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Abstract:
About 41 ka years ago a short but full reversal of the Earth’s magnetic field occurred. First evidence for this event was found in lavas from the French Massif Central by Bonhommet & Babkine (1967). Together with further lavas with magnetization directions that neither resemble a normal nor a reversed polarity of the Earth’s magnetic field (Plenier et al., 2007) a common mean radiometric age of 41 ka (Singer et al., 2009) has been determined for the lavas giving evidence for the ‘Laschamp’ event. This event was named after a village close to the type locality. Paleointensity investigations showed that the geomagnetic field during the Laschamp event was characterized by low field intensities (Roperch et al., 1988; Chauvin et al., 1989). Six sediment cores recovered from the SE Black Sea also document the Laschamp excursion. The data give evidence for a 400 years long fully reversed state of the geomagnetic field associated with minimum field strengths less than 10 % compared to the modern field. Parallel to these drastic variations in geomagnetic field strength the Black Sea sediments also recorded fast temperature changes during the last ice age, first found by oxygen isotope analyses on Greenland ice cores (Dansgaard et al., 1993; Svensson et al., 2008). Thus, geomagnetic field variations could be directly paralleled to climatic variability throughout the last ice age in great detail, testing the hypothesis that there might be a link between both processes. However, data from the Black Sea unequivocally exclude a direct impact of the Earth’s magnetic field on climate variability.
