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Cambios en el dióxido de carbono durante un evento anóxico oceánico vinculado a la intrusión en el carbón de Gondwana

Jennifer C McElwain¹, Jessica Wade-Murphy, Stephen P Hesselbo

¹Department of Geology, The Field Museum, 1400 S. Lake Shore Drive, Chicago, Illinois 60605-2496, USA.

|May 27, 2005

Resumen

Los eventos anóxicos oceánicos (OAE) están relacionados con los cambios en el ciclo del carbono. Este estudio utiliza datos estomales de hojas para demostrar que la intrusión de magma, no los hidratos de metano, probablemente causó el OAE de Toarcian.

Área de la Ciencia:

Paleoclimatología Paleoclimatología
La geoquímica es la geoquímica.
Paleontología Paleontología.

Sus antecedentes:

Los eventos anóxicos oceánicos (OAE) están marcados por un aumento del enterramiento de carbono orgánico, las excursiones de isótopos de carbono y las extinciones marinas.
El OAE de Toarcian (hace 183 millones de años) está vinculado a una excursión negativa de isótopos de carbono, posiblemente causada por la liberación de metano.
Dos hipótesis para el inicio de la OAE de Toarcian implican la liberación de metano de hidratos de gas marino o rocas orgánicas ricas en magma.

Objetivo del estudio:

Para investigar los mecanismos causales de la excursión del isótopo de carbono negativo del OAE de Toarcian.
Para reconstruir los niveles de dióxido de carbono atmosférico de alta resolución durante el OAE de Toarcian.
Para probar las hipótesis de intrusión de hidrato de gas versus magma para la iniciación de la OAE de Toarcian.

Principales métodos:

Análisis de la frecuencia estomatal de hojas fósiles para determinar las concentraciones pasadas de dióxido de carbono atmosférico.
Análisis geoquímico de alta resolución de registros de isótopos de carbono marinos y terrestres.
Modelado paleoclimático para inferir cambios de temperatura global.

Principales resultados:

Los niveles de dióxido de carbono atmosférico mostraron un descenso inicial de 350 ± 100 p.p.m.v., seguido de un aumento abrupto de 1.200 ± 400 p.p.m.v. durante la excursión del isótopo de carbono negativo.
Refrigeración global inferida de 2,5 ± 0,1 °C y posterior calentamiento del efecto invernadero de 6,5 ± 1 °C.
Las fluctuaciones de dióxido de carbono observadas son inconsistentes con una catastrófica liberación de metano de los hidratos de gas.

Conclusiones:

El patrón de cambio de dióxido de carbono atmosférico durante la iniciación de la OAE de Toarcian apoya una hipótesis de intrusión de magma.
Los hallazgos sugieren que la intrusión de los carbones de Gondwana por las doleritas Karoo-Ferrar condujo a la liberación de metano termogénico, causando la excursión del isótopo de carbono negativo.
Este estudio proporciona información crucial sobre los desencadenantes y las consecuencias ambientales de los eventos anóxicos oceánicos.

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