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LA FASE POST-NAPPE NELLA TOSCANA MERIDONALE. NUOVA INTERPRETAZIONE SULL'EVOLUZIONE DELL'APPENNINO SETTENTRIONALE
No full textEvoluzione Paleogeografica dell'area di Frosini, settore meridionale del Bacino di Radicondoli nel Tortoniano superiore (Toscana, Italia)
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Late Miocene Paleogeography of the Monte Soldano Area, Southeastern Part of Volterra Basin, Tuscany, Italy
No full textClimatic and tectonic signature in the fluvial infill of an upper Pliocene valley (Siena basin, northern Apennines, Italy).
No full textFacies associations map of the Pliocene marine deposits of the central-southern Siena Basin (Tuscany, Italy)
Full text linkThe Siena Basin is a post-collisional basin of the inner Northern Apennines (Tuscany, Italy) characterized by a thick siliciclastic Neogene infill, mainly composed of marine sediments with subordinate alluvial deposits close to basin margins. The central-southern sector of the basin shows a more complex stratigraphy with the occurrence of sandy deposits also in distal areas, far from the basin margin. The aim of this paper is to provide a new 1:10,000-scale geological map of this key sector (about 45 km2) of the Siena Basin, helpful for a better reconstruction of its sedimentary evolution. The new fieldwork was based on the identification and mapping of different facies associations (expression of different sedimentary environments), whose shifts in time and space provide elements to understand the basin-fill history. The recognition of two main intra-Pliocene erosional surfaces allowed the subdivision of the succession into three alloformations. Therefore, a more complex depositional history, with respect to the previous knowledge for this key-sector of the Siena Basin, has been reconstructed, thus highlighting the importance of this kind of approach with respect to the classical lithostratigraphic criteria
The Mesozoic continental rifting in the Mediterranean area: insights from the Verrucano Tectonofacies of southern Tuscany (Northern Apennines, Italy)
No full textIn the Alpine-Mediterranean region, the continental redbeds and shallow-marine siliciclastics related to the early depositional phases of the Late Permian-Mesozoic continental rifting are referred to as the most common representative of the ‘‘Verrucano tectofacies’’. The Verrucano- type successions exposed in southern Tuscany are diachronous, spanning from Triassic to earliest Jurassic in age, and accumulated within the Tuscan domain, a paleogeographic region of continental crust that due to the opening of the Piedmont–Ligurian ocean formed part of the Adria passive-margin. They belong to the metamorphic Verrucano Group and the non-metamorphic Pseudoverrucano fm. Viewed overall, these Verrucano-type successions appear to manifest five episodes or pulses of an ongoing continental rifting. With the exception of the first episode that developed entirely within a terrestrial setting, each one is represented by basal Verrucano-type continental siliciclastics overlain by compositionally mixed marine deposits, which resulted from four diachronous, post-Middle Triassic transgressions. This suite of tectonic pulses produced the progressive westward widening (backstepping) of the Tuscan domain in the rifting south-Tuscany area
Sedimentary and ichnofacies analysis of the epiligurian Ponsano sandstone (northern Apennines, Tuscany, Italy)
No full textSeveral stratigraphic sections have bcen measured in the Rencine and Ponsano area to Define, trough sedimentary and ichnofacies analysis, the depositional paleoenvironment of the late Serravallian•early Tortonian Ponsano sandstone Formation. The section of Rencine is characterized mainly by medium•fine sandstones (Sm facies).
Few and thin layers of conglomerate are interbedded with sandstones,.No sedimentary structures have been recognized except for few remnants of planar cross- eds. In the section of Ponsano, the Ponsano Sandstone can be subdivided into two parts. The lower part is characterized by marlstones (Ms facies) at the bottom and medium-fine sandstones (Sm facies) in the middle and upper parts. The upper part is characterized by Ms at the bottom, Sm in the middle, and an alternation of pebble conglomerates (Cp), coarse conglomerates (Cb) and coarse sandstones (Sc) at the top. Fossils concentrations (f) occur throughout. The sandstone faeics are highly bioturbated, and most primary sedimentary structures are obscurcd: only remnants of even lamination, cross bedding and hummocky cross stratificationcould be recognized locally.
Trace fossils are indicative of the mixcd Cruziana-Skolithos and the Skolithos icnofacics. Sedirnentary and ichnofacics data indicate that the Ponsano Saodstone was deposited in Shallow water environment. The morlstone faeies are indicative inner shelf, the sandstone facies of shoreface. Conglomerates are referred to a fluvio- deltaic environment
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