ON THE PALYNOLOGY AND STRATIGRAPHY OF THE NUBIAN SANDSTONE IN LIBYA AND EGYPT

The so-called Nubian Sandstone outcrops along a wide area from Algeria to the Red Sea. It forms two regressive phases. The lower is represented in Egypt by the Basal Clastic Unit and the Desert Rose Unit. In Libya it is represented by the Mesak Sandstone, Sarir Sandstone, Cabao Sandstone and Kiklah Formation. Both successions are covered by a carbonate sequence, resulting from the Tethyan transgression during the Cenomanian. In Egypt however, the upper regressive phase is represented by the Taref Sandstone which was deposited during a brief period of active progradation, following the Tethyan incursion. This is not observed in Libya.

Comparison of palynological studies in Libyawith those documented by Penny (1986) and Schrank (1992) in Egypt reveals many similarities. The Basal Clastic Unit, dated as Hautrauvian-Barremian, may be equivalent, at least to a part of the Neocomian Cabao Sandstone in NW Libya. Jarmah Member of the Mesak Formation was dated as Berriasian on the basis of Pilosisporites and Trilobosporites.The Matruh Shale was assigned to the Aptian by Penny (1986) on the basis of Tricolpites, and the Abu Balls Formation as Aptian-Albian by Schrank (1992) on the basis of Tricolpites and Rousisporites radiatus. Whereas, there is no equivalent to the Aptian in NW Libya, the Aptian-Albian of Egypt is similar to Zone 1 of the Kiklah Formation and As Sarir Sandstone, which were dated as early Albian on the basis of Afropollis spp., and Perotriletes pannuceus, an Albian element not recorded in Egypt. The Plant Beds were dated as Cenomanian by Schrank (1992) on the basis of advanced angiosperm pollen. In Libya, equivalent bodies were considered Vraconian, representing the uppermost Albian, because it lacks Cenomanian pollen (e.g. Tricolpites mutabilis).

Comparison of local sea-level changes with global sea-level curves is used to reconstruct paleogeography. Integration of palynology with geological data and tectonic implications indicates that, despite similarity in paleogeographic processes of the Nubian Sandstone, geological and structural settings remain different. The “Nubian Sandstone” provides a typical succession that can be studied in the light of sequence stratigraphy.