Paleomagnetic study of the Paleocene-Eocene Tarawan Chalk and Esna Shale: Dual polarity remagnetizations of Cenozoic sediments in the Nile Valley (Egypt)

A paleomagnetic study of the Paleocene-Eocene Esna Shale and Tarawan Chalk at the Dababiya and Qreiya sections near Luxor in central Egypt reveals stable normal and reverse polarity magnetizations. However, these (neritic) pelagic marine sediments have evidently been remagnetized because 1) the stable magnetizations are carried by hematite with no evidence of a primary magnetic mineral like magnetite, 2) the magnetic polarity stratigraphy is not consistent between the sections and with patterns expected from global magnetobiostratigraphic time scales, and 3) the directions correspond to late Cenozoic directions and are far from expected early Cenozoic reference directions for Africa. Our interpretation suggests that reported paleomagnetic results from other Cenozoic sediments from the Nile Valley suffered a similar fate. We suggest that the remagnetization may be associated with weathering and fluid flow during Neogene uplift and rifting in the formation of the early Nile Valley.