Jökull - 01.01.2013, Side 47

Stratigraphy, 40Ar–39Ar dating and erosional history of Svínafell, SE–Iceland
Figure 13. Formation and erosion history of the Svínafell massif. a) Glacial erosion during the Matuyama period carved
the lower strata by several hundred meters (SR2), followed by a sequence of lavas (formations SV6 to SV9). A few lavas
of normal magnetic polarity (black), correlated with Olduvai-chron (C2n: 1.78–1.95 Ma), indicate that at least 250-m-deep
valleys had formed in the Hafrafell-Svínafell area prior to 2 Ma. Glaciers eroded most of the N-lava sequence during erosion
event SR3. The Svínafell sediments (SV10) were deposited in lakes formed as the glaciers retreated. Erosion surface SR4
was formed by readvancing glaciers, followed by a thick tillite deposit (SV12). b) A minor erosion surface (SR5) divides
two major volcanic sequences from the Öræfajökull volcanic center (SV13 and SV14–SV23). c) Subsequent erosion events
(SR11 and SR12) eroded the "Svínafell valley", down to about 250 m a.s.l., followed by accumulation of lava flows (SV37).
d) At present, the Svínafell glacier has carved the Svínafell valley, down to about 100 m a.s.l. – Myndun Svínafells. a)
Jökulrof á Matuyama segultímabilinu nam nokkur hundruð metrum (rofflötur SR2). Síðan runnu hraunlög niður dalinn,
jarðmyndanir SV6 til SV9. Nokkur rétt segulmögnuð hraunlög (svört) frá Olduvaisegultíma (C2n: 1.78–1.95 Ma), sýna að
300–400 m djúpir dalir mynduðust á milli Hafrafells og Svínafells fyrir um 2 milljón árum. Svínafellssetlögin mynduðust í
stöðuvötnum í dalnum (SV10) í kjölfar jökulhörfunar. b) þykk bergmyndun frá Öræfajökulseldstöðinni (SV13) hlóðst ofan á
jökulbergslagið SV12 við eldgos undir jökli. Síðan varð minniháttar rof (SR5) áður en þykkur stafli af hraunlögum (SV14–
SV23) lagðist á Svínafellið. c) Jökullinn gekk síðan aftur fram og gróf sig niður í um 250 m hæð áður en hraunlög runnu
yfir dalinn (jarðmyndun SV37). d) Svínafellsjökull hefur grafið sig í 100 m hæð.
Mapping has revealed a total of 12 erosion surfaces,
SR1 to SR12, in the Svínafell massif (Figure 3). The
stratigraphic framework for these surfaces is summa-
rized in Table 3 but here each erosion surface is de-
scribed in more detail within a stepwise schematic
representation of Svínafell’s erosion history (Figure
13). After that the erosional evolution is summarized
into four stages (Table 4).
SR1. This erosion surface cuts through formation SV4
in Hrútagil (Figure 5). Above and below are tholei-
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