| For the reconstruction of past climate, environment, and provenance areas, a considerable array of proxy parameters is available in the geosciences. These may be biotic or abiotic, and include for example microfossil and nannofossil contents and ratios, pollen, grain size distributions, geochemical tracers and stable isotope records. Mineral-magnetic proxies still are less common, but are rapidly gaining importance. Magnetic measurements have a number of distinct analytical assets: 1) they can be perfomed on virtually all types of samples without tedious sample preparation; 2) they offer grain size dependent information (on the magnetic minerals, often iron oxides) with a particular sensitivity for the important sub-micrometer grain size range that is difficult to assess with other analytical techniques; 3) they are very sensitive; 4) they are comparatively rapid and mostly non-destructive so that they can be used in conjunction with other analytical techniques. However, it should be kept in mind that a single magnetic parameter is often non-unique. Therefore, multiple parameters need to be determined before a proper interpretation can be made. A second drawback is that while the measurement in itself is comparatively rapid, its operator demand is substantial. With the proposed acquisition of a '2G' DC-SQUID magnetometer with 'in-line' alternating field (AF) demagnetization facilities, and facilities to induce anhysteretic and isothermal remanent magnetizations (ARM and IRM respectively) as well as their AF demagnetization, these disadvantages are overcome: it will be possible to determine various mineral-magnetic parameters automatically, thus maximizing instrument time with minimal operator attention. The requested instrumentation will upgrade the AF demagnetization equipment of the 'Fort Hoofddijk' laboratory to a state-of-the-art level. This pertains specifically to the paleomagnetic and magneto-cyclostratigraphic research carried out by the 'Fort Hoofddijk' group. The interpretation of the natural remanent magnetization (NRM) in rocks during stepwise progressive demagnetization forms the basis of any paleomagnetic study. The rock-magnetic parameters that can be derived from the IRM and ARM acquisition curves provide important constraints on the interpretation of paleomagnetic data as well. The instrumentation requested thus clearly serves a dual purpose. The diagnostic value of IRM and ARM acquisition curves for geoscientific purposes has very recently been enhanced considerably due to exciting developments in rock magnetism, in part resulting from research that was carried out in the Utrecht paleomagnetism group. This development in particular has spurred the motivation to aim for the requested 2G magnetometer, in addition to an advanced level of automation which is a major analytical advantage in itself. |
