Rock magnetic characterization and paleomagnetic directional analysis of Isla San Pedro Nolasco dikes, Gulf of California, Mexico
Por:
Alva-Valdivia, Luis M., Vidal-Solano, Jesus R., Velderrain-Rojas, Luis A., Gonzalez-Rangel, Jose A.
Publicada:
1 ago 2021
Categoría:
Geochemistry and petrology
Resumen:
Isla San Pedro Nolasco is located in the central-eastern part of the
Gulf of California, formed by late Miocene (ca. 9-11 Ma) hypabyssal
rocks, between the Sonora coast and oblique-divergent Pacific-North
America plate boundary. Continental blocks exposed as islands in the
Gulf of California host key geological evidence for understanding the
evolution of the plate boundary. We present a detailed rock magnetic
study of 31 independently oriented paleomagnetic cores from late Miocene
dikes collected from a southeastern bay of the island. Opaque microscopy
and rock magnetic properties suggest that magnetic mineralogy is mainly
Ti-poor titanomagnetite or magnetite with limited maghemite and rarely
titanohematite. Magnetization has two components. The primary and more
stable is of medium to high temperature (300-560 degrees C) or high
fields (up to 100 mT). The primary thermal remanent magnetization (TRM)
and the oxide mineral textures observed suggest that cores from these
dikes provide high reliability for paleomagnetic analysis. The mean
paleomagnetic direction is as follows: Dec = 354.86 degrees, Inc = 46.2
degrees, alpha 95 = 5.2, k = 44. Comparison of these results to the 10
Ma paleomagnetic pole for North America indicates that Isla San Pedro
Nolasco has experienced no vertical-axis rotation but has displaced
similar to 100 km to the northwest, similar to independent estimates for
fault offset along with this structural system from the northern Gulf of
California and regional tectonic reconstructions. These results,
supported by detailed geological studies, indicate that the island was
detached from mainland Mexico by transtensional faulting in the late
Miocene Gulf of California shear zone that also formed the adjacent
Yaqui pull-apart basin.
Filiaciones:
Alva-Valdivia, Luis M.:
Univ Nacl Autonoma Mexico, Lab Paleomagnetismo, Inst Geofis, Circuito Invest Cient, Mexico City 04510, DF, Mexico
Vidal-Solano, Jesus R.:
Univ Sonora, Div Ciencias Exactas & Nat, Dept Geol, Hermosillo 83000, Sonora, Mexico
Velderrain-Rojas, Luis A.:
Univ Nacl Autonoma Mexico, Inst Geol, Estn Reg Noroeste, Posgrad Ciencias Tierra, Hermosillo 83000, Sonora, Mexico
Gonzalez-Rangel, Jose A.:
Univ Nacl Autonoma Mexico, Lab Paleomagnetismo, Inst Geofis, Circuito Invest Cient, Mexico City 04510, DF, Mexico
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