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Introduction:
The site of Bois Louis-Bois Epenin is an individual and original site by its very flat terrain and very original geology, unique (one of the few sectors of the Artois outcrops of Devonian layers of sandstone Matringhem intercalated with schist) that contribute to the existence of a large number of habitats likely to accommodate a wide variety of vegetation.
The career of the lake has been exploited in the late 19th and early 20th century. From the road, the aerial part was treated first in search of sandstone (about 12m) and then following the sandstone benches it was about 15m deep. The work was very artisanal, with pickaxes, stones forks, sedans on narrow rails that were ripées the crowbar to get closer to the extraction. A pump left side of the quarry dewatering assured. The coils were lift on an inclined plane is next to the river and to the crusher.
One morning the workers found the fully water-filled career. All equipment, pumps, sedans, rails and tool shed were engulfed. The lake was formed in a single night of the winter 1890-1891, (operations began in 1880).
Sandstone's formation :
Sandstone is a detrital rock that formed about 370 million years ago during the primary era in the Devonian period on the Famennian stage.
A detrital rock is a rock formed by the accumulation of sediments, so sandstone comes from the accumulation of sand banks deposited at the bottom of the sea that undergo the phenomenon of sedimentation: under their own weight, these deposits are packed and gradually sunk (phenomenon of subsidence).
By diagenesis (all chemical and mechanical processes that affect a sedimentary deposit), the sand grains are cemented by precipitation and crystallization of dissolved salts in the pore water.
If the degree of cementation is weak, the rock is so friable as if it's high, the rock is hard and consistent.
Sandstone is then, a sedimentary rock composed of grains of sand (quartz or silica) connected by a variable nature of cement (siliceous, calcareous or ferruginous) which the quality and color of the sandstone depends on: clear or yellowish white to grayish, the sandstone can also be colored in yellow, red or green by iron oxides.
The sandstone can sometimes be hillock: its surface has bumps.
Limestone formation:
Limestone is a sedimentary rock which was formed at the bottom of the sea who took up all our region, 60 and 80 million years ago.
The rock is made up of a lot of limestone particles (nanofossils visibles at the electronic microscope) who are the rests of limestone elements from very little single-celled algaes which hard parts (coccoliths) were fossilised at the bottom of the sea during a lot of years. This formed a submission of several meters of limestone in our region where some fossils can be found.
Thus, at Cretaceous period, during some tens millions of years, at the bottom of the seas and all over the world, wonderful and amazing layers of limestone were formed with hundreds of these coccoliths (from greek« cocco »which means « seed », and « lit » which means « stone » ).
Reminder on "Earthcaches": There is no container or logbook on the given coordinates. Just visit the site and answer the questions by e-mail or by the Message Center.There is no need to wait for my reply, feel free to log immediately after. If the answers are incorrect, I will let you know. Happy caching!
To validate your visit:
1-. N 50°26.283 E 002°30.390: What is the size and the maximal depth of the lake? What is the origin of the water?
2-. N 50°26.269 E 002°30.401: What rock do you see there? How do you recognize it?
3-. N 50°26.270 E 002°30.262: What rock do you see there? How do you recognize it?
4-. N 50°26.285 E 002°29.938: What rock do you see there? How do you recognize it?
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