Stratigraphic-paleogeographic evolution of Eastern Sardinia Jurassic passive margin carbonates: synthesis and future developments.
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Data di Pubblicazione:
2015
Citazione:
Stratigraphic-paleogeographic evolution of Eastern Sardinia Jurassic passive margin carbonates: synthesis and future developments / F. Jadoul. ((Intervento presentato al convegno GEOSED tenutosi a Cagliari nel 2015.
Abstract:
During the Mesozoic, Sardinia belonged to the European Peritethys domain. Its Jurassic stratigraphic evolution is comparable, for sedimentary and climatic-paleogeographic characteristics, to coeval successions in NE Spain and SW Provence, that record the Middle Jurassic rifting phase affecting the south European margin of the Tethys. The 500-650 m thick Middle-Upper Jurassic carbonate succession of Eastern Sardinia documents the presence of a Jurassic structural high and the its sedimentary evolution along the eastern margin, close to an inferred erosional escarpment. This NE-SW trending structural high, about 75 km wide, was dominated by deposition of prevalent shallow water deposits, with low accommodation rates, up to the Early Oxfordian. The recent biostratigraphic redefinition of regional sedimentary events, the well-preserved depositional geometries and the carbonate facies associations permitted i) to define the geological history of the Eastern Sardinia Jurassic carbonate succession and ii) to reconstruct the tectono-sedimentary evolution of a well-preserved, but still poorly studied, passive margin of the Tethys.
The syn-rift Jurassic succession of Eastern Sardinia, mainly preserved in structural troughs, begins with discontinuous lenses (up to 40 m thick) of polygenic fluvial conglomerates, sandstones, lacustrine facies and coastal marine mixed calcarenites and quartzarenites at the top. The upper boundary of this Bajocian-Early Bathonian succession (Genna Selole Fm., Fig. 1) is still mater of discussoin (Dieni et al., 1983, 1985; Costamagna & Barca, 2004; Costamagna 2008, 2015). This siliciclastic unit is overlain by 500-650 m of Bathonian to Berriasian prevalent shallow-water carbonates: Dorgali, Mt. Tului and Mt. Bardia formations (Amadesi et al., 1967). This lithostratigraphic subdivision is still reliable: the three formations document the evolution of a persistent shallow-water carbonate depositional system characterized by different stratigraphic architectures and lithofacies associations. This succession records regional tectono-sedimentary, climatic and diagenetic events, that control lithostratigraphic boundaries and provides constraints for stratigraphic correlations. Recently, reviews of the lithostratigraphic classification have been cently proposed (Dieni e al., 1985, 2013; Costamagna & Barca, 2004; Costamagna et al., 2007; Jadoul et al., 2010, Lanfranchi et al., 2008, 2011; Casellato et al. 2012. The new lithostratigraphic schemes (Fig.1) evidence nomenclatural problems and the need of a redefinition of the litostratigraphic boundaries.
The first marine deposits, covering a pedogenized Variscan Basement or the Middle Jurassic continental succession, are Early Bathonian in age. The first marine depositional sequence (Bathonian, Perda Liana Mb., Dieni et al., 2013; and Dorgali Fm., Fig.2) documents a coastal paleogeography with a few open bays generally characterized by low accommodation. Transgressive, open marine, fine-grained bioturbated to bioclastic limestones with siliciclastic inputs at the base evolve to oolitic, mainly dolomitized, grainstones towards the top. This sequence, more than 100 m thick southward (Tacchi area, Dieni et al 2013), is thinner in the northern, eastern areas, (8-40 m in the Baunei-Dorgali Supramonte, N. M.Albo successions). The first regional depositional hiatus, recorded by Fe- rich hardgrounds (Upper Bathonian after Dieni et al, 1966) frequently associated with siliciclastic input, marks the top of this unit. The overlying Lower Callovian-Lower Oxfordian carbonates (upper Dorgali Fm. or the coeval basinal carbonates at the base of the S’Adde and Baunei fms.), are thinner, associated to the last terrigenous inputs and locally dolomitized. They are characterized by a few
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Keywords:
Stratigraphy, paleogeography, Jurassic , Sardinia
Elenco autori:
F. Jadoul
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