High-resolution sedimentary records from several locations over the globe that cover up to four glacial-interglacial cycles are being studied for their paleoclimatic properties as well as for their paleomagnetic information. Eighteen cores from the Black Sea as well as four cores from the Sea of Marmara with different temporal resolution are under detailed investigation. Especially the paleomagnetic records from these mid northern hemisphere sites shall be supplemented by data to be obtained from four cores recovered from the SE Pacific and three cores from the Drake Passage, Antarctica. Records of geomagnetic field variations from mid to high southern latitudes, especially documentations of geomagnetic excursions, are quite sparse and are of great importance for developments of representative geomagnetic field models.
The paleomagnetic study of a first set of sediment cores already revealed an excellent record of the Laschamp geomagnetic excursion 41,000 years ago. In the Black Sea area, it is expressed as a short, only 440 years lasting, but full reversal of the Earth's magnetic field. This reversed field configuration was characterized by field intensities of about 25% of the present-day value. The transitional fields during N-R and R-N reversals (N: normal poarity, R: reversed polarity), respectively, were associated with field intensities partly even as low as 5% of the present-day value. Thus, the shielding against charged particles from space (galactic cosmic rays) was impaired, leading to an increase in cosmogenic radionuclide (10Be, 14C, 36Cl) production. These isotopes were studied before at high-resolution only in ice cores from Greenland and Antarctica, which do not carry a paleomagnetic signal.
The Black Sea sediments under investigation cover the last glacial cycle with high sedimentation rates from 25 to 40 cm/kyr. Obtained paleomagnetic data comprise the best dated and most detailed record of the Laschamp geomagnetic excursion from the northern hemisphere. Moreover, the recording sediments are characterized by a fairly homogeneous lithology. Therefore, they offer the unique chance to directly study the flux of 10Be within the frame of a high-resolution paleomagnetic record obtained from the same archive. For this, in an initial study with 50 10Be samples, the central, fully reversed part of the Laschamp excursion, bracketed by the two pronounced field lows of the transitional field configurations, is being investigated, too.
Currently, further time windows related to postulated geomagnetic excursions are under investigation. The final goal is to provide, for both the Black Sea region as well as for the SE Pacific/Antarctic region, well-dated continuous high-resolution paleomagnetic reference records, comprising inclination, declination, and relative paleointensity, that are embedded in records of paleoclimatic variation from the past two glacial-interglacial cycles.
Dr. Monika Korte, Helmholtz Centre Potsdam GFZ, Section 2.3 (Geomagnetic field evolution)
Prof. Helge Arz, Institute for Baltic Sea Research (IOW), Rostok-Warnemünde, Germany (Paleoclimatology)
Dr. Antje Weckwerth, Institute for Baltic Sea Research (IOW), Rostok-Warnemünde, Germany (Paleoclimatology)
Dr. Markus Czymzik, Institute for Baltic Sea Research (IOW), Rostok-Warnemünde, Germany (Cosmogenic radionuclides)
Dr. Frank Lamy, Alfred-Wegener Institute (AWI) for Polar and Marine research, Bremerhaven, Germany (Paleoclimatology)
Prof. Raimund Muscheler, Department of Geology, Faculty of Science, Lund University, Sweden (Cosmogenic radionuclides)
Dr. Özlem Makaroğlu, Istanbul University, Engineering Faculty, Dept. of Geophysics, 34320, Avcilar, Istanbul, Turkey (Paleomagnetism)
Chinese Scholarship Council
University of Lund