Contributions to the Petrology of Upper Cretaceous of El Duwi Formation at Gabal El Galala El Qibliya area, North Eastern Desert, Egypt

Abstract

The Upper Cretaceous succession exposed at Saint Anthony , Saint Paul, and Wadi El Dakhl areas was measured and studied in detail. The studied sequence is subdivided lithostratigraphically, into the Galala Formation (Cenomanian-Early Turonian), Wata Fotrmation (Late Turonian), El Duwi Formation (Coniacian-Santonian), and Sudr Chalk (Campanian-Maastrichtian), Esna Shale (Paleocene-Early Eocene) and Thebes Formation (Early Eocene). The examined rock units in Gabal El Galala area include El Duwi Formation and Sudr Chalk were studied lithostratigraphically, petrography, mineralogy, geochemistry, radioactivity and tectonic setting. On the other hand, the major and trace elements were focused on the studied rock units. The Upper Cretaceous exposures in southeastern Galala represented by Carbonate – dominated successions inter-bedded with shale, a few sandstone beds, and marl horizons and capped by Sudr chalk. The average chemical compositions of the shale from the study area are (33.37-59.55%) for SiO2, (6.51-16.49%) for Al2O3, (1.07-2.33 %) for CaO, (1.16-2.09%) for MgO, (0.99-3.10%) for Na2O, (0.45-1.6%) for K2O, (1-2.86%) for P2O5, (5.37-8.865%) for Fe2O3, (31-791 ppm) for Rb, (291-1500 ppm) for Zr, (331-2834 ppm) Sr, (15-61 ppm) for Ga, (89-711 ppm) for V and (9-45 ppm) for U. Detailed environmental scanning-electron microscope (ESEM) study was carried out on the shale and Chalk. This study appears the characterization of the assembly as pyrite, gypsum and jarosite. The tectonic setting reveals that the shale and chalk of the upper Cretaceous in El Duwi Formation were originated from greywacke in active continental margin area.