Christian Di-Giovanni

University of Orléans | UO · Institut des Sciences de la Terre d'Orléans ISTO

Determining the riverine carbon fluxes to oceans is critical for an improved understanding of C budgets and biogeochemical cycles (C, O) over a broad range of spatial and time scales. Among the particulate organic carbon (POC) involved in these fluxes, those yielded by sedimentary rocks (petrogenic POC: pPOC) remain somewhat uncertain as to their s...

A 14-m long sedimentary sequence (core PAV12) was collected in the deepest part of Lake Pavin, a maar lake located in the French Massif Central. The PAV12 sedimentary sequence documents the lake's environmental evolution since its formation 7000 years ago. The relationships between the catchment's vegetation cover, erosion processes and changes in...

Ce travail, effectué dans le cadre du GIS Draix "étude de l'érosion en montagne », s'est intéressé à l’érosion des "terres noires" (marnes jurassiques) du bassin de la Moyenne Durance. Il s’est traduit par une approche multi-compartiments (sols – eaux) – multi analytique (analyses optiques, géochimique), sur les bassins versants expérimentaux de Dr...

Lake sediments are relevant natural seismographs over long time scale. However, because tectonicevents are not systematically recorded in lake sediments, one forthcoming challenge forpaleoseismology is to better assess lake sensitivity to earthquakes. To this end, a limnogeologicalinvestigation, including hydroacoustic mapping techniques, cores sam...

Ce poster présente l’historique des glissements subaquatiques liés à l’activité sismique modérée de la région Auvergne. Une approche régionale a été menée sur quatre systèmes, incluant deux lacs de maar (Pavin et Chauvet), un lac de barrage volcanique (Montcineyre) et un lac glaciaire (Guéry). La caractérisation des remplissages lacustres s’appuie...

Environ 60 000 seuils, barrages et retenues construites par l'Homme sont au total référencés sur l'ensemble des cours d'eau de métropole. Seuls 10% des ouvrages ont un usage économique bien identifié, mais l'ensemble a provoqué une dénaturation des cours d'eau que ce soit en contexte de plaine ou en moyenne et haute montagne. En amont de leurs rete...

Les sédiments naturels récents ont toujours attisé la curiosité des scientifiques. Les sédiments urbains, témoins privilégiés de notre histoire récente, sont encore méconnus des sédimentologues. Pourtant ces sédiments accumulés dans les réseaux d'assainissement sont une opportunité pour mieux comprendre la dynamique de sédimentation dans ces milieu...

L'étude des matières organiques particulaires (MOP) et du carbone organique associé (COP) véhiculées par les cours d'eau intègre des thématiques scientifiques comme le transfert sédimentaire (origine des matériaux), le devenir des contaminants associés à ces MOP (adsorption, désorption) et le cycle du Corg (bilan et flux de COP à l'interface contin...

Ce poster présente l’utilisation d’un traceur pédogénétique pour reconstituer l’érosion des sols au cours de l’Holocène récent. Une étude intégrée multi-paramètres est appliquée à quatre systèmes lacustres contrastés d’Auvergne. Les résultats montrent des taux d’érosion des sols variant de 1 à 400 t/km²/an. Les différences inter-sites s’expliquent...

L'identification et la quantification des biomarqueurs moléculaires dans les sédiments sont classiquement effectuées suite à leur extraction de la matrice, excluant ainsi toute information sur leur localisation. Si cette pratique permet de reconstituer à des échelles pluri-centimétriques les paléoenvironnements, elle ne peut expliquer la distributi...

The climatic transition between Eocene and Oligocene (EOT) is marked by the change from a greenhouse to an icehouse climatic mode that affects both the marine and terrestrial realms. Terrestrial ecosystems are more sensitive to climate changes but suffer from the lack of continuous records. Recently, the BRGM retrieved a 340 m-long core from the Re...

Water budget is one of the main challenges to paleoclimate researchers in relation to present-day global warming and its consequences for human societies. Associated soil degradation and erosion are thereby becoming a major concern in many parts of the world and more particularly in the Alps. Moreover, humans are considered as geomorphologic agents...

Water budget is one of the main challenges to paleoclimate researchers in relation to present-day global warming and its consequences for human societies. Associated soil degradation and erosion are thereby becoming a major concern in many parts of the world and more particularly in the Alps. Moreover, humans are considered as geomorphologic agents...

Les varves, lamines, rythmites, parfois observées dans les sédiments lacustres peuvent résulter de forçages saisonniers, solaires ou orbitaux (Glenn et Kelts, 1991). La sédimentation argileuse Eocène-Oligocène du bassin de Rennes est caractérisée par un faciès laminé dont la signification temporelle reste à déterminer. L'objectif de ce travail est...

La transition climatique Eocène/Oligocène (E/O) est l'un des changements majeurs au cours du Cénozoïque. Elle se traduit par la mise en place de calottes glaciaires développées et permanentes aux pôles. La majorité des études ayant été réalisée en domaine marin, son impact sur les écosystèmes continentaux reste méconnu. Les dépôts lacustres de l'Eo...

High-resolution seismic profiling has been combined with geochemical analyses of both watershed samples and five lacustrine cores retrieved from two natural lacustrine basins of glacial origin: Lakes Majeur and Sigriou (1630 m a.s.l. and 1995 m a.s.l. respectively, Eastern French Pyrenees). Identifying specific minerogenic and organic markers of au...

High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and river-bed samples from the lake’s catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic...

Understanding potential consequences of the actual global warming requires mastering past environments evolution linked with anthropic and/or climate variability. High altitude proglacial lakes are key natural archives because they can accurately detect phases of glacial fluctuations and related environmental changes. Lake Blanc Huez (LBH, 2500 m a...

Ce travail, effectué dans le cadre du GIS Draix "étude de l'érosion en montagne », s'est intéressé au devenir du carbone organique fossile (COF) contenu dans les "terres noires" (marnes jurassiques) du bassin de la Moyenne Durance. Il s’est traduit par une approche multi-compartiments (sols – eaux) – multi analytique (analyses optiques, géochimique...

High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and river-bed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic...

ABSTRACTA key issue in the study of the carbon cycle is constraining the stocks and fluxes in and between C‐reservoirs. Among these, the role and importance of fossil organic carbon (FOC) release by weathering of outcropping sedimentary rocks on continental surfaces is still debated and remains poorly constrained. Our work focuses on FOC fluxes due...

Understanding potential consequences of the actual global warming requires mastering past environments evolution linked with anthropic and/or climate variability. High altitude proglacial lakes are key natural archives because they can accurately detect phases of glacial fluctuations and related environmental changes. Lake Blanc Huez (LBH, 2500 m a...

Dans le cadre de l’ANR LAMA (2008-2011) et en collaboration avec l’ETH de Zurich, une analyse interdisciplinaire est menée sur un remplissage lacustre alpin du nord de l’Italie : le Lac Ledro. L’objectif de l’étude est de comprendre la sédimentation Holocène de ce lac de basse altitude dont le bassin versant est caractérisé par un relief de type mo...

This study relates to the input and fate of fossil organic matter (FOM) in the modern environment, and focuses on two experimental watersheds overlying Jurassic marls: Le Laval and Le Brusquet (1km2 in area), located near Digne, Alpes-de-Haute-Provence, France. Considering that FOM delivery is mainly a result of different processes affecting sedime...

This work focuses on FOC fluxes due to weathering and erosion of marls in some experimental catchments (Draix, Alpes de Haute Provence, France). These catchments disclose a typical badlands geomorphology where erosion rate can exceed 500 t ha–1 y–1 and hence, can release FOC contained in sedimentary rocks in the drainage network. Organic matter fro...

Le remplissage sédimentaire des mares de Bangou-Bi et de Tankalawal (SW Niger) a fait l’objet d’une étude de son contenu organique qui fournit des informations sur l’origine et les conditions de dépôt du matériel sédimentaire. Deux carottes mesurant respectivement 140 cm (carotte BB2) et 60 cm (carotte TK1) ont été étudiées. Les échantillons ont ét...

Classical palynofacies method, which consists in an organic concentrate microscopic qualitative observation after mineral phase dissolution, is commonly used in order to study sedimentary organic matter. In the present study we develop a new quantitative palynofacies method that allows organic particles mass concentrations to be determined in studi...

Fate of Fossil Organic Carbon (FOC), originating from sedimentary rock weathering, is a major unknown into carbon cycle. Generally considered as degradable and as a CO2 source for the atmosphere, its occurrence was highlighted by numerous studies in various pools, such as rivers, soils and recent sediments, indicating a potential resistance to weat...

The study of the greenhouse gases behaviour, as CO2, requires estimations of carbon fluxes between soils, biosphere, hydrosphere and atmosphere. Such estimates generally do not take into account Fossil Organic Carbon (FOC) fluxes, originating from rock weathering and erosion of ancient and recent sediments. However, at a global scale, the lonely ch...

The biogeochemical carbon cycle, which plays an undeniable role in global climate change, is defined both by the size of carbon reservoirs (such as the atmosphere, biomass, soil and bedrock) and the exchange between them of various mineral and organic carbon forms. Among these carbon forms, fossil organic carbon (FOC) (i.e., the ancient organic mat...

Palynofacies analysis is based on transmitted light microscope study of organic constituents isolated and concentrated by acid and basic digestions. Published results of studies of present-day terrestrial environments show that two complementary approaches successfully characterize particulate organic matter (OM) from palynofacies analyses. The fir...

Quantification in grams per metres squared per year of the sediment accumulation in a flood plain (‘marsh’) located in the southwestern Parisian basin showed that there is no close relationship between the accumulation of organic matter (OM) and mineral matter (MM) during the late Holocene, and provided an accurate view of the distinct yield and st...

Rock-Eval pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. Nevertheless, this technique can be used for bulk characterization of the immature organic matter in soil samples and recent sediments. We studied 76 samples from seven soil classes and showed that their pyrograms can be d...

Palynofacies' analysis was developed for petroleum exploration, but it is now commonly used to differentiate the major constituents of the sedimentary organic matter (SOM) in Postglacial deposits. Our work aimed at studying the SOM distribution in a present wetland of the Seine estuary (Vernier Marsh) in order to provide comparative elements to int...

This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock-Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental sur...

The Tianshan range is among the Asia's largest mountain chains. It spreads over an EWdistance of 2500 km with summits higher than 7000 m. The range's geologic record attests to a complex history of Paleozoic subduction-related processes, but the living topography appears to be mainly due to a new phase of Cenozoic reactivation induced by the India-...

Accumulation of organic matter in fens of fluvial valleys is often related to a low terrigenous matter delivery and to palaeoenvironmental conditions inducing low mechanical erosion. These assumptions come from the interpretation of contents in organic (MO) and mineral (MM) matters in sediments, expressed in percents, and then exactly anticorrelate...

Accumulation of organic matter in fens of fluvial valleys is often related to a low terrigenous matter delivery and to palaeoenvironmental conditions inducing low mechanical erosion. These assumptions come from the interpretation of contents in organic (MO) and mineral (MM) matters in sediments, expressed in percents, and then exactly anticorrelate...

The Taligny marsh is located downstream in the Négron River catchment (southwestern Parisian basin). 33 boreholes performed in the marsh show that it contains a maximum thickness of 5.80 m sediments. Their composition varies from a sandy-gravely end in the lower part of the pile to a peaty end in the upper part, the silty phase being the most abund...

CO2 concentration is regulated by processes controlling the carbon fluxes occurring between different carbon pools such as atmosphere, ocean, hydrosphere, soil, biomass, and lithosphere. However, some controversies persist on the nature and quantification of carbon stocks and fluxes acting in supergene environment such as soils and rivers pools. Fo...

Application of Rock-Eval pyrolysis to soil organic matter (SOM) quantitation and characterization has been explored by the study of about 100 soil samples taken from a variety of soil profiles from different ecosystems at different latitudes. A straightforward illustration of these possibilities can be obtained from a Hydrogen Index (HI in mg hydro...

L'objectif de cette étude pluridisciplinaire est d'estimer l'impact des activités humaines sur le flux et le stockage de matières dans le bassin lacustre de Sarliève à l'Holocène, et en retour, d'évaluer l'impact des modifications anthropiques du milieu (sols et zones humides) sur ces activités. La méthode consiste à quantifier la matière (solide e...

Soil organic matter is one of the key components in the global carbon cycle understanding. Its description and quantification has then been subject to many investigations. The present work is driven by the following question: does soil organic matter (OM) only depends on the vegetal net primary production or also on the incorporation of organic mat...

Black Carbons (BC=soots and charred particles) and Geologic Carbon (GC) form a cluster which can be defined as Refractory Carbon (RC), by considering their inertia to the degradation. Despite their occurring in the different surface carbon reservoirs, their contribution to the carbon biogeochemical cycle is still poorly known. Admitting their inert...

We propose in this study an initial estimation of the annual organic matter yield induced by chemical weathering of carbonates and shales considering their global surface at outcrop and their organic matter content. The calculation also uses data on river fluxes resulting from carbonate rocks and shales weathering in major world watersheds, publish...

Bien qu'observée depuis plus d'un siècle dans les cours d'eau, les sédiments et plus récemment dans les sols (un exemple parmi d'autres : [1]), la contribution potentielle de carbone organique (Corg) que nous qualifierons de géologique et libéré par l'altération des formations géologiques n'a que rarement été, excepté [2], prise en compte dans les...

Except ancient tectonic structures, the main morphological elements of the western Paris Basin are essentially associated to the Quaternary periglacial climates.

Several approaches based on isotopic and/or molecular markers applied to determine organic matter (OM) sources. Although such chemical methods are quite successful, there are limitations.

Bien qu'observée depuis plus d'un siècle dans les cours d'eau, les sédiments et plus récemment dans les sols (un exemple parmi d'autres : [1]), la contribution potentielle de carbone organique (Corg) que nous qualifierons de géologique et libéré par l'altération des formations géologiques n'a que rarement été, excepté [2], prise en compte dans les...

In the Négron River catchment area (162 km2), surface-sediment stores are composed of periglacial calcareous grèze (5 × 106 t) and loess (21 × 106 t), and Holocene alluvium (12*6 × 106 t), peat (0*6 × 106 t) and colluvium (18*5 × 106 t). Seventy-five per cent of the Holocene sediments is stored along the thalwegs. Present net sediment yield, calcul...

The aim of this paper is to propose an initial estimation of the annual organic matter yield induced by chemical weathering of carbonates and shales, considering their global surface at outcrop and their organic matter content. The calculation also uses data on river fluxes resulting from carbonate rocks and shales weathering in major world watersh...

L'objectif du programme est d'estimer l'impact des activités humaines sur le flux et le stockage de matières dans les bassins fluviatiles à l'Holocène, et en retour, d'évaluer l'impact des modifications anthropiques du milieu (sols et zones humides) sur ces activités. La méthode consiste à quantifier la matière (solide ou dissoute) prélevée aux ver...

The aim of this paper is to propose an initial estimation of the annual organic matter yield induced by chemical weathering of carbonates and shales, considering their global surface at outcrop and their organic matter content. The calculation also uses data on river fluxes resulting from carbonate rocks and shales weathering in major world watersh...

Quantity of solid matter yielded and stored during the Holocene period in the whole Loire catchment was calculated from two little catchments located in the Massif Central and in the Parisian Basin. The Massif Central produced tenfold more solid matter than the Parisian Basin (56.109 t versus 5,5.109 t) and fourfold less dissolved matter (6,9.109 t...

Optical analysis (palynofacies) of the organic matter (OM), occurring in various compartments (soils, bedrock formations, lacustrine chalks) of the lacustrine basin of Chaillexon (Doubs, France) has led to the definition of organic markers. Their variable contributions were observed in suspended matters taken over a period of a year (annual scale)...

The present study is based on the optical (palynofacies) and geochemical (pyrolyse Rock–Eval) characterization of the organic matter occurring both in bedrock, soils, river sediments (suspended matter and bedload) in a Draix Erosional Research Basin (Cemagref). Results confirm firstly the contribution of reworked organic matter in modern fluxes. Nu...

Optical analysis (palynofacies) of the organic matter (OM), occurring in various compartments (soils, bedrock formations, lacustrine chalks) of the lacustrine basin of Chaillexon (Doubs, France) has led to the definition of organic markers. Their variable contributions were observed in suspended matters taken over a period of a year (annual scale)...

Ce travail s'appuie sur l'étude de la matière organique présente dans les sols, substratum géologique et particules fluviatiles, d'un bassin versant équipé par le Cemagref. L'analyse des palynofaciès confirme la contribution significative de matière organique fossile dans les cours d'eau actuels. La pyrolyse Rock-Eval permet de discriminer les form...

The particulate organic matter isolated from soils and from underlying geologic formations from Various french watersheds was studied under the light microscope to determine palynofacies composition. The results reveal that modern humus contain notable amounts of ancient organic constituents inherited from the geologic substratum. This ancient cont...

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaill...

The analysis of lacustrine sediments, humus layers and bedrock organic matter in the Peyssier watershed (Hautes-Alpes, France), points out to the occurrence of Mesozoic OM mainly composed with opaque particles in present lacustrine sediments and humus layers. This result shows that opaque particles found in recent sediments and soils must not be sy...

Geochemical analysis of sedimentary organic matter in recent lacustrine sediments appears to be a useful tool in providing information concerning past environmental conditions. However, such analysis is often made without knowing the geochemical characteristics of the organic matter derived from the watershed and, more explicitly, its soils. The pr...

The optical analysis in the Chaillexon watershed (Doubs, France), of the present soils' humus layers' organic matter points out the contribution of Meso-Cenozoic organic matter in addition to the one produced by vegetal cover. Their relative occurrence varies in each layer: in the reverse of that of vegetal organic matter, the relative amount of Me...

Chaillexon lake (Doubs, France) has been settled by a rock collapse about 12,000 years ago. That trap represents a continuous sedimentary record for the late and post-glacial period. The optical analysis of the organic matter settled in the Meso-Cenozoic substratum of the watershed and in the sedimentary infilling points out the incorporation of Me...

The sedimentary infilling of Brenets paleolake is studied to characterize and quantify changes in material flows since the last glaciation. The lithology and geometry of the various sedimentary units are mapped from 35 boreholes. These spot observations are supplemented by geophysical exploration including seismic refraction and electrical sounding...

A landslide dammed the upper Doubs valley around 12 ka B.P. forming a lake that has now been filled to 9/10ths of its original volume. Sediments from the enclosing basin reveal three phases. - 12 to 9 ka B.P., exclusively detntal material from mechanical erosion. - 9 to 6 ka B.P., material dominated by elements in solution, from chemical erosion. -...

Chaillexon lake has been created by a rock collapse that has dammed the valley of the Doubs river 12,000 years ago. The available space was and is still filling up by the river and that trap represents a continuous record for the Post-glacial. The study is based on the characterization of geochemical and optical organic markers in the actual waters...

At the end of the last glacial period, about 12 000 yr BP a landside blocked the upper part of the Doubs valley. It results in a natural reservoir which is nowadays filled up to 9/10 of its initial volume by sediment. Geometry and nature of the lacustrine infilling are known owing to some 40 drillings and its chronology is based on palynological da...