Abstract

Detailed study of the foraminifera and calcareous nannofossils in the Abu Gharadig wells, from the Paleocene to Middle Eocene limestones of the Apollonia Formation and the Late Eocene to Oligocene greenish-gray shale of the Daba"a Formation has led to the recognition of 21 planktonic foraminiferal zones and 17 calcareous nannofossil biozones. Two prominent major gaps are recognized within the Paleocene, which include (a) The basal hiatus cover most of the Early Paleocene (NP1 to NP2 nannofossil Zones) which corresponds to absence of planktonic foraminiferal zones of P0, Pα, P1a & lowermost part of P1b b) The second hiatus comprises mainly Late Paleocene (NP6 to NP7/8 nannofossil Zones)) which corresponds to absence of planktonic foraminiferal Zone of P4. The Paleocene sediments of the wells AG-32 and AG22 are attributed to nannofossil zones NP3 to NP5 equivalent to the planktonic foraminifers zones of P1c to lowermost part of Zone of P4. Whereas nannofossils Zone NP9 is equivalent to the planktonic foraminifers Zone of P5. These hiatuses are thought to be related to eustatic sea-level falls as well as to compressional tectonic phases. The Eocene/Oligocene boundary in terms of foraminifers and calcareous nannofossils, appears to be complete, it occurs within the lowermost part of Daba'a formation in the studied wells and could be placed at extinction of Late Eocene index fossil of Turborotallia cerroazulensis, and Turborotalia cunialensis followed by a significant size reduction of the genus Pseudohastigerina and the extinction of the hantkeninids (Hantkenina alabamensis), which mark the Eocene/Oligocene boundary