Paleomagnetism and rock magnetic properties of Late Pleistocene volcanism from El Pinacate Volcanic Field, northwest Mexico

• Published in: Journal of South American earth sciences 2019-12, Vol.96, p.102368, Article 102368
• Main Authors: Rodríguez-Trejo, A., Alva-Valdivia, L.M., Vidal-Solano, J.R.
• Format: Article
• Language: English
• Subjects: El Pinacate volcanic field; Northwest Mexico; Paleointensity; Secular variation
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2019.102368

The Pinacate Volcanic Field is a Neogene volcanic sequence at the northwestern part of Mexico. This paleomagnetic study (directional and paleointensity) will continue to improve the global paleomagnetic databases. It is the first full vector paleomagnetic analysis within the more than 400 volcanic structures of the Pinacate Volcanic Field, e.g. scoria, cinder cones, large ‘pahoehoe’ and ‘aa’ lava flows. A total of 140 oriented standard paleomagnetic cores from 16 sites of lava flows were collected. Rock magnetic experiments such as thermomagnetic analyses show that Ti-poor titanomagnetite is the main magnetic carrier of the remanence. Microscopy of oxide minerals supports this observation. Parameters from hysteresis and FORC diagrams suggest pseudo-single domain grain sizes or a mixture of single and multidomain particles. The directional analysis of 11/12 volcanic structures provides a mean paleomagnetic direction and corresponding mean paleomagnetic pole (calculated from the site VGPs): Dec = 0.1°, Inc = 54.5°, n = 11, α95 = 6.7°, k = 48, Plat = 86.5°, Plong = 247.8°, A95 = 7.5°, respectively. The mean paleointensity, obtained by using the Thellier-Coe protocol, and estimated from seven volcanic structures is 42.2 ± 3.6 μT, and VDM is 8.1 × 1022Am2. The obtained directions are compatible with the Late Pleistocene paleodirection as expected from the geocentric axial dipole (GAD) field. The virtual geomagnetic pole scatter (Sb) was calculated at 13.5° which is consistent with the paleosecular variation value expected from El Pinacate latitude. •First paleomagnetic study of the Late Pleistocene volcanism from El Pinacate Volcanic field.•Mineral microscopy and rock magnetic results suggest Ti-poor titanomagnetite as the main magnetic carrier of remanence.•Mean paleointensity, 42.2 ± 3.6 μT and VDM 8.1 × 1022 Am2 were determined for the volcanic activity of the last 50 ka.•Directional and paleointensity analysis match with the expected GAD for the last 50 ka in Mexico.•Secular variation of the earth magnetic field was compared with global compilations published.