Geological formation of the Paris Basin, alternating layers of different rocks:
The Paris Basin is based on a crystalline basement deeply buried. After erosion in the Cambrian, the region is covered by a shallow sea and sediments (sandstones and shales) are deposited. The Paris Basin is then identified a high plateau north and south by two mountain ranges. By the end of the Carboniferous and Permian, the Paris Basin region collapses.
• Early Triassic, depression thus created sees detrital sediment rocks from erosion of the surrounding Hercynian massifs, forming layers of sandstone. Towards the end of the Triassic, the basin is covered by a shallow tropical sea that left deposits.
• At Jurassic clastic deposition after a period, the sea covering the basin people that will leave coral carbonate deposits (limestone). At the same time, under the combined weight of the sediments and the fragmentation of Pangaea, the basin sinks
• In the Cretaceous, the basin is found in the northern part emerged. The South, however, is regularly flooded by the sea. This period is rich in sandy deposits. Late Cretaceous, when a major global marine transgression, the sea again invaded the entire basin and deposited thick layers of chalk, formed by the accumulation of shells (testing) limestones.
• In the Paleocene, the whole continental crust rises under the pressure of the Alpine orogeny in the south. Southern Paris basin finds emerged, while its eastern part, the Vosges, lifts, curving sedimentary layers and falling edges of the bowl. These layers carried aloft will thus highly exposed to erosion, this erosion and give rise to the formation of Cuestas, erosion releasing the old layers. During that time, the sea pushed to the northwest, shelly limestone deposits. Withdrawing it will leave room for lagoons depositing marl. At the end of the Paleocene, the sea returns, sand and clay deposits, then withdrawing leaves behind lakes that sedimented limestone.
• At the beginning of the Eocene period of marine transgressions and recessions, the sea from the north-west, invaded again the center of the basin, until Champagne. Of sand and clay and limestone deposit.
• In the Miocene, the current drainage system, the Seine and the Marne, is set up. The basin is so dominating a vast plain just the level of the sea.
• In the Pliocene, the region is raised by tectonic forces: rivers face a steeper slope, sink there, digging in sedimentary layers updating Cretaceous chalk. Erosion of land carried aloft accelerates the formation of Cuestas.
• During the Pleistocene glaciations, the sea level drop. Rivers take a steeper slope and continue to dig their valley.
A panel on site tells you this landscape:
Landforms, landscape support that is offered to you have a history. It begins there are about 80 million years (secondary era). The sea then covering the entire Paris Basin: a vase is deposited and gave birth to the chalk. Deposits of various origins followed the cover of. There are "only" a few tens of thousands of years, all training was covered by silt (fine grinding of rocks) brought by winds from the North.
This is consistent strata alternating layers and furniture which led the presence of Talus (1) and escarpments (2) of slopes to valleys ledge (3), trays or benches (4).
Rock fragmentation of phenomena by alternating freezing and thawing and mass movements affecting soaked materials thawing water, also help to explain the significance of the slope down remblaiements (5) and the valley bottoms (6).
To validate this cache you must:
A) Associate photos with the number, or ledge Plateau, slope, escarpment and valley floor backfilling observing the landscape around and in front of you.
B) Look south describe the elements of the relief that you see?
C) On site, a sign gives you the number of the site, give us the number.
D) A photo taken of you at this point of view, would be welcome (optional).
Log in this cache found it and send me your answers proposals or via my profile or via email geocaching .com ( Message Center ) , and I will contact you in case of problems .