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Palaeomagnetic Results from the Lopra-1/1A re-entry well, Faroe Islands

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  • N. Abrahamsen, Danmark
  • Geologisk Institut, Geofysik
  The palaeomagnetic dating and evolution of the Faroe Islands are discussed in the context of new density and rock magnetic results from the deepened Lopra-1/1A well. The reversal chronology of the c. 6½ km thick basalt succession is also described. The polarity record of the Faroe Islands may now be correlated in detail with the Geomagnetic Polarity Time Scale. The lowermost (hidden) part of the lower basalt formation correlates with Chron C26r (Selandian age), the top (exposed) part of the lower basalt formation correlates with Chrons C26n, C25r and C25n (Selandian and Thanetian age) and the middle and upper basalt formations correlate with Chron C24n.3r (Ypresian). Inclinations indicate a far-sided position of the palaeomagnetic poles, which is characteristic of results from most Palaeogene volcanics from the northern North Atlantic region.

The density, magnetic susceptibility and magnetic remanence of 20 specimens from one solid core (1½ m in length) and 26 sidewall cores between -2219 and -3531 m below sea level (b.s.l.) from the well suggest that the volcanic materials can be divided into two characteristic groups; solid unaltered basalts and altered basalts and tuffs. The magnetic properties are typically log-normally distributed and the carriers of remanence are Ti-poor Ti-magnetites with Curie temperatures close to 580°C. The inclination of the 1½ m core at -2380 m b.s.l. is dominantly negative (two plugs at the very top of the core do show normal polarity, but they are likely to be misoriented as all specimens appear to be from one flow). Magnetic logging (magnetic susceptibility and field intensity) down to 3515 m b.s.l. was made in Lopra-1/1A together with other geophysical logs but did not yield conclusive inclination data.

OriginalsprogEngelsk
TidsskriftGeological Survey of Denmark and Greenland, Bulletin
Vol/bind9
Sider (fra-til)51-65
Antal sider15
ISSN1604-8156
StatusUdgivet - 2006

    Forskningsområder

  • Palæomagnetisme, bjergartsmagnetisme, magnetisk polaritet, pladetektonik, Færøerne, Nordatlanten, Lopra, vulkanisme

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