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Are burnt sediments reliable recorders of geomagnetic field strength?

Published online by Cambridge University Press:  20 January 2017

Manuel Calvo-Rathert*
Affiliation:
Departamento de Física, EPS, Universidad de Burgos, Av. de Cantabria, s/n, 09006 Burgos, Spain
Ángel Carrancho
Affiliation:
Departamento de Física, EPS, Universidad de Burgos, Av. de Cantabria, s/n, 09006 Burgos, Spain
Florian Stark
Affiliation:
Geomagnetism Laboratory, School of Environmental Sciences, University of Liverpool, UK
Juan José Villalaín
Affiliation:
Departamento de Física, EPS, Universidad de Burgos, Av. de Cantabria, s/n, 09006 Burgos, Spain
Mimi Hill
Affiliation:
Geomagnetism Laboratory, School of Environmental Sciences, University of Liverpool, UK
*
*Corresponding author. Fax: + 34 947 259349. E-mail address:mcalvo@ubu.es (M. Calvo-Rathert).

Abstract

This study tests if burnt soils and sediments can provide reliable records of geomagnetic field strength at the time of burning by carrying out an experiment to reproduce the prehistoric use of fire on a clayish soil substratum. Rock magnetic experiments showed that in the upper 0–1 cm of the central part of the burnt surface, remanence is a thermoremanent magnetization carried by single-domain magnetite and that samples are thermally stable. Fourteen specimens from that area were subjected to paleointensity experiments with the Coe method (1967). An intensity of 42.9±5.7 μT was estimated below 440°C, whereas at higher temperatures magneto-mineralogical alterations were observed. Corresponding successful microwave intensity determinations from two specimens gave a mean value of 47.6 μT. Both results are in reasonable agreement with the expected field value of 45.2 μT. Burnt soils of archeological fires thus have the potential to record accurately the paleofield strength and may be useful targets for archeointensity investigations. Coincident results obtained from two different paleointensity determination methods support this conclusion.

Type
Short Paper
Copyright
University of Washington

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