Jökull - 01.01.2017, Page 25

Svavarsdóttir et al.
Figure 2. Geological map of
the NRZ (modified from Jóhann-
esson and Sæmundsson, 1998)
showing sample locations from
the Bárðardalur region (red tri-
angles), basement rocks of Bárð-
arbunga (B: orange filled circles),
Gæsavötn and Dyngjuháls (Gæ
and D: blue filled circles), Urðar-
háls (U: purple filled circles),
Gígöldur (G: green filled circles),
and Hrímalda (H: black filled cir-
cle). Basement rocks and inter-
glacial lavas are shown in blue,
green, grey and yellow, sub-
glacial formations in light brown,
Holocene lavas in pink, histor-
ical lavas in dark brown, and
the location of the Holuhraun
lava flow (2014–2015). Trölla-
dyngja (Trö), Kiðagil (Ki), and
Svartárkot (Sv). The red strip-
pled outline denotes the Fig-
ure 7. – Jarðfræðikort af
Bárðardal og nærliggjandi eld-
stöðvakerfum á hálendinu norð-
an Vatnajökuls (byggt á korti H.
Jóhannessonar og K. Sæmunds-
sonar, 1998). Sýnatökustaðir eru
sýndir með lituðum hringjum og
rauðum þríhyrningum.
in Bárðardalur (Vilmundardóttir and Kaldal, 1991;
Hjartarson and Kaldal, 2004; Hjartarson, 2004) agree
with the view that Gígöldur crater row is the most
likely eruption site for the highly porphyritic lavas
in Bárðardalur. The geological map of Hjartarson
(2004) depicts several lava units in Bárðardalur valley,
including the historical Frambruni (Fjallsendahraun)
lava, which flowed down towards Bárðardalur from
the central highlands.
In the following presentation, we will adopt the
names and division of Bárðardalur lavas used by
Hjartarson and Kaldal (2004), namely: (1) Kinnar-
hraun lava (9500 BP; Sigurgeirsson et al., 2015),
(2) Útbruni lava (9300 BP; Sigurgeirsson et al.,
2015), (3) Bárðardalshraun lava (>8000 BP; Sigur-
geirsson et al., 2015), (4) Kvíahraun lava (4000 BP;
M. Á. Sigurgeirsson, unpublished), and (5) Frambruni
lava (<1362 AD; Sigurgeirsson et al., 2015).
Sampling and sample details
A total of 17 rock samples of basaltic lava flows from
various parts of the Bárðardalur region were selected
for chemical analyses (red triangles in Figure 2). A
detailed study of the petrological and petrographical
characteristics of these lavas, including the origin of
20 JÖKULL No. 67, 2017