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Ciclo de nitrógeno basado en oxígeno en el camino hacia el Gran Evento de Oxidación

Alice Pellerin¹, Christophe Thomazo^2,3, Magali Ader⁴

¹Laboratoire Biogéosciences, UMR CNRS 6282, Université de Bourgogne, Dijon, France. alice.pellerin-lefebvre@u-bourgogne.fr.

|August 21, 2024

Resumen

La Tierra temprana

Área de la Ciencia:

Geoquímica
Paleobiología
La historia temprana de la Tierra

Sus antecedentes:

Los isótopos de nitrógeno sedimentario (δ¹⁵N) siguen los procesos redox y la oxigenación temprana.
El Gran Evento de Oxidación (~ 2.45 Ga) no muestra un cambio importante de δ15 N, lo que sugiere ciclos desacoplados de nitrógeno y oxígeno.
Los valores positivos de δ15 N (2.8 2.6 Ga) indican un precursor de la oxigenación, pero su origen no está claro.

Objetivo del estudio:

Investigar el origen de los valores positivos de δ15N en las rocas del Precámbrico.
Determinar el momento y las implicaciones de la evolución temprana del ciclo del nitrógeno.
Identificar la evidencia de los ciclos crípticos de oxígeno antes de la acumulación de oxígeno atmosférico.

Principales métodos:

Análisis de la composición isotópica del nitrógeno (δ¹⁵N) en rocas sedimentarias de 2.68 años de edad.
Estudio geoquímico de la Formación Serra Sul, en el Cratón Amazónico.
Interpretación del ciclo del nitrógeno en las primeras condiciones redox de la Tierra.

Principales resultados:

Descubrimiento de valores de δ15 N fuertemente positivos (> 30 ‰) en sedimentos marinos de 2,68 Ga.
Los hallazgos se atribuyen a la oxidación regional del amonio relacionada con un ciclo críptico de oxígeno.
La evidencia sugiere que la fotosíntesis oxigenada estuvo activa alrededor de 2.7 Ga.

Conclusiones:

El "evento de isótopos de nitrógeno" marca una reorganización biogeoquímica temprana.
Este evento precedió a una significativa oxigenación atmosférica.
Indica los primeros pasos hacia el Gran Evento de Oxidación.

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