Paleontology
Gers,
a land of vestiges
The Gers Department takes up the centre
of the Basin of Aquitaine. Its geological history is
therefore closely linked to such structure. The best
represented period stands in the Tertiary era: it is
the middle Miocene, between 11 and 16 million years
ago. During that period, the Atlantic Ocean flooded
the Basin of Aquitaine several times. The coastline
then moved toward the interior of the country, up to
Gers. The marks of those past events can still be seen
nowadays through the sediments and fossils which they
contain.
The sea deposits of the middle Miocene are grouped together
under the general name of "Tawny Sands". Continental
deposits are represented by a set of molassic grounds
which contain many remains of land species. The site
of Sansan gained a world reputation in the palaeontology
field. However, Sansan is not an isolated case within
the Department. Many other deposits, such as La Romieu,
Simorre, Manciet., are also famous all over the world.
The Gers geological heritage offers a
real journey through time.
15 million years ago, the region is a
marshy steppe, sprinkled with many lakes and bordered
with a tropical forest. This is the place where many
animal species, which live close by, meet when they
come to water. The climate at that time is subtropical
damp, with regularly alternated dry periods and humid
seasons. Vegetation is made up of grasses, pines, alders,
nettle trees, bamboos, reeds, moss, mushrooms…
Many animals move around in that landscape, among which
the most spectacular ones are several species of rhinoceros
and elephants. We can find many trails of smaller herbivores,
among which cervidae (antelopes) and suidians (warthogs)
are predominant species. Carnivores are also of different
sizes, from genets to "plantigrade lions",
and felines the size of a panther. Primates, which arrived
through migration, live in the forest. Other occupiers
of the biotope are more discreet: birds, birds of prey,
rodents, reptiles and batrachians for instance.
The ocean is some dozen kilometres away,
northbound, near Lectoure. Deep changes are in process.
The sea level changes and the climate tends to get dryer.
Some animals then disappear and other evolve. A migration
wave from Africa and Eurasia brings new species, which
are going to thrive and follow a particular evolution
in Western Europe. The site of Sansan, discovered by
Edouard Lartet in 1834 in the heart of Gascony, illustrates
such an evolution and remains the essential witness
of the ecological transformations which are being carried
out. The stake of such a key-moment in history is the
setting up of wildlife such as we know it nowadays all
over the European continent.
An amazing memory site!
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