رصيف جيري

الرصيف الجيري Carbonate platform ، هو تركيب بحري يتكون أساسا من كربونات الكالسيوم ، ويرتفع عن المنطقة المحيطة به.

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 هندسة الرصيف الجيري

 الشعاب

Generalized cross-section of a typical carbonate platform.

 البحيرةالداخلية

An example of carbonate mud sedimentation in the internal part of the Florida Bay lagoon. The presence of young mangroves is important to entrap the carbonate mud.

 الرصيف الجيري في السجل الجيولوجي

The Cimon del Latemar (Trento province, Dolomites, northern Italy) represents the internal lagoon of a fossil carbonate platform. Continuous sedimentation took place in an environment as the one described in the image of the Florida Bay and, given a strong subsidence, led to the formation of a sedimentary series that therefore acquired considerable thickness.

High Atlas middle Liassic carbonate platform of Morocco with first order autocyclic regressive cycles

Détails de cycles émersifs métriques dans deux coupes du Lias moyen distantes de 230km; à noter les niveaux de tempêtes et tsunami (?) riches en foraminifères déplacés. Maroc.

Virtual metric "shallowing upward sequence" observed all along (more than 10,000 km) the south Tethyan margin during middle Liassic times. The (micro)fossils are identical till Oman and beyond.

 معرض الصور

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  "Shallowing upward" cycle in the middle Lias of the high Atlas (Morocco). Algal dolomitized laminations on top.

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  "Shallowing upward" cycles in the lagoonal Lias of the Musandam Peninsula. (N-Oman).

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  "Shallowing upward" liassic cycles arranged in decametric sequences, Musandam Peninsula, (N-Oman).

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  "Shallowing upward" cycle in the Middle Jurassic (Saghtan form.) of the jbel Laghdar Range (Oman).

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  Dessication figures on top of a regressive sequence; Middle liassic, High Atlas, Morocco.

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  Ammonites and belemnites washed over a supratidal surface (calcretes and "teepees"); Middle Liassic of the High Atlas, Morocco.

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  Hurrican breccia cemented (early diagenesis) at the surface of a bed, top of a regressive, metric, sequence. Middle Lias, High Atlas.

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  Vadose ferrugenous pisolites (soil) and coastal (tempestite) sediment with birdseyes in an outer platform environment. Aerial diagenesis. Middle liassic, High Atlas, Morocco.

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  Meniscus and point contact cement in a marine grainstone with displaced foraminifera (by tide and hurricans) on the supratidal flat of the middle liassic platform of Morocco. Top of emersive cycle. Middle Atlas.

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  Reworked calcretes concretions from the supratidal environment in a marine (dolomitised) sediment displaced by hurricans on the inner platform flat. Top of emersive sequence. High Atlas, Morocco.

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  Stalactitic cement in sediment from the supratidal zone, vadose environment, top of "shallowing upward" sequence. Middle Liassic, High Atlas. Thin section. L = 0.3 mm.

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  Giant dinosaur tracks (sauropod) on top of a regressive sequence, Middle Liassic, High Atlas, Morocco.

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  Parallel dinosaurs tracks on top of a regressive sequence, Middle Liassic, High Atlas, Morocco.

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  Vadose stalactitic cement filling an horizontal cavity in a marine coastal sediment, outer platform. Birdseyes in the allodapic (tidal or tempestite) grainstone point to an aerial diagenesis. High Atlas, Morocco.

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  Autocyclic filling (metric to hectometric) sequences in the Middle Liassic lagoon, South (Todhra) of the High Atlas, Morocco.

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  "Teepee" structure, due to increasing sediment volume by dolomitisation on the inner platform supratidal flat. Top of emersive cycle. Middle Lias, High Atlas.

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  Quaternary to recent equivalent of a "shallowing upward sequence", cores in a Tunisian "chott", intertidal laminations in yellow.

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  Recent "teepee" structures in a Tunisian salt lagoon, "chott".

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  Recent equivalents of "shallowing upward sequences", cores in a Tunisian salt lagoon, "chott".

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  Top of a regressive sequence with algal laminations (yellow) and crystallised gypsum, salt lagoon "chott", Tunisia.

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  Eolian bioclastic (calcareous algae and porcellaneous foraminifera) sand dune on Tunisian shore.

 انظر أيضا

• Ocean bank (topography)
• Bahama Banks

 الهوامش

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 المصادر

• Carannante G., Esteban M., Milliman J. D., Simone L., 1988, Carbonate lithofacies as paleolatitude indicators: problems and limitations. Sedimentary Geology, v. 60, pp. 333-346.
• Davaud E. & Septfontaine M. (1995): Post-mortem onshore transportation of epiphityc foraminifera: recent example from the Tunisian coast line.- Jour. Sediment. Research, 65/1A, 136-142.
• Schlager W., 2005, Carbonate sedimentology and sequence stratigraphy. SEPM, Tulsa, Oklahoma, 200 pp. ISBN 1-56576-116-2
• Wilson J. L., 1975, Carbonate Facies in Geologic History, Springer-Verlag, 471 pp. ISBN 3-540-07236-5
• Bosellini A., 1984, Progradation geometries of carbonate platforms: examples from the Triassic of the Dolomites, northern Italy. “Sedimentology”, v.31:1-24
• "Bahamas Introduction" (Accessed 3/8/06)
• About.com: Geologic Map of Florida (Accessed 3/8/06)
• Pinet P. R., 1996, Invitation to Oceanography. St. Paul: West Publishing Company, ISBN 0-314-06339-0
• Septfontaine M. 1985, Depositional environments and associated foraminifera (lituolids)in the middle liassic carbonate platform of Morocco.- Rev. de Micropal. 28/4 265-289. See also www.palgeo.ch/publications.