PAPACORA-200 - Paleoclimate, Paleomagnetism, and Cosmogenic Radionuclides of the past 200,000 years

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 geomagnetic Laschamp excursion as derived from Black Sea sediments: Variations of the Virtual Axial Dipole Moment (VADM) together with the values for the years 1900 and 2010 (top) in the context of climatic variations of the past 30.000 to 60.000 years as reconstructed from Greenland icecores (middle), and the migration of the virtual geomagnetic (North) pole (VGP) in the course of the Laschamp excursion at around 41,000 years (bottom).
Temporal variations of the magnetic declination in the area of the Black Sea during the geomagnetic Laschamp excursion, illustrated by a virtual compass needle (1sec = 100yrs).
Paleoclimate and Geomagnetic Field from 10,000 to 70,000 years before present: Temperature variations as derived from oxygen isotopes (d18O) from Greenland icecores (top) and variations of the Virtual Axial Dipole Moment (VADM) derived from Black Sea sediments (bottom), between: Variations in production rates of the cosmogenic radionuclides 10Be (Greenland icecores) and 14C (IntCal09; Lake Suigetsu), anticorrelated to the geomagnetic field strength.
Preliminary reconstruction of the geomagnetic field strength (slope NRM/ARM) of the past 70,000 years as well as from 120,000 to 170,000 years B.P. (top), together with the number of samples per 200 year bin (bottom; status from 2015).

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.

Partners:
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)

Funding:
Chinese Scholarship Council
University of Lund
TUBITAC

  • Liu, J., Nowaczyk, N., Frank, U., Arz, H. W. (subm) A 20–15 ka high-resolution paleomagnetic secular variation record from Black Sea sediments – no evidence for the 'Hilina Pali excursion'? Earth and Planetary Science Letters
  • Nowaczyk, N., Liu, J., Frank, U., Arz, H.A (2018) high-resolution paleosecular variation record from Black Sea sediments indicating fast directional changes associated with low field intensities during marine isotope stage (MIS) 4. Earth and Planetary Science Letter | doi:10.1016/j.epsl.2017.12.009
  • Nowaczyk, N., Frank, U., Kind, J., Arz, H. (2013): A high-resolution paleointensity stack of the past 14 to 68 ka from Black Sea sediments. Earth and Planetary Science Letters, 384, 1-16. | doi:10.1016/j.epsl.2013.09.028
  • Nowaczyk, N., Arz, H. W., Frank, U., Kind, J., Plessen, B. (2012): Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments. Earth and Planetary Science Letters, 351-352, 54-69. | doi:10.1016/j.epsl.2012.06.050

Contact

Norbert Nowaczyk
Group Leader
Priv. Doz. Dr. Norbert Nowaczyk
Climate Dynamics and Landscape Evolution
Telegrafenberg
Building C, Room 321
14473 Potsdam
+49 331 288-1369
Profile

Contact

Jiabo Liu
PhD Student
Jiabo Liu
Climate Dynamics and Landscape Evolution
Telegrafenberg
Building A 58, Room 0.1
14473 Potsdam
+49 331 288-1359
Profile