Determination of Paleointensity of Geomagnetic Field on the Red Sea Basalts by the Thellier–Coe Method when Heating in Argon and Air

The paleointensity of geomagnetic field was determined by the natural residual magnetization of Holocene basalts from the Red Sea rift zone using the Thellier method in the Coe modification when heating in air and argon. It was shown that when basalts are heated in air, mineralogical changes occur in titanomagnetite, the carrier of residual magnetization, at temperatures that are 50–100°C lower than the maximum blocking temperature, which complicates the determination of paleointensity. It has been established that carrying out the Thellier–Coe procedure in argon allows avoiding the oxidation of titanomagnetite and thus significantly improving the quality of paleointensity determination. When heating in air, only 50–60% of the natural residual magnetization can be used to calculate paleointensity, while when heating in an argon environment, up to 87% can be used, with the quality factor being 1.5–3 times higher. The calculated value of paleointensity determined by heating in argon is 10–20% lower than by heating in air. The paleointensity of 62±1 μT obtained for the Red Sea basalts turned out to be approximately 1.7 times higher than the modern field in this region according to the IGRF13 model. The high value of paleointensity allows us to attribute the formation period of the studied basalts to the time of the Levantine Iron Age Anomaly of 1.5–0.5 thousand years BC.