Geoscience Reference
In-Depth Information
development of soils. As pedology progresses, we know approxi-
mately which climatic conditions could lead to the formation of
a bauxite or of a Vertisol.
These methods have enabled the reconstruction of climatic variations
in the Recent Quaternary. Table 2.1 summarizes the major oscillations
according to a widely used terminology.
Post-glacial climates
Table 2.1
Climatic oscillations at the close of the Quaternary in the Northern
Hemisphere.
Geo Glaciation
Period
Dates (BC*)
Climates, vegetation
logy
Subatlantic
Present to -2500
Current humid-
temperate: beech,
oak, spruce
Post-glacial
Subboreal
-2500 to -4500
Cold, dry periods
(continental): oak
<1000 m, beech and
spruce > 1000 m
Atlantic
-4500 to -9700
Warm, humid
(oceanic): oak, ash
Dryas III (
Younger
-9700 to -11000
Cold: tundra with birch,
Dryas
)
pine
Late glacial
Allerød
-11000 to -12700
Temporarily warmer:
pine and birch
Dryas II (
Older
-12700 to -14150
Cold: tundra
Dryas
)
Recent Würm Bölling
-14150 to -14300
Moderately warm:
tundra and birch
Dryas I (
Oldest
-14300 to -18000
Cold (Arctic): tundra
Dryas
)
*BC = Before Christ. The table is very approximate because it does not take into account every kind of
detailed climatic oscillation. Also, the changes are gradual, involving arbitrary limits; lastly, the climate
obviously changes with the site considered!
2.2 ROCKS
2.2.1 Observations
During their surveys of the land, geologists early on recognized the
influence of the rock on the nature of soils. This realization, paradoxically,
