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See detailInfluence of sedimentary setting on the use of magnetic susceptibility : examples from the Devonian of Belgium
Da Silva, Anne-Christine ULg; Mabille, Cédric ULg; Boulvain, Frédéric ULg

in Sedimentology (2009), 56

Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea-level variations ... [more ▼]

Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea-level variations. This paper explores the link between magnetic susceptibility, depositional setting and environmental parameters. These environmental parameters include distal–proximal transects, microfacies successions and fourth-order trends on different carbonate platform types (platform, ramp, carbonate mound or atoll) during different Devonian stages (Eifelian, Givetian and Frasnian). Average magnetic susceptibility values over a distal–proximal-trending facies succession vary markedly with depositional setting. On carbonate platforms, average magnetic susceptibility generally increases towards the top of shallowing-upward sequences. On a distal–proximal transect, average magnetic susceptibility is intermediate for the deepest facies, decreases for the reef belts and increases to a maximum in the back-reef zone. In ramps and atolls, magnetic susceptibility trends clearly differ; average magnetic susceptibility generally decreases towards the top of shallowing-upward sequences and is highest in the deepest facies. The strong relationship between magnetic susceptibility, facies and sequences implies a strong environmental influence. However, the different responses in the different latform types suggest that sea-level changes leading to variation in detrital input is not the only parameter controlling average magnetic susceptibility values. Other primary or secondary processes also probably influenced magnetic mineral distribution. Primary processes such as carbonate production and water agitation during deposition are probably key factors. When carbonate production is high, the proportion of magnetic minerals is diluted and the magnetic susceptibility signal decreases. High water agitation during deposition will also selectively remove magnetic minerals and will lead to low average magnetic susceptibility values. These parameters explain the lowest values observed on the reef platform, inner ramp and atoll crown, which are all in areas characterized by higher carbonate production and greater water agitation during deposition. The lowest values observed in the lagoon inside the atoll crown can be related to detrital isolation by the atoll crown. However, other parameters such as biogenic magnetite production or diagenesis can also influence the magnetic signal. Diagenesis can change magnetism by creating or destroying magnetic minerals. However, the influence of diagenesis probably is linked strongly to the primary facies (permeability, amount of clay or organic matter) and probably enhanced the primary signal. The complexity of the signal gives rise to correlation problems between different depositional settings. Thus, while magnetic susceptibility has the potential to be an important correlation tool, the results of this investigation indicate that it cannot be used without consideration of sedimentary processes and depositional environments and without strongbiostratigraphical control. [less ▲]

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See detailTowards a palaeogeographical and sequential framework for the Givetian of Belgium
Boulvain, Frédéric ULg; Mabille, Cédric ULg; Poulain, Geoffrey et al

in Geologica Belgica (2009), 12

This paper starts with a review of facies and reef morphologies from the Givet Group in the Ardenne area. Platform initiation and evolution are analyzed and related to external factors at a global scale ... [more ▼]

This paper starts with a review of facies and reef morphologies from the Givet Group in the Ardenne area. Platform initiation and evolution are analyzed and related to external factors at a global scale (sea level changes, climate changes), at a regional scale (local subsidence, change in detrital supply) and to internal factors like organic communities composition. More specifically, the location of reef barriers are related to sea level changes and a sequence stratigraphic canvas is proposed. [less ▲]

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See detailMagnetic susceptibility evolution and sedimentary environments on carbonate platform sediments and atolls, comparison of the Frasnian from Belgium and Alberta, Canada
Da Silva, Anne-Christine ULg; Potma, Ken; Weissenberger, John A. W. et al

in Sedimentary Geology (2009), 214

Magnetic susceptibility (MS) measurements on carbonate rocks are considered as a proxy for impurities delivered to the carbonate environments. In the absence of strong climatic or tectonic variations ... [more ▼]

Magnetic susceptibility (MS) measurements on carbonate rocks are considered as a proxy for impurities delivered to the carbonate environments. In the absence of strong climatic or tectonic variations, bulk MS values have been linked to sea level variations, because sea-level fall increases clastic supply and therefore increases magnetic mineral deposition. In this paper we explore the relationship between the average magnitude of bulk MS, with shallowing-up sequences and facies evolution in different Devonian carbonate complexes. Similarities and differences between these parameters have been scrutinized in carbonate attached platform and detached platforms (mounds and/or atolls) from Belgium and Canada. In the carbonate attached platforms from Belgium and Canada, the MS patterns are directly related to depositional environment. Mean MS values increase from the most distal towards the most proximal facies and towards the top of the majority of fourth-order shallowing-up sequences. These trends are in agreement with theoretical background (MS increases with regression). In the Belgian detached platform, the average MS pattern generally shows an opposite behaviour of that observed in the attached carbonate platforms. Average MS decreases towards the most proximal facies and towards the top of a majority of the fourth-order shallowing-up sequences. This behaviour can be explained by the influence of sedimentary rate and water agitation during deposition. A high sedimentary rate will dilute the magnetic minerals in the atoll facies and the highwater agitation during deposition may be expected to have prevented the deposition of the magnetic grains. So, the combination of these two effects will result in the observed low values in the atoll crown and lagoonal facies. In the Canadian detached platform, MS is mainly negative. This means that the limestones are very pure. The technique does not appear to be appropriate in these rocks. The variations of average MS behaviour by platform type can imply difficulties in correlating carbonates from different settings. A comparison of time equivalent mound and platform deposits shows that after an important regressive surface, the MS values are increasing for the platform deposits and decreasing for the mound. So MS evolution can be in complete opposition (caused by highly different sedimentary rates) in different depositional settings. The MS signal preserved in carbonate rocks is probably mainly related to 1) varying clastic supplies; 2) varying carbonate accumulation rates (dilution of the magnetic minerals by high carbonate production) and 3) potentially diagenesis. [less ▲]

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See detailAnnual report 2009 of the IGCP-580 Project.
Da Silva, Anne-Christine ULg; Whalen, Michael; Hladil, Jindrich et al

Report (2009)

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See detailEtude comparative des modèles sédimentaires et diagénétiques entre les versants nord et sud des Pyrénéens de la plate-forme carbonatée du Paléocène moyen.
Loisy, Corinne; Cerepi, Adrian; Da Silva, Anne-Christine ULg et al

in 12e Congrès Français de Sédimentologie – Rennes 2009 – Livre des résumés, Publ. ASF, n°64 (2009)

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See detailApplication of magnetic susceptibility on Palaeozoic sedimentary rocks
Spassov, Simo; Da Silva, Anne-Christine ULg; Whalen, Michael et al

in Abstract book of the IAGA 11th Scientific assembly (2009)

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See detailcontribution to understanding of sedimentological and diagenetic processus related to a major emersive surface : example of the middle paleocene unconformity (MPU).
Loisy, Corinne; Kiefer-Ollier, Eloise; Cerepi, Adrian et al

in Book of Abstracts - 26th IAS meeting, Alghero, Sardenia (2009)

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See detailVariations in stratigraphic and reservoir properties adjacent to the Mid-Paleocene sequence boundary, Campo section, Pyrenees, Spain
Da Silva, Anne-Christine ULg; Loisy, Corinne; Cerepi, Adrian et al

in Sedimentary Geology (2009), 219

The Paleocene of the Campo section, Spain has different sedimentological characteristics above and below the Mid-Paleocene Unconformity. Beneath the unconformity sediments are dominated by evaporitic ... [more ▼]

The Paleocene of the Campo section, Spain has different sedimentological characteristics above and below the Mid-Paleocene Unconformity. Beneath the unconformity sediments are dominated by evaporitic carbonates and collapse breccias. Above it they are characterized by continental detrital beds alternating with paleosols. Different subaerial features are observed and correspond to different porosity values, pore–throat sizes and micrite morphologies. Unexposed or intertidal facies have low porosity, low throat–pore size (mesoporosity) and well preserved rhombic crystals. Intermediate exposed facies (paleosols) possess medium porosity, medium pore–throat size (microporosity) and mainly micro-rhombic crystals. Finally, the facies corresponding to high exposure intensity and to evaporitic original facies presents high porosity, permeability, large pore–throat size and rounded micritic crystals. These observations show that the emersion phase caused important dissolution, especially when associated with an easily dissolved original lithofacies. [less ▲]

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See detailEnvironmental reconstruction of the Frasnian Carbonate Platform using sedimentology and magnetic susceptibility.
Da Silva, Anne-Christine ULg; Boulvain, Frédéric ULg

in Abstracts and field guide, 6th Annual Conference of SEPM-CES SEDIMENT 2009 (2009)

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See detailA magnetic susceptibility curve for the Devonian limestone.
Boulvain, Frédéric ULg; Da Silva, Anne-Christine ULg

in 12e congrès français de sédimentologie, ASF Rennes, livre des résumés Publi.ASF 64 (2009)

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See detailapplication of magnetic susceptibility on different carbonate platform types.
Da Silva, Anne-Christine ULg

Scientific conference (2008, November 27)

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See detailDetailed sedimentological study of a non-classical succession for Trois-Fontaines and Terres d'Haurs formations (Lower Givetian, Marenne, Belgium)- Introduction of the Marenne Member
Mabille, Cédric ULg; De Wilde, Clotilde ULg; Hubert, Benoît et al

in Geologica Belgica (2008), 11

This work details for the first time the sedimentology of the Marenne quarry. It exposes a remarkable succession of strata from the Trois-Fontaines Formation and the base of the Terres d’Haurs Formation ... [more ▼]

This work details for the first time the sedimentology of the Marenne quarry. It exposes a remarkable succession of strata from the Trois-Fontaines Formation and the base of the Terres d’Haurs Formation. Two sections (Marenne East and Marenne Centre) are investigated within the quarry. The first one (115 metres) covers both formations and is characterized by a mixed carbonate-siliciclastic succession replacing the classical base of the Trois-Fontaines Formation. We propose here to include these particular facies into a new member of the Trois-Fontaines Formation, the Marenne Member. The second one (48 metres) exposes a reefal lens also attributed to this new Marenne Member. Magnetic susceptibility was used to confirm geometric correlations previously obtained between these two sections. Petrographic study leads to the definition of 14 microfacies which are integrated into three palaeoenvironmental models. The first model (six microfacies) is proposed for the Marenne Member. In this ramp model, terrigenous inputs are particularly important. The mid-ramp is composed of four microfacies more or less influenced by storm events. The inner ramp (limited to the FWWB vicinity) is characterized by the development of the reefal lens and by peloidal microfacies. The upper part of Trois-Fontaines Formation is depicted by a back-reef model (three microfacies) which is mainly dominated by lagoons. However, intermittent agitation and non-restricted settings allow the local development and the reworking of branching organisms. The last model proposed (five microfacies) concerns the Terres d’Haurs Formation and corresponds to a ramp profile with the development of shoals. Those shoals locally protect semi-restricted lagoons. Algal mats are also observed. The last part of the work concerns the sedimentary dynamics and proposes sea level variations as the key parameter probably responsible for the succession of these three depositional settings. [less ▲]

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See detailDeposition within the vicinity of the Mid-Eifelian High : detailed sedimentological study and magnetic susceptibility of a mixed ramp-related system from the Eifelian Lauch and Nohn formations (Devonian ; Ohlesberg, Eifel, Germany)
Mabille, Cédric ULg; Pas, Damien ULg; Aretz, Markus et al

in Facies (2008), 54

This study focuses on the base of the Eifelian stage and on the abandoned Ohlesberg quarry. The exposed section (92 m thick) is related to the Lauch and Nohn formations. Petrographic study leads to the ... [more ▼]

This study focuses on the base of the Eifelian stage and on the abandoned Ohlesberg quarry. The exposed section (92 m thick) is related to the Lauch and Nohn formations. Petrographic study leads to the defnition of 11 microfacies which are integrated in a palaeogeographical model. It corresponds to a complex ramp setting where carbonate, mixed and siliciclastic deposits coexist. The microfacies evolution is interpreted in terms of bathymetric and lateral variations, showing a general shallowing upward trend and transitions between carbonate-dominated and siliciclastic-dominated sedimentary domains. This interpretation is supported by trends in magnetic susceptibility data. Even if the proximity to emerged areas appears to be the major influence on magnetic susceptibility values, the influence of carbonate productivity and wave agitation is also noted. The Ohlesberg section clearly points to the local and regional complex facies architecture, and advocates to variegated depositional environments along the Mid-Eifelian High. [less ▲]

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See detailMultidisciplinary approach to reconstruct the Belgian Frasnian platform - facies, carbon isotopes and magnetic susceptibility
Da Silva, Anne-Christine ULg; Mabille, Cedric; Boulvain, Frédéric ULg

in . SDGG, Heft 58 – Abstract Volume – 26th IAS Regional Meeting/SEPM-CES SEDIMENT 2008 (2008)

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See detailMagnetic susceptibility correlation of km-thick Eifelian–Frasnian sections (Belgium–Czech Republic).
Boulvain, Frédéric ULg; Da Silva, Anne-Christine ULg; Mabille, Cedric et al

in SDGG, Heft 58 – Abstract Volume – 26th IAS Regional Meeting/SEPM-CES SEDIMENT 2008 – Bochum (2008)

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See detailFrasnian laminar stromatoporoid biostromes.
Da Silva, Anne-Christine ULg

in Vennin, Emmanuelle; Aretz, Markus; Boulvain, Frédéric (Eds.) et al Facies from Palaeozoic reefs and bioaccumulations (2008)

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See detailCarbon isotope lateral variability in a Middle Frasnian carbonate platform (Belgium): significance of facies, diagenesis and sea-level history
Da Silva, Anne-Christine ULg; Boulvain, Frédéric ULg

in Palaeogeography, Palaeoclimatology, Palaeoecology (2008), 269

Carbon isotopic variations of Frasnian shallow-water carbonates from Belgium are related to facies and major sea-level trends. The influence of the diagenetic overprint was assessed in order to determine ... [more ▼]

Carbon isotopic variations of Frasnian shallow-water carbonates from Belgium are related to facies and major sea-level trends. The influence of the diagenetic overprint was assessed in order to determine the primary signal of the Frasnian carbonates. Shallow-water microfacies are characterized by biostromes with stromatoporoids and lagoonal deposits dominated by carbonate mud and calcareous algae with subaerial exposure surfaces. The diagenetic history was controlled by three main events: early meteoric diagenesis (short-term subaerial exposure during deposition), late meteoric diagenesis (major Famennian regression) and burial diagenesis. The oxygen isotopic values are almost constant with respect to facies, original material (carbonate mud and cement) and sedimentological units (no differences before or after the main regression). This homogeneity is related to resetting during late meteoric diagenesis. The carbon isotopic values are related to facies (with the more negative values for the shallowest facies) and to major sea-level variations (most negative values after the main regression). This pattern is interpreted as being related to primary signals. This trend was enhanced by early meteoric diagenesis and the influence of more negative values from paleosols. The carbon isotope patterns reflect the influence of sea-level and water circulation on shallow water deposits and this influence implies that shallow-water carbonates are not necessarily good material for assessing the primary isotopic values of the ocean because of the influence of long residence time (“aging”) of the platform-top water and because of early diagenesis. [less ▲]

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See detailFrasnian reefs, mounds and atolls from Belgium: sedimentology and palaeogeography. Fieldtrip PRE-5
Boulvain, Frédéric ULg; Da Silva, Anne-Christine ULg

in 26th Regional Meeting of the International Association of Sedimentologists- SEPM-CES Sediment 2008 Meeting Bochum, août 2008. Excursion guidebook (2008)

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