Apuan Alps tectonic window
geological interpretation
 

Near Passo del Vestito, along the provincial route Massa-Arni, there is an unique panoramic view on the Apuan Alps tectonic window and geometrical relationships between the Massa Unit and Autochthonous Auct. Unit.
Here, the physical landscape presents large outcrops of Mesozoic-carbonate sequence, with the evidence of main tectonic structures, from the mountain ridge to the valley bottom of Frigido river.

The location of panoramic viewpoint, along the provincial route from Massa to Arni

Geological interpretation of the spectacular landscape and outcrops of the Frigido's Valley:
From here it is easy to observe one of the most suggestive geologic panoramic views in the Apuan Alps, already illustrated by Domenico Zaccagna, engineer and geologist in 1881.
It is possible to see two main ridges; in the background the ridge includes the peak of these main mountains from east towards east: Sagro, Grondilice, Contrario, Cavallo, Tambura, Sella and Macina. In foreground the Mandriola crest, above the village of Resceto, joins at M. Cavallo towards the north east.
We can observe and identify the geological structure of the Apuan Alps consisting in  a fold system of kilometric anticlines and synclines that caused repetitions of  rocks, showing different age and composition.
From the western portion of the geological panoramic view toward the east we can see:
Mt. Sagro Syncline (n. 1 on the picture); Vinca Anticline (n. 2); Orto di Donna Syncline (n. 3);  Mt. Tambura Anticline (n. 4).

Structural interpretation of the Apuan tectonic window in the northern area:
1) Mt. Sagro syncline; 2) Vinca anticline; 3) Orto di Donna syncline; 4) Mt. Tambura anticline
fl) lower phyllites; pf) porphiroids and porphiritic schists; gr) “grezzoni” dolomites; md) dolomitic marbles; m) marbles s.s.; cs) cherty limestones; d) radiolarites

Geological map of the Frigido's Valley with the location of panoramic viewpoint
 

The Autochthonous Auct. Unit too is formed by a paleozoic basement (fl-pf), deriving from previous orogenic structures, with an initial age presumably dating back to the Cambrian.
The Meso-Cenozoic cover begins with a classic “Verrucano” characterized by polygenic conglomerates, calcareous metasandstones and siliciclastic dolomites intercalated with metabreccias presumably deriving from a transitional (from continental to littoral) depositional environment. They are followed by the “grezzoni” dolomites (gr) of the Late Triassic carbonate shelf, which are followed by micritic fossiliferous metalimestones of the “Colonnata” limestones and marlstones. They are then followed by the Megalodont-bearing Marbles intercalated with polygenic metabreccias and chloritoid schists which testify episodes of emersion of the carbonate platform with the formation of lateritic-bauxitic layers and the deposition of debris flows at the bottom of the tectonically active scarps.
Marbles with different dolomitization levels, crystalline dolomites, marbles and monogenic metabreccias are typical of the overlying formations of dolomitic marbles (md) and marbles s.s. (m), witnessing to the development of a new carbonate platform formed after that of the “Grezzoni” dolomites in the Late Triassic. Upward, pinkish marbles, cherty limestones (cs), calcschists and quartzites are a sign of the drowning of the marble carbonate platform and the beginning of an hemipelagic sedimentation.

cs     = cherty limestones
             (Early Jurassic)

m      = marbles s.s.
            (Early Jurassic)

md    = dolomitic marbles
             (Early Jurassic)

gr      = "grezzoni" dolomites
              (Late Triassic)

fl-pf  = paleozoic basement
             (?Cambrian-?Devonian)
           fl) lower phyllites;
           pf) porphiroids and  
           porphiritic schists;

Stratigraphic section of the Autochthonous Auct. Unit in the Frigido Valley

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