The use of archaeomagnetism to answer archaeological and geomagnetic questions with particular focus on determination of the strength of the geomagnetic field In the Middle East during the Bronze Age

摘要

The principles of archaeomagnetism can be applied to answer archaeological and geomagnetic questions and examples of both are presented in this thesis. Firstly, this thesis demonstrates the use of archaeomagnetism to establish the maximum palaeotemperature reached in a kiln at the Oylum Höyük archaeological site in Turkey. A maximum temperature of between 600 and 700 °C was determined confirming that the feature was more likely to have been a lime kiln than a bread oven. Archaeomagnetism was next used to determine the relative ages of different construction events on the St Jean Poutge archaeological site in Southern France. The results of archaeointensity experiments on 137 core samples taken from bricks and tiles confirmed the different relative ages of two construction events. Average intensity values determined using Thermal Thellier-Thellier methods were 56±7 and 58±8 for the 2nd Century AD and 68±6 and 68±7 for the 3rd Century AD. There is an increasing body of evidence that the geomagnetic field in the Middle East during the Bronze Age reached exceptionally high field values extremely quickly. Both archaeomagnetic jerks (marked by sharp cusps in geomagnetic field direction coinciding with intensity maxima) and geomagnetic spikes (where the field rises and falls over a period of less than 30 years with associated virtual axial dipole moment fluctuations of at least 70 ZAm2 /~38 µT) have been proposed to have occurred in the Middle East between 3000 BC and 0 BC. Here, Coe and IZZI method archaeointensity experiments were carried out on 154 Bronze Age pot sherds from two archaeological sites in Turkey, Tell Atchana and Kilise Tepe, and 2 archaeological sites in Cyprus, Marki Alonia and Bellapais Vounous. In addition, thermal Thellier experiments were conducted on 18 mud brick cores from Tell Atchana. The results of these experiments were corrected for cooling rate whilst experimental design mitigated the effects of anisotropy. A success rate of 56% was recorded overall. The effects of applying cooling rate corrections, anisotropy corrections and the impact of varying archaeointensity selection criteria cut-off values, on the results, are discussed in this thesis. An average field value of 47µT was determined for Turkey over the time period ~2200-~700 BC which is indistinguishable from the current average field value. An archaeointensity value of 84 µT (153 ZAm2) was measured for the time period 800-600 BC. This is consistent with data from other authors who found evidence of high geomagnetic field intensity in the Middle East around 1000 BC. It is proposed here that this geomagnetic intensity high was of a longer duration and felt over a wider geographic area than has previously been suggested. Contrary to previously published studies based in Syria, evidence is presented here of decreasing geomagnetic field intensity in Cyprus between 2400 BC and 1900 BC. The proposal that an archaeomagnetic jerk was experienced in Cyprus over this time period is therefore rejected.