Le nom d'Oxfordien a été proposé en 1829 par Brongniart (d'Oxford , ville anglaise), et employé par les géologues dans diverses acceptions. Aujourd'hui on le défini comme l''étage le plus ancien du Malm (Jurassique supérieur). Il suit le Callovienet précède le Kimméridgien. On y distingue trois sous étages, du plus ancien au plus récent : l'Argovien, le Rauracien et le Séquanien.
En ce qui concerne les Ammonites, c'est le règne des Cardioceras, des Pachyceras, des Neumayria, des Ochetoceras, etc. Au point de vue stratigraphique, il importe de constater que l'Oxfordien succède à une grande trangression callovienne, qui a pour effet l'invasion par la mer d'une partie des masses continentales, telles que le continent nord-atlantique, le continent indo-malgache, tandis que, par compensation, la mer est partiellement refoulée hors des géosynclinaux, vraisemblablement par suite de plissements peu considérables, préludant aux mouvements alpins.
ET ON Y TROUVE QUOI COMME FOSSILES ????
Des ammonites , des bellemnites , des bivalves , des restes d oursin
Pour valider cette cache vous devrez REPONDRE A CES QUESTIONS
1- A quelle etape le fossile apparaît à la surface du sol ???
2-Quel est l age approximatif d un fossile trouvé dans l oxfordien ????
3-QUELLE EST LA COULEUR DES MARNES SUE LE SITE ?????
4-De quelle ére fait partie L'Oxfordien ???
5- poster une photo de vous avec un fossile trouvé sur place ( optionel)
BON GEOCACHING
I propose here a journey in time.
During this time or n men were not yet the surface of our beautiful planet. For this I'll let you discover lOXFORDIAN and its fossils
-HOW SE FORM A FOSSIL?
According to a broad definition, a fossil is what remains of a being who lived in the distant past andhaving survived thanks to a preservation under natural conditions.
The fossils we have are body parts, or traces left by the living creature when she was still alive (in thiscase, spoken of trace fossils). They form when plants or dead animals are preserved before completelydeteriorate to finally part of the sedimentary rock of the Earth. Fossilization occurs, the plant or the animal concerned must be buried pretty quickly, usually under a layer of mud. Then comes a chemicalprocess ensuring the preservation through mineral changes in original fabrics.
Fossils are the essential evidence of the details of prehistoric life. In many parts of the world, hundreds ofmillions of fossils were discovered, thus opening a window in the history and structure of life on Earth.
Process of fossilization
Legend:
1. the animal dies and falls to the bottom of the sea.
2. mud and sand fill the shell.
3. the shell is covered by sludge.
4. over the years, the sludge will turn into rocks.
5. the layers of rocks back above the sea level.
6. thanks to erosion, the fossil appears on the surface of the ground.
a short video to show you here ––– http://www.erasme.org/libre/environnement_SVT/animations/la_fossilisation.swf
L OXFORDIAN BUT WHAT IS IT ?
To observe the geological survey site map
Thanks to this we can contact that we are in a place oxfordian
OXFORDIAN
The oxfordian the first stratigraphic stage of the late Jurassic (Malm). It extends from-161,2 4 to 155.7 ±4 million years.
The Oxfordian name was proposed in 1829 by Brongniart (of Oxford, English City) and is used bygeologists in various meanings. Today is defined as l ' floor the oldest of the Malm (Jurassic). It followsthe Callovienet above the Kimmeridgian. There are three floors, from oldest to newest: the Aargau, theRauracien and the Sequanien.
In regards to the Ammonites, it is the reign of Cardioceras, of Pachyceras, of Neumayria, of Ochetoceras, etc. Stratigraphic standpoint, it is important to note that the Oxfordian succeeded a great transgressioncallovienne, which effect is to invasion by sea for part of the land masses, such as the North Atlanticcontinent, the continent indo-Malagasy, while by offsetting, the sea is partially repressed outgeosyncline, likely as a result of little substantial folding, prelude to the Alpine movements.
AND THERE IS WHAT FOSSILS?
Ammonites, bellemnites, bivalves, Sea Urchin
To validate this cache you will need to
-1 what stage the fossil appears on the surface of the ground?
2 - What is the age approximate d a fossil found in oxfordian l?
3. WHAT IS THE COLOR OF THE MARLS SUE SITE?
4 - what part does era the Oxfordian?
5 post a picture of you with a fossil found there (optional)
GOOD GEOCACHING