Palaeomagnetic Dating and Environmental Magnetism of Sedimentary Records

Principal Investigators: M. Melles

To enhance age control on sedimentary records investigated within the framework of CRC 806 (from both past and newly proposed CRC phases), project F6 primarily aims at conducting paleomagnetic dating. Earth's magnetic field varies on a range of time scales: from decades to millions of years. Distinctive global and local changes in inclination, declination and intensity, which have been accurately determined in time, can be used to correlate sedimentary horizons to this pre-defined time scale. This will corroborate dating by other methods and allow age models to be further refined.

Three types of geomagnetic behaviour related to different time scales within the framework of the CRC can be used practically:

  1. globally defined geomagnetic field excursions that have occurred over the last 120 ka;
  2. broad regional and global trends in directions and relative paleointensity during the past 250 ka, and
  3. smaller-scale regional changes in paleosecular variation (PSV) over the last 10 ka and potentially beyond. In addition, measurements of rock magnetic paleoclimate proxies, such as magnetic susceptibility, S-ratio and other grain size and compositional indicators will be conducted on selected records to complement other proxies in reconstructing environmental and climatic histories.

Paleomagnetic measurements will be made using a cryogenic magnetometer (2G Enterprises) at the University of Cologne that will be upgraded with:

  1. a long core sample holder;
  2. in-line three-axis alternating field (AF) demagnetization coils; and
  3. a direct current field coil system to impart an anhysteretic remanent magnetization (ARM) allowing determination of relative paleointensity.

This upgrade will greatly enhance analytical efficiency. Employing magnetic methods will improve both temporal constraints on sedimentary sequences studied as part of CRC 806 and our understanding of how the sedimentary environment responds to environmental and climatic changes.

 

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RWTH Aachen University

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