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Alta intensidad geomagnética durante la mitad del Cretácico a partir de los análisis de Thellier de cristales de
J A Tarduno1, R D Cottrell, A V Smirnov
1Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, 14627, USA. john@earth.rochester.edu
Science (New York, N.Y.)
|March 7, 2001
Resumen
El momento dipolar geomagnético fue tres veces más fuerte durante el supercrono de polaridad normal del Cretácico. Este hallazgo apoya un vínculo entre la baja frecuencia de inversión geomagnética y la alta intensidad del campo.
Área de la Ciencia:
- La geofísica es la geofísica.
- El paleomagnetismo es el paleomagnetismo.
- Teoría de la geodinámica Teoría de la geodinámica
Sus antecedentes:
- Las simulaciones numéricas sugieren que la eficiencia de la geodinámica se correlaciona con la intensidad del dipolo y la baja frecuencia de inversión.
- Los datos existentes de paleointensidad han indicado una disociación entre la frecuencia de reversión y la paleointensidad.
- El supercrono de polaridad normal del Cretácico (CNPS) representa un período prolongado de polaridad geomagnética estable.
Objetivo del estudio:
- Para investigar el momento del dipolo paleomagnético durante el CNPS.
- Para probar la hipótesis de una correlación entre la baja frecuencia de inversión geomagnética y el alto momento de dipolo paleomagnético.
- Proporcionar nuevos datos de paleointensidad de la CNPS para resolver discrepancias con los datos existentes.
Principales métodos:
- Análisis de cristales de plagioclase de los basaltos de Rajmahal Traps (113-116 millones de años de edad).
- Aplicación de 56 experimentos de Thellier-Thellier para determinar la paleointensidad.
- Cálculo del momento dipolar paleomagnético promediado en el tiempo.
Principales resultados:
- El momento de dipolo paleomagnético durante el CNPS se determinó como de 12,5 +/- 1,4 x 10^22 A/m.
- Este valor es aproximadamente tres veces mayor que el momento dipolo medio del Cenozoico y el Cretácico Temprano-Jurásico Tardío.
- Los períodos de frecuentes inversiones geomagnéticas en el Cenozoico y el Mesozoico se caracterizaron por momentos de dipolo inferior.
Conclusiones:
- El estudio proporciona pruebas sólidas que apoyan una correlación entre la baja frecuencia de inversión geomagnética y la alta intensidad del campo geomagnético.
- Los hallazgos desafían las interpretaciones anteriores de la frecuencia de reversión desacoplada y la paleointensidad.
- La geodinamo puede operar de manera más eficiente, produciendo un campo de dipolo más fuerte, durante períodos prolongados de polaridad estable.
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