MAGNETOMINERALOGY AND REVISED EXCURSIONS FOR THE LAST INTERGLACIAL GLACIAL CYCLE IN THE GRANDE PILE LACUSTRINE SEQUENCE, FRANCE

A paleomagnetic record for the Grande Pile lacustrine sequence deposited during the last interglacial-glacial cycle has been constructed based on continuous sampling (n = 792) of a 15-m-long oriented core (GPXX). The NRM intensity, magnetic susceptibility, and saturation isothermal remanent magnetization show pronounced variations related to the climatic zonations in the sequence. The stratigraphic consistency of the paleomagnetic directions vary considerably due to variations in signal/noise ratios. Paleosecular variation patterns occur throughout most of the core, as well as several zones of inferred geomagnetic excursions. The application of magnetic fabric (AMS) shows that some apparent Lanterne (Weichselian) excursions reside in deformed sediments, while anomalous paleomagnetic directions in the 70,000 to 120,000 yr B.P. time interval appear in sediments with low signal/noise ratios and a high degree of compaction. The signature is hence not likely to reflect genuine records of geomagnetic field variations in these levels. Discrepancies between the magnetostratigraphy of GPXX and a previously investigated core implies that the earlier claimed regional correlations based on the paleomagnetic signature of low intensity levels should be critically reassessed. The Grande Pile sequence is not regarded as a magnetostratigraphic standard for the last interglacial-glacial cycle. © 1992.