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La transición entre el Cretácico y Terciario
Science (New York, N.Y.)
|March 25, 1983
Resumen
El límite entre el Cretácico y Terciario.
Área de la Ciencia:
- Paleontología Paleontología.
- Geología Geología Geología.
- La geoquímica es la geoquímica.
Sus antecedentes:
- El límite Cretácico-Terciario (K-T) marca una transición significativa en la historia de la Tierra, caracterizada por grandes cambios en la fauna y una anomalía de iridio.
- Las interpretaciones anteriores sugirieron un evento de impacto extraterrestre como la causa principal de estos fenómenos del límite K-T.
- Las variaciones en los registros fósiles y datos geoquímicos presentan complejidades en la comprensión de la transición K-T.
Objetivo del estudio:
- Evaluar críticamente la hipótesis de impacto extraterrestre para los cambios faunísticos del límite K-T y la anomalía de iridio.
- Explorar explicaciones alternativas para los registros geológicos y paleontológicos observados en la transición K-T.
- Para sintetizar diversos datos, incluidas las evidencias fósiles, la distribución del iridio y la mineralogía de arcilla, para reevaluar el evento del límite K-T.
Principales métodos:
- Análisis de secuencias fósiles de muestras de núcleo a través de la frontera K-T.
- Examen de los patrones de distribución del iridio y la abundancia de metales nobles en varios sitios.
- Evaluación de la mineralogía arcillosa y los efectos de deposición en las arcillas de la capa límite.
Principales resultados:
- Se observaron variaciones significativas en los tiempos e intervalos de transición de los fósiles dependiendo de la ubicación y los indicadores fósiles.
- Inconsistencias identificadas en la distribución del iridio, cantidades totales y abundancias normalizadas de metales nobles en diferentes sitios.
- Se resaltaron los posibles efectos de deposición en la reducción de los ambientes y la distinta mineralogía arcillosa en la capa límite.
Conclusiones:
- La hipótesis del impacto extraterrestre se cuestiona debido a las variaciones en los datos fósiles y geoquímicos.
- Los eventos terrestres, como el vulcanismo extenso, la regresión del nivel del mar y los cambios paleoclimáticos, ofrecen explicaciones más plausibles para los cambios en los límites K-T.
- La investigación continua en diversos fenómenos terrestres es crucial para una comprensión completa de la transición Cretácico-Terciario.
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