Paleomagnetism of Quaternary sediments from Anholt, Denmark: Onset of the Blake Event and Eem

Abstract

Trie c. 70 m non-marine Weichselian sands and clays from two consecutive borings, Anholt II and III, show normal polarity and inclinations somewhat shallower (c. 115°) than the axial dipole field value, which may be explained by a moderate compression of the sediment. Most of the marine shallow water silty clays of the Saalian (isotope stage 6) and Eemian (isotope substage 5e) sections (74-81 m) also show normal inclinations, except for two samples at the very top part of the recovered Eemian stage, which are distinctly reversely magnetized. The reversed section of the Pleistocene sediments (in Anholt III) is interpreted to belong to the earliest part of the short reverse geomagnetic Blake event. Correlation via biostratigraphy and oxygen isotopes provides an estimate for the onset of the Blake reversal at about 123 ka which, together with the termination date of 117 ka from Lac de Bouchet, possibly suggest an age of about 123-117 for the Blake reversal.