MESOZOIC SEQUENCE OF FUERTEVENTURA (CANARY-ISLANDS) - WITNESS OF EARLY JURASSIC SEA-FLOOR SPREADING IN THE CENTRAL ATLANTIC

The Fuerteventura Jurassic sedimentary succession consists of oceanic and elastic deposits, the latter derived from the southwestern Morocca n continental margin. Normal mid-oceanic-ridge basalt (N-MORB) flows a nd breccias are found at the base of the sequence and witness sea-floo r spreading events in the central Atlantic. These basalts were extrude d in a postrift environment (post-late Pliensbachian), We propose a To arcian age for the Atlantic oceanic floor in this region, on the basis of the presence higher up in the sequence of the Bositra buchi filame nt microfacies (Aalenian-Bajocian) and of elastic deposits reflecting tectono-eustatic events (e.g,, late Toarcian to mid-Callovian erosion of the rift shoulder). The S-l sea-floor oceanic magnetic anomaly west of Fuerteventura is therefore at least Toarcian in age. The remaining sequence records Atlantic-Tethyan basinal facies (e.g., Callovian-Oxf ordian red clays, Aptian-Albian black shales) alternating with elastic deposits (e.g., Kimmeridgian-Berriasian periplatform calciturbidites and a Lower Cretaceous deep-sea fan system). The Fuerteventura N-MORB outcrops represent the only Early Jurassic oceanic basement described so far in the central Atlantic. They are covered by a 1600 m, nearly c ontinuous sedimentary sequence which extends to Upper Cretaceous facie s.