In paleomagnetism, periods of high field intensity have been largely ignored in favor of the more spectacular directional changes associated with low field intensity periods of excursions and reversals. Hence, questions such as how strong the field can get and how fast changes occur are still open. In this paper we report on data obtained from an archaeometallurgical excavation in the Middle East, designed specifically for archaeomagnetic sampling. We measured 342 specimens from 72 samples collected from a 6.1 m mound of well stratified copper production debris at the early Iron Age (12th-9th centuries BCE) site of Khirbat en-Nahas in Southern Jordan. Seventeen samples spanning 200 yr yielded excellent archaeointensity results that demonstrate rapid changes in field intensity in a period of overall high field values. The results display a remarkable spike in field strength, with sample mean values of over 120 μT (compared to the current field strength of 44 μT). A suite of 13 radiocarbon dates intimately associated with our samples, tight control of sample location and relative stratigraphy provide tight constraints on the rate and magnitude of changes in archaeomagnetic field intensities.
Bibliographical noteFunding Information:
We thank Jason Steindorf for many of the measurements, Amotz Agnon and Jeff Gee for their comments and Dr. Fawwaz al-Khraysheh, Director General, Department of Antiquities of Jordan for his support of the archaeological field work. Paleomagnetic and rock magnetic measurements were done primarily at the paleomagnetic laboratories of SIO with ATRM and TRM acquisition studies being done at HUJI. This study was supported by the US–Israel Binational Science Foundation Grant No. 2004/98 , NSF grant EAR0636051 and the US–Israel Educational Foundation Fulbright Grant for Ph.D. students 2006–2007.
- Iron Age
- copper slag
- secular variations