GACILIEN SOIL COMPOSITION
La Gacilly owes its varied landscapes and picturesque terrain to a geological feature: the formation of a large syncline (actually a valley) that crosses Brittany from Quimper to Saint-Julien de Vouvantes near Châteaubriant. The peaks of the fold (or anticline) appear in La Gacilly with the heights of the Primary era: the Forêt Neuve and Graslia on one side and the Landes de Couesmé, the Forêt Noire and the Glouzie on the other.
The Primary era left a lot of slate schist at the bottom of the syncline; it outcrops in many places in and around the commune: Bout-du-Pont, Grée Saint-Jean, Villeneuve, La Bergerie, La Forêt Noire, Saint-Jugon, and Saint-Jacob. The following eras mainly brought sedimentary rocks, primarily sandstone, which appear in particular at the top of anticlines such as Graslia (white sandstone) or at the top of Grée Saint-Jean and the heights of Châtelier and Saint-Jugon (puddingstone sandstone).
Wetlands
These environments are created by the accumulation of repeated precipitation on impermeable or poorly drained soils. Shallow bodies of water form in depressions in the ground, on the shores of lakes, rivers, or oceans. They can also be formed by the dead arm of a watercourse. Alluvial deposits, which slow down the flow of rivers and streams, can also give rise to the formation of marshy environments.
Wetlands are transitional environments between land and water, characterized by their ability to retain water. Their presence is influenced by geology, soil type, climate, and topography.
The different types of wetlands
There are many different types of wetlands: marshes, peat bogs, meadows, riparian forests, etc. Each one is unique and home to a multitude of species of flora and fauna that would be endangered if the site were to disappear.
There are three main types of wetlands:
Coastal wetlands: Located by the sea, these environments can be regularly submerged due to the tides. Coastal wetlands include lagoons, mangroves, mudflats, and salt marshes. The plants that live there have a superpower: they tolerate salt, unlike almost all other species!
Peat bogs and fens (continental): In general, these areas are often saturated with water and have peaty soil. Organic matter never decomposes completely there. They are home to a very characteristic moss, sphagnum, which spreads out in spongy mats. Peat bogs are essential to many species of birds, plants, and insects.
Alluvial wetlands (continental): These are wetlands that form in the floodplains of rivers, at the bottom of valleys. Traditional agricultural practices, such as grazing or mowing wet meadows, have often shaped these landscapes. The meadows are therefore more or less wet and more or less rich in minerals.