Late Triassic–early Jurassic block tilting along E–W faults, in southern Tunisia: New interpretation of the Tebaga of Medenine

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.

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“…According to Soussi [] and Raulin et al . [], this rifting lasted up to the Middle Jurassic. As indicated by Raulin et al .…”

Section: Evidence For a Late Devonian Extensional Deformation In Nortsupporting

confidence: 66%

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

et al. 2013

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“…The architecture of the Levant and Egyptian margins and the orientation of the Eratosthenes seamount (approximately NE‐SW, Figure ) and transform faults (Figure ; Montadert et al, ; Tassy et al, ) support a NW‐SE direction of extension (e.g., Barrier et al, ; Chamot‐Rooke, Rangin, et al, ; Frizon de Lamotte et al, ; Gardosh et al, ; Gardosh & Druckman, ; Garfunkel, , ; Garfunkel & Derin, ; Tari et al, ). Evidence for rifting over the same period is also reported in Libya (Arsenikos et al, ), Tunisia (Raulin et al, ), and Sicily (Basilone et al, ; Basilone, Sulli et al, ). Syntectonic basaltic flows are observed in the Levant margin (early Lower Jurassic Asher volcanics; Garfunkel & Derin, ) and onshore and offshore Sicily (e.g., early Middle Jurassic; Basilone et al, ; Patacca et al, ; Yellin‐Dror et al, ).…”

Section: The East Mediterranean Tectonic Settingmentioning

confidence: 57%

“…Constraints on crustal thickness are solely derived from indirect methods (e.g., gravity inversion; Cowie & Kusznir, ). The thick sediment deposition evidenced offshore Tunisia indirectly suggests a significant crustal thinning (Figure a; Frizon de Lamotte et al, ; Raulin et al, ). A thick sedimentary cover is also observed over the Pelagian shelf (Jongsma et al, ) even if crustal thinning seems less important toward the Malta escarpment (Figure a; see global map in Cowie & Kusznir, ).…”

Section: Deep Structure Of the Ionian Basin And Of Its Margins: Regiomentioning

confidence: 99%

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

et al. 2019

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We revisit the nature, structure, and evolution of the Ionian Basin and its surrounding passive margins (Apulia, Eastern Sicily/Malta, and Cyrenaica margins). Relying on geological observations (wells, dredges, and dives) and seismic calibrations from the surrounding platforms and escarpments, we present age correlations for the deepest sedimentary sequences of the Ionian Basin. Two‐ship deep refraction seismic data combined with reprocessed reflection seismic data enable us to identify, characterize, and map these thick sedimentary sequences and to present a consistent seismic stratigraphy across the basin. At a larger scale, we present new geological transects illustrating the tectonostratigraphic relationships between the Ionian Basin and its surrounding rifted margins. On this basis, we suggest that a Late Triassic‐Early Jurassic rifting preceded the late Early Jurassic to Middle Jurassic formation of the Ionian Basin. The combination of geophysical and geological arguments suggests that the entire deep basin is floored with oceanic crust of normal thickness, but with high seismic velocity in the upper part. Upscaling our results in the framework of the eastern Mediterranean, we propose that the Ionian Basin represents the remnant of a short‐lived oceanic basin resulting from the interaction between two propagating oceans: the Central Atlantic and the Neo‐Tethys.

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“…The Tunisian Atlas was subjected to two principal tectonic phases, the first one was extensional and began in the Late Triassic with opening of the Tethys Ocean (Raulin et al 2011). In the central Tunisian Atlas, this extensional phase is well distinguished in the Cretaceous sedimentary successions by the synsedimentary control of ENE-WSW orien ted normal fault F2, whose elongation axes are NW-SE directed with subsidence of north-western compartments.…”

Section: Synthesis and Discussionmentioning

confidence: 99%

Kinematic evolution and quantification of deformation in external orogenic zones: a case study from the Tunisian Atlas

Bensalem¹,

Amamria²,

Ghanmi³

et al. 2016

Geologica Carpathica

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Abstract:The quantification of deformation is one of the main objectives studied by geologists in order to control the evolution of tectonic structures and their kinematics during different tectonic phases. One of the most reliable methods of this theme is the direct calculation of quantity of deformation based on field data, while respecting several parameters such as the notion of tectonic inheritance and reactivation of pre-existing faults, or the relationship between the elongation and shortening axis with major faults. Thus, such a quantification of deformation in an area may explain the relations of thin-and thick-skinned tectonics during this deformation. The study of structural evolution of the Jebel Elkebar domain in the southern-central Tunisian Atlas permits us to quantify the deformation during the extensional phase by a direct calculation of the vertical throw along normal faults. This approach is verified by calculation of thickness of eroded strata in the uplifted compartment and of resedimented series, named the Kebar Formation, in the downthrown compartment. The obtained results confirm the importance of the Aptian-Albian extensional tectonic regime. The extent of deformation during the compressional phase, related to reactivation of pre-existing faults, is less than that of extensional phases; indeed the compressive reactivation did not compensate the vertical throw of normal faults. The geometry of the Elkebar fold is interpreted in terms of the "fault-related fold" model with a décollement level in the Triassic series. This permitted the partition of deformation between the basement and cover, so that the basement was allowed for a limited transport only, and the maximum of observed deformation was concentrated in the thin-skinned tectonics.

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Late Triassic–early Jurassic block tilting along E–W faults, in southern Tunisia: New interpretation of the Tebaga of Medenine

Cited by 72 publications

References 29 publications

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

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

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

Kinematic evolution and quantification of deformation in external orogenic zones: a case study from the Tunisian Atlas

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