Jökull - 01.01.2012, Síða 67

Holocene marine tephrochronology on the Iceland shelf
Table 3. Holocene silicic, intermediate and basaltic tephra layers in the 0.1–1 km3 volume range that have not
been reported in marine sediments on the Iceland shelf and are potential tephra markers. *The volumes for
tephra layers HM and HN are calculated within 0.5 cm isopach. – Súr, ísúr og basísk gjóskulög, í 0,1–1 km3
stærðarflokki, sem ekki hefur verið lýst í sjávarseti á landgrunninu fram að þessu og eru möguleg gjóskuleiðar-
lög. *Rúmmál gjóskulagana HM og HN er reiknað út frá 0,5 jafnþykktarlínum.
Silicic and Basaltic Volcanic Age Volume Tephra Reference
intermediate tephra system cal. BP (km3) distrib.
tephra layers layers (before 1950) uncomp.
Askja 1875 Askja 75 2 E Thorarinsson, 1963
K-1755 Katla 195 ∼1 E, SE Thorarinsson, 1975; Larsen, 2010
K-1721 Katla 229 0.33 W, NW Thorarinsson, 1955; Larsen, 2010
K-1625 Katla 325 0.5 E, SE Thorarinsson, 1981; Larsen, 2010
H-1597 Hekla 353 0.29 S, SE Thorarinsson, 1967; Larsen et al., 1999
H-1510 Hekla 440 0.32 S Thorarinsson, 1967
K∼1500 Katla 450 0.5 W Thorarinsson, 1969; Larsen, 2000
H-1389 Hekla 561 0.15 SE Larsen et al., 1999
Ö-1362 Öræfajökull 588 10 S, SE Thorarinsson, 1958
H-1341 Hekla 609 0.18 SE Larsen et al., 1999
K-1262 Katla 688 0.48 NE Larsen, 2010
H-1206 Hekla 744 0.4 SE Larsen et al., 1999
H-1158 Hekla 792 0.33 NE Thorarinsson, 1967; Larsen et al., 1999
Eldgjá 934 Katla 1016 ∼4.5 S, SE Hammer et al., 1980; Larsen, 2000, 2010
Grákolla (G) Torfajökull 1950±45 NE Larsen and Eiríksson, unpubl.
Askja (A) Askja 1950±45 S, SE Larsen and Eiríksson, unpubl.
H-X Hekla ∼ 2300 0.45 E, NE Larsen and Vilmundardóttir, 1992;
Óladóttir et al., 2011a
H-A Hekla 2540 0.55 W Róbertsdóttir, 1992;
Róbertsdóttir et al., 2002b;
Sigurgeirsson and Sveinbjörnsdóttir, 1999
H-Y Hekla ∼ 2600 0.6 E Larsen and Vilmundardóttir, 1992;
Óladóttir et al., 2011a
H-B Hekla ∼ 2740 W Róbertsdóttir, 1992
SILK-UN Katla 2850±50 0.29 E, NE Larsen et al., 2001
H-C Hekla 2800±70 NW Thorarinsson, 1964; Róbertsdóttir, 1992
H-M Hekla 2970 0.46 SE Larsen et al, 2002b; Óladóttir et al., unpubl.
H-N Hekla 3040 0.66 SE Larsen et al, 2002b; Óladóttir et al., unpubl.
SILK-LN Katla 3390±70 0.22 NE Larsen et al., 2001
H-S Hekla 3800±120 2 E, SE Larsen et al., 2001; 2012
Sn-2 Snæfellsjökull 4400±160 N, NE Steinthórsson, 1967;
Jóhannesson et al., 1981
SILK-A8 Katla ∼7350 SE Larsen et al., 2001
Sn-3 Snæfellsjökull >8000 N, NE Jóhannesson et al., 1981
A13 Torfajökull ∼8350 SE Larsen et al., 2001; Óladóttir et al., 2008
Søndergaard, 2005; Kristjánsdóttir et al., 2007). The
Saksunarvatn ash and Vedde Ash are the only tephra
layers that are found on all of the shelf areas that have
been investigated, i.e. north, west and south (Figure 1,
Table 2). Other tephra markers have only been identi-
fied, until now, in a single core (Table 2).
A transect from the western part of the North Ice-
land shelf to east Iceland is shown in Figure 3, where
marine cores MD99-2269 and MD99-2275 are cor-
related to the Svartárkot soil section in north Iceland
(Larsen et al., 2002 and unpublished data) and Kára-
hnjúkar in east Iceland (Óladóttir et al., 2011a) (Fig-
ure 2) (Gudmundsdóttir et al., 2012). Nine tephra
layers can be correlated between cores MD99-2269
and MD99-2275. Here four of these tephra layers,
KOL1372, KOL3-2269/3373, KOL2-2269/2912 and
KOL1-2269/2780 are correlated based on age and
chemical composition. These tephra layers could be
potential regional tephra markers on the shelf as they
originate from KOL or the TFZ. In addition to these
nine tephra layers correlated between cores MD99-
2269 and MD99-2275, 21 and 22 layers, identified in
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