Mesozoische Flysch-Ablagerungen auf der Kanareninsel Fuerteventura

Abstract

ZusammenfassungAus dem Basalkomplex der Kanareninsel Fuerteventura werden pr~ivulka-nische Sedimentserien besebrieben, die aus insgesamt fiber 1000 m miichtigen Kalk-, Ton-, Mergel-, Sand-und Siltsteinen bestehen; die jiingsten haben nach Foraminiferen Oberkreide-Alter. Die gesamte Schichtserie umfal3t naeh einem Vergleich mit Profilen aus dem gegenfiberliegenden afrikanisehen Gebiet wahrseheinlieh aul3erdem noeh Jura und Unterkreide. Die Sehichten sind zu einem ESE-streichenden Cebirge mit wenigstens teilweise iiberkippter Lagerung strukturiert.Danach sind die Ostkanaren keine ,,ozeanischen" Inseln; sie geh/Sren geologisch zum afrikanischen Kontinent oder zum Kontinentalsehelf. Die Sedimentserie wird von den autometamorphen basahisehen G~ingen des ~iltesten Vulkanismus der Insel durehtrfimert. Der Beginn des kanarischen Vulkanismus lag dana& frfihestens in der Oberkreide. Aufgrund entspreehender geologischer Verh~iltnisse auf der Kapverdeninsel Maio wird ein 5hnlicher Bau des afrikanischen Kontinentalrandes im Bereich beider Archipele angenommen. AbstractThe western part of the chiefly volcanic island of Fuerteventura (Canary Islands) is underlain by a series of more than 1000 m of limestones, shales, marls, siltstones, and sandstones. The sedimentary rocks strike ESE, are partly overturned, and are at least as old as Upper Cretaceous, based on foraminifera. The entire sequence may also comprise Jurassic and Lower Cretaceous rocks as is shown by comparison with similar series on the neighbouring African continent.Thus Fuerteventura is part of the African continent or of the continental shelf and is no true "oceanic" island. The sedimentary rocks show striking similarities with the island of Maio (Capverde Islands) supporting similarities in the structure of the continental margin in both areas.

Cretaceous ammonites from Fuerteventura, Canary Islands

“…Fossils date the sediments as early Cretaceous and younger; however, in this part of the Atlantic oceanic sediments could be as old as late early or middle Jurassic. Indeed, if confirmed, the impressions o f Posidonia' reported by Rothe (1968) from Barranco de Ajui (Unit B below) would extend the age of the sequence to the middle or early Jurassic. Earliest volcanic activity on Fuerteventura is documented by basaltic breccias, pillow lavas and volcaniclastic sandstones which overlie with apparent conformity and intercalate with Upper Cretaceous chalks and marls (Robertson & Stillman, 1979a;Le Bas, Rex & Stillman, 1986).…”

“…3). Rothe (1968) stated that the Mesozoic sequence in this area was disposed in a major east-west-trending isoclinal overturned syncline. In contrast, Robertson & Stillman (1979 a), while confirming that the beds were predominantly overturned, established that the succession becomes uniformly younger towards the north, on the basis of sedimentary structures in redeposited sediments.…”

“…Units A to C are not dated palaeontologically; however, Rothe (1968) mentions 'impressions ' of Posidonia from Unit B and infers a Liassic to late Jurassic age for Units A to C.…”

“…Units F and G (Marl-Calcarenite Unit and Thicker Bedded Marl and Chert Unit) consist of pelagic, partly redeposited limestones (Series 5 of Rothe, 1968). The lower part of the sequence comprises about 30 m of white to light grey foraminiferal/radiolarian chalks and marls with lesser calcarenites and a few calcirudites becoming more frequent up-section.…”

“…1; Rothe, 1968;Robertson & Stillman, 1979 a;Robertson & Bernoulli, 1982). These sediments were deposited near the continent-ocean boundary adjacent to the African margin; they were uplifted in Tertiary times and are now exposed as part of the 'Basal Complex' of the island ( Fig.…”