Dispersión del campo magnético terrestre obtenida a partir de remanencias primarias en lavas

Resumen

A total of 120 sites with geochronological control have been sampled in the Transmexican Volcanic Belt (TMVB). They span the spatial and temporal activity of this volcanic arc. The mean paleo-magnetic directions, obtained from volcanic rocks in the age range 10-5 Ma and 5-0 Ma, do notdiffer from their respective reference directions. In both data sets, virtual geomagnetic poles (VCPs)have been selected using Fisher's precision parameters and optimum cutoft angles (Vandamme,1994). This results in a circularly symmetrical data distribution with normal and reverse modes thatare indistinguishable from antipodal. VCP dispersions are consistent with those from globally distributed observations analysed by McFadden et al. (1991) and McElhinny & McFadden (1997) torthe Miocene and the Plio-Quaternary, respectively. Abnormally low scatters of VCPs have beenreported in previous studies of Miocene and Quaternary lavas of the TMVB. An analysis of all thepublished paleomagnetic data from this arc, when selected in terms of the same quality criteria, donot either support the persistence of a magnetic anomaly in the studied region, in agreement withthe present study.