I have previously treated the geology of Colli Tortonesi DOC but, while the treatment was comprehensive, the final product was unconsolidated. I address that shortcoming in this post.
The Villalvernia-Varzi Line is a key feature of the regional geology. It is an east-striking, slightly dipping fault zone which separates the sedimentary structures of the Tertiary Piedmont Basin to its south of from the Epiligurian Unit sediments in the wedge-top basin to its north. The role that this line has played is evidenced in the two charts following which show the comparative parent-rock geology. The Line is represented by the Antognola Formation in both of the charts.
In the charts below, we see evidence of at least four tectonic events south of the line and no equivalent activity in the north.
The chart immediately following shows a lack of alignment in sediment deposition within the two basins except for Sant'Agata Marl in the middle of the Late Miocene and no evidence of deposition in the Epiligurian Units post that phase. It is unclear as to whether that lack of deposits post the Sant'Agata phase was due to erosion in the Epiligurian column or an early uplift.
Screen shot from Festa, et al., Geological Map of the Villalvernia-Varzi Line |
As shown in the chart below, the parent rocks have eroded down to primarily limestone, clays and marls.
Descriptions of these soil types can be found on my soils page but I have also used the wein+ glossary to construct the table shown below.
Table 1. Soil types described in Colli Tortonesi (Descriptions curated from Wein+)
Soil Type | Description |
Limestone |
|
Chalk |
|
Clay |
|
Marl |
|
Sand |
|
Lime Tuff |
|
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