Geological studies and thermal treatment of some Paleogene deposits in east Beni Suef region, Egypt

Abstract

Geological setting, facies characteristics, and geochemistry, including TGA (thermo-gravimetric analysis) of Paleogene deposits in east Beni Suef region (Egypt), were studied in the present work. Lithostratigraphically, the area consists of three rock units, arranged from oldest to youngest: Tarbul Member of Beni Suef Formation (Middle-Late Eocene), Maadi Formation (Late Eocene), and Gebel Ahmar Formation (Oligocene), this last formation registered for the first time in the east of Beni Suef area (Egypt). Seven microfacies types (F1–F7) were determined by the microscopic examination of the studied samples in low- to high-energy and shallow-subtidal marine conditions. The lithostratigraphic, petrological, and geochemical results revealed that the Eocene succession in the present area is composed mainly of carbonates as well as siliciclastics. The Oligocene Gebel Ahmar Formation consists mainly of silica and iron oxides. The enrichment of the rock units with iron oxides in the studied area, as well as the high proportions of trace elements such as Zr, Ba, V, and Sr, in particular in the Gebel Ahmar Formation, reflects the influence of the hydrothermal solutions during the Oligocene. TGA, which monitors weight changes during heating at a constant rate, was used to determine the thermal stability and volatile component content of the materials. The ferruginous sandstone of Gebel Ahmar Formation exhibits various decomposition phases when exposed to thermal influences, with TGA indicating an initial mass decrease starting at 61.8 °C. In contrast, the ferruginous limestone of the Maadi Formation shows a single-phase mass decrease between 650 and 875 °C.