Les ammonites du Lias inférieuret moyen du Haut-Atlas de Béni Méllal (Maroc): Taxinomie et biostratigraphie à haute résolution

Hariri, Khadija El; Dommergues, Jean‐Louis; Meister, Christian; Souhel, Abdellatif; Chafiki, Driss

doi:10.1016/s0016-6995(96)80025-8

Cited by 21 publications

(11 citation statements)

References 6 publications

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“…, 2001). These transgressive beds yielded small ammonites of the genus Arnioceras which, according to data of El Hariri et al. (1996), indicate the Early to Late Sinemurian boundary interval.…”

Section: Resultsmentioning

confidence: 83%

Biosedimentology of the Early Jurassic post‐extinction carbonate depositional system, central High Atlas rift basin, Morocco

2008

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This study documents a Liassic example of the long-ranging effects of mass extinction on carbonate systems. Biohistoric constraints inherent in the Liassic carbonate depositional system are deciphered from normal-marine, sub-tidal deposits of the central High Atlas rift basin (Morocco) through ?Hettangian/ Sinemurian to Early Toarcian times. The integration of results from the analysis of lithofacies, depositional geometries, microfacies, macrobenthos, carbonate build-ups, carbon and oxygen stable isotopes, and rare earth element + yttrium distribution patterns allows the intrinsic (or biohistoric) control on the central High Atlas deposits to be separated from extrinsic factors, such as basin development and palaeoclimate. The survival interval in the aftermath of the end-Triassic mass extinction persisted until the Early Sinemurian indicated by a severely depleted carbonate system impoverished in skeletal organisms. A tectonic pulse at the Early to Late Sinemurian boundary interval caused a basin widening with immigration of a marine fauna. However, until the latest Sinemurian (macdonelli Subzone of the raricostatum Zone) the deposits were dominated by filter-feeding benthic heterotrophs (sponges, brachiopods, polychaetes and crinoids). During this stage, primary production within the enlarged basin must have been largely planktonic and there was a net-flux of organic matter to the sea floor (oxygen minimum zone). A regional radiation of organic-walled phytoplankton is inferred to explain the selective success of the filter-feeding community and the occurrence of sponge mounds. Thus, significant effects of the end-Triassic mass extinction are still present during the Late Sinemurian. Through almost the entire Pliensbachian a highly productive, shoal-rimmed carbonate platform existed; it developed subsequent to tectonic reorganization and a marine recirculation event (radiolarian facies, Dd 13 C )1AE1, strongly negative Ce-anomaly). Photosymbiotic sediment producers (mainly large bivalves) now state the success of specialists and environmental equilibrium conditions. In the latest Pliensbachian the climax stage was reached with the development of a coralgal reef-rimmed carbonate platform. The Liassic carbonate depositional system experienced a terminal, multicausal Early Toarcian drowning event during which most of the large bivalves became extinct.

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Section: Resultsmentioning

confidence: 83%

Biosedimentology of the Early Jurassic post‐extinction carbonate depositional system, central High Atlas rift basin, Morocco

2008

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“…3b). et al 1996, 2010Lachkar et al 1998 ;Guex et al 2008) où l'extension stratigraphique de Arnioceras gr. rejectum est plus large car l'espèce précède le plus souvent les couches à Asteroceras avant de s'associer à lui dans la sous-chronozone à Stellare, voire dans des niveaux élevés de la sous-chronozone (Lachkar et al 1998).…”

Section: La Formation Zaghouan En Tunisie Atlasique Septentrionaleunclassified

“…Dans le domaine téthysien, l'extension du genre Arnioceras est mal connue et les espèces qui lui sont rapportées sont peu informatives en termes biochronologiques. Sa première apparition est difficile à dater car dans de nombreuses régions de la marge nord-africaine (Haut-Atlas, Chaînes Bétiques), comme dans la Dorsale tunisienne, le genre apparait précocement dans la séquence fossilifère du Sinémurien, avant les premiers Asteroceratinae, et son âge ne peut être précisé (Braga et al 1985 ;El Hariri et al 1996, 2010Lachkar et al 1998). Pour ces premiers niveaux sans Asteroceras, un âge chronozone à Turneri à partie inférieure de chronozone à Obtusum serait admissible (Dommergues & Meister 2017).…”

Section: Le Sinémurien De La Formation Zaghouanunclassified

“…-Le genre Parasteroceras, avec la seule espèce P. rakusi, est un Asteroceratinae original, apparemment endémique au Sinémurien tunisien où il abonde, dont l'âge est difficile à replacer dans les échelles classiques. Les rares citations confirmées de ce genre en dehors de la Tunisie proviennent du Haut-Atlas (El Hariri et al 1996) Âge de l'assemblage 2. L'absence du genre Asteroceras et la présence du genre Aegasteroceras concourrent à le situer dans une tranche de temps étendue de la partie terminale de la souschronozone à Stellare, à un niveau équivalent du biohorizon à Sagittarium nord-ouest européen, à tout ou partie de la souschronozone à Denotatus (Fig.…”

Section: Le Sinémurien De La Formation Zaghouanunclassified

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Le Jurassique du Jebel Ressas (Tunisie). Identification du Sinémurien supérieur dans la Formation Zaghouan. Précisions stratigraphiques et paléobiogéographiques sur le Sinémurien de Tunisie

Fauré¹,

et al. 2021

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http://geodiversitas.com/43/4 RÉSUMÉ La révision de la succession lithostratigraphique du Jurassique du Jebel Ressas (Dorsale tunisienne, Tunisie) permet d'identifier toutes les formations déjà définies par ailleurs dans la Dorsale tunisienne. La Formation Zaghouan y est nouvellement datée du Sinémurien supérieur par des ammonites appartenant aux chronozones à Obtusum (sous-chronozone à Stellare) et à Raricostatum (sous-chronozone à Raricostatum). Six taxons d'Ammonitina appartenant aux genres Asteroceras (A. gr. saltriense (Parona, 1896), A. cf. meridionalis Dommergues, Meister & Mettraux, 1990), Arnioceras (A. gr. ceratitoides (Quenstedt, 1849) -rejectum Fucini, 1902), Epophioceras (E. cf. landrioti (d'Orbigny, 1850)) et Paltechioceras (P. bavaricum (Böse, 1894), P. cf. charpentieri (Schafhäult, 1847)) sont décrits et figurés. Ces ammonites permettent de corréler la « Formation Zaghouan » avec les « Niveaux condensés du sommet de la Formation Oust », déjà bien connus pour leur riche ammonitofaune sinémurienne et dont les âges sont ici réévalués. Les affinités paléobiogéographiques des ammonites du Sinémurien de Tunisie sont discutées.

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“…(2004) and absolute ages after Walker and Geissman (2009). Ammonite sub‐zones after El Hariri et al. (1996).…”

Section: Methodsmentioning

confidence: 99%

Sequence development in an isolated carbonate platform (Lower Jurassic, Djebel Bou Dahar, High Atlas, Morocco): influence of tectonics, eustacy and carbonate production

et al. 2011

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Six sequences, each with a distinct shape, stratal anatomy, bounding surfaces, lithofacies composition and stacking patterns, were identified in the Djebel Bou Dahar isolated carbonate platform which developed in a half‐graben in the High Atlas marine rift basin during the Early Jurassic. Sequences are believed to have a complex, multi‐process origin as the result of tectonic processes (regional subsidence and fault‐block rotation) overprinting the eustatic signal. In addition, changing carbonate producers with shifting centres of deposition and relative accumulation potential influenced the filling and anatomy of the accommodation space that had been created by the hybrid tectonic and eustatic processes. Sequences I and II are tabular in shape and interpreted to primarily reflect the combined processes of uniform tectonic subsidence and eustacy which resulted in a ramp to shelf carbonate system with lagoon and tidal flat lithofacies. Onset of a rifting episode around the base of the Lotharingian and fault block rotation were responsible for the development of the angular unconformity with the underlying Sequence II, and the progressive development of a shallow‐water isolated platform and the wedge‐shaped depositional Sequences III to VI during the Lotharingian and Pliensbachian. Concurrent variations in palaeoceanographic conditions and in the carbonate factory caused a shift towards a flat‐topped platform geometry with high‐energy coated grains and sub‐photic sponge‐microbial deposition around the margin. The aggradational to retrogradational character of Sequences III, IV and VI is inferred to be a result of the combined effect of in situ carbonate production coupled with high rates of creation of accommodation space in the hanging wall. Environmental effects on carbonate production were the most probable cause for drowning of the Djebel Bou Dahar platform during the Toarcian but also influenced the filling and geometry of Sequences IV to VI. This study suggests that the commonly accepted model of pulse‐driven sequence‐development in half‐grabens may not be fully applicable for the Djebel Bou Dahar, where a more continuous rotation at sequence scale, associated with subsidence pulses of the Djebel Bou Dahar block, seems to have interacted with eustacy and carbonate production to generate sequences. Continuous rotation is suggested by the presence of regular patterns of diverging strata and numerous minor exposure surfaces in lagoonal deposits of Sequences V and VI. In addition, this study demonstrates that eustacy and variations in the carbonate factory might be as significant as tectonics in sequence development and platform drowning in carbonate platforms within rift basins. This observation could imply that the effects of eustacy and the carbonate factory might not have been correctly recognized in other similar carbonate platforms due to a tectonic‐biased interpretation.

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Les ammonites du Lias inférieuret moyen du Haut-Atlas de Béni Méllal (Maroc): Taxinomie et biostratigraphie à haute résolution

Cited by 21 publications

References 6 publications

Biosedimentology of the Early Jurassic post‐extinction carbonate depositional system, central High Atlas rift basin, Morocco

Biosedimentology of the Early Jurassic post‐extinction carbonate depositional system, central High Atlas rift basin, Morocco

Le Jurassique du Jebel Ressas (Tunisie). Identification du Sinémurien supérieur dans la Formation Zaghouan. Précisions stratigraphiques et paléobiogéographiques sur le Sinémurien de Tunisie

Sequence development in an isolated carbonate platform (Lower Jurassic, Djebel Bou Dahar, High Atlas, Morocco): influence of tectonics, eustacy and carbonate production

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