Upper Campanian-Maastrichtian calcareous nannoplankton biostratigraphy and paleoecology in Wadi Qena, Eastern Desert, Egypt

摘要

The Upper Campanian/Maastrichtian calcareous nannofossils from the Hawashiya and Umm Omeiyied exposed sections at Wadi Qena, have been examined. The studied interval is represented by the Sudr Formation. This formation rests uncomfortably on the Upper Campanian Rakhiyat Formation and is uncomfortably underlain by the Paleocene Dakhla Formation. The studied calcareous nannofossils assemblage is highly diverse and comprises mostly of well-preserved specimens. The assemblages include abundant Watznaueria spp., Arkhangelskiella spp., and Micula spp., in addition to many other taxa. Both studied sections are divided into seven calcareous nannofossils biozones that cover the Upper Campanian-Maastrichtian interval, respectively, the biozones from older to younger: (UC15e/CC22, UC16/CC23a, UC17/CC23b, UC18/CC24, UC19/CC25a, UC20a/CC25b, and UC20b/CC25c) biozones. The paleoecological analysis of calcareous nannofossils in the studied interval depended on a set of statistical indices like the total number of nannofossils, abundance, diversity, fertility, and productivity of the calcareous nannofossils. In addition, some species of calcareous nannofossils are selected to determine cycles of temperature fluctuations in the water surface that ranged between cold and warm. The paleoenvironmental analysis emphasizes the significance of some indicator nannofossil taxa in the reconstruction of the productivity model in the Tethyan Realm, during the Upper Cretaceous times.