THE CENOMANIAN-TURONIAN OCEANIC ANOXIC EVENT OAE2 (BONARELLI EVENT) IN SOUTHERN TETHYS: PALYNOLOGICAL AND GEOCHEMICAL APPROACH, ABU GHARADIG BASIN, EGYPT

The sediments, palynological, total organic carbon (TOC), stable carbon and oxygen isotopes (δ13C, organic) of the Upper Cretaceous (Cenomanian-Turonian) Bahariya and basal Abu Roash formations at the southern Tethys margin were studied in two deep wells (AG-5 and AG-13), Abu Gharadig oil field, North Western Desert, Egypt. Some of the marine (dinoflagellate cysts) as well as the terrestrial (spores and pollen grains) palynoflora reveal extinction and origination patterns that are known elsewhere, although other species may be survived across the Cenomanian-Turonian boundary. This implies an influence control of global changes on the palynoflora, i.e., impact of Oceanic Anoxic Event OAE2 (Bonarelli Event), rather than changes in the local environmental conditions. The basal part of the Abu Roash Formation, 'G' Member (late Cenomanin) shows a positive δ13C excursion of the organic fraction. The TOC is generally high between 2.20 and 3.04 % in the lower Abu Roash Formation: organic-rich shale of 'G' and carbonates of 'F' members (late Cenomanian and early Turonian respectively), which indicates that these two members are the main Cretaceous source rocks in the Abu Gharadig Basin and have a type I-II kerogen composition. They are distinguished by abundance of amorphous organic matter AOM and Chlorococcalean algae, mainly Pediastrum and Scenedesmus along with subordinate dinoflagellate cysts and terrestrial palynomorphs.