Evidence for Late Devonian vertical movements and extensional deformation in northern Africa and Arabia: Integration in the geodynamics of the Devonian world

Abstract

The Upper Paleozoic geodynamic evolution is discussed at the scale of a wide part of Gondwana from North Africa to Arabia. With the aim of giving an integrated tectonic scenario for the study domain, we revisit six key areas, namely, the Anti‐Atlas Belt (Morocco), the Bechar Basin (west Algeria), the Hassi R'Mel High (central Algeria), the Talemezane Arch (south Tunisia), the Western Desert (Egypt), and, finally, the High Zagros Belt (Iran). Below the so‐called “Hercynian unconformity,” which is in reality a highly composite discontinuity, surface and subsurface data display a well‐known arch‐and‐basin geometry, with basement highs and intervening Paleozoic basins. We show that this major feature results mainly from a Late Devonian event and can no longer be interpreted as a far effect of the Variscan Orogeny. This event is characterized by a more or less diffuse extensional deformation and accompanied either by subsidence, in the western part of the system, or by an important uplift of probable thermal origin followed by erosion and peneplanation. By the end of the Devonian, the whole region suffered a general subsidence governed by the progressive cooling of the lithosphere. Such a primary configuration is preserved in Arabia with typical sag geometry of the Carboniferous and Permian deposits but strongly disturbed elsewhere by the conjugated effects of the Variscan Orogeny during the Carboniferous and/or by subsequent uplifts linked to the central Atlantic and Neo‐Tethys rifting episodes. In conclusion, we try to integrate this new understanding in the geodynamics of the Late Devonian, which at world scale is characterized by the onset of the Variscan Orogeny on the one hand and by magmatism, rifting, and basement uplift on the other hand.

Style of rifting and the stages of Pangea breakup

“…On the contrary, it is known that uplift above asthenosphere upwelling can develop without rift growth. It is, for instance, the situation of the “Morocco Hot Line” during the Neogene [e.g., Frizon de Lamotte et al ., ; Michard et al ., ] and of the Gondwanian Arches during the Late Devonian [ Frizon de Lamotte et al ., ].…”

Style of Atlassic tectonic deformation and geodynamic evolution of the southern Tethyan margin, Tunisia

“…The Atlas is considered as a type-example of intercontinental chain resulting from the collision between Africa and Eurasia since the late Cretaceous (Caire, 1977;Mattauer et al, 1977;Zargouni, 1984;Ziegler et al, 1995;Laville et al, 2004). The complex structural framework of the chain may reflect basement and stratigraphic heterogeneities of North Africa extensional margin inherited from the Paleozoic and Mesozoic times (Guiraud, 1998;Beauchamp et al, 1999;Laville et al, 2004;Missenard et al, 2007;Gabtni et al, 2011a;Roure et al, 2012;Frizon de Lamotte et al, 2013). The eastern Tunisian Atlas (Fig.…”

Discussion on Palaeozoic discontinuities in the Kuh-e Surmeh area (Zagros, Iran)

“…This unconformity has been already described in the literature and is referred as the so-called "Hercynian unconformity" with comparison to the Hercynian orogeny developed in Europe, North Africa and North America (Sharland et al, 2001;Haq and Al-Qahtani, 2005). However, the geodynamic significance of this Carboniferous orogeny is questioned in the High Zagros Belt (Iran) as no evidence of compressional deformation has been observed Frizon de Lamotte et al, 2013).…”

“…Frizon de consider that this unconformity is incorrectly called the "Hercynian unconformity" as it does not correspond to the same object as the one described in Western Africa. Instead, Faqira et al (2009) andFrizon de Lamotte et al (2013) propose a structuration of the Arabian Plate in the arch-and-basin geometry and discuss their impact on the Palaeozoic petroleum system. This geometry, developed in the Arabian Plate, was reached by the end of the Devonian and is linked to a massive uplift accompanied by a diffuse extensional deformation in the region located outside the vicinity of the Variscan orogenic belt.…”

“…are cropping out (Wolfart, 1981;Davoudzadeh et al, 1986;Ghavidel-Syooki and Winchester-Seeto, 2004;Mobasheri, 2005). At the scale of the Arabian Plate, the Palaeozoic is mainly known by subsurface data and the bottom of the Permian Carbonates is observed in seismically deep profiles (Insalaco et al, 2006;Frizon de Lamotte et al, 2013).…”