Jökull - 01.12.2006, Page 75

Pleistocene rhyolitic volcanism at Torfajökull, Iceland
ÁGRIP
Nýlegar argon-argon aldursgreiningar á súru bergi af
Torfajökulssvæðinu gefa aldur á bilinu 67-384 millj-
ónir ára. Efnagreiningar á aðalefnum og snefilefnum
sýna ennfremur að elsta bergið er mest þróað, sem
gefur til kynna að Torfajökulseldstöðin hafi verið virk
í a.m.k. 400 þúsund ár. Stærstu þekktu gosin á svæð-
inu, Rauðfossafjöll og Illihnúkur, urðu á síðustu ísöld,
fyrir um 70 þúsund árum. Súrir stapar gefa hugmynd
um ísþykkt jökulhettunnar á myndunartíma. Yngri
gos eru öll mun minni og blönduð basískri kviku sem
gæti bent til aukinna áhrifa gliðnunar eftir ísöld.
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