Orvieto (Umbria, Italy): A quest for wine excellence

Orvieto, located in the southwestern portion of Umbria, has had a long and storied wine history beginning in the Etruscan age, through the Roman period, and into the Medieval and Renaissance periods. The Papal Curia was especially fond of the wine of the region and is credited with introducing non-indigenous varieties such as Trebbiano into the zone. The historic wine of the region has always been a sweet wine but the wine of today is better known for its dry character.

The Duomo at Orvieto

Favorable factors for winemaking in Orvieto
Donata Castagnoli (The wine-producing territory of Orvieto, Journal of Wine Research) has identified a number of factors which favor wine production in Orvieto:

• The presence of hill slopes with good exposure (south-facing)
• Flat areas limited to the Paglia and Tevere river valleys
• A suitable altitude
• The presence of volcanic clay soils (the soils of the region have been covered in a recent post)
• Tuffaceous detrital Rupe as key enabler of the vinification process
• The soft soil (up to 45-m deep on the hill) allows multi-level caves to be dug out allowing gravity-fed, cool-temperature vinification and cool, light-free aging
• Proximity to the large, sophisticated markets of Rome and Florence.

Quest for ever-increasing quality
In the modern era, winemaking in Orvieto has been characterized by efforts focused on increasing the quality of the wine. The first such initiative was the Miniterial Decree of 23 October 1931 which restricted the production of "typical wine" to the territories of Orvieto, Basche, Ficulle, Monterubraglio, Porano, Castel Giorgio, and Atlerona. Since that initial effort, a series of Ministerial Decrees, DOC Production Regulations, and mods to those regulations have been instituted  (Table 1) in order to advance the quality goals.

                                                   Table 1. Orvieto Regulatory History

Ministerial Decree	Production Regulations	Stipulation
23 Oct., 1931		Production of “typical wine” established in territories of Orvieto, Baschi, Ficulle, Monterubiaglio, Porano, Castel Giorgio, and Allerona
	1971	DOC; Orvieto and Orvieto Classico
	1991	DOC regulations revised to improve ampelographic composition
	1997	Yield reduction to 8 tons/ha for Orvieto superior New vineyards no less than 3000 vines/ha
	1998	Establishment of Rosso Orvietano DOC Includes the entirety of communes partly delimited by Orvieto DOC Identifies main (70% of wine) and secondary varieties Max of 10 tons/ha yield Establishment of Lago di Corbara DOC Entire commune of Baschi and part of Orvieto Red wines
	2003	Grechetto as the primary variety (40 - 80% of finished wine) Late harvest type included; yields cannot exceed  tons/ha
3 August, 2010		8 different wine types for Orvieto and Orvieto Classico Simple name secco (dry) abboccato, amabile, dolce (all sweet) superiore (superior) vendemmia tardiva (late harvest) muffa nobile (noble rot); max yield of 5 tons/ha
8 March 2011		Grants DOC Lago di Corbara right to include white and single-variety wines in production

Source: Derived from Castagnoli.

In parallel with the changes in regulatory law -- and sometimes driven by it -- changes have occurred in the Orvieto viticultural environment. In the 1960s, grape-growing was one part of a mixed farming environment. Specialized cultivation increased steadily during the 1960s, gradually replacing mixed farming. The DOC Production Regulations of 1971 changed things dramatically in that it stipulated a monoculture and prohibited the planting of dissimilar clones in close proximity to each other. This focus on grape-growing has resulted in an increase in wine production from 2.5 million bottles in the 1970s to 20 million bottles in 2010.

The Wines
Orvieto is essentially a white wine region with two included small red wine DOCs (Lago di Corbara and Rosso Orvietano). Th regulations stipulate that the Orvieto wine must be made form Procanico and Grechetto (minimum 60%) and 40% maximum of other suitable white grapes. The wine can be labeled Classico if the grapes were grown in one of the communes mentioned in the 1931 Ministerial Decree and can be labeled Superiore or Classico Superiore if: (i) the yield is kept to 8 tons/ha; (ii) alcohol is at least 12%; and (iii) the wine is aged a minimum of three months.

Orvieto continues the production of its historic sweet wines under a variety of labels. The most interesting of these are the late harvest and "noble rot" sweet wines. Orvieto was the first region in Italy to be recognized for noble rot sweet wines, a situation arising from a "fortuitous combination of autumn morning mists alternated with correct sunshine hours and levels and a good daytime ventilation" (Castagnoli).

Both of the red wine DOCs are blends and provide vehicles for showcasing international and better-known Italian varieties.

The production values of the various Orvieto wines are provided in the tables below.

Table 2. Vineyard Surface Area by Wine

DOC	Vineyard Surface (ha)	Percent
Orvieto	330	15.14
Orvieto VT	208	9.2
Orvieto Classico	1550	71.08
Rosso Orvietano	661	3.03
Lago di Corbara	336	1.54

Source: Derived partially from Castagnoli

Table 3. 2009 Wine Production by Type

Wine	Certified Wine (L)
Orvieto Classico	79,850,380
Orvieto	26,202,700
Orvieto Classico Abboccato	8,250,800
Orvieto Classico Anabile	7,468,230
Orvieto Classico Superiore	4,331,550
Rosso Orvietano	1,257,300
Lago di Corbara	856,070
Orvieto Anabile	375,000
Orvieto Abboccato	101,000
Orvieto Classico Superiore Dolce	83,000

Source: Castagnoli

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Umbria (Italy) and Orvieto landscapes and soils

Umbria, one of the smallest of the Italian regions, lies almost dead center on the peninsula and is the only region to border neither a body of water or a country. I recently visited the region and, as part of my reportage, will explore some of its landscape and soils characteristics in this post.

Source: olio2go.com

One hundred million years ago, much of Italy was an ocean floor. According to Menichetti and Coccione, the Umbria - Marche sedimentary basin formed in the late Triassic in a passive continental margin of the southern Tethys Ocean. In that basin, a 3000-m-thick stratigraphic succession "records the thermal and mechanical subsidence history from the Jurassic carbonate platforms to the pelagic realm of the Paleogene, while its upper part consists of Neogene terrigenous clastics that accumulated in a migratory foredeep system reflecting the encroachment of the Apennic deformation and sedimentation patterns into the Adriatic foreland" (Menichetti and Coccione).

Source: rocksinmyheadtoo.com

In describing the Apennines, a distinctive feature of the Italian Peninsula, and, as such, Umbria, Vezzani, et al., paint a picture of "lithotechnic assemblages that evolved through interaction between the African and European plates in the central Mediterranean with: (i) Mesozoic development of the Tethyan domain; (ii) Cretaceous-Eocene oceanic subduction; (iii) Oligocenic-Miocene and Pliocene convergence, continental collision and shortening; and (iv) late-Miocene - present extensional collapse of the contractional edifice." The Vezzani - Menichetti and Coccione arguments are tightly aligned.

According to Moti, geologic processes through the ages have resulted in the following soils distribution:

• Alluvial sediments and debris along major river valleys
• Gravels, sands, and clays deposited during the Pliocene and early Pleistocene
• Marly deposits during the Oligocene - Miocene
• Stratigraphic Umbria-Marche deposits from the Jurassic-Miocene
• In the southwest, volcanic deposits from the eruptions of the Vulsino volcano.

This distribution is illustrated graphically in the figure below.

Schematic geologic map of Umbria.
Blue = Limestone; Gold = Sandstone rocks;
 Yellow = Inter-mountain basins; and
Purple = Volcanic complexes (Source:
Andrea Moti, researchgate.net)

Orvieto Landscape
Orvieto, one of the three major Umbrian wine regions, is centered around the town of Orvieto in southwest Umbria which, itself, sits on the northern edge of a broad volcanic plateau (alfina) which originated in the Quaternary period. Orvieto is shown in the map below.

Source: adventourus.com

The geological configuration of the Orvieto area is a direct result of neotectonic and volcanic events which took place in the Quaternary. The marine clays revealed by the departing sea experienced an extensional tectonic stage during the lower Pleistocene, resulting in a NW-SE fault. Magma flows and pyroclastics from the Vulsino volcano terminated against the raised block of this fault and backfilled to form the Alfena Plateau. Alfina Plateau formation dates from the middle Pleistocene.

Over time, the River Paglia and its tributaries cut the volcanic tuff of the Alfina Plateau into mesas (Bardano and Orvieto, for example) or buttes (Rocca Ripensa, for example). The distribution of soils in the Orvieto area is shown in the figure below. Note that the main difference between this distribution and the broader Umbrian distribution is the addition of a volcanic layer to the series.

1, talus (Oligocene); 2, recent and present alluvial sediments,
also terraced (Oligocene - Upper Pleistocene); 3, volcanic rocks
of the Alfina plateau (Middle Pleistocene); 4, gravels, sands and
clays (marine clastic sediments, Lower Pleistocene - Pliocene);
5, marls and sandstones (pre-Pliocenic bedrock); 6, River Paglia
and its main tributaries. Source: Moti.

The middle Pliocene clays form the base of the stratigraphic sequence in the Orvieto area and serves as reservoir for water flowing through from the uppermost layers. This is the old seabed present before the emergence of the Apennine range and these clays tend to be bluish in color -- tending towards grey -- and have high calcium carbonate content (marly clays). In some areas the CaCO₃ content can exceed 40% (argillaceous marls). These clays are also characterized by a good percentage of micaceous silt.

In mesas, there is a thin layer of volcanic origin from a fluvial-lacustrine environment that is called the Albornoz series. This soil type is probably incorporated into the topmost layers in non-mesa, non-butte structures.

The topmost stratigraphic layer in mesas, and a significant component of the recent alluvial sediments, is the effluvia of the Vulsino eruptions which occurred over a 300,000-year period. This lithoidal tuff with black scoriae includes "yellow-orange tuff of lithoidal texture with numerous inclusions of pumice and extremely friable rock of a grey color that incorrectly takes the name of pozzolano." Both the pozzolano and tuff have natural porosity.

Bibliography
Andrea Moti, An Example of Possible Application of Detailed Geological Maps. The 11 DOC/DOCG Destined to Wine Production in Umbria, researchgate.net
Corrado Cencetti, et al., The Rock of Orvieto (Umbria, Central Italy), researchgate.net
Mario Menichetti and Rodolfo Coccione, Umbria - Marche Apennine geological field trip, researchgate.net
Livio Vezzani, et al., Geology and Tectonic Evolution of the Central-Southern Apennines, Italy

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