Download Formulaire de dépôt des sujets de thèse de l`Ecole Doctorale SDLM

Doctoral School: SDLM
Doctoral thesis proposal subject
Research Unit
Research Unit: Géosciences Rennes
Research Team: Paléoenvironnements, Paléomagnétisme et Dynamique des bassins
Supervision
Supervisor: Sylvie BOURQUIN
Research Unit: Géosciences Rennes, UMR6118
% thesis supervision (≥ 30%) : 40%
Employer/Academic institution: CNRS/ Rennes 1 University
HDR: yes
PhD student in progress: 1
e-mail: [email protected]
Tél. : 02 23 23 61 06
Co-supervisor: Anne-Catherine PIERSON-WICKMANN
Research Unit: Géosciences Rennes, UMR6118
% thesis supervision (≥ 30%) : 30%
Employer/Academic institution: Rennes 1 University
HDR: yes
PhD student in progress: 1
e-mail: [email protected]
Tél. : 02 23 23 32 27
Co-supervisors:
% thesis supervision (≥ 30%): 30%
Laurent BECCALETTO
Research Unit: Unité Géologie des Bassins et Stockages
Employer/Academic institution: BRGM Orléans
HDR: no
PhD student in progress: 0
e-mail: [email protected]
Pierre PELLENARD
Tél. : 02 38 64 39 85
Research Unit: Biogéosciences, UMR6282
Employer/Academic institution: Burgundy University
HDR: no
PhD student in progress: 0
e-mail: [email protected]
Tél. : 03 80 39 63 66
Funding
First funding agency: BRGM
Percentage: 50%
Funding: acquired
Second funding agency: ARED
Percentage: 50%
Funding: in progress
Doctoral thesis topic
Title: Paleoenvironmental reconstructions in a late-orogenic context: the case of the late Carboniferous-Permian basins of
the Massif Central and the Paris Basin (France)
Keywords: Volcano-sedimentary continental deposits, facies description (cores and outcrops), isotopic and elementary
geochemistry, geochronology, subsurface data interpretation and correlation (well-log, seismic), sequence stratigraphy
PhD Project
The main objective of this thesis is to clarify the history of the northwest European sedimentary basins from the end of the
Carboniferous to the end of the Permian. The idea is to trace their tectonic, climatic and palaeoenvironmental evolution since
the end of the Variscan orogen (dismantling of the reliefs, Armorican Massif and Massif Central, France) until the beginning of
the development of the intracratonic Mesozoic basins.
The late Carboniferous-Permian series are outlined on the periphery of the Variscan massifs (including the Massif Central and
the Armorican Massif), and in subsurface beneath the Meso-Cenozoic basins (including the Paris Basin). It is now accepted
that these basins are contemporaneous with the break-up of the Variscan orogen and record the ultimate stages of its
evolution. The sediments were deposited in semi-graben or pull-apart basins, which translate on the surface a deep tectonic
activity, either crustal (metamorphic domes, crustal shearing) or lithospheric (thinning of the mantle, delamination). These
basins have recorded continental sedimentation, whose thickness can reach several kilometers. A more precise stratigraphic
framework will have to be constructed, in particular from interstratified volcanic horizons, currently poorly studied.
Moreover, the final assembly of Pangea at late Palaeozoic Variscan cycle has led to a continentalization of large spaces,
unparalleled in later geological periods. From the global climatic point of view, after the end of icehouse conditions during the
early Permian, an increasingly hot climate gradually emerged, causing the desertification of vast regions. However, the late
Carboniferous-Permian transition is currently very poorly constrained in Europe.
In detail, the first objective is to reconstruct the late Carboniferous-Permian depositional environments and their spatiotemporal evolution, via (1) an integrated basin study (facies sedimentology, petrography and clay mineralogy, organic matter
and stratigraphic correlations), (2) re-evaluation of palynological data (collaboration with the University of Vigo, Spain), and
(3) a characterization of volcanic events coupled with new radio-isotopic U / Pb ages. This study will then specify the
relationships between the late Variscan tectonic events, the rifting dynamics, and the evolution of the sedimentation
environments. The second objective of this thesis is to estimate the erosion / sedimentation balances over time, highlighting
the erosion (the Variscan Orogen) and sedimentation zones, and characterizing the evolution of the palaeolandscapes and the
palaeoclimate in a well-known tectonic context.
Initially, this study will target the sedimentary sequences from the Paris Basin and the Massif Central. The study of the
sedimentary and volcanic rocks will be carried out on the basis of data from both cores (available at BRGM) and outcrops
(Massif Central); the acquisition of palynological, geochronological (U/Pb zircon) and geochemical (on both organic matter
[atomic ratio C / N, δ13Corg, δ15N] and sediments [major elements and traces]) data will also be carried out. Correlations
between outcrop and subsurface data will allow the definition of a stratigraphic framework for these basins. In a second step,
the comparison with data from other European basins will allow correlations and thus palaeogeographic reconstructions to
be made, highlighting erosion, transport and sedimentation zones over time. The evolution of paleoclimates in the western
European late-Variscan tectonic context during this specific period of Earth's history will accordingly be discussed.
Collaboration:
This study will be conducted in collaboration Olivier Averbuch of Lille University (structural geology) and with José
Bienvenido DIEZ of the Vigo University (paleopalynology). PhD candidate will also supervise Master students.
Candidate
The PhD candidate should have a MSC degree in Geoscience. He/she should be familiar with the description of sedimentary
sequences (facies sedimentology, petrographic and mineralogical analyses, sequence stratigraphy); a first experience in this
field is required, either from outcrop or core studies. The candidate should also be interested in lab work (isotopic and
elementary chemistry, geochronology), and interpretation of subsurface data (well-logs, seismic); it should lastly be able to
deal with the geodynamic evolution of the area (tectonic vs climatic controls).