Jökull - 01.12.1964, Síða 11

Fig. 5. Soil sections from the Kringilsárrani and Snæfell areas. For location see fig. 1.
of Kringilsárrani, just before the sloping to-
wards the jökulsá valley begins. This section
is shown as Cf 16a on fig. 5 and on the photo
fig. 6. In this section we recognize 3 rhyolitic
tephra layers. The uppermost and thickest one
is from the great Öræfajökull eruption in 1362.
Its average thickness in the Kringilsárrani area
is between 2 and 2.5 cm, or about half a cm
thicker than shown on the isopach map in my
monograph of this eruption (Thorarinsson 1958,
fig 27), but on the whole my thickness mea-
surements of this layer on Brúaröræfi, as well
as in the Snæfell area in 1964, fit tolerably
well into the picture of the distribution of the
1362-tephra given on that map.
JÖKULL 1964
The other two rhyolitic layers are the Hekla
layers designated as H3 and H4. According to
radiocarbon datings their age is 2800 and 4000
years respectively. (Kjartansson, Thorarinsson,
Einarsson 1964, pp. 115—120). The layer of
loess-soil from H4 down to the sub-soil contains
many undisturbed black tephra layers, and
its thickness below H4 is about the same as above
that layer.'l'here is therefore no doubt that here
undisturbed building up of soil has taken place
since the withdrawal of the Wúrm ice from
this area. Thus it is definitely proved by tephro-
chronology that the 1890-advance brought Brú-
arjökull to its maximum extension on Kringils-
árrani since the withdrawal of the Wúrm ice.
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