Publication: Southward migration of continental volcanic activity
in the Sierra de Las Cruces, Mexico:
palaeomagnetic and radiometric evidence
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Publication Date
2000
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Elsevier Science B.V., Amsterdam
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Abstract
New Palaeomagnetic data for 30 sites (271 samples) and K–Ar data from five units in the Sierra de Las Cruces,
western Basin of Mexico, provide constraints on the spatial-temporal evolution of arc magmatism in the central
Trans-Mexican Volcanic Belt. The normal and reversed directions show a polarity pattern with a consistent spatial
zonation perpendicular to the NNW–SSE trend of the range. The magnetostratigraphy and K–Ar dates indicate that
volcanic activity in the Sierra de Las Cruces migrated southeastward at a mean rate of 1.6 cm/a, between 3.6 and
1.8 Ma, and that the rate of migration may have been higher, up to 4 cm/a, during the Gauss Chron. Normal and
reversed directions pass the reversal test at a 95% confidence level. The mean Plio-Quaternary palaeomagnetic
direction for Sierra de Las Cruces is D=350.7°, I=30.6° (N=25, k=30.7, α95=5.3°). The declination deviates to the
west of the expected direction, which suggests that small counterclockwise rotations could take place during formation
of the Sierra de Las Cruces volcanics.