Source: grid.unep.ch |
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. Source:http://www.virtual-geology.info/lozere/lozere.html |
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.
Period
|
Action/Occurrence
|
Result
|
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)
|
|
|
Oligocene
(36 - 24 My)
|
Thick deposits of conglomerates, sandstones, limestone accumulated in the foothills of the young hills
|
Rhone Valley axis collapsed
|
Miocene
(24 - 5 My)
|
|
|
Pliocene
(5 - 2 My)
|
|
|
Quaternary
(2 - My)
|
Erosion changed the look of the landscape
|
|
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