A high-resolution paleointensity stack of the past 14 to 68 ka from Black Sea sediments

Abstract

Detailed paleo- and mineral magnetic analyses of a sediment composite record from the southeastern Black Sea yielded a high-resolution, well-dated paleointensity record. Though hampered by some larger hiatuses in some cores, and contaminated by diagenetically formed greigite, the paleomagnetic composite record obtained from the preserved primary detrital magnetite phase reflects a highly dynamic geomagnetic field during the last glacial period. Relative variations of paleointensity inferred from the sedimentsʼ magnetisations were converted into a record of the virtual axial dipole moment (VADM). Lowest VADM values are linked with the Laschamp (0.50×1022 Am2at 41.0 ka), the Norwegian–Greenland-Sea (1.5×1022 Am2at 64.5 ka), and the Mono Lake (3.0×1022 Am2at 34.5 ka) geomagnetic excursions. The fully reversed field during the Laschamp excursion exhibits a VADM of 2.0×1022 Am2 which is more than 25% of the present day axial dipole moment (7.628×1022 Am2). Rates of change calculated from the Black Sea VADM record also give some information on how to assess the global decay of the present-day geomagnetic field, which is significantly enhanced in the area of the South Atlantic Anomaly. Comparison with provided ΔC14 and 10Be records confirm, partly in the very detail, the non-linear anti-correlation of geomagnetic field intensity and the production of cosmogenic radionuclides in the Earthʼs upper atmosphere. However, discrepancies in the timing of lows and highs in the compiled records points out that the combination of different data sets from different archives remains a challenge.