Search results for " Carbon isotopes"
showing 10 items of 25 documents
Onset of the Messinian Salinity Crisis: Sedimentological, petrographic and geochemical characterization of the pre-salt sediments from a new core (Ca…
2022
The present study aims to reconstruct the environmental changes leading to the Messinian Salinity Crisis during the transition from the Tortonian-Messinian marine conditions to the Messinian evaporitic environments. The core 3AGN2S04, recently drilled in the Caltanissetta Basin (Sicily), was analyzed to reveal the petrographic, mineralogical and geochemical characteristics of the late Tortonian – early Messinian pre-salt sediments. In particular, the facies characterization of the carbonates and organic-rich shales of the Calcare di Base (CdB) member allowed to understand its significance in the paleoenvironmental evolution towards salt deposition and to the reconstruct the brecciation proc…
A geochemical traverse along the “Sperchios Basin e Evoikos Gulf” graben (Central Greece): Origin and evolution of the emitted fluids
2014
The studied area is a 130 km long fast spreading graben in Central Greece. Its complex geodynamical setting includes both the presence of a subduction slab at depth responsible for the recent (Quaternary) volcanic activity in the area and the western termination of a tectonic lineament of regional importance (the North-Anatolian fault). A high geothermal gradient is made evident by the presence of many thermal springs with temperatures from 19 to 82 C, that discharge along the normal faults bordering the graben. In the period 2004e2012, 58 gas and 69 water samples were collected and their chemical and isotopic analysis revealed a wide range of compositions. Two main groups of thermal waters…
Dynamics and identification of soil microbial populations actively assimilating carbon from 13C-labelled wheat residue as estimated by DNA- and RNA-S…
2007
International audience; This work is the first report on the use of DNA-, RNA-SIP approaches to elucidate the dynamics and the diversity of bacterial populations actively assimilating C derived from plant residues labelled at more than 90% (13)C. Wheat-residues, were incorporated and incubated into soil microcosms for 28 days. At the end of the incubation time, no more than 55% of the total CO(2) released was (13)C-labelled, suggesting the occurrence of an important priming effect process. After 7 days, more than 30% of the whole DNA extracted were labelled, allowing an efficient separation of labelled from unlabelled DNA using density gradient centrifugation. The genetic structure of bacte…
Noble gas and CO2 isotopic signatures of the lithospheric mantle underneath Mexico and the Canary Islands: clues from mantle xenoliths and arc lavas
2022
Studying the isotopic composition of fluids trapped in mantle xenoliths opens avenues to understand the origin and cycling of volatiles in the Earth’s upper mantle. In this PhD dissertation, new and in most cases the very first data regarding the isotopic (noble gases and CO2) characterization of the lithospheric mantle portions of three different geodynamic environments are presented: (i) Central and NW Mexico, a continental setting dominated by extension; (ii) the Transmexican Volcanic Belt (TMVB) a subduction setting, and (iii) the Canary Islands, particularly El Hierro and Lanzarote, two oceanic islands formed by mantle plume-derived intraplate volcanism. In total 32 peridotites (includ…
High-resolution records of growth temperature and life history of two Nacella limpet species, Tierra del Fuego, Argentina
2020
Stable isotope ratios in patelloid limpets of the genus Patella have been established as proxies for coastal environmental change at sub-monthly resolution along the eastern North Atlantic and Mediterranean Sea. Nacella deaurata (Gmelin, 1791) and N. magellanica (Gmelin, 1791) are common intertidal species of patelloid limpets inhabiting the coast of Tierra del Fuego, Argentina/Chile and are commonly found in Holocene archaeological deposits. Here, we examine oxygen and carbon isotope ratios (δ18Oshell and δ13Cshell, respectively) of modern specimens of N. deaurata and N. magellanica to test the hypotheses that: 1) they form their shells in isotopic equilibrium with ambient water; and 2) pr…
Variability in δ13C values between individual Daphnia ephippia: Implications for palaeo-studies
2018
The stable carbon isotope ratio (δ13C value) of Daphnia spp. resting egg shells (ephippia) provides information on past changes in Daphnia diet. Measurements are typically performed on samples of ≥20 ephippia, which obscures the range of values associated with individual ephippia. Using a recently developed laser ablation-based technique, we perform multiple δ13C analyses on individual ephippia, which show a high degree of reproducibility (standard deviations 0.1–0.5‰). We further measured δ13C values of 13 ephippia from surface sediments of three Swiss lakes. In the well-oxygenated lake with low methane concentrations, δ13C values are close to values typical for algae (−31.4‰) and the rang…
Geochemical characterisation of gases along the dead sea rift: Evidences of mantle-co2 degassing
2016
International audience; The Dead Sea Transform (DST) fault system, where a lateral displacement between the African and Arabian plates occurs, is characterised by anomalous heat flux in the Israeli area close to the border with Syria and Jordan. The concentration of He and CO2, and isotopic composition of He and total dissolved inorganic carbon were studied in cold and thermal waters collected along the DST, in order to investigate the source of volatiles and their relationship with the tectonic framework of the DST. The waters with higher temperature (up to 57.2 °C) are characterised by higher amounts of CO2 and helium (up to 55.72 and 1.91 * 10-2 cc l-1, respectively). Helium isotopic dat…
Carbon dynamics of soil organic matter in bulk soil and aggregate fraction during secondary succession in a Mediterranean environment.
2013
Clarifying which factors cause an increase or decrease in soil organic carbon (SOC) after agricultural abandonment requires integration of data on the temporal dynamics of the plant community and SOC. A chronosequence of abandoned vineyards was studied on a volcanic island (Pantelleria, Italy). Vegetation in the abandoned fields was initially dominated by annual and perennial herbs, then by Hyparrhenia hirta (L.) Stapf, and finally by woody communities. As a consequence, the dominant photosynthetic pathway changed from C3 to C4 and then back to C3. Conversion of a plant community dominated by one photosynthetic pathway to another changes the 13C/12C ratio of inputs to SOC. Using the time si…
The organic carbon derived from sewage sludge as a key parameter determining the fate of trace metals.
2007
8 pages; International audience; In a sandy agricultural soil of south-west of France, continuously cultivated with maize and amended with sewage-sludge over 20 years, the behavior of three trace metals (Cu, Pb, and Zn) was studied during the sludge applications (1974-1993) and after its cessation (1993-1998). Using the delta13C analysis, the dynamics of different sources of organic matter were followed in order to elucidate the influence of the sludge-derived organic matter on the fate of trace metals in the soil and its particle size fractions. This study revealed that sludge-derived organic matter contributed to the formation of macroaggregates through the binding of preexisting microagg…
Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris…
2014
Abstract Lower Toarcian strata (Lower Jurassic) have been extensively studied with a view to understanding the oceanographic, climatic and biological processes that drove the Earth's system into an Oceanic Anoxic Event (OAE). For this time period, the evolution of the European marine seaways is now relatively well constrained owing to multiple geochemical studies, but investigations regarding climatic trends in the continental realm remain sparse. In the present study, we test the clay mineralogy as a continental climate-sensitive proxy in the well-documented Sancerre core (southern Paris Basin). We compare variations in the kaolinite content with p CO 2 fluctuations (derived from paired ca…