Les Blocs de Grès de Fontainebleau, France
N 48° 25.171 E 002° 43.507
31U E 479661 N 5362966
[FR] Les grès de Fontainebleau sont célèbres par les rochers de forme bizarre qui sont très convoités par les amateurs d'escalades. [EN] The sandstone boulders of Fontainebleau are famous for their bizarre shapes and are loved by rockclimbers.
Waymark Code: WM3YYD
Location: France
Date Posted: 06/08/2008
Views: 91
[FR] L'essentiel du massif est constitué par le sable "de Fontainebleau", dépôt maritime tertiaire (Stampien inférieur; 35 millions d'années). Localement, le sable est consolidé en grès. Il repose sur le calcaire de Brie (Sannoisien supérieur) et sur des marnes vertes (Sannoisien moyen).
Au-dessus de l'énorme couche sableuse se déposa le calcaire d'Etampes (Stampien supérieur), formant des plateaux et lui-même recouvert au quaternaire par des dépôts éoliens de sables et de limons. L'érosion ayant dégagé les masses de grès formées à l'intérieur du sable, la circulation des eaux creusa des "Gorges", provoqua des "Chaos", dénuda des "Rochers" imposants et isola des "Monts" (dénominations locales dans la toponymie).
[EN] Towards the end of the tertiary era (35 million years ago), the Stampien sea (named after the city of Etampes), filled a gulf which encompased the area of Paris and opened towards the English channel. As the waters receded very pure quartzite sand was deposited in the area of Fontainbleau, the thickness of which can attain 60 meters. The sand was soon covered by a vast lake in which Etampes limestone was deposited which protected the sand from intrusions of discoloring oxides, which explains their purity qnd whiteness. Alternating wet and dry periods allowed the water laden with silica to cement the sand and thereby transform it into sandstone.
At the time the Alps and Pyrenees emerged, the Fontainebleau massif and the Paris region were raised up out of the water : the relief was oriented West Northwest - East Southeast, and dunes formed in the quaternary age.
Next, due to the action of erosion, the relief reversed itself : the water carrying away the sand, left behind the more resistant sandstone layers. The undermining by water, and the release of the underlying sand along the border of the ridges caused the sandstone to collapse, which gave rise to the present "chaotic" nature of the sandstone boulders.
Waymark is confirmed to be publicly accessible: yes
Access fee (In local currency): .00
Requires a high clearance vehicle to visit.: no
Requires 4x4 vehicle to visit.: no
Public Transport available: yes
Parking Coordinates: Not Listed
Website reference: Not listed
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Visit Instructions:
No specific requirements, just have fun visiting the waymark.