Anomalous directions of the natural remanent magnetization in Late Pleistocene marine sediments from the coast of Mauritania (West Africa)

Two closely located deep-sea cores taken along the coast of Mauritania cont ain zones of anomalous directions of the natural remanent magnetization (NR M) which fall mainly within the potential time-spans of the published excur sions/events (e/e) of the Earth magnetic field for the last 220 kyr. In two cases even reversed polarity is seen. In all cases in which anomalous dire ctions are detected the sediments show a strong change in magnetic properti es, such as natural and anhysteretic remanent magnetization and low field s usceptibility. Changes of the magnetic parameters and anomalous remanence d irections coincide with rapid changes of stable oxygen isotope ratios, i.e. , correspond to isotope stage or substage boundaries, and thus correspond t o glacial/interglacial transitions. The good accordance of ages of the obse rved anomalous directions with previously identified e/e may be partially c aused by the large uncertainty in dating of many of these previously determ ined short e/e. Therefore, it is concluded that climatically controlled cha nges of the ferromagnetic mineralogy with related remagnetization and miner al interactions cause the anomalous MIM directions. On the other hand, if o ne considers the correlation between anomalous directions, climatic changes and published e/e to be significant, one is led to postulate either that b oth Earth field related directional changes of the NRM and climatically ind uced mineralogical changes are caused by a common mechanism or that changes in climate with changing sea level and changing ocean circulation triggere d the e/e of the geomagnetic field. (C) 1999 Elsevier Science B.V. All righ ts reserved.