ABSTRACT
The Jurassic of the Ah1 Mado in northern Somalia (Figure 1) consists of a pre-Toarcian unit of terrestrial clastics (Adigrat Fm.) and an early Toarcian to early ? Tithonian marginal marine to open marine sedimentary unit (Ah1 Mado Group) comprising three transgressive-regressive cycles in the Early, Middle and Late Jurassic. The Adigrat Fm. disconformably rests upon Precambrian basement (Inda Ad Fm.) and the Ah1 Mado Group is disconformably overlain by the Lower Cretaceous (Aptian). The early Toarcian and Callovian-Kimmeridgian transgressions are coupled with a global eustatic sea leve1 rise and early rifting processes between East- and West-Gondwana. The lateral and vertical facies distribution points to a continous subsidence of the Ah1 Mado Basin in the Early and Middle Jurassic followed by a drastic change of the facies pattern in the Late Jurassic (early? Tithonian), probably as a result of tectonic movements. The stratigraphic and sedimentologic results suggest a post-Jurassic uplift of the “Erigavo-Mukalla-High”.
