The municipal territory of Châtillon, crossed by the large glacial valley of Dora Baltea, is located in the middle Aosta Valley.

From a geological point of view, this territory almost completely consists of rocks of the ophiolitic Zermatt-Saas unit (Piedmont zone, Penninicum).
However, some slices of Austroalpine basement rocks crop out in the area near Châtillon, on the left side of Dora Baltea.
In particular, the main slice, ca. 1 km long, crops out between the church of Châtillon and the rock wall above the railroad to the west of the little town; it consists of fine-grained gneiss and albite schists with local eclogite relics showing a late Alpine greenschist facies metamorphic overprint (Dal Piaz & Martin, 1988). A second significant slice crops out (partly within the municipal territory of Châtillon and partly within the municipal territory of Saint-Vincent) at the base of the south slope of Mont Zerbion, at an altitude of 900-950 m, to the northeast of Domianaz village; it consists of coarse-grained kinzigitic gneiss with large porphyroblasts of pre-Alpine sillimanite substituted by fine polycrystalline aggregates of Alpine kyanite. The red-brown pre-alpine biotite is generally transformed into assemblages of phengite and garnet. Associated rocks are glaucophane- and magnesiochloritoid-bearing eclogitic micaschists with mafic eclogite boudins.

The territory on the right side of Dora Baltea is part of the Mont Avic serpentinite massif, a southern prolongation of the Zermatt-Saas unit. Serpentinite consists of antigorite, magnetite, and coarse-grained titanclinohumite, forsterite, diopside, chlorite, and amphibole, which are reminiscent of the original mantle texture. Serpentinite encloses rodingitic dykes and lenses bordered by magnetite-rich chlorite schist. The rodingite localities of Ponte delle Capre (Pont des Chèvres) and Bellecombe are well known among the mineral collectors for their splendid fissure minerals (grossular, andradite, vesuvianite, diopside, epidote, etc.). Other mafic rocks, consisting of (not rodingitized) metagabbro and metabasalt with relict eclogitic minerals, occur as tectonic slices associated with serpentinite, calcschist, and sulphide-rich epidosite. Along the northern slope of Mont Barbeston, SW of Bellecombe, small outcrops of eclogites in metabasites are present. Their typical mineral assemblage includes omphacite, almandine-rich garnet, rutile, zoisite, and sometimes glaucophane, phengite, and quartz. Choriteschists, consisting of chlorite, almandine, magnesiochloritoid, talc, paragonite, mica-epidote pseudomorphs after lawsonite, minor quartz, and carbonates, also occur.

Fossils

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Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Ch%C3%A2tillon,_Aosta_Valley
Wikidata ID:	Q34966
GeoNames ID:	6542138

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References