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Las evaporitas de hace dos mil millones de años capturan la gran oxidación de la Tierra

C L Blättler¹, M W Claire^2,3,4, A R Prave²

¹Department of Geosciences, Princeton University, Princeton, NJ 08544, USA. blattler@princeton.edu.

Science (New York, N.Y.)

|March 24, 2018

Resumen

Los océanos paleoproterozoicos contenían sulfato significativo, lo que indica una acumulación sustancial de oxidantes durante la oxigenación temprana de la Tierra. Esta investigación proporciona restricciones clave en esta transición crítica en la historia de la Tierra.

Área de la Ciencia:

Geoquímica
Sedimentología
Paleoceanografía

Sus antecedentes:

La era Paleoproterozoica (hace 2.5 a 1.6 mil millones de años) fue testigo de grandes cambios en la química atmosférica y oceánica.
El aumento de la oxidación alteró profundamente la superficie de la Tierra, pero los datos cuantitativos sobre esta transición siguen siendo escasos.

Objetivo del estudio:

Para investigar la sedimentología, la mineralogía y la geoquímica de una sucesión de evaporitos de 2 mil millones de años.
Para limitar cuantitativamente las concentraciones de sulfato marino durante la era Paleoproterozoica.

Principales métodos:

Análisis sedimentológico detallado de un depósito de evaporita de unos 800 metros de espesor.
Examen mineralógico y geoquímico de las unidades de halita, anhidrita-magnesita y dolomita-magnesita.

Principales resultados:

La sucesión comprende una unidad de halita basal, seguida de capas ricas en anhidrito-magnesita y dolomita-magnesita.
Los minerales de evaporita indican concentraciones de sulfato marino de al menos 10 millimoles por kilogramo.
Este depósito de sulfato era equivalente a más del 20% de la capacidad de oxidación moderna del océano y la atmósfera.

Conclusiones:

Se produjo una acumulación sustancial de oxidantes superficiales durante el evento de oxigenación paleoproterozoica.
Los hallazgos proporcionan restricciones cuantitativas cruciales en los primeros ciclos biogeoquímicos de la Tierra.

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