Paleomagnetic evidence for rotation during Stephano-Permian extension in southern Massif Central (France)

摘要: We present results of a preliminary paleomagnetic study devised as test tectonic model proposed by Van Den Driessche and Brun [1] to interpret the main structural features Montagne Noire (South Massif Central, France). This suggests that crustal extension during Stephanian Permian times is responsible for major fiat-lying detachment. The inferred geometrical relationships between fault azimuth direction befieved induce counter-clockwise rotation Paleozoic cover its northward motion. In order this model, we have sampled Autunian (Lower Permian) grey red sandstone beds within two basins opened extension, Lod+ve St-Affrique basins. six sites (three in each basin) using thermal demagnetization procedures, reveals presence 3 magnetization components. A first one (A), which unblocked below 400 o C, interpreted recent overprint due weathering sandstones. B component 575 C. assumed be primary, although gentle dip does not allow fold test. It fits Lower field Lod~ve basin (in situ: D m = 194 °, I 6 o, k 50, tilt corrected: - 10 53). contrast, it shows systematic difference declination 173 2.5 101, 172 lm= 37). post-Autunian at least 20 basin, thus supporting implications model. Finally, sediments from yield third (C) with unblocking temperatures up 670 °C carried hematite. Its also consistent direction, showing hematite crystallisation occurred early diagenesis history sediments.