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Abstract:

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.

Registro:

Documento: Artículo
Título:Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows
Autor:Mejia, V.; Opdyke, N.D.; Vilas, J.F.; Singer, B.S.; Stoner, J.S.
Filiación:Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611-2120, United States
Departamento de Geologia, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon 2, Buenos Aires, 1428EHA, Argentina
Department of Geology and Geophysics, University of Wisconsin-Madison, 1215 West Dayton Street, Madison, WI 53706, United States
INSTAAR, University of Colorado, 1560 30th Street, P.O. Box 450, Boulder, CO 80309-0450, United States
Palabras clave:Geocentric axial dipole; Lava flow; Paleomagnetic secular variation; Pali-Aike Volcanic Field; Patagonia; Time-averaged field
Año:2004
Volumen:5
Número:3
DOI: http://dx.doi.org/10.1029/2003GC000633
Título revista:Geochemistry, Geophysics, Geosystems
Título revista abreviado:Geochem. Geophys. Geosyst.
ISSN:15252027
Registro:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15252027_v5_n3_p_Mejia

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Citas:

---------- APA ----------
Mejia, V., Opdyke, N.D., Vilas, J.F., Singer, B.S. & Stoner, J.S. (2004) . Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows. Geochemistry, Geophysics, Geosystems, 5(3).
http://dx.doi.org/10.1029/2003GC000633
---------- CHICAGO ----------
Mejia, V., Opdyke, N.D., Vilas, J.F., Singer, B.S., Stoner, J.S. "Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows" . Geochemistry, Geophysics, Geosystems 5, no. 3 (2004).
http://dx.doi.org/10.1029/2003GC000633
---------- MLA ----------
Mejia, V., Opdyke, N.D., Vilas, J.F., Singer, B.S., Stoner, J.S. "Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows" . Geochemistry, Geophysics, Geosystems, vol. 5, no. 3, 2004.
http://dx.doi.org/10.1029/2003GC000633
---------- VANCOUVER ----------
Mejia, V., Opdyke, N.D., Vilas, J.F., Singer, B.S., Stoner, J.S. Plio-Pleistocene time-averaged field in southern Patagonia recorded in lava flows. Geochem. Geophys. Geosyst. 2004;5(3).
http://dx.doi.org/10.1029/2003GC000633