Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0003-4975

hal-01563338
http://hal.univ-brest.fr/hal-01563338
DOI : 10.1016/j.athoracsur.2016.03.093
PUBMED : 27262916

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
Apatite fission track analysis (AFTA) data are used to bring new light on the long-term and recent history of the Baikal rift region (Siberia). We describe the evolution of the topography along a NW-SE profile from the Siberian platform to the Barguzin range across the Baikal-southern Patom range and the northern termination of Lake Baikal. Our results show that the Baikal-Patom range started to form in the Early Carboniferous and was reactivated in Middle Jurassic-Lower Cretaceous times during the orogenic collapse of the Mongol-Okhotsk belt. Samples located in the Siberian platform recorded a continuous sedimentation up to the early Carboniferous but remain unaffected by later tectonic episodes. The Barguzin basin probably started to form as early as Late Cretaceous, suggesting a continuum of deformation between the postorogenic collapse and the opening of the Baikal Rift System (BRS). The initial driving mechanism for the opening of the BRS is thus independent from the India-Asia collision. AFTA show a late Miocene-early Pliocene increase in tectonic extension in the BRS that confirms previous thoughts and might reflect the first significant effect of the stress field generated by the India-Asia collision.
ISSN: 0278-7407

hal-00420895
https://hal.archives-ouvertes.fr/hal-00420895
DOI : 10.1029/2008TC002404

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Aims: The aims of this study were to compare short-and long-term outcomes for clinical T2N0 oesophageal cancer with analysis of (i) primary surgery (S) versus neoadjuvant therapy plus surgery (NS), (ii) squamous cell carcinoma and adenocarcinoma subsets; and (iii) neoadjuvant chemoradiotherapy versus neoadjuvant chemotherapy.Methods: Data were collected from 30 European centres from 2000 to 2010. Among 2944 included patients, 355 patients (12.1%) had cT2N0 disease; 285 (S) and 70 (NS), were compared in terms of short-and long-term outcomes. Propensity score matching analyses were used to compensate for differences in baseline characteristics.Results: No significant differences between the groups were shown in terms of in hospital morbidity and mortality. Nodal disease was observed in 50% of S-group at the time of surgery, with 20% pN2/N3. Utilisation of neoadjuvant therapy was associated with significant tumour downstaging as reflected by increases in pT0, pN0 and pTNM stage 0 disease, this effect was further enhanced with neoadjuvant chemoradiotherapy. After adjustment on propensity score and confounding factors, for all patients and subset analysis of squamous cell and adenocarcinoma, neoadjuvant therapy had no significant effect upon survival or recurrence (overall, loco-regional, distant or mixed) compared to surgery alone. There were no significant differences between neoadjuvant chemotherapy and chemoradiotherapy in short-or long-term outcomes.Conclusion: The results of this study suggest that a surgery alone treatment approach should be recommended as the primary treatment approach for cT2N0 oesophageal cancer despite 50% of patients having nodal disease at the time of surgery.
ISSN: 0959-8049

hal-01666517
https://hal.univ-lorraine.fr/hal-01666517
DOI : 10.1016/j.ejca.2015.11.024

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes (erosion and sedimentation). The study of long-lived morphologic markers formed by these interactions can help in quantifying the competing effects of tectonics, erosion and sedimentation. In regions experiencing active extension, river-long profiles and faceted spurs (triangular facets) can help in un- derstanding the development of mountainous topography along normal fault scarps. In this study, we devel- oped analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault. This paper focuses on the effect of the fault slip rate on the morphologic evolution of the foot- wall by performing three analogue experiments with different fault slip rates under a constant rainfall rate. A morphometric analysis of the modelled catchments allows comparing with a natural case (Tunka half- graben, Siberia). After a certain amount of fault slip, the modelled footwall topographies of our models reaches a dynamic equilibrium (i.e., erosion balances tectonic uplift relative to the base level) close to the fault, whereas the topography farther from the fault is still being dissected due to regressive erosion. We show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of re- gressive erosion are linearly correlated with the fault throw rate. Facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting. A stream-power law is computed for the area wherein rivers reach a topographic equilibrium. We show that the erosional capacity of the system depends on the fault slip rate. Finally, our results demonstrate the pos- sibility of preserving convex river-long profiles on the long-term under steady external (tectonic uplift and rainfall) conditions.
ISSN: 0040-1951

hal-00646966
https://hal.archives-ouvertes.fr/hal-00646966
https://hal.archives-ouvertes.fr/hal-00646966/document
https://hal.archives-ouvertes.fr/hal-00646966/file/preprint_Strak_2011.pdf
DOI : 10.1016/j.tecto.2011.10.005

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics. In this paper, we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes (erosion, transport, and sedimentation), coupled with accurate model monitoring techniques. This approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end-member geological settings: compression, extension, and strike–slip.Experimental results outline first that experimental morphologies evolve significantly at a short time scale. Numerous morphologic markers form continuously, but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them. For the compressional setting, the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging-wall and by avulsion of deposits on fan-like bodies. Terrace formation is irregular even under steady tectonic rates and erosional conditions. Terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution. For the extensional setting, the dynamics of hanging-wall sedimentary filling appears to control the position of the base level, which in turn controls footwall erosion. Two phases of relief evolution can be evidenced: the first is a phase of relief growth, and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin. During the phase of relief growth, the formation of triangular facets occurs by degradation of the fault scarp, and their geometry (height) becomes stationary during the phase of upstream propagation of the topographic equilibrium. For the strike–slip setting, the complex morphology of the wrench zone, composed of several interacting fault segments, enhances the interactions with the drainage network. Because of the widening of the main fault zone toward the surface, a significant amount of distributed deformation is observed along the wrench zone. Locally, where two terminations of fault segments interact, less than a quarter of the far field displacement can remain measurable using fault offsets, leading to a systematic underestimation of the real fault slip rate.These different experimental examples illustrate the great potential of the approach coupling deformation mechanisms and erosion–transport–sedimentation processes to investigate qualitatively and quantitatively the morphotectonic evolution of tectonically controlled landscapes.
ISSN: 0169-555X

hal-01243587
https://hal.archives-ouvertes.fr/hal-01243587
DOI : 10.1016/j.geomorph.2015.02.011

Éditeur(s) : HAL CCSD Elsevier
Résumé : In the context of an ongoing monitoring study on the impacts of gold-mining activities on critical ecosystem processes, we explored the use of soil Denitrifying Enzyme Activity (DEA) and Substrate Induced Respiration (SIR) as ecosystem indicators in tropical rainforests of French Guiana. We also propose DEA/SIR ratio as ecosystem attribute able to describe the state of an ecosystem and to reflect changes in ecological processes. With this purpose, we measured SIR, DEA and DEA/SIR ratio in five gold-mining areas and five surrounding natural reference rainforests. We also measured indicators in two conditions of spontaneous regeneration of vegetation (stratified or not) and two conditions of soil rehabilitation (prior preparation of soils or not). We showed a high variability of DEA, SIR and DEA/SIR ratio in the natural reference forests. This pointed out the necessity to identify relevant reference systems - i.e. proving a close match in all relevant ecological dimensions - to compare with closed perturbed systems in order to assess the levels of alterations after disturbances. Results showed a high impact of gold mine on microbial processes with a strong decrease of DEA (10-fold lower), SIR (2-fold lower) and DEA/SIR ratio (8-fold lower) in perturbed areas in comparison with natural reference forests. The type of spontaneous vegetation (stratified or not) influenced the values of indicators as well as prior rehabilitation of soils, demonstrating the capacity of DEA. SIR and DEA/SIR ratio to respond in proportion to the perturbation (robustness) and to the different levels of restoration (sensitivity). The systematic decrease of the ratio DEA/SIR observed in the studied perturbed situations demonstrates clearly that the structure of microbial communities has been also modified. The ratio DEA/SIR proved to be robust and sensitive, and able to describe in fairly fine way changes of soil microbial communities in terms of structure and function in gold mine areas and during processes of restoration. We propose to use DEA, SIR and DEA/SIR ratio as bioindicators of both structural and functional aspects of C and N cycling in soils. Together with others bioindicators based on key supporting functions in soils, these indicators should accurately evaluate the ecological potential of natural ecosystems and the levels of degradation in case of land-use changes. (C) 2012 Elsevier Ltd. All rights reserved.
ISSN: 1470-160X

hal-01190730
https://hal.archives-ouvertes.fr/hal-01190730
DOI : 10.1016/j.ecolind.2012.01.021
PRODINRA : 213639

Éditeur(s) : HAL CCSD
Résumé : Poster
We deployed a temporary local seismic network in the North Tanzanian Divergence (NTD) for 6 months in 2007 (35 stations, SEISMOTANZ'07 experiment). The region is characterized by major changes in the magmatic/tectonic nature of the rift, at the place where the eastern branch of the East African Rift enters the Tanzanian craton. More than 200 earthquakes were accurately located south of Lake Manyara.
Iceland in the Central Northern Atlantic : hotspot, sea currents and climate change
Plouzané, France

hal-00482059
http://hal.univ-brest.fr/hal-00482059
http://hal.univ-brest.fr/hal-00482059/document
http://hal.univ-brest.fr/hal-00482059/file/poster_albaric.pdf

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
We present new results on the long-term throw rates of active normal faults in the North Baikal Rift (NBR), eastern Siberia, based on a statistical analysis of triangular faceted scarps. Fault-bounded ridges in the NBR display typical morphologies with several contiguous facets separated by fault-perpendicular catchments. Over a range of 20 fault segments analyzed, triangular facet heights vary from similar to 200 to >900 m. As fault scarps have been developing under similar long-term climatic conditions, we infer that the scatter in mean facet height arises from long-term differences in fault throw rate. We compare the morphology of NBR facets with results obtained in a previously published numerical model of facet growth. Using facet height as an input, model results provide estimates of the long-term fault throw rate. NBR throw rates vary between 0.2 and 1.2 mm yr(-1). The throw rates are then compared with the cumulated throw, which has been constrained by geophysical and stratigraphic data in the basins. This provides an estimate of the age of fault and basin initiation. We show that the modern stage of basin development started circa 3 Myr ago, except for the North Baikal basin (similar to 8Ma). Our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage.
ISSN: 0278-7407

hal-00455985
https://hal.archives-ouvertes.fr/hal-00455985
DOI : 10.1029/2009TC002555