Comprehensive paleomagnetic study of a succession of Holocene olivine-basalt flow: Xitle Volcano (Mexico) revisited

Abstract

A detailed paleomagnetic study of a young Late Holocene olivine-basalt flow from the Xitle volcano in the southern Basin of Mexico was completed to evaluate the consistency and reliability of the record derived from fresh well-preserved and exposed lava flows. One-hundred oriented standard paleomagnetic cores corresponding to 10 different lava effusion episodes were collected from unit-flow V. Thermomagnetic analyses show that bulk magnetic properties and remanence is carried in most cases by Ti-poor titanomagnetite, presumably resulting from oxy-exsolution processes during the initial flow cooling. Unblocking temperature and coercivity suggests pseudo-single domain magnetic grains for these (titano)magnetites. Thermal and alternating field demagnetizations show well-defined univectorial magnetizations. Most sites present a mean direction with small angular dispersion around the dipolar direction for central Mexico. The overall mean direction (N = 10, Dec = 1.1• , Inc = 34.1• , k = 531 and α 95 = 2.1 • ) is characterized by small angular dispersion and inclination close to the dipolar value for the locality. Anisotropy of magnetic susceptibility lineation agrees with the geologically-inferred flow direction. Various samples from the 10 lava flows were selected for Thellier paleointensity experiments because of their stable remanent magnetization and relatively low within-site dispersion. According to reliability parameters, the obtained paleointensities are of reasonably good quality. Nine mean paleointensities range between 48.6 and 73.9 μT. The overall mean paleointensity of 59.9-7.7 μT is higher than the present-day field of 43 μT, consistent with the global data for this time-period. Most samples presented alteration during the cooling rate test, and no correction was made to these samples. Those samples on which cooling-rate correction was applied give a flow mean lower than the raw paleointensity data, as was expected.

Palaeosecular variation for 0.1-21 Ka from the Okataina Volcanic Centre, New Zealand

“…The values range from 54.1 to 74.7 μT, and the mean of specimen palaeointensities is 64.3±6.7 μT (n = 10), indicating a standard deviation of 10.4%. This is not unusual because a large dispersion of palaeointensities from a single lava flow has often been reported (e.g., Böhnel et al, 2003;Alva-Valdivia, 2005). Nevertheless, it might indicate an intrinsic limitation of the Thellier's experiments that a large dispersion is observed from such excellent materials.…”

Analysis of geomagnetic secular variation for the last 1.5 Ma recorded by volcanic rocks of the Trans Mexican Volcanic Belt: new data from Sierra de Chichinautzin, Mexico

“…The ChVF has been previously studied reported by twelve paleomagnetic studies (Herrero-Bervera and Pal, 1977;Urrutia-Fucugauchi and Martin del Pozzo, 1993;Mooser et al, 1994;Gonzalez et al, 1997;Mora-Alvarez et al, 1991;Böhnel et al, 1997;Böhnel and Molina-Garza, 2002;Urrutia-Fucugauchi, 1996;Vlag et al, 2000;Morales et al, 2001;Alva-Valdivia, 2005; Maghoub, 2019) for rocks younger than 40 ka. One of these papers (Mooser et al, 1994) was not included in the analysis because important information as the sampling location, age and demagnetization protocols were not given in the publication.…”

“…There were many paleomagnetic studies focusing on field directions and intensities, during the last 30 years (e.g. Herrero-Bervera and Pal, 1977;Urrutia-Fucugauchi and Martin Del Pozzo, 1993;Böhnel et al, 2003;Alva-Valdivia, 2005), but new radiocarbon and argon-argon ages, obtained in the past 15 years (e.g. Siebe, et al, 2004b, Guilbaud, et al, 2015, Jaimes-Viera, et al, 2018 open exciting perspectives for secular variation studies.…”

Patrimonio natural de la Reserva Ecológica del Pedregal de San Ángel y áreas cercanas: sitios de interés geológico y geomorfológico al sur de la Cuenca de México

“…En particular, algunas estructuras recurrentes en las lavas han sido asociadas a la interacción explosiva entre la lava y agua en el subsuelo, los llamados "tubos de explosión" de Waitz y Wittich (1910), pero Walker (2009) interpreta como zonas de suturas entre flujos contiguos (ver Figura 7: sitio Entrada Principal -CU). Cabe mencionar que las propiedades magnéticas y paleomagnéticas de las lavas han sido estudiadas extensivamente (Herrero-Bervera et al, 1986;Cañón-Tapia et al, 1995y 1996Alva-Valdivia, 2005;Morales et al, 2006).…”