Pierre Weill

Université de Caen Normandie | UNICAEN · Laboratoire de Morphodynamique Continentale et Côtière

This study addresses the scarcity of evidence on the relationship between benthic communities and coarse-grained sediments in the eastern English Channel. The region's geological history contributes to its predominantly coarse sediment composition. The study employs ternary plots to visualize benthic species' preferences and tolerance for sediment...

The seabed of the English Channel (EC) corresponds to an extensive network of paleo-valleys, partly filled at the present-day with coarse sediments, reaching sometimes several metres thick, which represent an important source of accessible aggregates. The extraction of these aggregates is currently experiencing significant growth along the French c...

Se realizó un estudio tafonómico y experimental de las fosforitas bioclásticas del Ordovícico en el Noroeste Argentino, compuestas por fragmentos de braquiópodos linguliformes, con el propósito de determinar los procesos sedimentarios y mecanismos de concentración que condujeron a su acumulación. Por primera vez, se investigó experimentalmente el c...

Le benthos est classiquement utilisé comme témoin intégrateur des conditions environnementales dans lesquelles il se trouve. Parmi celles-ci, la nature des sédiments, très souvent caractérisée par la taille moyenne des grains (granulométrie), est un paramètre essentiel puisqu'il constitue l'habitat benthique. En conséquence, en Manche, la distribut...

The flow velocity over mobile sandy dunes subjected to unidirectional current was investigated using a UB-Lab 2C, an acoustic velocity profiler newly developed by UBERTONE. A space-localized wavelet approach was used in order to detect the temporal evolution of the main dune’s wavelength. The acoustic tool has provided promising results concerning...

Coastal barriers are dynamic systems, the morphology and architecture of which are controlled by local hydrodynamics, sea‐level fluctuations at different timescales, geological heritage and sediment composition. Coastal barriers may be composed of siliciclastic sediments, bioclastic sediments, or a mixture of both. Mixed siliciclastic–bioclastic se...

Phosphorites composed by linguliform brachiopod shells represent a poorly known phosphorus source. As mineral precursors for P-fertilizers, they are an increasingly important resource for agricultura! activities. Linguliform brachiopod shells have a stratiform organo-phosphatic microstructure, which produces bioclasts characterized by their low den...

This study focuses on the architectural characterization of a mixed sand‐and‐gravel spit in relation to its multi‐decadal evolution. The spit, located in the Somme estuary in northern France, is a 5 km long sedimentary body made of several amalgamated ridges with a hooked terminus. Flint pebbles originating from the erosion of Cretaceous chalk clif...

The behavior of the shelly beach ridge system forming a more or less continuous barrier lying along the southern coast of the hypertidal Mont-Saint-Michel bay (NW France) is examined using a set of various data including aerial photographs since 1947, sediment cores collected in back-barrier salt marshes, ground penetrating radar profiles, and diff...

Physical stratigraphy, architecture and evolution of barrier systems in hypertidal environments (tidal range above 6 m) are understudied, and depositional controls are poorly understood compared with wave‐dominated barrier systems and barrier spits in microtidal, mesotidal and macrotidal settings. Based on vibracores, ground‐penetrating radar, radi...

L'objectif du projet Sédibaie était de comprendre comment les replats de marée du Sud de la Baie du Mont Saint Michel et les bancs coquilliers qui les bordent ont fonctionné au cours des derniers siècles, et de déterminer quels ont été les différents facteurs de cette évolution. Plusieurs actions ont été menées qui permettent de traiter trois échel...

Bioclastic particles derived from mollusc shell debris can represent a significant fraction of sandy to gravelly sediments in temperate and cool‐water regions with high carbonate productivity. Their reworking and subsequent transport and deposition by waves and currents is highly dependent on the shape and density of the particles. In this study, t...

Field measurements and laboratory calibrations of suspended sediment concentration in tidal bores. Tidal bore or Storm / Tsunami events in sedimentary records? Acoustic / Optical / Direct sampling in highly turbid flows? Filters to extract turbulence?

The La Bassée floodplain area is a large groundwater reservoir controlling most of the water exchanged between local aquifers and hydrographic networks within the Seine River basin (France). Preferential flows depend essentially on the heterogeneity of alluvial plain infilling, whose characteristics are strongly influenced by the presence of mud pl...

The La Bassée floodplain area is a large groundwater reservoir controlling most of the water exchanged between local aquifers and hydrographic networks within the Seine River Basin (France). Preferential flows depend essentially on sediment fills, whose characteristics are strongly influenced by paleomeander heterogeneities. A detailed knowledge of...

Up-to-date monthly time series of Northern Hemisphere atmospheric circulation pattern indices (1950–2015 CE) were retrieved from the Climate Prediction Center, NOAA. The study focused on the NAO, East Atlantic (EA) and East Atlantic–West Russia (EA–WR) patterns, which are the first three dominant patterns involved in wave climate variability across...

Present-day coastal barriers represent around 15% of the world’s oceanic shorelines, and play an important role as early warning indicators of environmental change. Among them, wave-dominated barriers are dynamic landforms that tend to migrate landward in response to storms and sea-level change. High rates of sediment supply can locally offset the...

This thematic issue of Comptes rendus Geoscience gives an overview of the works presented in the frame of a session dedicated to “Coastal sediment dynamics” at the 14th Congress of the French Association of Sedimentologists, held in Paris, France, from 5 to 7 November 2013. In total, 23 papers were presented in this session, both in the form of ora...

The Cellular Automata for Turbidite systems (CATS) model is intended to simulate the fine architecture and facies distribution of turbidite reservoirs with a multi-event and process-based approach. The main processes of low-density turbulent turbidity flow are modeled: downslope sediment-laden flow, entrainment of ambient water, erosion and deposit...

As an introduction to this thematic issue on “Modelling approaches in sedimentology”, this paper gives an overview of the workshop held in Paris on 7 November 2013 during the 14th Congress of the French Association of Sedimentologists. A synthesis of the workshop in terms of concepts, spatial and temporal scales, constraining data, and scientific c...

Tidal bores are complex but popular phenomena that occur in estuarine rivers during rising tides. Until recently, few studies were devoted to the understanding of this process, although it should have a significant influence on sediment erosion and deposition in estuarine systems. Herein, we propose to reconstruct the evolution of sediment concentr...

Tidal bores are believed to induce significant sediment transport in macrotidal estuaries. However, due to high turbulence and very large suspended sediment concentration (SSC), the measurement of sediment transport induced by a tidal bore is actually a technical challenge. Consequently, very few quantitative data have been published so far. This p...

A coupled sedimentary and hydrogeological model is used to quantify the impact of sedimentary heterogeneities and sinuosity on groundwater fluxes in an alluvial plain deposited by a meandering fluvial system. A 3D heterogeneous alluvial plain model is built with the stochastic/process-based model FLUMY, that simulates the evolution and the sediment...

Coupled hydrological-hydrogeological models, emphasising the importance of the stream-aquifer interface, are more and more used in hydrological sciences for pluri-disciplinary studies aiming at investigating environmental issues. Based on an extensive literature review, stream-aquifer interfaces are described at five different scales: local [10 cm-...

Submarine canyons are the main conduits for sediment transfer from continental shelves to deep abyssal plains. A large number of bathymetric and seismic surveys provide detailed information on their morphology and structure, shedding light on the mechanisms involved in their formation. However, because of the difficulty in deploying instruments in...

English version here : https://www.researchgate.net/publication/281989051_Process-based_modelling_for_a_finer_characterization_of_meandering_fluvial_reservoir_heterogeneities_FLUMY_and_the_Miocene_Loranca_Basin

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 evolutio...

The relationship between short-term morphodynamics and internal structure of shelly chenier ridges is investigated using ground-penetrating radar and core X-ray analysis, complemented with a comparison of aerial photographs. These cheniers are located on the uppermost part of a macrotidal flat in Mont-Saint-Michel bay (North-Western France). They a...

Forcing parameters of chenier ridges formation and internal structure are investigated using field data and wave flume experiments. This work focuses on modern, coarse bioclastic beach ridges such as those located on the uppermost part of the tidal flat in Mt. St. Michel Bay (NW France), in the context of a prograding megatidal chenier plain. These...

The growing interest in quantification of vertical ground motion stems from the need to understand in detail how the Earth's crust behaves, for both scientific and social reasons. However, only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies. Although there are many lo...

During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000 km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the...

Cheniers from Mont-Saint-Michel bay (France) are coarse shelly sand ridges migrating on the mudflat up to the salt marshes where they accumulate and merge in a littoral barrier. In this macrotidal setting and low wave forcing, the cheniers are rarely submerged. However, they are found to move up to several metres during coincidence of spring tide a...

The objective of this thesis is to characterize the genesis, growth and stabilization of cheniers in a macrotidal setting. These transgressive beach ridges, anchored in a silty to muddy prograding sequence, are the result of a balance between fine sediment inputs from fluvial or tidal dynamics, and reworking of coarse sediment by waves. Through the...

L'objectif de cette thèse est de caractériser la genèse, la croissance et la stabilisation de cheniers en contexte macrotidal. Ces cordons littoraux transgressifs, ancrés dans une séquence fine progradante, sont le résultat d'un équilibre entre apports de sédiments fins par une dynamique fluviale ou tidale, et remaniement de sédiment grossier par l...

With increasing concerns about climate change and sea-level rise, there is a need for a comprehensive understanding of the sedimentary processes involved in the erosion, transport and deposition of sediment on the continental shelf. In the present paper, long-term and large-scale seabed morphological changes on the south-west Australian continental...