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La oxigenación temprana del medio ambiente terrestre durante el Mesoproterozoico
John Parnell1, Adrian J Boyce, Darren Mark
1School of Geosciences, University of Aberdeen, Aberdeen AB24 3UE, UK. j.parnell@abdn.ac.uk
Nature
|November 12, 2010
Resumen
Los datos geoquímicos revelan una fraccionamiento significativo de isótopos de azufre en antiguas rocas terrestres, lo que indica condiciones ricas en oxígeno durante la era mesoproterozoica. Esto sugiere la evolución temprana de complejos ciclos de azufre y formas de vida dependientes del oxígeno.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Paleoclimatología Paleoclimatología
- Biogeoquímica La biogeoquímica es la bioquímica.
Sus antecedentes:
- Los datos geoquímicos de antiguas rocas sedimentarias rastrean la evolución atmosférica y oceánica de la Tierra.
- Se proponen eventos clave de oxigenación para las eras Paleoproterozoica y Proterozoica tardía, vinculados a la evolución de los metazoos.
- Los datos de fraccionamiento de isótopos de azufre (Δ(34) S) muestran un cambio de <25 ‰ a ≥50 ‰ hace alrededor de 1 Gyr, interpretado como un ciclo evolutivo de azufre microbiano.
Objetivo del estudio:
- Para investigar la fraccionamiento de isótopos de azufre en las sucesiones terrestres del Mesoproterozoico.
- Para caracterizar el mal entendido ciclo del azufre durante este período geológico.
- Evaluar las implicaciones de la fraccionamiento observado para los niveles de oxígeno atmosférico y la evolución microbiana.
Principales métodos:
- Análisis de datos geoquímicos de antiguas sucesiones sedimentarias.
- Medición de las proporciones de isótopos de azufre (Δ34S) en rocas terrestres del Mesoproterozoico (1.18 Gyr de antigüedad) de Escocia.
- Interpretación de los datos isotópicos en el contexto del ciclo microbiano del azufre (reducción del sulfato, oxidación del sulfuro, desproporcionamiento).
Principales resultados:
- Descubrimiento de valores de Δ34S superiores a 50 ‰ en una sucesión mesoproterozoica terrestre de 1.18 Gyr.
- Evidencia de desproporción de azufre, probablemente involucrando bacterias oxidantes de sulfuro, en lechos rojos y pizarras negras lacustres.
- Estos hallazgos sugieren un entorno terrestre del Mesoproterozoico con suficiente oxígeno para soportar una biota especializada.
Conclusiones:
- El medio ambiente terrestre del Mesoproterozoico fue oxigenado antes de lo indicado anteriormente por los registros de azufre marino.
- La presencia de fraccionamiento significativo de isótopos de azufre implica comunidades microbianas activas adaptadas a condiciones ricas en oxígeno.
- Este estudio proporciona información crucial sobre la oxigenación temprana de la Tierra y la evolución de la vida microbiana.
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