Offer Description
– work environment:Â
The ANR MiKroAVEN project aims to assess the impact of intraterrestrial microbial ecosystem activity on the functioning and habitability of the Critical Zone. This thin superficial layer of the Earth, whose dynamics rely on the coupling of hydrological, geological, and biological processes, is subject to numerous pressures—both anthropogenic and natural—that make it vulnerable to current global change. However, its deepest compartment remains poorly studied, and the impact of endemic subsurface microorganisms—now known to constitute the majority of terrestrial prokaryotes—on its functioning is still poorly constrained.
The MiKroAVEN project seeks to address this challenge by focusing on the interplay between geobiology, physico-chemistry, and geomorphology in karst environments. As transition zones between the subsurface and the surface, these environments serve as natural laboratories for studying the influence of intraterrestrial life on the Earth’s superficial layers. Through a multidisciplinary approach involving specialists from various fields, MiKroAVEN will investigate how the activity of subsurface microorganisms affects rock weathering and fluid geochemistry—particularly through the (re)mobilization of metal elements from the environment.
The project will be centered on the Larzac karst system, whose hydro-physico-chemical behavior has been studied for several years within the Larzac Observatory (OZCAR). This ongoing monitoring will be complemented by precise tracking of the microbial ecology of the system, as well as in situ microbial weathering experiments conducted in various sinkholes (avens) within the system, and under laboratory conditions. This will make it possible to characterize the impact of microbial activity on rock weathering, the remobilization of trace metals (TMs), and the geochemistry of fluids—and, more broadly, on the composition of the Earth’s surface envelopes.
– main mission:Â
The postdoctoral researcher will be responsible for Work Package 1 (WP1) of the ANR MiKroAVEN project. Based on a combined approach integrating geomorphology, geophysical methods, and mineralogical/geochemical analyses, WP1 aims to decipher the geomorphological and hydrodynamic processes that control water supply and quality, and to define the habitability of the karst system (i.e., where and under what environmental conditions life can exist, as well as the potential chemical imbalances generated by water-rock interactions).
The objective of WP1 is therefore to complete the geomorphological study of key cave systems. This study is based on in situ data (https://data.oreme.org/observation/karst3d) and will be enhanced by geophysical approaches to provide a comprehensive framework for understanding cave formation and sediment infill.
In addition to the in-depth work carried out on the Durzon system, special attention will be given to a more detailed description of the Gourneyras karst system. However, identifying ghost-rock on a karst plateau such as Larzac is nearly impossible from the surface. Therefore, in order to estimate the relationship between the bedrock and the ghost-rock in these areas, LIDAR and photogrammetry data from the cliffs at the edge of the plateau will be used to interpret ghost-rock weathering. This approach should allow for the detection of ghost-rock corridors, which will then be studied through localized drilling and chemical characterization of rock samples, complementing the geochemical analyses.
This approach will be further enhanced by dating cave infills using cosmogenic radionuclides, following the methodology developed by Malcles. This analysis will help determine whether the karstogenesis of the caves is linked to ghost-rock processes or solely to hydrodynamic dynamics.
– activities:Â
Rock and water sampling.
Geomorphological surveys of karst and weathering landforms.
Geophysical measurements (ERT, SRT, gravimetry, etc.).
The net salary is €2,203 month
Contract duration: 12 months
Where to apply
E-mail: cedric.champollion@umontpellier.fr
