Le bassin sédimentaire a phosphates du Togo (Maastrichtien-Eocène): stratigraphie, environnements et évolutionThe phosphate sedimentary basin of Togo [Maastrichtian-Eocène): stratigraphy, environments and evolution)

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Résumé

Les observations faites à l'affleurement de la carrière de Tabligbo (matériaux pour la fabrication de klinker) et à celles de Hahotoé et Kpogamé (phosphates), ainsi que l'analyse de cinq forages, permettent d'affiner la stratigraphie du bassin côtier togolais: rajeunissement des Calcaires de Tabligbo (Paléocene supérieur) et des Argilites feuilletées à palygorskite (Eocène inférieur).

Un aperçu de l'environnement du gisement de phosphates est proposé à travers l'évolution sédimentaire et dynamique du bassin: transgression sur une marge continentale, approfondissement progressif du milieu avec dépôt et conservation de la matière organique, phosphates en début de régression, fléchissement de la marge avec jeu différential des blocs donnant naissance à un piège structural pour les phosphates, accumulation et altération de la phospharénite.

Abstract

Studies carried out in the quarries at Tabligbo (klinker feed materials) Hahotoé and Kpogamé (phosphate extraction), coupled with core sample analyses of five boreholes, have led to a more precise stratigraphy of the Togo coastal basin and a younger age for the Tabligbo Limestones (Upper Palaeocene) and the palygorskite fissile-laminated Clays (Early Eocene).

An outline of the depositional environment of the phosphate deposits is proposed through the sedimentary and dynamic evolution of the basin: transgression on to the continental margin, followed by a progressive deepening of the basin with deposition and preservation of organic matter; phosphates at the start of the regression; differential displacements of faulted blocks make a structural trap for the phosphates; accumulation and alteration of the phospharenite.

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  • Cited by (17)

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