Abstract
Abstract Geomagnetic field variations at archeomagnetic timescales can be obtained from well-dated heated structures and archeological potsherds. Here, we present the first archeointensity results obtained on Portuguese ceramics (1550 to 1750 AD) collected at Brazilian archeological sites. The results are compared to those obtained from Western Europe and currently available geomagnetic field models. Continuous thermomagnetic and IRM acquisitions curves indicate that Ti-poor titanomagnetite is responsible for the remanence in these ceramic fragments. Five fragments (24 samples) out of twelve analyzed yielded reliable intensity estimates. The row archeointensity data were corrected for TRM anisotropy and cooling rate effect. The mean dipole moments are obtained for three different age intervals: 1550±30 AD, 1600±30 AD and 1750±50 AD. Mean intensities vary from 37.9±4.2 μT to 54.8±7.6 μT in agreement with the previously reported data for 1550 AD and 1750 AD. Relatively weaker, but still highly dispersed, values were obtained for 1600 AD ceramics.
Highlights
The variations of the Earth’s magnetic field at archeomagnetic timescales (102 to several 103 of years) can be obtained from well-dated heated structures and archeological potsherds
Directional and intensity data obtained from these materials have been used to produce reference curves for the past few millennia
Reference curves, which reveal the variations in the intensity of the geomagnetic field are available for several regions, including North America, Meso-America, Eastern Asia, Eastern and Western Europe (e.g., Kovacheva, 1997; Yu et al, 2000; Morales et al, 2001; Bowles et al, 2002; Genevey et al, 2003; Soler-Arechalde et al, 2006; see the compilations of Valet, 2003; Perrin and Schnepp, 2004; Korte et al, 2005)
Summary
The variations of the Earth’s magnetic field at archeomagnetic timescales (102 to several 103 of years) can be obtained from well-dated heated structures and archeological potsherds. Reference curves ( called master curves), which reveal the variations in the intensity of the geomagnetic field are available for several regions, including North America, Meso-America, Eastern Asia, Eastern and Western Europe (e.g., Kovacheva, 1997; Yu et al, 2000; Morales et al, 2001; Bowles et al, 2002; Genevey et al, 2003; Soler-Arechalde et al, 2006; see the compilations of Valet, 2003; Perrin and Schnepp, 2004; Korte et al, 2005). Archeointensity data for Western Europe are concentrated on archeological sites from France (e.g., Chauvin et al, 2000; Gallet et al, 2002; Genevey and Gallet, 2002; Gallet et al, 2005) while only few results are available for the Iberian Peninsula (Kovacheva et al, 1995; Gomez-Paccard et al, 2006). The principal aim of this study is to try to contribute
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