Paleomagnetic Laboratory Specifications
- 3-Axis superconducting (SQUID) magnetometer
Manufactured by SCT with electronics by 2G Enterprises, Mountain View, CA.
Operates at liquid helium temperature −269°C (4 K).
One of the most sensitive in the world (required for measuring carbonates and coal).
Measures remanence intensities as weak as 2 × 10 – 9 emu/cm3.
Computerized, with graphical interface for real-time data analysis.
- Magnetically shielded room
Magnetometer & demagnetization equipment are housed inside a magnetically shielded room.
Ambient magnetic field inside shielded room is < 0.5% of the Earth's magnetic
Minimizes acquisition of viscous remanent magnetization (VRM) for enhanced signal-to-noise ratio.
Required for accurate analysis of magnetite-bearing lithologies, like gray carbonates and sandstones.
- Thermal demagnetization equipment
large-capacity, 3-zone electrical furnace (non-inductively wound); thermal
gradient < 5°C.
Controlled by 3 thermocouples; monitored by a 4th thermocouple nested among the samples.
Allows batches of 100 specimens to be thermally demagnetized in a single run.
Demagnetization temperatures from 100° to 700° C.
Separate cooling chamber, with ambient field < 2 nT; cooled with forced air.
Conventional Schonstedt TSD-1 thermal demagnetizer for small batches of "pilot" samples.
- Alternating field demagnetization equipment
3-Axis, tumbling AF specimen demagnetizer manufactured by SCT, Mountain View, CA.
Reversing motor, for minimizing acquisition of rotational remanent magnetization (RRM).
Peak fields from 25 to 1,500 Oersteds (2.5 to 150 mT).
- Chemical demagnetization equipment
Apparatus for chemical demagnetization using strong reducing solutions
under partial vacuum.
- Magnetic susceptibility equipment
Bartington MS2 susceptibility meter and MS2B probe.
Resolution 2 × 10 – 7 cgs.
Used for determining magnetic mineralogy and grain-size distribution.
Peak fields up to 1.8 T.
Imparts saturation isothermal remanence (SIRM) to magnetite and pyrrhotite-bearing specimens.
Thermal demagnetization of "composite IRM" permits identification of magnetite, maghemite, pyrrhotite, greigite, hematite, goethite.
- Custom software for analysis of paleomagnetic data
Least-squares lines (principal component analysis) algorithm of Kirschvink (1980).
Principal component analysis algorithm of Onstott (1980).
Modal analysis algorithm of Van Alstine (1980).
Plotting of stereonet and rose diagrams using programs written in MATLAB environment.
- Quality Assurance Program
All measurements traceable to U.S. National Bureau of Standards and to our own reference samples.
Reference samples checked against 3 different magnetometers at other paleomagnetic laboratories.
Sample rotations permit fourfold redundancy in remanence measurements.
All data analysis and reporting by senior personnel.