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La datación de fallas poco profundas en la corteza terrestre
B A van der Pluijm1, C M Hall, P J Vrolijk
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA. vdpluijm@umich.edu
Nature
|July 13, 2001
Resumen
La datación radiométrica de fallas poco profundas es un desafío debido a las edades minerales mixtas. Este estudio introduce un nuevo método utilizando el modelado de rayos X para fechar de manera confiable la actividad de fallas cercanas a la superficie, revelando un cambio significativo en el régimen de estrés en el oeste de América del Norte.
Área de la Ciencia:
- Geología Geología Geología.
- Geocronología Geocronología.
- La tectónica es la tectónica.
Sus antecedentes:
- La datación radiométrica de fallas superficiales de la corteza terrestre es difícil debido a las bajas temperaturas que impiden la recristalización mineral.
- Las zonas de fallas poco profundas conservan poblaciones mixtas de phyllosilicates detrital y authigenic, lo que complica la determinación de la edad.
- La pérdida de argón-39 (39Ar) durante la irradiación puede conducir a edades erróneamente antiguas al datar minerales de arcilla.
Objetivo del estudio:
- Desarrollar y presentar un método fiable para la datación de la actividad de fallas cercanas a la superficie.
- Para caracterizar las poblaciones de arcilla en el surco de fallas utilizando el modelado de rayos X y la encapsulación de muestras.
- Para determinar la edad de la falla de empuje de Lewis en las Montañas Rocosas canadienses e inferir la historia tectónica.
Principales métodos:
- Utilizando el modelado de rayos X para caracterizar las poblaciones de minerales de arcilla en el surco de fallas.
- Empleando técnicas de encapsulación de muestras para mejorar la precisión de la datación.
- Aplicación de la datación radiométrica a muestras de fallas de la falla de empuje de Lewis.
Principales resultados:
- La falla de empuje de Lewis en el sur de las Montañas Rocosas canadienses data de aproximadamente 52 millones de años.
- Esta edad indica un rápido cambio en el régimen de estrés del oeste de América del Norte de la contracción a la extensión durante el Eoceno.
- La edad de elevación / exhumación y la fuente sedimentaria de las rocas se estimaron en aproximadamente 172 millones de años.
Conclusiones:
- El método presentado fecha confiablemente la actividad de fallas cercanas a la superficie.
- La edad del Eoceno de la falla de Lewis proporciona información crucial sobre la evolución tectónica del oeste de América del Norte.
- El estudio destaca la importancia de la caracterización de las poblaciones minerales para estudios geocronológicos precisos en zonas de fallas frágiles.
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