抄録
Shales in the upper Cretaceous-lower Tertiary in Egypt including the middle Campanian Qusseir Formation, the late Campanian-early Maastrichtian Duwi Formation, and the Masstrichtian-Danian Dakhla Formation show variable distribution of clay minerals. Duwi shales have higher smectite (85%) and lower kaolinite contents (15%) compared to Qusseir and Dakhla shales that have higher kaolinite (65 and 45% respectively) and lower smectite contents (35 and 55% respectively).
Chemical analyses indicated that these rocks were derived from the same source, the Pre-Cambrian igneous rocks located in the south and southern east of Egypt, and there is no relation between clay minerals distribution and sea level changes and depositional environments. The change in the clay mineral assemblage is attributed to climatic changes. Duwi shales are formed under and to semiarid conditions while variegated and Dakhla shales are formed under humid and tropical conditions. Therefore, the climate changed from tropical to and and then back to tropical during the upper Cretaceous-lower Tertiary in Egypt.
