A real natural archive


The Pilat Dune has recorded all wind events experienced by the Aquitaine coast.



A real natural archive
Cold, dry, and windy periods have led to sand accumulation and have alternated with warm and wet periods which have enabled vegetation to develop.

The remains of vegetation correspond to paleosols which are visible from the beach to the top of the dune.
 





Sand accumulation has occurred intermittently over time in 5 phases :
 
1  The Landes plateau extended on the current Grand dune site from 8000 BC to 2000 BC. It was flat and covered notably in maritime and Scots pine. This first level corresponds to paleosol 1. It contains numerous strains and types of plant remains dating from that period. It lies on an alios type of subsoil (a black and compact layer resulting from the natural cementation of sand, iron oxide and organic matter).  
 
2 I n prehistoric times, several horizontal layers of sand were deposited. Their surface corresponds to paleosol 2, at a height of around 3m. This level contains the remains of vegetation dating from 2000 BC to 500 BC and denotes the first advance of the sand.  This ancient area was inhabited by man in the VII century BC.
 
And then three generations of dune overlapped. 
 
3  Between 500 AD and 1000 AD, the ancient parabolic dunes were formed during the cold medieval period with its frequent wind storms. At the end of the Middle Ages, the climate became warmer and more humid, allowing vegetation to grow in Aquitaine. Between 1000 AD and 1500 AD, old dunes get covered with forests.  This corresponds to paleosol 3. This ground, only a few centimetres thick, undulates at mid height. It contains wood dating from the XVI century. Remains from that period, such as pipes, flint instruments, ceramics and coins, emerged during archaeological excavations.        

4  When the climate changed in the year 1500, strong winds brought a new series of dunes of the barchan kind, called "modern dunes", which invaded the old dunes and also covered villages and crops. A consular decree of 1801, signed by Napoleon, allowed the fixing of the dunes by sowing maritime pines. Nicolas Brémontier, a road and bridge engineer was in charge.
 
The Grave dune, which once occupied the present site of the Pilat dune, was thus stabilised in the early XIX century. The highest palaeosol (paleosol 4) corresponds to its surface. A cultivated pine forest extended there at that time, where resin harvesting pots were found.
 
Around 1860, the effect of erosion at the foot of the Grave dune set in motion the advent of the present Pilat dune.

It took the Pilat dune 4000 years to appear, while 40 million years were required to form the Pyrenees. On a geological scale, the grand dune is very recent!
 

A real natural archive