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PhD in Biogeochimy applied to archaeological wood

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Français - Anglais

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General information

Reference : UMR7209-ALEDUF-001
Workplace : PARIS 05
Date of publication : Wednesday, July 22, 2020
Scientific Responsible name : PhD supervisors : Thanh Thuy NGUYEN TU ( METIS), Alexa DUFRAISSE,( AASPE), Co-supervisors : Anne POSZWA (LIEC), Julien BOUCHEZ (IPGP) et Stéphane PONTON (SILVA)
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 2 November 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The destruction of the frame of the Notre-Dame de Paris cathedral, during the fire of April 15th, 2019, provides an exceptional opportunity for obtaining original data on the provenance of the cathedral frame wood across four main phases of the construction work (12th, 13th, 14th, and 19th centuries). Although the wood used for the construction of the cathedral frame is thought to be of local origin, evidence is still lacking to support this hypothesis. Notably, historical sources suggest that the Yonne River basin could have acted as a supply area, with the wood brought to Paris by rafting.

From the working hypothesis that trees acquire a geochemical and isotope composition reflective of those of the rocks and soils they grow onto, geochemical signatures can be measured in (potentially carbonized) wood of the Notre-Dame frame and compared to those of modern trees growing on "reference" sites identified as potential supply areas for the Notre-Dame wood. This PhD project will make use of two isotope source tracers that characterize the rock types over which trees grow: the isotope ratios of strontium (87Sr/86Sr) et neodymium (143Nd/144Nd).

A prerequisite to this study is to better constrain the effects of carbonization on the wood elemental and isotope composition (87Sr/86Sr et 143Nd/144Nd). The first step will consist in a controlled experimental calibration of the dendro-chemical and isotope effects of carbonization, using present-day oak wood. Potential sites of origin for the Notre Dame wood (identified through a dendro-chronological study) will be selected first as such "test" regions. Therefore, the candidate's work will consist in establishing new dendro-chemical references from the sampling - and the elemental and isotope analyses - of wood from modern trees growing within these potential sites of origin.
Elemental and Sr-Nd isotope signatures of wood samples from the Notre-Dame frame will be determined and compared to those of the references in order to better constrain the wood supply areas during the four major construction phases of the cathedral. This will in turn shed light onto forest management, as well as socio-economical and environmental contexts in the Paris region during the Middle Ages.
To our knowledge, this project will feature the first application of Nd isotopes to archaeological wood provenance. The combination between Sr-Nd isotopes and elemental composition could lead to a new powerful tool for dendro-provenancing, with a strong potential for geographical determination as shown by previous studies integrating a series of isotopic systems.

Work Context

Host Research Units METIS and AASPE in which the PhD candidate will perform most of his/her work are affiliated to the Institutes of Ecology and Environment (INEE) and of Earth and Planetary Sciences (INSU) of the French National Center for Scientific Research (CNRS)
The Research Unit METIS's research object is the continental surface, adressing in particular the physical and biogeochemical functioning of soils and surficial and deep waters, and their evolution under a variety of forcing types (climate, land use, geomorphology...).
Within the Biogeochemistry department of METIS, the Team "Organic and Mineral Geochemistry of the Environment" (GOME) focuses on the chemical and isotope composition of continental environments to better constrain their functioning, reconstruct their past characteristics, and appraise their future changes. Several projects in archaeochemistry are currently led within the Team GOME, aiming to characterize past interactions between humans and their environment.
The PhD candidate will be affiliated to the Grad School "Geosciences, Natural Resources, and Enviroment" (ED 398) which ensures training in and by research for French or foreign PhD candidates wishing to acquire skills in the field of Geosciences, combining basic research and applications to exploration, exploitation, and protection of natural resources

This project will develop within the supervision of the "Wood and Frame" Working Group of the Notre-Dame Scientific Task Force under the aegis of the Ministry for Culture and the CNRS.
The PhD candidate will be co-supervised by several researchers with expertise ranging from the effects of carbonization on the geochemical composition of wood (PhD supervisors: Thanh Thuy NGUYEN TU (HDR, METIS), Alexa DUFRAISSE (AASPE, HDR in June 2020)) to wood elemental and isotope composition (co-supervisors: Anne POSZWA (LIEC), Julien BOUCHEZ (IPGP) and Stéphane Ponton (SILVA)). The PhD candidate will work in several locations:
Within the Research Unit METIS, TT Nguyen Tu is a specialist in the biogeochemical characterization of plant organic matter, in particular of wood and charcoal. She has recognized expertise in the evaluation of the degree of carbonization and molecular and isotope composition of ancient organic matter, as well as in the reconstruction of past environments using organic matter isotope composition. The labs and instruments at METIS will enable the preparation of modern and archaeological wood samples, as well as the experimental carbonization of wood from the reference sites.
Research Unit AASPE « Archaeozoology, archaeobotany : Societies, Practices and Environments » focuses on bioarchaeology. A. Dufraisse will bring to the table her expertise on experimental carbonization and dendro-anthracological methods.
Research Unit IPGP « Paris Institute for Physics of the Globe» will provide the capacity to measure and interpret Sr and Nd isotope composition on a variety of geological and biological material, including soils and wood. J. Bouchez's expertise lies in the interpretation of geochemical signatures in terms of evolution of continental surfaces under the effects of erosion, weathering, and plant uptake.
Research Unit LIEC « Interdisciplinary Laboratory for Continental Environments » will provide expertise in soil science and know-how for soil and plant characterization. A. Poszwa is experienced in the use of Sr isotopes in soil-tree systems. The clean lab at LIEC will be used for wood sample mineralization, selective extractions of soils, et elemental analyses of all solutions by ICP-MS.
Research Unit SILVA focuses on forest ecology, growth, and health status - and more broadly, on wood. The team is involved in the operation of several experimental forested sites, and has solid experience with measurement and interpretation of data on forests. S. Ponton will provide expertise in dendrochronology and dendrochemistry applied to past and modern forests using wood elemental composition (EDS, WDS, ICP-MS et ICP-AES) and densitometry.

Constraints and risks

Interdisciplinarity: work between different laboratories, collaboration with researchers in various fields.

Project in relation with the progress of the restoration work of the cathedral.

Work in clean labs with strong acids.

Additional Information

Deadline for application (CV + application letter + M1/M2 scores and ranking + M2 dissertation+ letters of recommendation): September 15th, 2020
Interviews: mid-September/mid-October 2020

T.T. NGUYEN TU (UMR METIS, Sorbonne Université/CNRS) :
A. POSZWA (UMR LIEC, Univ. Lorraine/CNRS) :

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