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

Paleomagnetic directions were obtained from stepwise alternating-field or thermal demagnetization of 53 lava flows from southern Patagonia (latitudes 49.5°-52.1 °S) that include the Pali-Aike volcanic field and the Meseta Viscachas plateau lavas. In addition to previous Miocene-late Quaternary ages...

Descripción completa

Guardado en:
Detalles Bibliográficos
Publicado: 2004
Materias:
Geocentric axial dipole
Lava flow
Paleomagnetic secular variation
Pali-Aike Volcanic Field
Patagonia
Time-averaged field
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v5_n3_p_Mejia
http://hdl.handle.net/20.500.12110/paper_15252027_v5_n3_p_Mejia
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_15252027_v5_n3_p_Mejia
record_format dspace
spelling paper:paper_15252027_v5_n3_p_Mejia2023-06-08T16:19:31Z Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows Geocentric axial dipole Lava flow Paleomagnetic secular variation Pali-Aike Volcanic Field Patagonia Time-averaged field Paleomagnetic directions were obtained from stepwise alternating-field or thermal demagnetization of 53 lava flows from southern Patagonia (latitudes 49.5°-52.1 °S) that include the Pali-Aike volcanic field and the Meseta Viscachas plateau lavas. In addition to previous Miocene-late Quaternary ages of these flows, 40Ar/39Ar dates spanning from 0.1 to 15.4 Ma were obtained for 17 of the sites. All except one of the magnetic polarities coincide with the expected polarities of the magnetic polarity timescale [Cande and Kent, 1995] for the obtained 40Ar/39Ar ages. The mean direction from 33 sites (eliminating sites <4 Ma) that pass a selection criteria of α95 ≤5° is Dec = 358.7°,Inc = - 68.2°, α95 = 3.5°, a value that coincides within the statistical uncertainty with the direction of the geocentric axial dipole for that area (Inc = - 68.1°). Likewise, the mean virtual geomagnetic pole (VGP) coincides within the statistical uncertainty with the geographic North Pole. The secular variation described by the VGP angular standard deviation for these sites is 17.1°, a value expected for that latitude according to Model G of paleosecular variation [McFadden et al., 1988]. The characteristics of the data presented are optimum for time-averaged field (TAF) studies because of the good age control and good quality of the paleomagnetic data: (1) primary components of magnetization were obtained using principal component analysis [Kirschvink, 1980] from at least five points and maximum angular deviation ≤5°, (2) site means were calculated with Fisher statistics using at least three samples, and (c) 38 of the 53 flows had α95 ≤ 5°. No results (five sites) or high α95 values (≤5°) were obtained primarily from sites affected by lightning. Copyright 2004 by the American Geophysical Union. 2004 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v5_n3_p_Mejia http://hdl.handle.net/20.500.12110/paper_15252027_v5_n3_p_Mejia
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Geocentric axial dipole
Lava flow
Paleomagnetic secular variation
Pali-Aike Volcanic Field
Patagonia
Time-averaged field
spellingShingle Geocentric axial dipole
Lava flow
Paleomagnetic secular variation
Pali-Aike Volcanic Field
Patagonia
Time-averaged field
Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
topic_facet Geocentric axial dipole
Lava flow
Paleomagnetic secular variation
Pali-Aike Volcanic Field
Patagonia
Time-averaged field
description Paleomagnetic directions were obtained from stepwise alternating-field or thermal demagnetization of 53 lava flows from southern Patagonia (latitudes 49.5°-52.1 °S) that include the Pali-Aike volcanic field and the Meseta Viscachas plateau lavas. In addition to previous Miocene-late Quaternary ages of these flows, 40Ar/39Ar dates spanning from 0.1 to 15.4 Ma were obtained for 17 of the sites. All except one of the magnetic polarities coincide with the expected polarities of the magnetic polarity timescale [Cande and Kent, 1995] for the obtained 40Ar/39Ar ages. The mean direction from 33 sites (eliminating sites <4 Ma) that pass a selection criteria of α95 ≤5° is Dec = 358.7°,Inc = - 68.2°, α95 = 3.5°, a value that coincides within the statistical uncertainty with the direction of the geocentric axial dipole for that area (Inc = - 68.1°). Likewise, the mean virtual geomagnetic pole (VGP) coincides within the statistical uncertainty with the geographic North Pole. The secular variation described by the VGP angular standard deviation for these sites is 17.1°, a value expected for that latitude according to Model G of paleosecular variation [McFadden et al., 1988]. The characteristics of the data presented are optimum for time-averaged field (TAF) studies because of the good age control and good quality of the paleomagnetic data: (1) primary components of magnetization were obtained using principal component analysis [Kirschvink, 1980] from at least five points and maximum angular deviation ≤5°, (2) site means were calculated with Fisher statistics using at least three samples, and (c) 38 of the 53 flows had α95 ≤ 5°. No results (five sites) or high α95 values (≤5°) were obtained primarily from sites affected by lightning. Copyright 2004 by the American Geophysical Union.
title Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
title_short Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
title_full Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
title_fullStr Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
title_full_unstemmed Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
title_sort plio-pleistocene time-averaged field in southern patagonia recorded in lava flows
publishDate 2004
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v5_n3_p_Mejia
http://hdl.handle.net/20.500.12110/paper_15252027_v5_n3_p_Mejia
_version_ 1768543674168246272

Ejemplares similares