Plio‐Pleistocene time‐averaged field in southern Patagonia recorded in lava flows

摘要: [1] Paleomagnetic directions were obtained from stepwise alternating-field or thermal demagnetization of 53 lava flows southern Patagonia (latitudes 49.5°–52.1°S) that include the Pali-Aike volcanic field and Meseta Viscachas plateau lavas. In addition to previous Miocene-late Quaternary ages these flows, 40Ar/39Ar dates spanning 0.1 15.4 Ma for 17 sites. All except one magnetic polarities coincide with expected polarity timescale [Cande Kent, 1995] ages. The mean direction 33 sites (eliminating ≥4 Ma) pass a selection criteria α95 ≤ 5° is Dec = 358.7°, Inc −68.2°, 3.5°, value coincides within statistical uncertainty geocentric axial dipole area (Inc −68.1°). Likewise, virtual geomagnetic pole (VGP) geographic North Pole. secular variation described by VGP angular standard deviation 17.1°, latitude according Model G paleosecular [McFadden et al., 1988]. characteristics data presented are optimum time-averaged (TAF) studies because good age control quality paleomagnetic data: (1) primary components magnetization using principal component analysis [Kirschvink, 1980] at least five points maximum ≤5°, (2) site means calculated Fisher statistics three samples, (c) 38 had 5°. No results (five sites) high values (>5°) primarily affected lightning.