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El ciclo de azufre del Arqueo y la historia temprana del oxígeno atmosférico
D E Canfield1, K S Habicht, B Thamdrup
1Danish Center for Earth System Science (DCESS) and Institute of Biology, Odense University, SDU, Campusvej 55, 5230 Odense M, Denmark. dec@biology.ou.dk
Science (New York, N.Y.)
|April 28, 2000
Resumen
Los isótopos de azufre sedimentarios revelan la Tierra temprana.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Paleoclimatología Paleoclimatología
- Microbiología Microbiología.
Sus antecedentes:
- La historia de la acumulación de oxígeno atmosférico es crucial para comprender la vida temprana.
- Los isótopos de azufre en las rocas sedimentarias proporcionan un sustituto para las antiguas condiciones ambientales.
Objetivo del estudio:
- Para investigar la fraccionamiento isotópico de azufre durante la reducción microbiana de sulfato a altas temperaturas.
- Para determinar cómo las tasas de reducción de sulfatos afectan a la preservación de las firmas isotópicas en los sedimentos.
- Para reconstruir la evolución del oxígeno atmosférico y las concentraciones de sulfato de agua de mar en las eras Arcaico y Proterozoico.
Principales métodos:
- Fraccionamiento isotópico de azufre medido durante experimentos de reducción de sulfato microbiano hasta 88°C.
- Analizó los registros de isótopos de azufre sedimentarios de antiguas formaciones rocosas.
- Modelado la influencia de las tasas de reducción de sulfato en la preservación isotópica.
Principales resultados:
- La fraccionamiento isotópico de azufre se observó durante la reducción microbiana de sulfato a temperaturas de hasta 88°C.
- Las tasas de reducción de sulfato impactan significativamente en la preservación de las fraccionamientos biológicos de isótopos de azufre.
- El registro de isótopos sedimentarios de azufre indica niveles bajos de sulfato de agua de mar y niveles de oxígeno atmosférico en el Arcaico temprano (hace 3,4 a 2,8 mil millones de años).
Conclusiones:
- La atmósfera y los océanos del Arqueo temprano tenían oxígeno y sulfato limitados.
- La acumulación significativa de oxígeno atmosférico y sulfato de agua de mar comenzó a principios del Proterozoico (hace 2,5 a 0,54 mil millones de años).
- La geoquímica de isótopos de azufre es una herramienta poderosa para reconstruir los primeros ciclos biogeoquímicos de la Tierra.
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