Manifestation of the geomagnetic Mono Lake excursion in sediments of the northern part of the Barents Sea
Abstract
Palaeomagnetic characteristics of cores from three boreholes (AK-56, AK-87, AK-98) collected in the northern part of the Barents sea (79-80 N) during the expedition of the Research Vessel "Academician Karpinsky" in 1998 have been studied. The cores were taken from depths of 329, 377, and 473 m, respectively. In all three cores, changes in inclination from -80 to -150 degrees were observed at a depth of 110-130 cm (in 6-8 core samples), which suggests that this phenomenon can be attributed to a geomagnetic field excursion. Basing on dating of the lithologic Holocene-Pleistocene boundary, the sedimentation rate in this part of the Barents Sea can be estimated to be 5-7 cm/1000 years. In this case the age of the excursion is about 24 000 BP, i.e., it corresponds to the Mono Lake excursion. In the Barents Sea sediments, the manifestation of this excursion was revealed for the first time in the ACB-2 core taken in the central part of the sea. At a depth of 150-180 cm, all three cores (in 8-10 samples) were found to have a layer with abnormally high natural remanent magnetization (up to 6-11 nT with a mean value of 1.5 nT) and magnetic susceptibility (up to 1.0-1.7 x 10-3 SI with a mean value of 0.4 x 10-3 SI). Basing on lithological data, the time of formation of this layer can be estimated as approximately 30 000 - 35 000 BP. A reference layer at the depth corresponding to the Holocene-Pleistocene boundary with similar changes in magnetic susceptibility attributed to climate change was found in the cores taken from the central part of the Barents sea earlier. It is likely that sharp changes in magnetic properties of sediments in the northern part of the Barents Sea about 30 000 - 35 000 BP are also attributable to a sharp climate change (warming) during that period of time. This work was supported by INTAS, Grant 97-31008 and PFBR, Grant 00-05-64921.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....3066G