International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Upper Jurassic–Lower Paleogene lithostratigraphy and facies development in the Al Hamadah al Hamra area (Libya)

Pages: 3 - 18

Authors: YOUSEF M. SHIREF, JOSEPH SALAJ

Abstract: The 1st sedimentary complex of the Triassic to Upper Jurassic (up to Oxfordian) was deposited after long continental period of the uppermost Permian to lowermost Triassic (=about 8 Myr). This large sedimentary complex is divided by three hiatuses; two of them short only situated in the Upper Triassic sediments and by one long, corresponding to the Upper Jurassic–Barremian. After sedimentation of the continental Aptian to Albian strata of the Kiklah Formation, a new large Cenomanian to Eocene shallow marine sedimentary cycle with many gypsum lagoonal passages was deposited. They are represented by the Qasr Tigrinnah Member (Upper Turonian–Coniacian) and the Thala Member (Santonian to Upper Campanian). On the top of the Thala Member a hardground formed under arid conditions of sedimentation. The Upper Campanian/Maastrichtian Al Gharbiyah Formation was deposited in warm but humid conditions confirmed by the Fe-oxides and glauconitic levels. The Al Gharbiyah Formation with three neritic Members: the Bi’r Bu al Ghurab, the Lawdh Allaq (alternating with the Bi’r Az Zamilah Pelagic Member) and the Tar Member is represented and situated below the Upper Paleocene Tabaqah Formation, a new name. The boundary between the Maastrichtian and Danian is defined by last occurrence of Omphalocyclus macroporus Lamarck and by appearance of the Postrugoglobigerina daubjergensis (Broennimann) and Eoglobigerina danica (Bang). The Shurfah Formation is represented at its base by lagoonal sediments, higher up by pelagic chalky limestones and by the neritic Ammur Limestones at the top. The Kheir Formation and Gir Formation of the Ypresian and the Gedari Formation of the Lutetian are proved by planktonic foraminifers.

Keywords: Libya, Ghadames Basin, Jurassic-Paleogene, paleogeography, biostratigraphy, foraminifers

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