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El U-Pb envejece desde la Formación Doushantuo neoproterozoica, China
Daniel Condon1, Maoyan Zhu, Samuel Bowring
1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. dcondon@mit.edu
Science (New York, N.Y.)
|February 26, 2005
Resumen
La Formación Doushantuo en China se depositó hace entre 635 y 551 millones de años, coincidiendo con la deglaciación global. Sus fósiles animales son en su mayoría más jóvenes que 580 millones de años, con una significativa excursión de isótopos de carbono cerca de la parte superior.
Área de la Ciencia:
- Geocronología Geocronología.
- Paleoclimatología Paleoclimatología
- Paleontología Paleontología.
Sus antecedentes:
- La Formación Doushantuo en China tiene importantes registros paleontológicos y geológicos.
- Su tiempo de deposición y su relación con los eventos climáticos globales como la glaciación de Marino son cruciales para comprender la vida temprana.
- Estudios anteriores han sugerido un amplio rango de edad para la formación.
Objetivo del estudio:
- Para fechar con precisión la Formación Doushantuo utilizando el análisis de circón U-Pb.
- Para correlacionar el tiempo de deposición de la Formación Doushantuo con los eventos climáticos globales, específicamente el final de la glaciación marina.
- Para limitar la edad de la biota de Doushantuo e investigar las excursiones isotópicas de carbono asociadas.
Principales métodos:
- U-Pb zircón geocronología de los lechos de ceniza volcánica.
- Análisis de isótopos de carbono de muestras de carbonato.
- Análisis estratigráfico de secuencias.
Principales resultados:
- Las fechas del zircón U-Pb sitúan la deposición de la Formación Doushantuo entre hace 635 y 551 millones de años.
- La base de la formación es contemporánea con el final de la glaciación marina, lo que indica una desglaciación sincrónica.
- Los datos isotópicos de carbono y la secuencia estratigráfica sugieren que los fósiles animales de la formación son en gran parte más jóvenes que 580 millones de años.
- Se ha identificado una excursión significativa de isótopos de carbono negativos de carbonato en la formación más alta de Doushantuo, que data de hace aproximadamente 551 millones de años.
Conclusiones:
- La Formación Doushantuo registra un período crítico que abarca el final de la glaciación marina y la posterior deglaciación.
- Las restricciones de edad refinan nuestra comprensión del momento de la vida animal temprana dentro de esta formación.
- La excursión del isótopo de carbono negativo hace unos 551 millones de años representa un evento potencialmente global que afectó a los primeros ecosistemas.
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