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Enregistrement des variations eustatiques dans des dépôts littoraux du Pléistocène supérieur (San Giovanni di Sinis, Sardaigne occidentale)

Strasser, André
Published in Bulletin de la Société Géologique de France. 1991, vol. 162/3, p. 523-533
Abstract Tyrrhenian (Upper Pleistocene) coastal deposits in Sardinia have been studied since the last century, but have never been interpreted in terms of detailed sedimentology and sequential pattern. The present paper deals with an outcrop close to San Giovanni di Sinis on the western coast of Sardinia, where three depositional sequences can be identified. The lowermost sequence overlies an erosion surface which cuts into Messinian marls. A basal conglomerate including coralline algae, and sandstones displaying current ripples and beach lamination point to a coastal-marine depositional environment. The bulk of the sequence, however, is made up of eolian dunes with interstratified paleosols, and of colluvial deposits. An erosional surface terminates this sequence. The basal conglomerate of the second sequence contains pebbles with pedogenetic features, and is overlain by beach-laminated sands. Superimposed bioturbation and an important bed of in-situ Mytilus shells suggest that the coastal-marine environment passed into a lagoonal one. Ostracods, charophytes and pedogenesis indicate fresh-water influence and local emersion at the top of this sequence. Again, an erosional surface truncates the deposits. The third sequence starts with shoreface and foreshore deposits rich in coralline algae and ends with eolian facies. Locally, the eolian dunes prograde directly over shoreface and tidal-channel deposits. The major erosion surfaces probably formed during important drops of sea•level and correspond to sequence boundaries. The conglomerates are interpreted as transgressive deposits, whereas the shallowing-upward facies successions represent regressive highstand deposits. The three sequences of San Giovanni di Sinis may thus have formed during three successive sea-level fluctuations, which can tentatively be correlated with the three climatic cycles during the last interglacial, i.e. between 130,000 and 70,000 years B.P.
Keywords TyrrhenianSardiniaSedimentologySequence stratigraphyBeach depositsLagoonal depositsTidal channel depositsEolian depositsPedogenesisSea-level changes
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Research group Sedimentology, Biostratigraphy and Micropaleontology
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DAVAUD, Eric Jean et al. Enregistrement des variations eustatiques dans des dépôts littoraux du Pléistocène supérieur (San Giovanni di Sinis, Sardaigne occidentale). In: Bulletin de la Société Géologique de France, 1991, vol. 162/3, p. 523-533. https://archive-ouverte.unige.ch/unige:24433

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