Paleo-tectonic positions of Northeast Africa during Cretaceous–Paleocene: Paleomagnetic study on East Gilf Kebir Plateau basalts [59Ma], Southwestern Desert, Egypt

摘要

The middle/late Paleocene basalts which cover the Late Cretaceous sandstone in the East Gilf Kebir Plateau were sampled for paleomagnetic investigation. The progressive thermal demagnetization revealed that?The hematite component was parallel to the present-day field and the goethite overprint. Its pole is considered as representing recent low-temperature martitization of the magnetite upon exposure to intensive chemical alteration.?The magnetite-anchored component was N–S dual-polarity with shallow equatorial inclinations. Based on its overwhelming existence, this component was considered as the characteristic remanence of the sampled basalt. Its north pole (71.7°N/203.5°E) was considered as representing the geomagnetic field during the eruption of the basalt.The reliability of the East Gilf Kebir basalt (59±1.7Ma) pole was constrained by its comparison with synchronous poles rotated from the main tectonic units using Euler Pole rotation. This basalt pole places NE Africa, along its present N–S azimuth at a far south tropical paleo-latitude. Cairo [30°N], was at paleo-latitude 11.8°N in middle/late Paleocene (59Ma), that is about 18° south to its present-day latitude.Comparing the present pole with the Mansouri ring complex (132±10Ma) Early Cretaceous pole (47°N/259°E) and two poles from the Wadi Natash volcanic field; the alkali basalt (104±7Ma) Middle Cretaceous pole [55°N/250°E] and the trachyte/Phonolite (86–78Ma) Late Cretaceous pole [66.5°N/229°E], a Cretaceous–Paleocene segment [132–59Ma] of the Apparent Polar Wander Path [APWP] of Africa could be traced. These poles can, concurrently, verify the paleo-azimuth and paleo-latitude evolution of the African plate during the Cretaceous and Paleocene.