Tuesday, August 26, 2014

Construction of the Rhone wine region landscape

I have been selected to participate in a Press Trip to Chateauneuf du Pape and Tavel prior to DWCC14. I will, of course, be reporting on my findings both during and after the trip but, in keeping with my blog's mantra of "a story within a story," I will set the stage by describing, in ever-tightening circles, the environments within which the winemakers of those two regions operate. I begin here with the outermost circle, landscape formation in the Rhone River Basin, the broader region within which these two appellations are located.

Source: grid.unep.ch
The Rhône wine region runs along its namesake river for 250 km (150 miles) -- and 6 departèments -- between Lyon in the north and Avignon in the south with a division into northern and southern sub-regions at the point where the Drôme tributary intersects the main course. The Northern Rhône is characterized by a continental climate, granitic soils, steep slopes, and the mistral (a high-speed --140 km/90 miles per hour -- north wind that is funneled between the Massif Central and Vercors when there is high pressure over northern France and low pressure in the western Mediterranean) while the south has a more Mediterranean climate, the marin (a moist sea wind), and stony soils. What they both have in common, though, is a sea of red wine: only 2% of the region's production is white.

The Rhone Valley is a sedimentary basin but, unlike the expansiveness of its two better-known compatriots (Paris and Aquitaine basins), it is corridor-like and tightly bound between the unflinching basement rock of the Massif Central to its east and the younger rocks of the Alps to its west (Fanet, Great Wine Terroirs).

I have treated the formation of the Massif Central in my comparison of Douro and Beaujolais granite and schists. Suffice it to say that it was part of a vast mountain range (The Hercynian Mountain Belt) stretching from Britain to Eastern Europe which was formed as a result of a continental collision which ended 200 million years ago. This range has been severely eroded over millennia and in many places only exist as "basement" rock, hidden from view by sedimentary deposits. The figures below show the distribution of cover and basement rocks in current-day France as well as the composition of the varying rock types.

Basement and cover rocks of France.

Relationship between basement and cover rocks.
Source: http://www.virtual-geology.info/lozere/lozere.html
Formation timeline -- basement and cover rocks
Source: http://www.virtual-geology.info/lozere/lozere.html

The table below catalogs a series of events from the Lower Cretaceous onwards which have had contributory effects to the current Rhone Valley landscape. The figure immediately following shows the geologic construct of France as a whole and, outlined in black, that of the Rhone River Valley.

Lower Cretaceous
(135 - 96 My)
Reef limestone deposited on continental platform surrounding Vocontian Trough (deep undersea area south of today's Valence)
Hard limestone hills now surrounding the Rhone Valley
Upper Cretaceous
(96 - 65 My)
  • Vocontian Trough filled with sandstone/sandy limestone/marly-sandstone
  • First phase of folding in Provence due to uplift of Pyrenean-Provençal axis (through end of Eocene)
  • Formed right bank of Rhone, Tricastin, and Massif d’Uchaux
  • Forced the Jurassic and Cretaceous cover northward
(36 - 24 My)
Thick deposits of conglomerates, sandstones, limestone accumulated in the foothills of the young hills
Rhone Valley axis collapsed
(24 - 5 My)
  • Sea used the Rhone Valley as a corridor to link up to sea covering Central Europe
  • Alpine uplift reaches a crescendo
  • Sands, marly sands, sandy molasse deposited
  • Rhone digs itself through Miocene deposits as well as Urgonian limestone (formation of the Donzère defile)
  • Carves deep gash in basement granite north of present-day Tain l'Hermitage
  • Raising of the region along its eastern border
(5 - 2 My)
  • Final marine incursion
  • Deposits of fine argillaceous and argillaceous-sandy elements
(2 -  My)
Erosion changed the look of the landscape
  • Rubble and scree built up in the piedmont of the Urgonian limestone hills
  • Four levels of stony terrace systems formed along the Rhone and tributaries
MY = Millions of years. Data sourced from Fanet, Great Wine Terroirs.

The types of soils present in, as well as the location of, vineyards are a result of these landscape formation activities. In a follow-up post I will detail the vineyards and their soils.

©Wine -- Mise en abyme

No comments:

Post a Comment