Decadal to millennial scale archaeointensity variations in the Levant
Abstract
Recovering the absolute intensity of the past geomagnetic field (paleointensity) is a fundamental effort in the paleomagnetic research, but it is a complicated task. Paleointensity experiments should be carefully designed using sufficient number of specimens, and accurate correction for remanence anisotropy, cooling rate effects, and non-linear TRM (NLT). In addition, the basic assumption of the paleointensity method - a stable thermoremanent magnetization carried by single domain like particles - is hard to test using non-destructive methods. As a result, the interpretation of the paleointensity experiments can be non-unique and ambiguous. Moreover, the experimental difficulties compound with dating uncertainties related to the studied materials. We address each of these difficulties in an effort to construct a high resolution paleointensity curve of the Levant on archaeological time scales (archaeointensity). To address the experimental issues we apply the Thellier-type IZZI protocol with additional anisotropy, cooling rate, and NLT corrections. To ensure consistency, comparability, and objectivity of the interpretations we apply an automatic data analysis technique using an open code computer program (PmagPy Thellier GUI). To account for ambiguous interpretations we make the raw data, which include thousands of specimens, available in the MagIC database to allow other researchers to re-interpret and compile the datasets. Here we present the current status of the Levantine archaeointensity curve, and discuss its implication on our understanding of geomagnetic secular variations. The Levantine dataset includes mostly data from slag deposits - industrial heaps of metallurgic slag, and archaeological mounds ('Tel') - stratified sites created by cities rebuilt on top of others. The two types of records complement each other in a constructive fashion. The slag deposits provide records in a decadal resolution, while the mounds offer centennial to millennial scale resolution. In this contribution we report new data from Tel Megiddo, Israel (also known as Armageddon). We investigate 14 strata in Megiddo from the Early Bronze Age (ca. 3000 BCE) to the Late Iron Age (ca. 730 BCE). Five to ten potsherds samples from each stratum were analyzed for paleointensity. In addition, five in-situ furnaces were analyzed for a full-vector analysis. The new results demonstrate variations that range from relatively weak field corresponding to a virtual axial dipole moment (VADM) of less than 60 ZAm2 to VADM of more than 160 ZAm2. The prominent features in this dataset are two local minima at ca. 3000 BCE and ca. 2000 followed by a steady increase to a maximum at ca. 1000 BCE.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGP41B1121S
- Keywords:
-
- 1521 GEOMAGNETISM AND PALEOMAGNETISM Paleointensity;
- 1522 GEOMAGNETISM AND PALEOMAGNETISM Paleomagnetic secular variation;
- 1503 GEOMAGNETISM AND PALEOMAGNETISM Archeomagnetism