Saturday, June 24, 2017

Landscape formation of Val d'Orcia, home of Vini Franchetti's Tenuta di Trinoro

After my visit to Passopisciaro on Mt Etna, I flew to Tuscany for my visit to Vini Franchetti’s Tuscan estate Tenuta di Trinoro. I visited Il Palazzone in Montalcino on the Friday morning and then set off on what turned out to be a beautiful scenic drive through the rolling hills and cypress-tree-punctuated landscape of Val d’Orcia, the area in which the winery is located.  Before describing the visit, I briefly describe the area in which Tenuta di Trinoro is located.

The continued eastward movement of the Northern Apennines has resulted in the creation of a number of long (up to 200 km), narrow (up to 25 km wide), NE – SW-oriented structural depressions on the western side of the mountains in the Tuscany region. These depressions are bounded by normal faults along the margins and subdivided into basins by transfer zones/faults.
Radicofani is one such basin. It is bordered to its northwest by the pre-Neogene (pre-23 million years ago (mya)) bedrock of the Montalcino Ridge, to its west by the Neogene-Quaternary (23 mya to present) magmatic rocks of Mt. Amiata, and to its east by the pre-Neogene  bedrock of Mt Cetona and the Cetona Ridge. It is separated from the Siena Basin by the Grosseto-Pienza transfer fault.

Source: Martini, et al.
The pre-Neogene rocks of the basin are primarily composed of two superimposed thrust units (Martini, et al.):
·       Tuscan Unit
o   Lower portions range in age from Triassic (252.2 mya) to Oligocene (33.9 mya)
o   Exposed rock consists primarily of shelf components and turbiditic, poorly cemented sandstones (Macigno)
·       Ligurides
o   Range in age from Cretaceous (146.5 mya) to Eocene (33.8 mya)
o   Consists primarily of basinal silaceous limestone and argillaceous limestone (marlstone).
The Radicofani Basin began to form on the pre-Neogene substrates during the middle Miocene and “a thick sedimentary pile accumulated mainly during the early Pliocene." The turbiditic sandstone associated with the Tuscan Unit of pre-Neogene rocks appears to be the major contributor of sand for the basin. Other substrate rocks contributed pebbles, limestone cobbles, metamorphic detritus, and some sand.

The basin emerged toward the end of the Early Pliocene and, after a general uplift, no younger sedimentary record is apparent. Magmatism has affected the southern portion since the early Pliocene and volcanic eruptions occurred during the Pleistocene (1.8 mya – 10,000 years ago).
The landscape of Tuscan Pliocene marine basins are characterized by gentle slopes and mostly arable lands with permanent crops. The Radicofani Basin is a Tuscan Pliocene basin which houses Val d’Orcia, home of Tenuta di Trinoro. The Val d’Orcia landscape is characterized by clay-dominated rocks and gentle slopes which have been severely affected by soil erosion processes and widespread earth and mud flows.

The map below shows the general location of Val d'Orcia within the broader Tuscany while the one immediately following shows the location of Tenuta di Trinoro.

While archaeological evidence shows that grapes were grown in the area since Etruscan times, the Val d'Orcia region is not widely known for quality winemaking (As a region, it only attained DOC status in 2000) but that may be about to change. According to Antonio Galloni, "If I had to name the most exciting emerging viticultural area in Tuscany, Val d'Orcia would be it."

Mauro Coltorti, et al., Geomorphological map and land units at 1:200,000 scale of the Siena Province (Southern Tuscany, Italy), Journal of Maps, 7:1, 2011.
Martini, et al., Geological map of the Pliocene succession of the Northern Siena Basin (Tuscany, Italy, Journal of Maps, 7:1, 2011.

©Wine -- Mise en abyme

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