Paleointensity results from the mid Jurassic: Submarine basaltic glasses of ODP Site 801C
Abstract
Tremendous effort has been put into determination of the intensity behavior of the ancient geomagnetic field yet the details, particularly in the more distant past remain poorly constrained. Submarine basaltic glass has been shown to be nearly ideal material, rock magnetically speaking, for determining absolute paleointensity because it contains single domain magnetite, formed during the rapid quenching of basaltic melt in sea water. There were 38 glass occurances reported in 400 m of tholeiite at ODP Hole 801C. We prepared a total of 73 specimens from 17 samples and subjected them to the IZZI version of the absolute paleointensity experiment. Results from six samples (with a total of 18 specimens) that met our minimum reliability criteria had an average value of 12.8 ± 3 μT. This translates to a value for the virtual axial dipole moment of 32.8 ZAm2. These values are somewhat lower than values obtained from plagioclase crystals from three samples from 801C reported by Tarduno and Cottrell (2005). The latter were not obtained from the same cooling units. Taken together, the two data sets point to very low field strengths for the ~160 Ma lavas at Site 801. Tarduno, J.A. and Cotrrell, R.D., Dipole strength and variation of the time-averaged reversing and nonreversing geodynamo based on Thellier analyses of single plagioclase crystals, J. Geophys. Res., 110, doi:10.1029/2005JB003970, 2005.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGP43A1043T
- Keywords:
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- 1521 GEOMAGNETISM AND PALEOMAGNETISM / Paleointensity