Cenozoic and Mesozoic basalts from Egypt: a preliminary survey with a view to paleointensity

Abstract

Abstract Numerous phases of igneous activity took place in Egypt during the Mesozoic and the Cenozoic but no paleointensity results have ever been published from these rocks. Therefore a preliminary survey was conducted in the northern part of Egypt and in Sinai to test the suitability of these basalts for paleointensity determinations. Three Oligo-Miocene sites have been sampled north of Cairo: Abu Zaabal, Qatrani, and 6th of October City. In Sinai, we sampled Jurassic basalts in Wadi Budra and Oligo-Miocene rocks from Wadi Nukhul. The main magnetic carriers of these rocks are titanomagnetites with varying Ti content. Large secondary components are present in most middle Jurassic basalts and discrepancies remain in the directional analysis so this sill cannot be used for paleointensity experiments and the associated poles should not be considered for paleomagnetic reconstructions either. Directional analysis of the Oligo-Miocene basalts is very straightforward and updated mean VGPs have been calculated from the Cairo area (68.9°N, 91.3°E; Kappa = 274; A95 = 3.7) and from Wadi Nukhul (72.7°N, 13.4°E; Kappa = 528; A95 = 5.4). Pseudo-paleointensity results obtained as well from stable Egypt as from Sinai are promising, with values lower or similar (between 29 to 58 μT) to present-day field intensity.