Castellazzo GEOSITE
Item
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Title
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Castellazzo GEOSITE
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Description
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It is a large sub-rounded rocky block that lies on the grassy clearing enclosed by the ruins of the medieval 'Castrum Capriarum', on the top of a rocky hump that emerges some twenty metres from the alluvial plain of the Dora Riparia, on the border between the municipalities of Condove and Caprie in the Castellazzo region (Susa Valley). There are several aspects of interest that this geosite site presents: the multiplicity of shapes linked to the modelling of the ancient Quaternary glacier of the Susa Valley; the historical monumental context; the surreal landscape value of a rocky island miraculously preserved from the siege of anthropic activities and infrastructures with a strong environmental impact (quarries, motorway, power lines). The rocky block in the Castellazzo region is a typical example of an erratic boulder, i.e. a large stone element that fell by landslide onto the surface of a glacier and was transported by it further downstream, even over distances of kilometres (diagram 1).
Only with this mechanism is it possible to justify the presence of a rock block of a different lithological nature (metagranite) from that of the base and the adjacent slope, which consist of serpentinitic rocks.
On the basis of the distribution of lithotypes with a mineralogical composition similar to that of the boulder, and the considerable degree of rounding of the erratic boulder, it can be hypothesised that the most probable area of origin of the boulder itself is on the southern slopes of Mount Baraccone behind the present-day Borgone village.
The installation of the erratic boulder on the top of the mound in the Castellazzo region, and of numerous other boulders on the left slope in the Truc le Mura locality, took place at the time of the disappearance of the glacial mass that covered the Castellazzo mound (diagram 2).
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Lithology
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orthogneiss
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serpentinite
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Landform shape
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Erratic boulder on the top of the hill
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Event environment
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glacier related setting
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Event process
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deposition
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Older named age
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Pleistocene
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Interest
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Geomorphological
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Historical
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Bibliographic Citation
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Aigotti et al 2004
