Magnetic Mineralogy, Paleomagnetism, and Magnetostratigraphy of Nayarit Volcanic Formations, Western Mexico: A Pilot Study

The first rock-magnetic, paleomagnetic, and magnetostratigraphic study was carried out on Late Miocene volcanic formations from the Nayarit area (western Mexico) in order to provide constraints for the tectonic evolution of the western Trans-Mexican volcanic belt (TMVB) and southern Gulf of California extensional province (GEP), and to establish a reference magnetostratigraphy for the volcanic sequences. Rock-magnetic experiments show that remanence is carried in most cases by Tipoor titanomagnetite, resulting from oxy-exsolution of original titanomagnetite during the initial flow cooling. Unblocking temperature spectra and relatively high coercivities point to "small" pseudo-single domain magnetic grains for these (titano)magnetites. Single-component, linear demagnetization plots were observed in most cases. The mean paleodirection obtained in this study is I = 33.7°, D = 358.4°, k = 140, a95 = 3.0°, N = 17. This mean direction is in agreement with the expected paleodirections for the Late Miocene, as de...