Magnetostratigraphy of Palaeocene basalts from the Vaigat Formation of West Greenland

A palaeomagnetic study comprising the directional results from 289 individu al lava flows, sampled along eight sections in the Palaeocene basalts of We st Greenland, is reported. The eight individual sections are correlated usi ng lithostratigraphical marker horizons to form a single composite profile. Generally. the lithological correlation is in good agreement with the reco rd of geomagnetic secular variation. The total composite palaeomagnetic profile represents a stratigraphic thick ness of 1.6 km through the Vaigat Formation, which is the lowermost of the two volcanic formations formed during the main stage of plateau volcanism. Only two polarity zones are found in the composite profile, suggesting a ve ry short duration for the West Greenland main plateau-building volcanism. A r-40/Ar-39 dates support a high extrusion rate and also indicate that the l ower normal polarity zone is Chron C27n and that the upper reverse polarity zone is Chron C26r. The C27n-C26r transition is fully recorded along one of the sections (Nuusa p Qaqqarsua), with intermediate directions covering a 200 m thick successio n of lavas. A combined palaeomagnetic, held and geochemical study along thi s profile showed good agreement; that is, geochemically and geologically de rived single magmatic events show groupings of the palaeomagnetic direction s. Supposing a duration for the geomagnetic transition of 5000 years, the e ruption frequency during this period was as high as one how every 80 years.