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Campanian–Maastrichtian foraminiferal stratigraphy and palaeoenvironment of the Lower Tar Member in the Wadi Tar section, Western Sirte Basin (Libya)

Tshakreen S. O., Gasiński M. A., Machaniec E., Mącznik A.

Annales Societatis Geologorum Poloniae

2017

Vol. 87, No. 4

349--362

Upper Campanian–Maastrichtian sections on the western flank of the Hun Graben in the Western Sirte Basin (WSB) are displaying two major type facies based on the foraminiferal assemblages. The first one indicates open-marine to outer-shelf conditions, and is represented by numerous bathy-pelagic planktonic foraminiferal species referable to the Radotruncana calcarata, Globotruncana aegyptiaca and the lower part of the Gansserina gansseri Zone (all late Campanian).The second type facies indicates an inner-shelf environment and is represented in the middle-upper part of the Gansserina gansseri Zone (early Maastrichtian) and Racemiguembelina fructicosa (late Maastrichtian) dominated by epi-pelagic planktonic and large benthic foraminifers. Large benthic foraminiferal index species Siderolites calcitrapoides Lamarck and Omphalocyclus macroporus (Lamarck) occur in abundance by the middle–late Maastrichtian. Correlation between planktonic foraminiferal zonation and large benthic foraminiferal zonation is given. An open-marine to outer-shelf environment passed into shallower marine conditions during the late Campanian–early Maastrichtian to late Maastrichtian, then a slight deepening and again shallowing is noticed.

Cretaceous-Paleogene boundary problem in Libya: the occurrence of the foraminiferal species Abathomphalus mayaroensis (Bolli) in the Western Sirt Basin

Tshakreen S. O., Gasiński M. A.

Geological Quarterly

2004

Vol. 48, No 1

77-82

The position of the K/P boundary in wells in the Western Sirt Basin of Libya is problematic. The biostratigraphic definition of the K/P boundary in the subsurface is based on the extinction of the eponymous taxon of the standard latest Maastrichtian foraminiferal Abathomphalus mayaroensis Zone. We have unambiguously recognised this taxon from the Sirt Basin subsurface sections for the first time. All the latest Maastrichtian foraminiferal assemblages are dominated by planktonic foraminiferids. Some of specimens are pyritised, indicating organic flux to the basin floor, causing oxygen deficiency in the depositional environment. The occurrence of characteristic bathypelagic and some epipelagic species indicates that the environment of deposition is outer shelf–middle continental slope.