Tuesday, September 26, 2017

Soils of the Barolo Zone

In order to provide a full context for the discussion of the soils of the Barolo zone, I initially discussed the formation of the basement rocks, then followed that up with posts on the Tertiary Piedmont Basin, with one post each devoted to the Oligocene - Miocene deposit sequence and the Messinian Salinity Crisis and its deposits. This post on the soils of the Barolo Zone culminates the series.

Marco Giardino, Associate Professor of Applied Geomorphology at the University of Turin, is quoted in Kerin O'Keefe's Barolo and Barbaresco thusly: "About five million years ago, strong seismic activity beneath the Langhe Basin ... thrust the submerged land upwards, causing the trapped water to escape and forming the Langhe hills."

These hills are, according to Dr. Giardino, cuestas (ridges formed by tilted sedimentary rock) and, when they were initially formed, eroded such that newer layers moved to the lower parts of the slopes.These hills were subjected to further erosion when the Tanaro River changed from a northerly to an easterly course 60,000 years ago.

According to Kerin, the soils of the Langhe as a whole is comprised of "marine sediments characterized by a substratum of alternating layers of marls and sandstones." In her conversations with Ferdinando Vignolo-Lutati, he described the soils according to the sequences mentioned in a previous post. Those soils are presented in Table 1 below and the geologic formation associated with the region in Table 2. These data are summarized in the figure immediately following the tables.

Table 1. Barolo Zone soil characteristics (Source: Vignolo-Lutati quoted in Barolo and Barbaresco)
Soil Type Characteristics Location
Serravallian Alternating layers of beds of sand and sandstone layered with marls and sandy marls Almost all of Castiglione Falletto, Monforte d’Alba, Serralunga d’Alba, parts of Barolo and Grignano

Generally gray or yellowish sporadically interspersed with layers of bluish gray marls

Tortonian Principally gray and bluish marls Much of Barolo, small portion of Castiglione Falletto, most of La Morra and Verduno
Messinian Clays mixed with very fine sands  with concentrated calcareous content Parts of Verduno and La Morra

Table 2. Geologic soil formations (Source: Barolo and Barbaresco)
Formation Period Characteristics Location
Lequio Serravalian and Tortonian Silty marls comprised of clay, calcium carbonate and sandstone; ranges from light yellow, almost white, tending to gray Predominantly in Serralunga d’Alba and parts of Monforte d’Alba
Sant’Agata Fossili Marls Tortonian (predominantly) and Messinian (partly) Mainly calcareous clay and bluish-gray marls Villages of Barolo and La Morra
Arenarie di Diano d’Alba Serravalian and Tortonian Particularly rich in sand, especially in the subsoils Primarily in parts of Castiglione Falletto

In comparative terms, the Serravallian soils are seen to be richer in iron content than the Tortonian soils which are seen as richer in magnesium oxide and manganese and, with its calcareous marls, as being more fertile and compact than its counterpart.

©Wine -- Mise en abyme

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