Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We use a strike-slip fault analog model to study experimentally the role played by along-fault non-uniform and asymmetric applied normal stress on both coseismic slip and long-term fault behavior. Our model is based on a visco-elasto-plastic multi-layered rheology that allows to produce several hundreds of scaled analog microquakes and associated seismic cycles. Uniform or heterogeneous applied normal stress along the fault plane is imposed and maintained constant during the whole experiment durations. Our results suggest that coseismic slip patterns are strongly controlled by spatial normal stress variations and subsequent accumulated shear stress along fault strike. Major microquakes occur preferentially in zones of major shear stress asperities. Coseismic slip distributions exhibit a pattern similar to the along-fault applied normal stress distribution. The occurrence of isolated low to moderate microquakes where residual stresses persist around secondary stress asperities, indicates that stress conditions along the fault also control the whole variability of fault slip events. Moreover, when fault slip stability conditions are modulated by normal stress distribution, our experiments suggest that the along-fault stress heterogeneity influences the seismic cycle regularity and, consequently, long-term fault slip behavior. Uniform applied normal stress favors irregular seismic cycles and the occurrence of earthquakes clustering, whereas non-uniform normal stress with a single high amplitude stress asperity generates strong characteristic microquake events with stable return periods. Together our results strengthen the assumption that coseismic slip distribution and earthquake variability along an active fault may provide relevant information on long term tectonic stress and could thus improve seismic hazard assessment.
ISSN: 0012-821X

hal-01666379
https://hal.archives-ouvertes.fr/hal-01666379
DOI : 10.1016/j.epsl.2017.10.009

Éditeur(s) : HAL CCSD
Résumé : The heterogeneous nature and sometimes karstified carbonate environments has a direct impact on many environmental issues, such as coastal aquifers affected by saltwater intrusion. At the south of the island of Mallorca (Spain), the Llucmajor carbonate platform offers a privileged site for the study of such intrusions including the experimental site of Campos who meets the intrusion at shallow depth. The characterization of heterogeneous properties passes through a preliminary description of the properties of carbonate reservoirs, including those of the porosity. According to the wide range of sizes of heterogeneities from micrometer to hundreds of meters, the use of multiscale methods is required. This thesis focused on the determination of multiscale porosities from the microporosity to karstic porosity, and of relationships between observation scale changes of these properties. At the micron scale, high-resolution X-ray microtomography allows to extract the microporosity and the microporous network connectivity. At lower resolution (mm), X-ray tomography is also used to study the micro- and macro-porous network at the core scale which is already allocated to number of observations and measurements, including petrophysical. At the borehole scale, the wall images are used to identify the dissolved zones from centimeter macropores to plurimetric karstic cavities. At the larger scale, surface geophysics study the lateral extension of the karsts and heterogeneities. Finally, the porous structure of the studied site is integrated with its wide range of scales into the regional geology of the Llucmajor platform. Thus, the hydrogeophysical observatory set up on the site of Campos to monitor the spreading of salt water in the aquifer is integrated in its geological and petrophysical context, in order to refine the interpretation of its variations of salinity measurements during the time.
La nature hétérogène et parfois karstifiée des milieux carbonatés a un impact direct sur nombre de problématiques environnementales, comme celle des aquifères côtiers affectés par une intrusion d'eau salée. Au sud de l'ile de Majorque (Baléares, Espagne), la plate-forme carbonatée de Llucmajor offre un site privilégié pour l'étude de telles intrusions notamment avec le site expérimental de Campos, qui rencontre l'intrusion à faible profondeur. La caractérisation des propriétés hétérogènes du réservoir passe par une description préalable des propriétés des réservoirs carbonatés et notamment celle de la porosité. Au regard de la large gamme d'échelles d'hétérogénéités allant du micromètre à la centaine de mètre, l'utilisation de méthodes multi-échelles est nécessaire. Ce travail de thèse a porté sur la caractérisation multi-échelle de la porosité, allant de la microporosité à la porosité karstique, et l'établissement de relations entre les changements d'échelles d'observation de ces propriétés. A très petite échelle, la microtomographie haute-résolution à rayons X extrait à l'échelle du micron la microporosité et la connectivité des réseaux microporeux. A plus basse fréquence (celle du mm), la tomographie est également utilisée afin d'étudier le réseau micro- et macroporeux à l'échelle des carottes, à laquelle sont réalisées nombre d'observations et de mesures, notamment pétrophysiques. A l'échelle du puits, les images de paroi permettent d'identifier les zones de dissolution allant des macropores centimétriques aux cavités karstiques plurimétriques. A plus grande échelle, la géophysique de surface permet d'étudier l'extension latérale de ces karsts et hétérogénéités. Enfin, la structure poreuse du site étudié sur cette vaste gamme d'échelles est intégrée à la géologie régionale de la plate-forme de Llucmajor. Ainsi, l'observatoire installé sur le site pour surveiller la propagation de l'eau salée dans l'aquifère a pu être replacé dans son contexte géologique et pétrophysique, afin d'affiner l'interprétation de ses mesures de variations de salinité au cours du temps.
https://tel.archives-ouvertes.fr/tel-00633488

tel-00633488
https://tel.archives-ouvertes.fr/tel-00633488
https://tel.archives-ouvertes.fr/tel-00633488/document
https://tel.archives-ouvertes.fr/tel-00633488/file/TheseHebert.pdf

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1-10 cm, i.e. among branches of the same colony) to the reef scale (1-10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral-Symbiodinium symbiosis is a key process in scleractinian coral physiology, and Symbiodinium density provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link with Symbiodinium density. Density of Symbiodinium did not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events.
ISSN: 0025-3154

hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942
https://hal.archives-ouvertes.fr/hal-00905942/document
https://hal.archives-ouvertes.fr/hal-00905942/file/Ladriereetal2014.pdf
DOI : 10.1017/S0025315413001252

Éditeur(s) : Monachii ; Lipsiae : apud R. Oldenbourg in comm.
Extrait de : Flora brasiliensis : enumeratio plantarum in Brasilia hactenus detectarum quas suis aliorumque botanicorum studiis descriptas et methodo naturali digestas partim icone illustratas
Résumé : Édition : 1840-1906
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Université Toulouse III - Paul Sabatier. Service Commun de la Documentation
Permalien : http://www.manioc.org/patrimon/TLS17055
TLS17055

Éditeur(s) : Paris : Dufart père
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Martinique. Bibliothèque Schoelcher
Permalien : http://www.manioc.org/patrimon/SCH13036
SCH13036

Éditeur(s) : HAL CCSD Inter Research
Résumé : International audience
The main objective of the VULSACO (VULnerability of SAndy COasts to climate change and anthropic pressure) project was to investigate present day and potential future vulnerability of sandy coasts at the 2030 horizon, i.e. on a time scale related to climate variability. The method, based on a multidisciplinary approach bringing together geologists, geographers, physicists, social psychologists, engineers and stakeholders, was structured around 4 axes: field data analysis; numerical modelling; analysis of governance and stakeholder perceptions; and development of vulnerability indexes. This approach was designed to investigate vulnerability at a local scale and was applied to 4 contrasting beaches located in France: Sète Lido (Mediterranean Sea), Truc Vert and La Tresson beaches (Atlantic Ocean), and Dewulf (English Channel). The results focus on decadal and multi-annual beach trends at the Truc Vert beach site. There is almost no trend in beach volume at Truc Vert beach, although there is a variation in this parameter on a cycle of 2 to 3 yr, with variations related to wave energy and probably to indexes of climate variability. Numerical modelling identified the sensitivity of beach responses to changes in wave height and direction, especially in terms of subtidal morphology and the potential development of shoreline instability. Together with the observed offshore wave angle at the Biscay Buoy, these model results suggest that a potential change in wave angle due to climate variability could significantly modify the bars' morphology. The combination of data analysis and numerical modelling contributed to the development of vulnerability indexes designed for sandy coasts, which take into account climate-dependant variables such as waves. This allowed the differentiation of the sites in terms of vulnerability to erosion: Sète Lido and Truc Vert beach were the most and least vulnerable sites, respectively. These indexes help in identifying the dominant components of beach vulnerability, and provide potential for the study of how anthropogenic factors affect vulnerability. The study of stakeholder perceptions and decision-making with regard to climate-related risk also highlighted potential anthropogenic effects on beach vulnerability, and identified possible site-specific outcomes.
ISSN: 0936-577X

hal-00843946
https://hal-brgm.archives-ouvertes.fr/hal-00843946
DOI : 10.3354/cr01153

Éditeur(s) : London : Richard Phillips
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Archives territoriales de Guyane
Permalien : http://www.manioc.org/patrimon/GAD12003
GAD12003

Éditeur(s) : Edinburgh, London
Siècle(s) traité(s) : 19
Provenance : Université Caen Normandie. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/CAE19033_3
CAE19033_3

Éditeur(s) : Londres : John Stockolale
Siècle(s) traité(s) : 18
Droits : Domaine public
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG17063
ADG17063

Éditeur(s) : Paris : Firmin Didot Frères

Droits : Domaine public
Provenance : Archives territoriales de Guyane
Permalien : http://www.manioc.org/patrimon/GAD12001
GAD12001

Éditeur(s) : Cambridge : J. Bentham
Siècle(s) traité(s) : 18
Droits : Domaine public
Provenance : Archives départementales de Guadeloupe
Permalien : http://www.manioc.org/patrimon/ADG17077
ADG17077

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Most kimberlites contain abundant dunitic nodules. These are centimetre-sized, rounded and multi-grained assemblages of xenocrystic olivine with a wide range of compositions (Fo83 to Fo94). The absence of orthopyroxene and other mantle minerals and the range of olivine compositions have been attributed to reaction between mantle peridotite and (proto)kimberlitic fluid or melt, but the timing of the reaction is a subject of debate. In a kimberlite from the Kangamiut region of Greenland, nodule cores are surrounded by fine-grained outer margins with near-constant Fo contents (∼Fo88) but highly variable minor element contents (e.g. 500–2500 ppm Ni). These margins crystallized from the kimberlite melt and we show that their compositions can be explained by crystallization of olivine alone, if a high partition coefficient for Ni between melt and olivine (DNi > 20) is assumed. Orthopyroxene assimilation is not required, removing the constraint that its dissolution occurred during ascent of the kimberlite magma. Within some nodules, in addition to the usual core-to-margin gradients, we observe asymmetric compositional changes (variable Fo but near-constant minor element contents) across mobile grain boundaries. These changes document fluid percolation at the grain scale that occurred during dynamic recrystallization in the deforming lithospheric mantle. We note that chemical gradients associated with mobile grain boundaries are observed in olivines that cover the entire compositional range of the nodules, and propose that fluid-assisted dynamic recrystallization took place in dunite that was already compositionally heterogeneous. Reaction between peridotite and protokimberlitic melt or fluid and dissolution of orthopyroxene thus occurred within the lithospheric mantle, immediately (a few days) prior to the ascent of the kimberlite melt and the entrainment of the dunite nodules. We propose that the grain boundary zones probably mimic, at a fine scale, the fluid–peridotite interaction that caused, at a larger scale, orthopyroxene dissolution and formation of compositionally diverse olivine in kimberlites.
ISSN: 0022-3530

hal-01277963
https://hal.archives-ouvertes.fr/hal-01277963
DOI : 10.1093/petrology/egv054

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Geomorphic landscape features have been suggested as indicators of forest diversity. However, their explanatory power has not yet been explicitly tested at a regional scale in tropical rainforest. We used forest inventories conducted according to a stratified sampling design (3,132 plots in 111 transects at 33 sites) and holistic multi-scale geomorphological mapping derived from a Shuttle Radar Topography Mission digital elevation model to describe and explain spatial patterns in floristic composition across French Guiana (80,000 km2). We measured and identified 123,906 trees with DBH C20 cm and used constrained and unconstrained ordinations to analyze variations in the abundance of 221 taxa and 51 families. Variance partitioning and variograms were used to detect spatial patterns in species composition, compare the explanatory power of spatial and environmentalfactors, and select the variables that best explain forest composition. Strong floristic patterns corresponded to a major latitudinal gradient and significant sub-regional floristic structure. Geomorphological landscapes shaped by historic climate fluctuations and major geological events successfully captured these patterns and explained the variation in abundance of 80 taxa, corresponding to 65 % of the inventoried trees. Our findings suggest that long-term forest dynamics are under substantial ‘‘geomorphographic control’’. A geomorphological perspective on landscapes that incorporates current and past environmental filters and historical biogeographical processes could thus be used more systematically in tropical regions for regional planning and forest conservation
ISSN: 0960-3115

hal-01204224
https://hal.archives-ouvertes.fr/hal-01204224
DOI : 10.1007/s10531-014-0854-8
PRODINRA : 295767

Éditeur(s) : Officina reverendae camerae apostolicae (Rome)
Résumé : Ex-libris manuscrit

Provenance : Ville de Bordeaux. Bibliothèque municipale
Permalien : http://www.manioc.org/patrimon/BBX19056
BBX19056

Éditeur(s) : London : H. Colburn and R. Bentley
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Martinique. Bibliothèque Schoelcher
Permalien : http://www.manioc.org/patrimon/SCH13082
SCH13082

Droits : Domaine public
Provenance : Communauté d'agglomération de La Rochelle. Médiathèque Michel-Crépeau
Permalien : http://www.manioc.org/patrimon/MMC16099-18
MMC16099-18

Date de création : 1869-01-01

Éditeur(s) : London : Bell & Daldy
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA11001
FRA11001

Éditeur(s) : [S.l.] : Delagrave
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Université des Antilles. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/HASH010d08988893e8073d1ea073
HASH010d08988893e8073d1ea073

Éditeur(s) : HAL CCSD Geological Society of America
Résumé : International audience
In this study, a novel application of a statistical approach is utilized for analysis of downhole logging data from Miocene-aged siliciclastic shelf sediments on the New Jersey Margin (eastern USA). A multivariate iterative nonhierarchical cluster analysis (INCA) of spectral gamma-ray logs from Integrated Ocean Drilling Program (IODP) Expedition 313 enables lithology within this siliciclastic succession to be inferred and, through comparison with the 1311 m of recovered core, a continuous assessment of depositional sequences is constructed. Signifi cant changes in INCA clusters corroborate most key stratigraphic surfaces interpreted from the core, and this result has particular value for surface recognition in intervals of poor core recovery. This analysis contributes to the evaluation of sequence stratigraphic models of large-scale clinoform complexes that predict depositional environments, sediment composition, and stratal geometries in response to sea-level changes. The novel approach of combining statistical analysis with detailed lithostratigraphic and seismic refl ection data sets will be of interest to any scientists working with downhole logs, especially spectral gamma-ray data, and also provides a reference for the strengths and weaknesses of multi component analysis applied to continental margin lithofacies. The method presented here is appropriate for evaluating successions elsewhere and also has value for hydrocarbon exploration where sequence stratigraphy is a fundamental tool.
EISSN: 1553-040X

insu-00858238
https://hal-insu.archives-ouvertes.fr/insu-00858238
DOI : 10.1130/GES00913.1

Date de création : 1870-01-01

Éditeur(s) : London : Bell & Daldy
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA11002
FRA11002