Paleomagnetism and geochronology of the Pliocene-Pleistocene lavas in Iceland

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Abstract

Potassium-argon dates are reported on five basalt samples from the Pliocene-Pleistocene sequence of lavas in the Jökuldalur area, northeastern Iceland. These dates confirm the correlations previously made with the geological time scale by means of paleomagnetic stratigraphy. The R1 and N2 polarity epochs are shown to be equivalent to the Matuyama reversed and Gauss normal polarity epochs respectively. Within the N2 (Gauss) normal epoch up to three successive lava flows occur which are reversely magnetized. Dating of a normally magnetized basalt immediately below these reversed lavas gives a result of 3.10 ± 0.10 m.y., and confirms the reality of the Mammoth reversed event, first recognized in California. Two intercalations of normally magnetized lavas occur in the R1 (Matuyama) reversed epoch. The older of the normal flows may represent the Olduvai event; the younger normal polarity flow has been dated at 1.60 ± 0.05 m.y., and possibility indicates the presence of yet another normal event in the Matuyama reversed epoch. We propose the name Gilsáfor this possible additional event.

Immediately above the basalt dated at 3.10 ± 0.10 m.y., occurs a tillite, which suggests that regional glaciation commenced in Iceland at about this time. Hence, the base of the Pleistocene may be as old as 3 m.y.

Reference (18)

  • PjeturssonH.

    Om islands geologie

    Thesis

    (1905)
  • EinarssonT.

    Magneto-geological mapping in Iceland with the use of a compass

    Phil. Mag. Suppl.

    (1957)
  • RuttenM.G. et al.

    Paleomagnetic dating, glaciations and the chronology of the Plio-Pleistocene in Iceland

    Int. Geol. Congr. XXI Sess.

    (1960)
  • RuttenM.G. et al.

    Structure of the Central Graben of Iceland

    Int. Geol. Congr., XXI Sess.

    (1960)
  • WensinkH.

    Secular variation of earth magnetism in Plio-Pleistocene basalts of eastern Iceland

    Geol. Mijnbouw

    (1964)
  • CoxA. et al.

    Quarternary paleomagnetic stratigraphy

  • DoellR.R. et al.

    Geomagnetic polarity epochs: Sierra Nevada data 3

    J. Geophys. Res.

    (1966)
  • I. McDougall and H. A. Allsopp, Isotopic dating of the Newer Volcanics of Victoria, Australia, and geomagnetic polarity...
  • WensinkH.

    Paleomagnetic stratigraphy of younger basalts and intercalated Plio-Pleistocene tillites in Iceland

    Geol. Rubdsch.

    (1964)
There are more references available in the full text version of this article.

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