Joseph Canerot

Comparative study of the Lower and Mid-Cretaceous sequences on different Maghrebian shelves and basins-their place in the evolution of the North African Atlantic and Neotethysian margins

Abstract The Lower and Mid-Cretaceous sequences known from Morocco (coastal Essaouira-Agadir-Safi Basin and Eastern Rif Foreland), in Western Algeria (Daǐa Mountains) and finally in Southern Tunisia (Chott Range and Saharian Shelf) are presented from a biostratigraphic and sedimentologic viewpoint. This work shows, for the period considered, common features in the geodynamic evolution of the different regions, such as: 1. - generalization of the carbonate facies in the Early Cretaceous (Berrisian) and at the end of the Mid-Cretaceous (Cenomanian-Turonian) times; 2. - delineation of important discontinuities in the Valanginian and Bedoulian times. This evolution gives evidence of an undeniable influence of eustatism in this Northern part of Africa. Nevertheless, detailed differences allow us to distinguish: 3. - an “Atlantic-type” evolution characterized by discontinuities with gaps (Safi) or sudden variations of thickness (Essaouira-Agadir) at the Berriasian/Valanginian boundary, related to the Neocimmerian rifting and block-faulting phase. Later on, this evolution is underlined by a progressive acceleration of subsidence at the Aptian/Albian boundary, due to the removal of the mid-oceanic doming; 4. - a “Neotethysian-type” evolution (Eastern Rif Foreland, Western Algeria and Southern Tunisia) where local tectonic movements have probably generated the rapid growth of the external marly Bedoulian basins and the spreading of the Wealdian-type (Valanginian to Barremian) and Utrillas (Albian) terrigenous depositional systems. The latest event is linked to the Austrian tectonic phase responsible of variable gaps towards the Aptian to Albian transition.

Lithostratigraphy, biostratigraphy and sedimentary dynamics of the Lower Cretaceous deposits on the northern side of the western High Atlas (Morocco)

Abstract The analysis of a sedimentary succession on the northern side of the western High Atlas, from Essaouira to Amizmiz, has enabled us to identify, and describe, thirteen formations ranging in age from Tithonian to Clansayesian. The collection and determination of ammonite and echinoid faunas has allowed us to attribute a precise age to most of these units. Lower Cretaceous formations are organized into six main depositional sequences: Late Jurassic-Berriasian; Valanginian; Hauterivian-Barremian; Bedoulian; Gargasian; Clansayesian-Albian. This organization, the characteristics of the major discontinuities and the geometry of sedimentary succession allows recognition of the following events: a Late Berriasian distensive phase; a period of sea-level change and basin infilling during Valanginian, Hauterivian, Barremian and Bedoulian times under essentially eustatic control; an intra-Aptian tectonic phase; and a period of relative sea level rise and topographic levelling during Gargasian-Albian. This is essentially linked to the evolution of the North Atlantic ocean during the Early Cretaceous.

Comment to “Latest-Cretaceous/Paleocene karsts with marine infillings from Languedoc (South of France); paleogeographic, hydrogeologic and geodynamic implications by P. J. Combes et al.”

1 Laboratoire des Mécanismes et Transferts en Géologie, 39 allées Jules-Guesde, 31062 Toulouse cedex 4, France. 2 INRAP, ZA les Champs Pinsons, 13, rue du Négoce, 31650 Saint-Orens-de-Gameville, France. 3 37, avenue de Cousse, 31750 Escalquens, France. 4 École des Mines de Nancy, Département des Sciences de la Terre, LAEGO-Mines, 54042 Nancy, France. 5 École Nationale Supérieure des Mines de Paris, Géosciences, 35, rue Saint-Honoré, 77305 Fontainebleau, France.

Structural and sedimentologic relations between the High and the Middle Atlas of Morocco during the Jurassic time

Abstract The cartographic, sedimentologic and stratigraphic studies carried out on the Mesozoic deposits in the border zone between the Middle and the High Moroccan Atlas (regions of Naour and Aghbala) led us to specify the lithology of formations, the significant differences of thickness and the angular unconformities as well as stratigraphic hiatuses. All of this indicates a tectonic regime of transcurrent faults from the Bajocian–Bathonian period along the major fault zone “Aghbala–Afourer” in a N70° direction. A sinistral strike-slip movement along this major fault zone induced the development of folded and fractured zones in a N120° direction, which limited a small trough filled by the red continental formations. The whole system is covered thereafter by lower Cretaceous deposits.

Le cadre stratigraphique et géodynamique des altérites et des bauxites sur la marge ibérique des Pyrénées occidentales (France)

Abstract In the Western Pyrenees, the recent discovery of intra-Jurassic bauxites is not documented. In the present work, the authors show that the North-Pyrenean alterites are involved in two different Lower Cretaceous regression/transgression cycles related to the Neocomian-Aptian and the Uppermost Aptian-Lower Albian intervals. These alteration products allow two main successive Lower Cretaceous structuration phases of the southern, Iberian, continental margin of the Western Pyrenees. They induce the same geodynamic evolution sketch as in the opposite northern, European, continental margin developed at the same time in the Central Pyrenees, beyond the Axial Basin.

La Sierra Madre orientale (Mexique). Une rampe homoclinale mésocrétacée en bordure du golfe

Abstract New data from the Sierra Madre Oriental, in the Metztitlan, Xilitla and Sierra de El Abra areas, indicate a gradual, homoclinal ramp-type evolution from the Lower Cretaceous thin bedded outer-shelf Tamaulipas limestones to the Mid-Cretaceous massive innershelf Abra limestones. The common sedimentary model of an isolated Abra platform towering above the Tamaulipas basin through a reef barrier (Taninul fades) or through marine slope breccias (Tamabra Fm.) is rejected. The proposed interpretation can be extended to different platforms which developed in the western margin of the Gulf of Mexico and specially to the Golden Lane and Poza Rica areas where the Mid Cretaceous Abra carbonates provided important oil fields.