Started in october 2018 Late Cretaceous continental weathering evolution on the southern Atlantic margins of Africa and South America: contributions of a new geochemical tracer (combined Lu-Hf and Sm-Nd isotopic systems) coupled with the clay mineralogy

Funding: doctoral grant

Supervisors: Emmanuelle Pucéat ; cosupervisor: Pierre Pellenard

Defended the 29 april 2022

Abstract

The late Cretaceous records a pronounced decrease in temperatures on a global scale between 90 and 65 million years that marks the first step of the progressive climatic decline ultimately leading to our modern climate mode. This first cooling step is concomitant to a major tectonic uplift of the east South American and west African margins. The main objective of this project is to explore the potentially determinant impact of this tectonic uplift on the long-term cooling of the late Cretaceous. A new proxy, based on the coupled Lu-Hf and Sm-Nd isotope systems in clays, will be used to track the late Cretaceous continental weathering evolution on those margins, associated to clay mineralogy that tracks the hydrolysis and mechanical erosion variations. The three IODP sites studied have thus made it possible to show that in the late Cretaceous, the chemical alteration of silicates was intensified in response to the uplifts of the margins but that this response depended on the climatic and tectonic context and illustrated the competition between tectonics and climate on the continental chemical weathering of silicates. Finally, the concomitant evolution between the intensification of the weathering of the margins and the acceleration of the cooling suggests a contribution of the uplift to the late Cretaceous global climate cooling through an increased CO₂ consumption engendered by silicates chemical weathering.

Keywords

continental weathering – isotopic geochemistry – clay mineralogy – palaeoclimate – Cretaceous

Thesis advisory panel

Thierry Adatte
Germain Bayon

Jury

Nathalie Fagel, université de Liège, Belgique – reviewer
Christian France-Lanord, CRPG, Nancy – reviewer
Cécile RObin, université de Rennes 1 – examiner
Jérôme Gaillardet, IPGP, Paris – examiner
Nathalie Vigier, Laboratoire d’océanographie de Villefranche – examiner
Emmanuelle Pucéat, université Bourgogne Franche-Comté – supervisor
Pierre Pellenard, université Bourgogne Franche-Comté – cosupervisor
Michel Guiraud, université Bourgogne Franche-Comté – invited

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kc_raw_content:

Started in october 2018 Late Cretaceous continental weathering evolution on the southern Atlantic margins of Africa and South America: contributions of a new geochemical tracer (combined Lu-Hf and Sm-Nd isotopic systems) coupled with the clay mineralogy

Funding: doctoral grant

Supervisors: Emmanuelle Pucéat ; cosupervisor: Pierre Pellenard

Defended the 29 april 2022

 

Abstract

The late Cretaceous records a pronounced decrease in temperatures on a global scale between 90 and 65 million years that marks the first step of the progressive climatic decline ultimately leading to our modern climate mode. This first cooling step is concomitant to a major tectonic uplift of the east South American and west African margins. The main objective of this project is to explore the potentially determinant impact of this tectonic uplift on the long-term cooling of the late Cretaceous. A new proxy, based on the coupled Lu-Hf and Sm-Nd isotope systems in clays, will be used to track the late Cretaceous continental weathering evolution on those margins, associated to clay mineralogy that tracks the hydrolysis and mechanical erosion variations. The three IODP sites studied have thus made it possible to show that in the late Cretaceous, the chemical alteration of silicates was intensified in response to the uplifts of the margins but that this response depended on the climatic and tectonic context and illustrated the competition between tectonics and climate on the continental chemical weathering of silicates. Finally, the concomitant evolution between the intensification of the weathering of the margins and the acceleration of the cooling suggests a contribution of the uplift to the late Cretaceous global climate cooling through an increased CO₂ consumption engendered by silicates chemical weathering.

 

Keywords

continental weathering – isotopic geochemistry – clay mineralogy – palaeoclimate – Cretaceous

 

Thesis advisory panel

Thierry Adatte
Germain Bayon

 

Jury

Nathalie Fagel, université de Liège, Belgique – reviewer
Christian France-Lanord, CRPG, Nancy – reviewer
Cécile RObin, université de Rennes 1 – examiner
Jérôme Gaillardet, IPGP, Paris – examiner
Nathalie Vigier, Laboratoire d’océanographie de Villefranche – examiner
Emmanuelle Pucéat, université Bourgogne Franche-Comté – supervisor
Pierre Pellenard, université Bourgogne Franche-Comté – cosupervisor
Michel Guiraud, université Bourgogne Franche-Comté – invited

extrait:

lien_externe:

titre:

Evolution de l’altération continentale au cours du Crétacé supérieur sur la marge africaine : application d’un nouveau traceur géochimique (systèmes isotopiques combinés Lu-Hf et Sm-Nd) couplé à la minéralogie des argiles

date_de_debut:

octobre 2018

titre_these:

Evolution de l’altération continentale au cours du Crétacé supérieur sur la marge africaine : application d’un nouveau traceur géochimique (systèmes isotopiques combinés Lu-Hf et Sm-Nd) couplé à la minéralogie des argiles

date_de_debut_these:

octobre 2018

nom:

Corentin

date_de_debut_these_numerique:

201810