Agriculture Reference
In-Depth Information
• Limestone outcrops supporting Rendzinas and Calcareous Brown Soils (pH
7 and above), on which Chardonnay is grown. This terrain produces
especially distinctive wines in the Pouilly-Fuissé area.
Beaujolais . This is an extensive area of vineyards south of Mâcon, which is
divided into well-drained acidic Brown Soils on granite hills north of Villefranche-
sur-Saône (Haut-Beaujolais) and poorly drained clay soils to the south (Bas-Beau-
jolais). The grape variety is almost universally Gamay, and the region is famous
for its Beaujolais Nouveau, released for immediate consumption on the third
Thursday of every November.
The best wines (Cru Beaujolais) are produced on the steep hills (up to 600
m high) of the north, between Côte de Brouilly and St. Armour Bellevue, on shal-
low coarse-textured soils over granite and schist. Here, the Gamay grape, a po-
tentially vigorous variety, is restrained in its growth and produces wines of subtle
flavors. Variation in the metal content (e.g., manganese) of the granite and schist
is said to account for the individuality of the wines in this area (Wilson 1998).
The Napa Valley of California
9.5
Location, Climate, and Geology
The Napa Valley Viticultural Area, outlined in figure 9.8, occupies some 120,000
ha, of which ca. 16,000 ha are planted to vines. The area is situated just to the
north of San Pablo Bay near San Francisco. By world standards, Napa is small,
but it has a reputation for producing quality wines of distinctive character. Much
of this distinction is attributed to the range of mesoclimates, which become warmer
from south to north, and the soil types. California is the place where the Heat
Summation system of classifying climates for viticulture was developed (appendix
14). The rainfall ranges from ca. 750 to 1500 mm, depending on position in the
valley and elevation, and it falls mostly between November and April. The main
determinants of soil variation are geology and relief.
The Napa Valley is relatively young, having been formed by faulting and fold-
ing of old marine sediments ( 65 M yr B.P.) in Miocene times, followed by vol-
canic eruptions, which produced basaltic to rhyolytic lava flows and tephra, over
the last 5 M yr (Elliot-Fisk 1993). The resultant structure is a giant syncline in
which ultrabasic rocks of the ancient oceanic crust are overlain by more recent ma-
rine sediments, and these by the younger volcanic deposits and their erosion prod-
ucts. As shown by the east-west section through the Napa Valley in figure 9.9,
the oldest rocks outcrop high in the ranges on either side (up to 1350 m), and the
younger rocks outcrop progressively at lower elevations. Alluvial and colluvial fans
(locally called “benches”) occupy parts of the lower footslopes, and deep alluvial
clays, silts, sand, and gravel deposited by the Napa River cover the valley floor.
9.5.1
The Soils and Wines
Vineyards in the Napa are mainly confined to the fertile alluvial soil of the valley
floor and the fans or benches extending up the slopes. Vines do not grow well on
9.5.2
 
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