Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: I Effect on benthic community structure and food web     

Vincent Ouisse  Pascal Riera  Aline Migné  Cédric Leroux  Dominique Davoult 《Estuarine, Coastal and Shelf Science》2011

Freshwater seepages and ephemeral Enteromorpha spp. proliferation create heterogeneity at small spatial scale in intertidal sediment. Macrobenthic community diversity was compared between these two disturbances and their respective control points throughout the year 2007 at the Roscoff Aber Bay (Western English Channel, France). In March and September 2007, trophic community pathways of characteristic species were additionally studied using stable isotope ratios of carbon and nitrogen. The low salinity recorded at the freshwater seepage induced the exclusion of the main bioturbator and the presence of omnivores which modified the community composition by biotic pressure. Moreover, food web analyses clearly highlighted a separation at small spatial scale between the two trophic pathways of the impacted area and its control. On the contrary, little differences were observed owning to the ephemeral Enteromorpha spp. proliferation. This suggested a progressive and diffusive disturbance which was applied from the algal mat to the nearby area. However, seasonal changes were observed. First, the algal expansion phase increased the macrofauna diversity and foraminifers’ abundance (meiofauna) and then acted as a physical barrier decreasing sediment and water column exchanges and decreasing the fauna diversity. This study highlights the need to take into account small spatial heterogeneity to avoid misinterpretations in intertidal ecology studies.  相似文献   

Spatial and ontogenetic variability in the chemical composition of juvenile common sole (Solea solea) otoliths     

S.E. Tanner  R.P. Vasconcelos  P. Reis-Santos  H.N. Cabral  S.R. Thorrold 《Estuarine, Coastal and Shelf Science》2011

  相似文献   

Laboratory modeling of topographic Rossby normal modes     

Stefano Pierini  Adam M. Fincham  Dominique Renouard  Maria Rosaria D&#x;Ambrosio  Henry Didelle 《Dynamics of Atmospheres and Oceans》2002,35(3)

The physical modeling of topographic Rossby normal modes carried out at the “Coriolis” Rotating Platform (Grenoble), is presented. The basic feature of the bottom topography is a linear slope of 4.3 m×2 m delimited by two lateral walls. Since the studied motions are essentially barotropic, homogeneous water was used. Unsheared currents were generated by a simple movement of a wavemaker located in front of the topographic barrier. The conservation of potential vorticity for the currents flowing onto the channel slope produced Rossby waves: reflections at the lateral boundaries then led to the formation of propagating barotropic Rossby normal modes, whose frequencies and spatial structures were selected by the physical system. The currents were measured through the correlation imaging velocimetry (CIV) method, which allowed an extremely detailed synoptic map of the horizontal velocities in an area (13 m²) including the slope to be obtained every 30 s.A variety of experiments were performed in order to provide a complete process study in which the effect of different channel lengths and rotation periods could be tested. Two different lengths of the linear slope, 4.3 and 3.3 m, and rotation periods ranging from 30 to 50 s were considered. The qualitative analysis of the 2D current patterns, and the good agreement found between the measured eigenperiods and the periods obtained by means of a simple analytical model, show that in all cases the first Rossby normal mode was generated. Moreover, numerical simulations based on the shallow-water equations, for a geometry and paddle movements that match closely the experimental setup, allow to calibrate the analytical model and provide useful information on a discrepancy found between experimental and analytical eigenperiods due to an oscillation of the normal mode trajectory.  相似文献   

Bootstrap determination of the reliability of b-values: an assessment of statistical estimators with synthetic magnitude series     

Mendy Bengoubou-Val��rius  Dominique Gibert 《Natural Hazards》2013,65(1):443-459

We consider some practical issues of the determination of the b-value of sequences of magnitudes with the bootstrap method for short series of length L and various quantization levels $\Updelta m$ of the magnitude. Preliminary Monte Carlo tests performed with $\Updelta m = 0$ demonstrate the superiority of the maximum likelihood estimator b _MLE, and the inconsistency of the, yet often used, b _LR estimator defined as the least-squares slope of the experimental Gutenberg?CRichter curve. The Monte Carlo tests are also applied to an estimator, b _KS, which minimizes the Kolmogorov?CSmirnov distance between the cumulative distribution of magnitudes and a power-law model. Monte Carlo tests of discrete versions of the b _MLE and b _KS estimators are done for $\Updelta m = \{0.1, 0.2, 0.3 \}$ and used as reference to evaluate the performance of the bootstrap determination of b. We show that all estimators provide b estimates within 10?% error for L????100 and if a large number, n?=?2?×?10⁵, of bootstrapped sample series is used. A resolution test done with $\Updelta m = 0.1$ reveals that a clear distinction between b?=?0.8, 1.0, and 1.2 is obtained if L????200.  相似文献   

Deformation related to Miocene westward translation in the core of the Betic zone Implications on the tectonic interpretation of the Betic orogen (Spain)     

Dominique Frizon de Lamotte  Jean-Claude Guézou  Marie-Anne Albertini 《Geodinamica Acta》2013,26(4):267-281

Abstract

The Cenozoic westward motion of the Betic-Rif internal zone (“Alboran block”) between Iberia and Africa is constrained by paleogeographic considerations and by wrench faulting which affects both sides of the external zones. However, in the Alboran domain itself there was so far no evidence of significant internal deformation related to this westward displacement which was consequently consider as an en bloc” motion. Our work, in Eastern Andalucia, demonstrates that the main tectonic units building up the Betic zone should be regarded as large-scale tectonic sheets with a typical duplex style. The direction of the tectonic transport is to the West. At meso-scale, the major structures exhibit a combination of hindward and foreward dipping imbricates on the respective east and west sides of antiformal stacks or “rigid cores”. On a broader scale, the same geometric framework appears on both east and west sides of the Sierra Nevada window which we interpret as a tectonic culmination on the hangingwall of a Subbetic décollement zone. The development of this tectonics, in retrogressive metamorphic conditions, postdates the ductile deformation of the internal complexes. The morpho-tectonic relationships between the culmination of the metamorphic cores and the Neogene basins give a way to date the westward motion of the “Alboran System of Nappes” of the middle and upper Miocene.  相似文献   

Reply to comment on Duplex at the lateral tip of a thrust fault: the “La Cagalière” example (NE Pyrenees,France) by B. Laumonier et al     

Dominique Frizon de Lamotte  Christine Souque  Pascale Leturmy  Philippe Robion 《Geodinamica Acta》2013,26(2):183-184

  相似文献   

Géochimie et signification géotectonique des volcanites du Cryogénien inférieur du Saghro (Anti-Atlas oriental,Maroc) / Geochemistry and geotectonic significance of Early Cryogenian volcanics of Saghro (Eastern Anti-Atlas,Morocco)     

Abdelilah Fekkak  André Pouclet  Hassane Ouguir  Hassane Ouazzani  Lakhlifi Badra  Dominique Gasquet 《Geodinamica Acta》2013,26(6):373-385

Abstract

The Early Cryogenian groups of Sidi Flah, Kelaat Mgouna and Boumalne (Saghro, Anti-Atlas, Morocco) are constituted by turbiditic deposits and interbedded lavas, accumulated in tectonic basins. At Sidi Flah, volcanics are transitional showing initial rift tholeiites (IRT) fingerprint and alkali basalts of oceanic island basalt (OIB) compositions. At Kelaat Mgouna, volcanics consist of low-Nb continental tholeiites. At Boumalne, basalts are of IRT composition. The volcanic and sedimentary formations belong to a nascent rift caused by thermal doming along a SW-NE axis, the Saghro rift. The continental break-up occurred in the early Neopro- terozoic and during the Rodinia supercontinent dislocation, within a continent called “Ibero-saharian Craton” which was in front of the West-African Craton located near the South Pole. The Saghro rift is contemporaneous to the opening of an oceanic domain represented by Central Anti-Atlas ophiolites and related to the extension of the Brazialiano Ocean. © 2001 Éditions scientifiques et médicales Elsevier SAS  相似文献   

Internal architecture and evolution of bioclastic beach ridges in a megatidal chenier plain: Field data and wave flume experiment     

Pierre Weill  Dominique Mouazé  Bernadette Tessier 《Sedimentology》2013,60(5):1213-1230

Beach ridges in macrotidal environments experience strong multi‐annual to multi‐decennial fluctuations of tidal inundation. The duration of tide flooding directly controls the duration of sediment reworking by waves, and thus the ridge dynamics. Flume modelling was used to investigate the impact of low‐frequency tidal cycles on beach ridge evolution and internal architecture. The experiment was performed using natural bioclastic sediment, constant wave parameters and low‐frequency variations of the mean water level. The morphological response of the beach ridge to water level fluctuations and the preservation of sedimentary structures were monitored by using side‐view and plan‐view photographs. Results were compared with the internal architecture of modern bioclastic beach ridges in a macrotidal chenier plain (Mont St. Michel Bay, France) surveyed with ground‐penetrating radar. The experimentally obtained morphologies and internal structures matched those observed in the field, and the three ridge development stages identified in ground‐penetrating radar profiles (early transgressive, late transgressive and progradational) were modelled successfully. Flume experiments indicate that flat bioclastic shapes play a key role in sediment sorting in the breaker zone, and in sediment layering in the beach and washover fans. Water level controls washover geometry, beach ridge evolution and internal structure. Low water levels allow beach ridge stabilization and sediment accumulation lower on tidal flats. During subsequent water level rise, accumulated sediment becomes available for deposition of new washover units and for bayward extension of the beach ridges. In the field, low‐frequency water level fluctuations are related to the 4·4 year and 18·6 year tidal cycles. Experimental results suggest that these cycles may represent the underlying factor in the evolution of the macrotidal chenier coast at the multi‐decadal to centennial time scale.  相似文献   

Between outside and inside? Prison visiting rooms as liminal carceral spaces     

Dominique Moran 《GeoJournal》2013,78(2):339-351

This paper suggests that although carceral space seems to be sharply demarcated from the outside world, the prison wall is in fact more porous than might be assumed. The paper critiques Goffman’s theory of the ‘total institution’ by deploying a geographical engagement with liminality to theorise prison visiting rooms as spaces in which prisoners come face-to-face with persons and objects which come from and represent their lives on the ‘outside’. Drawing on a specific empirical example from recent research into imprisonment in the contemporary Russian prison system, it uses the example of visiting suites designed for long term ‘residential’ visits to explore the ways in which visiting spaces act as a space of betweenness where a metaphorical threshold-crossing takes place between outside and inside. The paper specifically explores the expression of that betweenness in the materiality of visiting, and in the destabilisation of rules and identities in visiting space. It contests the sense of linear transformation with which liminal spaces have previously been associated, suggesting that rather than spaces of linear transition from one state to another, liminal spaces can constitute a frustratingly repetitive, static or equilibriating form of transformation which is cumulative rather than immediate, and relates this suggestion to the wider study of prison visitation.  相似文献   

Structural, Geochronological and Geochemical Studies on Pre- and Syn-Kinematic Intrusions in the Kangguer - Huangshan Shear Zone, and Implications for Late Paleozoic Tectonic Evolution of the Eastern Chinese North Tianshan, Central Asia     

WANG Bo  CLUZEL Dominique  JAHN Bor-ming  SHU Liangshu  CHEN Yan  BRANQUET Yannick  BARBANSON Luc 《《地质学报》英文版》2013,87(Z1):316-316

  相似文献