Mesures d'ages absolus sur les series precambriennes et paleozoiques du Senegal oriental

Abstract

Abstract Absolute ages using the strontium method were obtained for Precambrian and Paleozoic rocks of the Senegal basin (Africa). These dates compare favorably with the previous work done recently in the area. The Birrimian series is the oldest unit, with an age of 2045 m.y. The Segou-Madinakouta series unconformably overlying the Birrimian is dated, at its base, as 1020 m.y. The date of 645 m.y. obtained for the Niokolo-Koba granite may represent later rejuvenation of an older granite and not the granitization itself. No age was obtained for the Faleme series. The Youkounkoun series is dated as 560 m.y. Metamorphism of the Koulountou series probably occurred at the beginning of the Gothlandian (430 m.y.). The Bakel series was metamorphosed at the end of the Devonian (355 m.y.), and again in the Triassic (206 m.y.).