Pasquier Virgil

University of Lausanne | UNIL · Institute of Earth Surface Dynamics

In situ iron isotope ratios (δ56 Fe) in sulfide measured by secondary ion mass spectrometry (SIMS) can provide valuable information on several of Earth's surface processes. SIMS relies on the use of a matrix-matched reference material to correct for instrumental mass fractionation. To date Balmat pyrite has been widely used as a reference material,...

Reconstructions of coupled carbon, oxygen, and sulfur cycles rely heavily on sedimentary pyrite sulfur isotope compositions (δ ³⁴ S pyr ). With a model of sediment diagenesis, paired with global datasets of sedimentary parameters, we show that the wide range of δ ³⁴ S pyr (~100 per mil) in modern marine sediments arises from geographic patterns in...

Reconstructions of past environmental conditions and biological activity are often based on bulk stable isotope proxies, which are inherently open to multiple interpretations. This is particularly true of the sulfur isotopic composition of sedimentary pyrite (δ34Spyr), which is used to reconstruct ocean-atmosphere oxidation state and track the evol...

The speciation of iron in sediments and sedimentary rocks is a widely used proxy for the chemistry and oxidation state of ancient water bodies. Specifically, the fraction of reactive iron out of the total iron (FeHR/FeT) and the fraction of pyrite iron out of the reactive iron pool (FePYR/FeHR) are thought to constrain the oxidation state and the p...

The numerous processes (superficial and deep) occurring on margins, their origins, consequences, interactions and quantifications are only very partially described and understood. The identification of the relative role of factors is sometimes completely contradictory between authors. Here, we showed the results of a long-term multidecadal and mult...

Triple oxygen isotope (∆¹⁷O with δ¹⁸O) signals of H2O and O2 found in sulfate of oxidative weathering origin offer promising constraints on modern and ancient weathering, hydrology, atmospheric gas concentrations, and bioproductivity. However, interpretations of the sulfate-water-O2 system rely on assuming fixed oxygen-isotope fractionations betwee...

Sulfur cycling is ubiquitous in sedimentary environments, where it mediates organic carbon remineralization, impacting both local and global redox budgets, and leaving an imprint in pyrite sulfur isotope ratios (δ 34 S pyr). It is unclear to what extent stratigraphic δ 34 S pyr variations reflect local aspects of the depositional environment or mic...

Understanding variation in the sulfur isotopic composition of sedimentary pyrite ( 34 S pyr) is motivated by the key role of sulfur biogeochemistry in regulating Earth's surface oxidation state. Until recently, the impact of local depositional conditions on  34 S pyr has remained underappreciated, and stratigraphic variations in  34 S pyr were i...

There is increasing concern with anthropogenic greenhouse gas emissions that ocean warming, in concert with summer and winter precipitation changes, will induce anoxia in multiple ocean basins, such as in the Mediterranean Sea. Although the hydrological changes in the eastern Mediterranean are quite well constrained, quantitative evidence of change...

There is increasing concern with anthropogenic greenhouse gas emissions that ocean warming, in concert with summer and winter precipitation changes, will induce anoxia in multiple ocean basins. In particular the Mediterranean Sea is susceptible to severe hydrological changes. Mediterranean hydroclimate is controlled primarily by two phenomena – the...

The terrigenous sedimentary budget of passive margins, records variations in past sedimentary fluxes, and thus can be used to infer past variations of Earth surface deformation processes or climate change. Accurate estimates of sediment fluxes over various times and spatial scales are therefore crucial. Traditionally, offshore sediment volume deter...

By its position, the Gulf of Lion is an ideal location for investigation of past ecological changes and processes affecting the sedimentary deposition. Previous work has highlighted the impacts of climatic and glacio-eustatic changes on the GoL stratigraphic organization, but also on terrestrial exports of organic matter.This isotopic study based o...

Rationale: Natural stable isotope ratios (δ13 Corg and δ15 N values) and associated elemental concentrations (i.e. total organic carbon and total nitrogen contents) preserved in marine sediments are frequently used for the determination of paleo-environmental processes such as the origin of organic matter. Previous studies highlighted biases in th...

Significance Changes in sulfur isotope ratios ( ³⁴ S/ ³² S) of marine sulfur phases are often attributed to global biogeochemical perturbations. Sediments collected on the shelf of the Gulf of Lion revealed remarkable sulfur isotopic fluctuations in sedimentary pyrite over the last 500,000 years, ranging between −44.0‰ and 32.3‰. We suggest this pa...

La Méditerranée Occidentale est le siège de nombreuses interactions sédimentaires, climatiques et océanographiques du fait de sa position géographique, à l'interface des hautes et des basses latitudes, et du flux Terre-Mer important et continu délivré par le Rhône et les rivières pyrénéo-languedociennes. De part sa position à l'exutoire du canyon d...