel, but was afterwards broken up by dis-
locations, so that it now occurs at diíferent levels above the sea.
The surtarbrand formation consists of diversely coloured layers of
clay and tuff with intercalated layers of lignite and coal-slate; in
many places leaves and fruits are excellently preserved in it, espe-
cially near Brjánslækur on the northern side of Breiðifjöriiur, and
at Tröllatunga and other localities near Steingrímsfjörður; in this
Fig. 4. Mountains near Kolviðarhóll (tuff and breccia).
last place it can be seen that large Tertiary woods havc been des-
troyed by pumice-eruptions and lava-streams. According to 0. Heer
the mean temperature of the year in north-west Iceland, at the time
of these Tertiary woods, was at least 9° C — probably somewhat
more (11°—12°); now the average temperature for the year in these
places is only 2°. The most common tree in western Iceland at
that time was Acer otopterix; its leaves are found in abundance
and excellently preserved in the clay-layers; there occurred in ad-
dition Sequoia Sterrtbergi, Pinus Steenstrupiana, P. microsperma, P.
aemula, P. brachyptera, Betula prisca, Alnus Kefersteinii, Ulmus diptera,
Quercus Olafssonii, Liriodendron Procaccini, Vitis islandica, Bhus Brun-
neri, Dombeyopsis islandica, etc.
The Palagonite formation is composed of different kinds of
tuffs and breccias, and in its upper divisions there is much moraine
material and scattered glacial gravel, as also some ice-striated lava-