Basin Evolution and Geochemical Modeling
Tectonic evolution of the Mesozoic / Cenozoic of North Africa
Postdoctoral Research by Dr Gianluca Badalini
Introduction:
This summary on the tectonic Mesozoic and Cenozoic evolution of North Africa has been compiled from a large number of papers, the most relevant of which are listed below.
The Mesozoic and Cenozoic evolution of the North Africa domain was controlled by the Late Permian and Mesozoic break-up of Pangaea and intraplate stresses, resulting in the opening of oceanic basins forming the Western Tethys, and by the convergence and suturing of Africa-Arabia with Eurasia during the Late Cretaceous and Cenozoic Alpine orogenic cycle (Ziegler and Roure, 1999).
The Permian-Recent tectonic cycle was characterized by a phase of regional extension, leading to the development of a series of rifts along what was to become the eastern margin of the Atlantic and the southern margin of the Tethys Ocean (Mengoli and Spinicci, 1985; Guiraud, 1998). Beginning with the initial break-up of Gondwana in the Permo-Triassic, this resulted in the formation of the present-day African continental margins and a series of intra-continental rift basins, located mainly on older (Late Proterozoic) shear zones (Janssen et al., 1993).
Along the northern African-Arabian plate margin rifting propagated westward from the northeastern Arabian margin to Morocco during the Permian and Triassic, and was accompanied by Mid-Late Triassic-Earliest Liassic extensive alkaline flow basalts (Guiraud, 1998). Rifting continued during the Liassic, and spread to the eastern Mediterranean around the Middle Jurassic (Dixon and Robertson, 1984). Spreading was consequently initiated in the Middle and Late Jurassic in the Atlantic and western Mediterranean and in the Early Cretaceous in the eastern Mediterranean (McGregor and Moody, 1998). A trend of Mesozoic passive margins and failed rifts was thus created extending from the Moroccan margin through the Atlas and Pelagian Basins to the Abu Gharadiq Basin in Egypt (Awad, 1984; Keeley and Massoud, 1998).
Epeirogenic warping and locally significant faulting affected sedimentation in some basins of the Saharan Platform. The formation of the Saharan basins has been affected by several tectonic phases during the Phanerozoic, resulting in faulted-block terrain (Furon, 1963). Although subsequent neotectonics influenced the structural features of the basins, the orientation of the principal structural elements is inherited in part from the tectonic trends of the Precambrian basement (Burollet, 1967).
The Palaeozoic basins were buried beneath a Tethyan passive margin wedge of continental clastic deposits, evaporites and carbonates (Boote et al., 1998). The central and southern Saharan basins outcrop along a NNW-SSE uplifted zone that runs along the Ougarta range, the Hoggar and the Reguibat massifs, and also on the South Illizi homocline, with the Tassili Najjer among the largest Palaeozoic exposures (Deynoux, 1983). During the Early Mesozoic the eastern Saharan syncline, including the Trias, Oued el-Mya, and Ghadames Basins subsided rapidly (Makhous et al., 1997). This resulted in the accumulation of up to 4 km of marine and, in places, continental Triassic, Jurassic, and Cretaceous sediments. In the northern Ghadames and Oued el-Mya basins, which were uplifted at the end of the Early Carboniferous, Palaeozoic strata were stripped off before a post-Hercynian transgression (Burollet, 1967, Makhous et al., 1997). Restriction of the western Tethys basin and post-Hercynian subsidence along the margin of the African landmass led to a new cycle of sediment deposition, which included a thick series of Triassic and Liassic evaporates. This two-stage history influenced source rock and reservoir rock diagenesis (Makhous et al., 1997).
The Middle Jurassic and younger section on the stable Saharan platform is dominated by relatively
lagoonal dolomites, evaporates, and shales. Cretaceous sediments consists of alternating evaporates, limestones, dolomites, and thin layers of sandstone (Makhous et al., 1997). Aptian-Albian nearshore carbonate facies are oil bearing in Tunisia. Tertiary sedimentation is particularly present in Tunisia. Tertiary sedimentation was largely confined to the northern margin of the platform where the effects of collision between Africa and Eurasia were manifested in the Eocene through the Miocene by Atlassic inversion and subsequent Maghrebian (Rif-Tellian) thrusting and nappe emplacement (Ziegler, 1988).
The main Mesozoic and Cenozoic tectono-sedimentary events are summarised in figure 1.
References:
Awad, G. M., 1984, Habitat of oil in Abu Gharadiq and Faiyum basins, Western Desert, Egypt: AAPG Bull., v. 68, p. 564-573.
Boote, D. R., Clark-Lowes, D.D., Traut, M.W., 1998, Palaeozoic petroleum systems of North Africa, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., ed., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 132: p. 7-68.
Burollet, P. F., 1967, General geology of Tunisia: Guidebook to the geology and history of Tunisia, Petroleum Exploration Society of Libya, p. 51-58.
Deynoux, M., 1983, Late Precambrian and Upper Ordovician glaciations in the Taoudeni Basin, West Africa, in M. Deynoux, ed.: West African palaeoglaciations: characterization and evolution of glacial phenomena through space and time, Abstract Symposium Till Mauretania, p. 43-86.
Dixon, J. E., Robertson, A.H.F., ed., 1984, The geological evolution of the Eastern Mediterranean, v. 17: London, Geological Society, London, Special Publication.
Furon, R., 1963, Geology of Africa: Edinburgh, Oliver and Boyd, 377 p.
Guiraud, R., 1998, Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., ed., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 132: p. 217-229.
Janssen, M. E., Stephenson, R.A., Cloetingh, S., 1993, Changes in plate motions and their control on the subsidence of rifted basin in the African plate, in M. Thorweihe, Schandelmeier, H., ed., Geoscientific research in Northeast Africa, Rotterdam, Balkema: p. 185-188.
Keeley, M. L., Massoud, M.S., 1998, Tectonic control on the petroleum geology of NE Africa, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., ed., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 137: p. 265-281.
MacGregor, D. S., Moody, R.T.J., 1998, Mesozoic and Cenozoic petroleum systems of North Africa, in D. S. MacGregor, Moody, R.T.J., Clark-Lowes, D.D., ed., Petroleum Geology of North Africa, London, Geological Society Special Publication, v. 132: p. 201-216.
Makhous, M., Galushkin, Y., Lopatin, N., 1997, Burial history and kinetic modelling for hydrocarbon generation, part II: applying the GALO model to Saharan Basins: AAPG Bull., v. 81, (10), p. 1679-1699.
Mengoli, S., Spinicci, G., 1985, Tectonic evolution of North Africa (from North Sinai to Algeria), in OAPEC, ed.: Proceedings of the Seminar on source and habitat of petroleum in the Arab countries, Oct 1984,p. 119-174.
Ziegler, P. A., 1988, Evolution of the Arctic-North Atlantic and Western Tethys, v. 43: Tulsa, Am. Assoc. Petrol. Geol. Mem., 198 p.
Ziegler, P. A., Roure, F., 1999, Petroleum systems of Alpine-Mediterranean foldbelts and basins, in B. Durand, Jolivet, L., Horváth, F., Séranne, M., ed., The Mediterranean Basins: Tertiary extension within the Alpine orogen, London, Geological Society Special Publication, v. 156: p. 517-540.