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Doctoral thesis
French

Géologie des massifs calcaires situés au front sud de l’unité de Ketama (Rif, Maroc)

Number of pages336
Imprimatur date1989-04-18
Abstract

Structural background:

The massifs under study are situated on the southern front of the Ketama and Beni-Ounai parautochthonous units, and on the northern edge of a complex foreland basin. This basin contains nappes, olistoliths and is marked by ramps.

The cartographic and structural study has shown that these massifs are:

1. ramps partly deep-seated and back-thrusted (the Tifelouest and Tafraout units).

2. rootless thrust-sheets (the Rhafsai and the jebel Afress units).

3. chaotic complexes (the Merzouk-Timchatouine jebel and the southern foreland of Tifelouest).

Stratigraphy:

The carbonated sedimentation begins with the dolomites of the Hettangian or of the lower Sinemurian, sometimes showing signs of limited inter- to supratidal environment (the Tifelouest, Tafraout and Rhafsai units). In the Ketama unit, parts of this platform are then reworked into debris flows.

During the midlle Sinemurian, a lagoon edged by bars on the NE is formed in the upper part (the Tifelouest, Tafraout and Rhafsai units). This period of eustatic elevation seems tectonically stable. On the lower part (the Ketama and jebel Afress units), circalittoral marls accumulate.

The platform collapses during the upper Sinemurian, after the appearance of the first Haurania amiji and aff. Pseudopfenderina butterlini and before that of the Lituosepta recoarensis. Spongy limestones and mud mounds accumulate in the upper part, are dislocated into mosaic-breccia and resedimented downstream, at the foot of the fault scarp. Certain olistoliths of jebel Merzouk show very thick tidalite sequences, probably dating from between late Sinemurian and early Carixian.

From middle Carixian (top of the Jamesoni zone - base of the Ibex zone) to the base of the Domerian (Stokesi zone), a condensed hemipelagic sedimentation comprising upper bathyal limestones with ammonites and crinoids is formed in the Rhafsai, Tifelouest and Tafraout units. In the Ketama and jebel Afress units, the faults scarps breccia and debris flows continue to accumulate.

From the Stokesi zone, (Protogrammoceras celebratum) marls appear and increase progressively. The environments become blatantly pelagic, with internal molds of ammonites, radiolarians, Globochaete and local belemnites (Rhafsai unit). Aragonitic bioclasts are dissolved. The condensed ammonitico-rosso facies outcrop to the N and E of the Tifelouest, Tafraout and jebel Afress units and the southern boundary of the Ketama unit.

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Citation (ISO format)
FAVRE, Philippe Edouard. Géologie des massifs calcaires situés au front sud de l’unité de Ketama (Rif, Maroc). 1989. doi: 10.13097/archive-ouverte/unige:175439
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