Sassalbo, Fivizzano, Massa-Carrara Province, Tuscany, Italyi

Regional Level Types
Sassalbo	Village
Fivizzano	Commune
Massa-Carrara Province	Province
Tuscany	Region
Italy	- not defined -

The village of Sassalbo takes its name from the white gypsum rock outcropping nearby.

The area Sassalbo-Cerreto Pass is characterised by outcrops of Triassic evaporites, with their associated sedimentary sequences, belonging to the Tuscan nappe. These evaporite deposits are ascribed to the Burano Formation and the Calcare Cavernoso Formation. Burano Formation is composed of metre-to-decametre alternations of gypsum-anhydrite and dolostones with minor halite, which were deposited mainly in a subaqueous environment. The Calcare
Cavernoso Formation, a rauhwacke at the base of the Tuscan nappe, is a carbonate siliciclastic sequence deposited during the Mesozoic ingression of the Tethyan ocean into the rift system, cutting the Variscan orogen and its European foreland (Passeri, 1975 and 1976). The "plastic" Late Triassic lithotypes acted as glide horizons for the detachment of the sedimentary Tuscan Nappe from the Paleozoic basement during the formation of the Apennine chain (Boccaletti et al., 1987; Carmignani & Kligfield, 1990).

Upstream of Sassalbo in the upper Rosaro hydrographic basin, which includes the valley drained by the affluent Canale dell'Acqua Torbida, there is one of the highest altitude evaporite karsts in Italy. Here, gypsum outcrops were locally affected by glacial processes, which destroyed previous surface forms and covered them with moraine deposits (Zaccagna, 1932). Caves (Grotta del Poggione di Val Rosaro, Grotta della Risorgente di Sassalbo, Tana del Poggiolo, Risorgente degli Scettici, and Tana delle Göbie), the longest of which is 450 m, testify a water circulation probably influenced by the evolution of the small glacier that occupied the high portion of valley. Glacial deposits also occur in caves and probably had a relevant role in speleogenesis, enhancing erosion processes during wet interstadial phases (Piccini, 2003; Chiesi et al., 2011). Two large fields of dolines are observable in the area starting from the Ospedalaccio and Cerreto passes and descending along the right side of the Rosaro stream valley and in the area starting from the summit of Monte Cunella and descending to Prati di Camporaghena (right side of the Canale dell’Acqua Torbida valley). A large sinkhole next to the village of Sassalbo opened at the beginning of March 2017 in the detrital cover of the Upper Triassic Burano evaporite Formation.

The head of the Canale dell'Acqua Torbida valley (Comano and Fivizzano municipalities), between Monte Alto and Ospedalccio Pass, is characterised by a high petrological diversity, due to the outcrop of rocks of different tectonic units. The rocks of the Tuscan nappe are here represented by: sandstones of the Macigno Formation (Upper Oligocene-Lower Miocene), which form the south slope of Monte Alto; pelagic, mainly shaly rocks of the Tuscan Scaglia (Cretaceous-Lower Oligocene); Upper Triassic evaporites. The allochthonous Ligurian and Subligurian units, remnants of the Ligurian-Piedmont Ocean (or Alpine Tethys), are represented by Helminthoid flysch (Upper Cretaceous), and Canetolo shale and limestone (Upper Palaeocene-Middle Eocene). Metamorphic slices of the Palaezoic basement are represented by metapelites, micaschists, and metabasits, which crop out in the area of Ospedalaccio Pass.

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References