The strength of the geomagnetic field at the Cretaceous-Tertiary boundary: palaeointensity results from the Deccan Traps (India) and the Disko Lavas (Greenland)

Abstract

The lavas of the Deccan Traps (India) and Disko Island (West Greenland) were both erupted close to the Cretaceous-Tertiary (K-T) boundary. Palaeointensities have been obtained from orientated samples from 47 Indian and 38 Greenlandic sites. The intensity values show considerable scatter, but the mean virtual dipole moment calculated for the Deccan is 4.2 ± 0.3 × 1022 Am2 and for Disko is 5.8 ± 0.6 × 1022 Am2 compared to the present value of about 8 × 1022 Am2. The proportion of samples containing multi-domain magnetite is somewhat higher than in some younger lavas, suggesting hydrothermal alteration, which could account for some of the scatter in the palaeointensity values. -from Authors