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4. Direct dating of brittle extensional deformation in the internal zones of the Rif Chain

Author

Münch, Philippe, Caillaud, Jacinthe, Monie, Patrick, Grauby, Olivier, Corsini, Michel, Ricci, Julia, Romagny, Adrien, Philippon, Mélody, Lanson, Bruno, Azdimousa, Ali, Ben Moussa, Abdelkhalak, Arnaud, Nicolas, and Sciencesconf.org, CCSD

Subjects
Western Mediterranean, [SDU] Sciences of the Universe [physics], 40Ar/39Ar dating, Fault gouge dating, T thermochronology, Rif belt, Low
Published
2021

6. Effect of emersion/immersion cycles on the elemental and isotopic compositions of the organic matter from surface sediments of an intertidal mud bank (French Guiana): a preliminary study

Author

Gontharet , Swanne, Artigas , Luis Felipe, Mathieu , Olivier, Lévêque , Jean, Milloux , Marie-Jeanne, Caillaud , Jacinthe, Philippe , Sylvie, Lesourd , Sandric, Gardel , Antoine, Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), Biogéosciences [UMR 6282] [Dijon] (BGS), Centre National de la Recherche Scientifique (CNRS)-Université de Bourgogne (UB)-AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), USR 3456, Centre National de la Recherche Scientifique (CNRS), Work financially supported by the Research Council of the Université du Littoral-Côte d’Opale., Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Biogéosciences [UMR 6282] (BGS), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens (LEEISA), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 ( LOG ), Université du Littoral Côte d'Opale-Université de Lille-Centre National de la Recherche Scientifique ( CNRS ), Biogéosciences [Dijon] ( BGS ), Université de Bourgogne ( UB ) -AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement-Centre National de la Recherche Scientifique ( CNRS ), Morphodynamique Continentale et Côtière ( M2C ), Centre National de la Recherche Scientifique ( CNRS ) -Université de Rouen Normandie ( UNIROUEN ), Normandie Université ( NU ) -Normandie Université ( NU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Université de Caen Normandie ( UNICAEN ), Normandie Université ( NU ), and Centre National de la Recherche Scientifique ( CNRS )

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [ SDU.STU.GC ] Sciences of the Universe [physics]/Earth Sciences/Geochemistry
Abstract

11 pages; International audience; In various marine environments, the combination of elemental ratios and stable isotopic compositions is usually used to trace the sources of organic matter (OM) in sediments. However, in intertidal areas, the sediments might be temporarily exposed to air during a more or less prolonged duration and the impact of this exposure on the latter parameter is unknown. The spatial variations of atomic Total Organic Carbon (TOC) and Total Nitrogen (TN) ratios, and δ(13) C and δ(15) N values, were measured on surface sediments of French Guiana, at the beginning and the end of five consecutive days of emersion during equinoctial tides, as well as at the beginning of a new emersion phase after returning to a normal tidal cycle. The concentrations of chlorophyll a and phaeopigments in sediments were also measured, in order to estimate the influence of microphytobenthos (MPB), growing at surface sediments, on these geochemical parameters. The results showed that the emersion/immersion cycles influenced the development of MPB at the surface sediments, which, in turn, significantly controlled the spatio-temporal changes in the atomic elemental ratios and the δ(13) C values. This variability seemed not to be significantly altered by OM degradation. On the contrary, sediments were always (15) N-enriched compared with OM sources, indicating that OM diagenetic processes mainly controlled their spatio-temporal fluctuations. The [TOC/TN]atomic ratios and the δ(13) C values, indicating the primary signal of OM sources, represented the most reliable geochemical proxies for calculating the relative contribution of OM sources to sediments in environments characterized by variable air exposure duration. The use of δ(15) N values in such environments is limited by OM degradation processes but their variation might enable the nature and the degree of these processes to be identified.

Published
2015
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7. A better understanding of mud cracking processes gained from in situ measurements on an intertidal mudflat in French Guiana

Author

Gardel, Antoine, Proisy, Christophe, Lesourd, Sandric, Philippe, Sylvie, Caillaud, Jacinthe, Gontharet, Swanne, Anthony, E. J., Brutier, L., Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Botanique et Modélisation de l'Architecture des Plantes et des Végétations (UMR AMAP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de la Recherche Agronomique (INRA)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD [France-Sud]), and Université du Littoral Côte d'Opale-Université de Lille-Centre National de la Recherche Scientifique (CNRS)

Subjects
Mud bank, [SDE.MCG]Environmental Sciences/Global Changes, Mangrove colonization, Desiccation, South America, Spring tide, ComputingMilieux_MISCELLANEOUS, Neap tide, Dynamics, Coast
Abstract

International audience; Recent work has revealed that desiccation processes can occur over elongated off-shore mud bars that form on Amazon-derived mud banks. Once mud cracks appear there, opportunistic mangroves, i.e. Avicennia germinans, commence the colonization process. Through the advantage of buoyancy of the mangrove propagules which can be trapped by the mud cracks, propagules can establish sometimes 1-2 kilometres offshore of the adult colonies. In a few months, these pioneer colonies become new sources of propagules, promoting rapid ecosystem expansion. Thus, mud cracking may be seen as an important factor in mangrove resilience. To investigate this phenomenon, a field experiment was conducted during the 2008 equinoctial spring tide in French Guiana in a study area located on the landward face of an elongated mud bar. A digital elevation model (DEM) was computed from DGPS and high-resolution laser station data. Meteorological data including air temperature and humidity, wind speed and orientation, rainfall, solar radiation, temperatures of the mud surface and at a depth of 30-cm, were recorded. Additionally, the water content of the upper mud layer was monitored along a topographic transect. An installed camera took instant photographs every half hour. Preliminary results show that climatic conditions are not the main parameter controlling the desiccation process. Strengthening and consolidation of mud are mainly controlled by mud elevation (water loss by draining) and by the local tidal signal (determinant in spatial behaviour). The DEM enabled computation of the tidal frequency emersion signal, an important tool in analyzing the spatio-temporal patterns of mud cracking and mangrove colonization.

Published
2009

8. Effect of emersion/immersion cycles on the elemental and isotopic compositions of the organic matter from surface sediments of an intertidal mud bank (French Guiana): a preliminary study.

Author

Gontharet S, Artigas LF, Mathieu O, Levêque J, Milloux MJ, Caillaud J, Philippe S, Lesourd S, and Gardel A

Abstract

Rationale: In various marine environments, the combination of elemental ratios and stable isotopic compositions is usually used to trace the sources of organic matter (OM) in sediments. However, in intertidal areas, the sediments might be temporarily exposed to air during a more or less prolonged duration and the impact of this exposure on the latter parameter is unknown., Methods: The spatial variations of atomic Total Organic Carbon (TOC) and Total Nitrogen (TN) ratios, and δ(13)C and δ(15)N values, were measured on surface sediments of French Guiana, at the beginning and the end of five consecutive days of emersion during equinoctial tides, as well as at the beginning of a new emersion phase after returning to a normal tidal cycle. The concentrations of chlorophyll a and phaeopigments in sediments were also measured, in order to estimate the influence of microphytobenthos (MPB), growing at surface sediments, on these geochemical parameters., Results: The results showed that the emersion/immersion cycles influenced the development of MPB at the surface sediments, which, in turn, significantly controlled the spatio-temporal changes in the atomic elemental ratios and the δ(13)C values. This variability seemed not to be significantly altered by OM degradation. On the contrary, sediments were always (15) N-enriched compared with OM sources, indicating that OM diagenetic processes mainly controlled their spatio-temporal fluctuations., Conclusions: The [TOC/TN]atomic ratios and the δ(13)C values, indicating the primary signal of OM sources, represented the most reliable geochemical proxies for calculating the relative contribution of OM sources to sediments in environments characterized by variable air exposure duration. The use of δ(15)N values in such environments is limited by OM degradation processes but their variation might enable the nature and the degree of these processes to be identified., (Copyright © 2015 John Wiley & Sons, Ltd.)

Published
2015
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