Nannofossil biostratigraphy of the Paleocene-lower Eocene succession in the Thamad area, east central Sinai, Egypt

Abstract

In the Thamad area, east central Sinai, two stratigraphic sections are measured and sampled; Gebel El Mishiti and G. El Keeh, in order to determine the nannofossil biostratigrapy of the Paleocene-lower Eocene rocks. Gebel El Mishiti section is considered one of the most complete sections across the K/P boundary in Egypt where all the exposed rocks at G. El Keeh belong to the lower Eocene Egma Formation. A nearly complete sucession of Paleocene nannofossil biozones is recorded from the Esna Formation at G. ElMishiti. They are arranged from base to top as follows: Markalius inversus (NP1), Cruciplacolithus tenuis (NP2), Chiasmolithus danicus (NP3), Ellipsolithus macellus (NP4), Fasciculithus tympaniformis (NP5), Heliolithus kleinpellii (NP6), Discoaster mohleri (NP7/8) and Discoaster multiradiatus (NP9) zones.The Danian/Selandian boundary is located at the base of Zone NP5 at the level of the first appearance of Fasciculithus taxa. TheSelandian/Thanetian boundary can be traced tentatively at the base of the Discoaster mohleri Zone (NP7/8). The Paleocene/Eoceneboundary is traced between the NP9a/NP9b subzonal boundary which is marked by the first appearances of Discoaster araneus, Rhomboaster calcitrapa, R. bitrifida and R.cuspis. The Paleocene /Eocene boundary lies within the upper part of the Esna Formation.A very thin layer of conglomeratic chalk with no paleontological break is located between Zone NP9 and NP10. However, a veryshort nannofossil break is noted within Zone NP10 (subzones NP10b and NP10c are missing) which is overlain by Zone NP11. The lower part of the latter covers the topmost part of the Esna Formation where its upper part lies within the base of the Egma Formation; therefore, a conformable relationship between the two formations is suggested. At Gebel El Mishiti, the lower Eocene nannofossil biozones NP11, NP12, NP13 and lower/middle Eocene Zone NP14 are recorded. On the other hand, Gebel El Keeh section, which is about 95m thick is only represented by the Discoaster sublodoensis Zone (NP14).

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