Evaluating the impact of the Toarcian oceanic anoxic event on neritic platform systems in NW-Africa
Final Report Abstract
The aims of the study were to better characterize the environmental perturbations of the late Early Jurassic by studying the shallow-water deposits of the Central High Atlas Basin. The focus was on the Toarcian Oceanic Anoxic Event, but in order to inscribe this event into a wider context of secular environmental changes, late Pliensbachian to earliest Aalenian deposits were studied. The late Early Jurassic is of special interest because it has experienced severe climatic shifts, were numerous “cold snap” and hyperthermal events have been reported and linked to the protracted activity of the Karoo-Ferrar large igneous province. The major results of this project are the following: The early Toarcian hyperthermal event is associated with an increase of tropical storm intensity. This supports the notion that present-day global warming event will have dire consequences for coastal communities located in Hurricane-prone regions. This is the first time that such an empirical verification of this connection is made from deep-time environmental archives. - A cold-snap event has occurred during the late Middle Toarcian. The timing of this cooling event is closely related to faunal turnover and neritic carbonate systems demise, arguing for a causal link between them. - The T-OAE is shortly preceeded by a major (>50m) sea-level drop that can be correlated across the entire western Tethys, arguing for an eustatic origin. - The neritic carbonate systems of the Central High Atlas Basin have reacted sensitively to the late Early Jurassic environmental perturbations. For each environmental perturbation (P-To boundary event, T-OAE event, late Middle Toarcian event), a drowning event is followed by renewal of neritic carbonate accumulation. Each time, new ecosystems, better adapted to the new environmental conditions, are taking the lead of carbonate production. - The main neritic carbonate demise event is not associated with the T-OAE, but with the P-To event. This latter was however not induced by a massive release of 13C-depleted carbon into the atmosphere compared to the T-OAE event, questioning the exact mechanisms for its initiation.
Publications
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2014. The middle Toarcian cold snap: trigger of mass extinction and carbonate factory demise. Global and Planetary Change, 117: 64-78
Krencker, F.-N., Bodin, S., Hoffmann, R., Suan, G., Mattioli, E., Kabiri, L., Föllmi, K.B. and Immenhauser, A.
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2015. Toarcian extreme warmth led to tropical cyclone intensification. Earth and Planetary Science Letters, 425:120-130
Krencker, F.-N., Bodin, S., Suan, G., Heimhofer, U., Kabiri, L. and Immenhauser, A.
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2016. Perturbation of the carbon cycle during the late Pliensbachian - Early Toarcian: New insight from high-resolution carbon isotope records in Morocco. Journal of African Earth Sciences, 116: 89-104
Bodin, S., Krencker, F.-N., Kothe, T., Hoffmann, R., Mattioli, E., Heimhofer, U. and Kabiri, L.
