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Causa extraterrestre para la extinción del Cretácico-Terciario
Science (New York, N.Y.)
|June 6, 1980
Resumen
Un impacto de un asteroide hace 65 millones de años probablemente causó las extinciones del Cretácico-Terciario. Este impacto explica los altos niveles de iridio que se encuentran en los sedimentos de todo el mundo, apoyando la hipótesis del impacto extraterrestre.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Paleontología Paleontología.
- Ciencias planetarias Ciencias planetarias.
Sus antecedentes:
- Los elementos del grupo del platino, como el iridio, son raros en la corteza terrestre.
- Las elevadas concentraciones de iridio en los sedimentos de aguas profundas sugieren una afluencia de material extraterrestre.
- El límite Cretácico-Terciario (K-T), hace 65 millones de años, marca un evento de extinción masiva.
Objetivo del estudio:
- Para investigar el origen de las anomalías de iridio en el límite K-T.
- Para probar la hipótesis de que el impacto de un asteroide causó las extinciones K-T.
- Para correlacionar la afluencia de material extraterrestre con los eventos de extinción masiva.
Principales métodos:
- Análisis de las concentraciones de iridio en los sedimentos de piedra caliza de aguas profundas de Italia, Dinamarca y Nueva Zelanda.
- Comparación de los niveles de iridio en el límite K-T con los niveles de fondo.
- Análisis químico de la arcilla límite y las capas de piedra caliza circundantes.
Principales resultados:
- Se encontraron aumentos significativos de iridio (30-160x de fondo) en el límite K-T en múltiples ubicaciones.
- Se confirma que el iridio es de origen extraterrestre, no de una supernova.
- La composición de la arcilla límite difiere notablemente de las calizas del Cretácico y Terciario, lo que apoya un origen derivado del polvo.
Conclusiones:
- Un gran impacto de asteroide (diámetro estimado 10 +/- 4 km) es la causa más plausible para las extinciones K-T.
- El impacto inyectó grandes cantidades de polvo en la estratosfera, causando oscuridad global y suprimiendo la fotosíntesis.
- Este mecanismo se alinea con la evidencia paleontológica de extinciones masivas y los hallazgos geoquímicos.
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