Constraints on Brunhes low-latitude paleosecular variation Iztaccihuatl stratovolcano, basin of Mexico

Abstract

The upper Iztaccihuatl stratovolcano formed during the Brunhes chron, which is supported by the normal polarity and the overall mean paleomagnetic pole (Steele, 1985). The period involved is probably long, in the range suggested by K-Ar dating studies (Nixon et al., .1986) of 580 000 to 76 000 years ago. Apparent discrepancy irt paleosecular variation estimates for the Basin of Mexico reported by Steele (1985) and Bohnel et al. (1990) depends on the methods and assumptions made concerning the statistical characteristics of the virtual geomagnetic pole (VGP) data populations. The mean pole is 88.1 °N, 34.0°E (B = 21, K = 88, A₉₅ = 3.4). The overall VGP population distribution is elongated and non-Fisherian. The VGP dispersion is affected by sources other than those of secular variation and may include undetected local! tectonic effects or excursions/events of the geomagnetic field. The best estimate SF is 7.4 °, some 7° smaller than that derived from latitude-dependent paleosecular variation models, but similar to values for the Hawaii, Pagan and Marianas islands and to a previous study in the Basin of Mexico. The region of central Mexico may form part of the central Pacific Brunhes low non-dipole region.