L. Ceinture-birimienne-du-secteur-de, Poura comporte trois types de formations: des roches volcaniques intrusives, effusives et pyroclastiques, des roches volcano-sédimentaires et des intrusions de granitoïdes. Les roches volcaniques comportent des ultrabasites, des basaltes qui peuvent se présenter en pillow-lavas

. Le-paysage-est-caractéristique-de-l-'ouest-africain, Il est marqué par des plateaux cuirassés à différentes altitudes. Chaque série de plateaux correspondrait à un événement climatique donné, La zone de Larafella (Figure 21) est caractérisée par un système latéritique

L. Inférieure, Elle est raccordée à l'unité moyenne et s'étale avec une pente très faible d'environ 1 %, jusqu'au Mouhoum

. La-différence-d, altitude avec l'unité haute est d'environ une vingtaine de mètres. Elle est également fortement cuirassée (jusqu'à 10 mètres)

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