A 640 KYR GEOMAGNETIC AND PALAEOCLIMATIC RECORD FROM LAKE BAIKAL SEDIMENTS

Abstract

Magnetic remanence vectors for 1737 samples from two ~100 m cores of Lake Baikal sediments are reported along with complete magnetic susceptibility profiles obtained from a pass-through system. Chronological control is established by means of two independent correlations; first, by matching susceptibility variations to the oceanic oxygen isotope record and second, by matching the relative palaeointensity variations to the SINT-800 global reference curve. These both imply an average deposition rate of 15 cm kyr-1 and a basal age of ~640 ka. Spectral analysis reveals the presence of Milankovitch signals at ~100 kyr (eccentricity), ~41 kyr (obliquity) and ~23 and ~19 kyr (precession). Stable remanence vectors are almost all of normal polarity. The few exceptions comprise brief intervals of low and/or negative inclinations which probably represent geomagnetic excursions. However, these are far less numerous than the high sedimentation rate would lead one to expect. Furthermore, only four of them can be readily matched to the-still poorly understood-global pattern. These are the Laschamp, the Albuquerque, the Iceland Basin and perhaps the West Eifel excursions which occurred at ~38 000, ~146 000, at 180 000-190 000 and at 480 000-495 000 yr ago, respectively.