|
The Saint-Mathieu dome is a dome-like upwarp in the metamorphic basement of the northwestern French Massif Central. It exposes a very deep and normally hidden parautochthonous unit at the surface. == Geography and geology == The Saint-Mathieu dome, named after the small town Saint-Mathieu in the Haute-Vienne department, is situated at the very northwestern edge of the Massif Central. To the southwest the dome structure is bordered by sediments of the Aquitaine Basin, the contact usually being marked by a border fault. On its eastern side the upwarp is overthrust by augengneisses (A) of the Lower Gneiss Unit (LGU), which between Saint-Jean-de-Côle in the South and the hamlet of ''Peyrassoulat'' (commune of Chéronnac) in the North override the Parautochthonous Micaschist Unit (PMU). The dome is bounded to the North by paragneisses of the Lower Gneiss Unit. The northwestern corner of the basement high is cut off by the Le Lindois Fault separating the dome's interior from the Mazerolles Unit in the Northwest and from Lias to the Southwest. The dome measures about 35 kilometers in its maximal meridional extension and about 25 kilometers in an East-West direction. Within the dome the following geological units can be discerned: * Parautochthonous Micaschist Unit (PMU), bounded to the West by the intrusive Saint-Mathieu Leucogranite (SML) and to the North by the Chéronnac Leucogranite. * Paragneisses (P), intruded by the Piégut-Pluviers Granodiorite (PPG). On its western side the upwarp is traversed by a North-South-striking fault zone, which separates the Piégut-Pluviers granodiorite from the paragneisses. This fault zone starts at ''Lacrète'' (commune of Étouars) in the South and terminates just south of Massignac in the North. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Saint-Mathieu Dome」の詳細全文を読む スポンサード リンク
|