دورة ترسيب
دورة الترسيب Cyclic sediments، هي تتابع رأسي من الصخور الرسوبية، تكون أثناء دورة طغيان - انحسار البحر transgressive - regressive cycle.
العمليات التي تنشئ دورة الترسيب
دورات تلقائية
"Shallowing upward" metric first order cycle in the Middle Liassic platform of the High Atlas, Morocco. Algal dolomitized laminations on top.
Recent equivalent of an emersive autocyclic cycle in a lagoonal to supratidal environment. Algal mats in yellow. Tunisia.
Stalactitic cement from a sample in the supratidal zone in vadose environment (air within the sediment), top of regressive cycle, middle Lias, High Atlas. Thin section, L = 0,5mm.
Hurricane breccia cemented on the surface of a bed, top of a "shallowing upward" cycle. Middle Lias, High Atlas.
Top of a metric regressive cycle with desiccations, surface of bed dolomitised. Middle liassic of the High Atlas, Morocco.
Washover, ammonites and belemnites (by storms) on top of a regressive cycle, supratidal environment. Middle liassic of the High Atlas, Morocco.
Giant dinosaur tracks, in a muddy sediment on top of a metric regressive cycle. Middle liassic, High Atlas, Morocco.
Metric to hectometric regressive cycles (related to an acceleration of the rate of subsidence); South of the High Atlas, Morocco.
Allocycles
"Shallowing upward" cycles in the lagoonal Liassic platform of the Musandam Peninsula(Oman). Possible allocyclic origin.
Possible allocyclic metric cycles, arranged in decametric sequences, limited by yellow algal, dolomitized levels, below depositional hiatus.
"Shallowing upward" cycles in the Middle Jurassic (Saghtan form.) of the jbel Laghdar Range (Oman).
مشكلات دراسة دورة الترسيب
المصادر
• Septfontaine, M. (1985): Milieux de dépôts et foraminifères (Lituolidae) de la plate-forme carbonatée du Lias moyen au Maroc.- Rev. Micropaléont., 28/4, 265-289. (Le modèle ancien proposé ci-dessous a son équivalent actuel au fond du golfe de Gabès et dans les chotts associés, voir Davaud & Septfontaine, 1995.
• Davaud, E. & Septfontaine, M. (1995): Post-Mortem onshore transportation of epiphytic foraminifera: recent example from the Tunisian coastline.- Jour. Sediment. Research, 65/1A, 136-142.
• Septfontaine, M. & De Matos, E. (1998): Pseudodictyopsella jurassica nov. gen., nov. sp., a new foraminifera from the Earlay Middle Jurassic of the Musandam Peninsula. Sedimentological and stratigraphical context.- Rev. Micropaléont., 41/1,71-87. (Dans cet article, on note l'absence du genre Orbitammina en Oman, souvent confondu avec Timidonella par les auteurs anglo-saxons).
- ^ عبد الجليل هويدي، محمد أحمد هيكل (2004). أساسيات الجيولوجيا التاريخية. مخطة الدار العربية للخط.
