High-resolution magnetostratigraphy of late quaternary sediments from LakeBaikal, Siberia: timing of
intracontinental paleoclimatic responses
Tien-Yen Lin
Abstract
Six cores were retrieved from LakeBaikal to establish their relative paleointensity records and excursion. Relative paleointensity records were mainly determined by NRM30mT/ARM30mT and calibrated accelerator mass spectrometry (AMS) 14C datings,and then compare them with £_18O of the ODP site 677, which represents the global climatic change. Combining relative paleointensity records and its characteristic direction,the author found there exist two geomagnetic excursions, Laschamp at ~42 ka and IcelandBasin at ~185 ka. In addition, during glacial, the clay-rich layers dominate, anhysteretic remanent magnetisation (ARM) is high, and magnetite dominate; during interglacial, the diatomaceous layers dominate, more biogenic material and detrital input, and hematite dominate.
Because LakeBaikal has high-resolution sediment record, complex depth/age curve, low sedimentary rate, hiatus, and sporadically distributed greigite, which is unstable to carry magnetic remanence, the authors have to remove all these problems to easily compare with two continuous marine datum. One is £_18O of ODP site 983, which has better benthic and planktonic datum than ODP site 984. Then they discovered that there had a time lag between the global ice volume change, 0.7 ka later, at ~185 ka, and sea surface cooling at ~192 ka. The other is £_18O of ODP site 984, which had better age model. Finally they established ¡§Synthetic curve Baikal 200¡¨ by six cores and£_18O of ODP site 984 and find out maybe there had another geomagnetic excursion, Blake at ~129 ka.
The average sedimentation rates range from 2.9 to 19.4 cm per ka. Such high rate variation means the sedimentary environment in LakeBaikal was unstable. This made it hard to have a good age model, based on tuning climatic records of Baikal with£_18O record at high resolution.
Reference
Demory, F., Oberha¡Lnsli,H.,Nowaczyk,N.R.,Gottschalk,M.,Wirth,R., Naumann,R., 2005. Detrital input and early diagenesis in sedimentsfromLake Baikal revealed by rock magnetism. Glob. PlanetChange 46, 145¡V166.
Demory, F., Nowaczyk, N.R., Witt, A., Oberhansli, H., 2005. High-resolution magnetostratigrap-hy of late Quaternary sediments from LakeBaikal, Siberia: timing of intracontinental paleoclimatic responses. Glob. Planet. Change 46, 167¡V 186.