Extension et developpement des phenomenes recifaux jurassiques dans le domaine atlasique marocain, particulierement au Lias moyen

Dresnay, Renaud du

doi:10.2113/gssgfbull.s7-xiii.1-2.46

Cited by 63 publications

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“…Throughout the Jurassic the shallow seas in northwestern Africa were largely a domain of carbonate deposition (Dresnay, 1971). Upper Jurassic shallow-water carbonates crop out on the Mazagan escarpment, 100 km east of Site 416 (Renz et al, 1975) and are widespread in the subsurface of the continental slope (Lehner and de Ruiter, 1977;Todd and Mitchum, 1977).…”

Section: Interpretation-drowning Of a Carbonate Platformmentioning

confidence: 99%

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Schlager¹

1980

Initial Reports of the Deep Sea Drilling Project

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The Tithonian-Hauterivian section of Site 416 contains about 10 per cent limestone and marlstone in well-defined beds between shale and sandstone. Depositional structures, grain composition, and diagenetic fabrics of the limestone beds as well as their association with graded sandstone and brown shale suggest their deposition by turbidity currents below calcite-compensation depth. Carbonate material was initially shed from a shallow-water platform with ooid shoals and peloidal sands. Soft clasts of deep-water carbonate muds were ripped up during downslope sediment transport. Shallow-water mud of metastable aragonite and magnesium calcite was deposited on top of the graded sands, forming the fine tail of the turbidite; it has been subsequently altered to tight micritic limestone that is harder and less porous than Coccolith sediment under similar overburden. Abnormally high strontium contents are attributed to high aragonite contents in the original sediment. This suggests that the limestone beds behaved virtually as closed systems during diagenesis.Drowning of the platform during the Valanginian is inferred from the disappearance of the micritic limestones, the increase in abundance of phosphorite, of ooids with quartz nuclei, and of the quartz content in the calciturbidites. In Hauterivian time, the carbonate supply disappeared completely. The last limestone layers are lithoclastic breccias which indicate that erosion has cut into well-lithified and dolomitized deeper parts of the platform rather than sweeping off loose sediment from its top.Of all Tithonian sections recovered from the Atlantic, only the one at Site 416 contains abundant shallow-water debris and was deposited below the calcite-compensation depth. It is probably located on mid-Jurassic or older crust that had already deeply subsided and was close to the continental slope by Tithonian time. The other sites, located on younger crust, stood high on the flank of the mid-ocean ridge, and were consequently above the compensation level and beyond reach of shallow-water detritus shed down the continental slope.

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Section: Interpretation-drowning Of a Carbonate Platformmentioning

confidence: 99%

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Schlager¹

1980

Initial Reports of the Deep Sea Drilling Project

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“…and Phylloceras sp., collected from the Tazigzaout lower member (Ait Addi, 2002 Fig. 2A); hence, the age of the Tazigzaout formation is probably older than the one proposed for the Calcaires corniche bars of the Central High Atlas and High Plateaux (in the Mechkakour area) by Choubert et al (1956), Du Dresnay (1971a and Du Dresnay (1979).…”

Section: Stratigraphic Settingmentioning

confidence: 77%

“…1b) where outcrop conditions are ideal for studying these facies. The Lower Jurassic buildups have been the subject of many studies (Menchikoff, 1936;Dubar, 1948;Bazin, 1968;Du Dresnay, 1971a, 1975-1977, 1987Chafiki et al, 2004 and others), whereas the Middle Jurassic carbonate builups have been the least studied (Beauvais, 1970;Du Dresnay, 1971b;Warme et al, 1975;Stanley, 1981;. Recent studies on the Lower and Middle Dogger series (Ait Ait Addi, 2000, 2002 provided new information about stratigraphical, morphological, and sedimentological features of the reef horizons.…”

Section: Introductionmentioning

confidence: 99%

The dogger reef horizons of the Moroccan Central High Atlas: New data on their development

Addi

2006

Journal of African Earth Sciences

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“…Ces édifices ne sont connus que dans le domaine sud alpin de Trento (Italie) (Krautter, 1996) au Pliensbachien et dans le bassin Lusitanien du Portugal au Lias terminal (Duarte et al, 2001). Sur la marge continentale sud-téthysienne, ce type de construction a vu, par contre, un remarquable foisonnement au Lias marocain (Du Dresnay, 1971Dresnay, , 1975) notarnment au Sinémurien du Haut Atlas central (Chafiki et al, 2001(Chafiki et al, , 2002.…”

Section: Introductionunclassified

“…Ells ont éte décrites pour la premiere fois par Dubar (1960Dubar ( -1962 qui les a atribué al'activité des spongiaires. Des appellations évocatrices telles «carbonate-mounds» ou «dolomite-mounds» (Du Dresnay, 1971Dresnay, , 1975Warme, 1986;Warme et al, 1988) et «lithoherms» (Evans et al, 1974;Evans et Kendall, 1977) ont été également utilisées pour désigner ces masses bioconstruites. L'objectif de ce travail est de présenter les principales caractéristiques des mud-mounds sinémuriens sur la transversale de Midelt-Errachidia.…”

Section: Introductionunclassified

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Chafiki¹,

Canérot²,

Souhel³

et al. 2004

Estud. geol.

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RÉSUMÉ ABSTRACTIn the central High Atlas of Morocco, the Liassic series present different mud-moundtype carbonate buildups, well developed in the Midelt area, towards the boundary between the Lower and the Upper Sinemurian. Near Foum Tillicht, these structures show a real evolution within the Upper Sinemurian interval, from simple small-scale bodies at the base, up to big and complex forms at the topo Their sedimentological and palaeontological features indicate microbolites and sponge buildups developed in deep and open marine conditions, within the subphotic zone, at the lower part of the storm wave interval.These buildups are closely linked to tectonic processes as they grow on the normal synsedimentary faults which affected the central atlasic area during the Lower Liassic period, leading to the breakup of the Early Sinemurian carbonate platform and the induced installation of the Upper Sinemurian subsiding basin. Silting by hemipelagic sediments led to death of buildings. Similar palaeogeographic changes and geodynamic evolution have been recently described from different structures in North Africa, Westem Europe and North America.

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Extension et developpement des phenomenes recifaux jurassiques dans le domaine atlasique marocain, particulierement au Lias moyen

Cited by 63 publications

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Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

The dogger reef horizons of the Moroccan Central High Atlas: New data on their development

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Extension et developpement des phenomenes recifaux jurassiques dans le domaine atlasique marocain, particulierement au Lias moyen

Cited by 63 publications

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Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

The dogger reef horizons of the Moroccan Central High Atlas: New data on their development

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Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform

Mesozoic Calciturbidites in Deep Sea Drilling Project Hole 416ARecognition of a Drowned Carbonate Platform