Geomagnetic paleosecular variation recorded in Plio-Pleistocene volcanic rocks from Possession Island (Crozet Archipelago, southern Indian Ocean)

摘要: Possession Island, in the Crozet Archipelago, consists of volcanic units erupted mainly between ~5 and 0.5 Ma. A paleomagnetic sampling was carried out along several sections distributed near northern, eastern, southeastern coasts. total 45 independent flows were sampled (320 samples). For each flow a precisely defined characteristic remanence direction usually isolated after careful progressive cleaning alternating fields. However, particularly complex behavior is often observed. The magnetostratigraphy lava pile quite simple, with reversed rocks lower part normal upper two sections. third section polarity throughout its whole thickness, including three excursional directions. We did not find any intermediate directions reverse magnetozones. Thus we have no evidence for recording Matuyama-Brunhes transition expected from previous study (Watkins, 1972). amplitude paleosecular variation, estimated between-flow dispersion field an axial dipole, 11.8 95% confidence limits 9.3 deg 14.0 deg. This value consistent general anisotropic statistical model variation Constable Johnson, 1999.