De la stratigraphie sismique à la stratigraphie séquentielle : 30 ans d’avancées

Ravenne Christian. De la stratigraphie sismique à la stratigraphie séquentielle : 30 ans d’avancées. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. p. 191

Évolution de la stratigraphie séquentielle depuis 1970

Cet article porte surtout sur les aspects et développements industriels de la stratigraphie séquentielle depuis le début des années 70 : les progrès de la sismique marine et l’exploration intensive des marges océaniques ont permis d’obtenir des données 2D de haute qualité et continues, depuis la plate-forme jusqu’aux domaines de bassins profonds. Cette période a vu la création de la stratigraphie sismique, qui à son tour a permis le considérable développement de la stratigraphie séquentielle à la fin des années 1980 et durant les années 1990. À la fin des années 1980, est apparue la nécessité de quantifier les informations et connaissances géologiques pour répondre aux besoins de l’industrie. La solution fut l’application des concepts de la stratigraphie séquentielle, qui se sont révélés être les outils clés pour la compréhension de l’évolution des systèmes sédimentaires et leur prédiction.This paper will address mainly industrial aspects of sequence stratigraphy since the seventies: new advances in seismic marine acquisition and large efforts for margins exploration, provided continuous 2D set of data, from platform environment to deep marine basins, revealing the importance of non-deposition periods. The seismic stratigraphy then allowed the development of the sequence stratigraphy at the end of the eighties and during the nineties. At the end of the eighties, a crucial need was formulated to quantify geology. The solution has been the use of sequence stratigraphy, as it was proven later that this tool was the key for understanding and then for prediction.</p

Sédimentologie du flysch des Aiguilles d'Arves (Alpes françaises)

Mémoire HS n° 13 - Géologie Alpine : Le détritisme dans le Sud-Est de la France - Colloque Association des Géologues du Sud-est - Grenoble 11-12 décembre 1986Le Flysch des Aiguilles d'Arves affleure dans la zone ultra-dauphinoise des Alpes françaises. L'analyse sédimentologique définit un domaine de sédimentation correspondant à un cône sous-marin vraisemblablement alimenté par le nord-est, l'est et le sud-est, et dont l'axe principal, allongé suivant une direction SE- NW, est situé au niveau des Aiguilles d'Arves

Geochemical variability induced by entrainment sorting: quantified signals for provenance analysis

International audienceA substantial part of the mineralogical and chemical heterogeneity of clay-poor sands, at the bed scale, results from tractive redistribution of the grains in the bedload. Since coarse and light particles are more easily entrained than denser and smaller heavy minerals, the latter commonly concentrate in grain scale lags, that alternate with sand depleted in these minerals. When sampled and analysed at the centimetre scale, this primary heterogeneity translates into nice geochemical covariations between the minor/trace elements that concentrate in some heavy minerals (Zr, Ti, P, Cr, V, Y, Ce among others). Regressing these variations allow us to derive two chemical fingerprints of the sand: one records the proportions between some heavy minerals, the other the average composition of framework grains, i.e., a sand composition corrected from the contribution of heavy minerals. Both relate to provenance and altow different sand beds to be compared in appropriate spider diagrams. The construction of these diagrams, their potential use and their limitations are discussed using two contrasting examples. Continental channel sandstones from the Ravenscar Group (middle Jurassic, Yorkshire, UK) illustrate how these geochemical fingerprints vary from the local to the Group scales and how robust they are against diagenetic overprint. At Ravenscar, the Zr vs. Ti. V. Cr covariations record the presence of Ti oxides and magnetite together with zircon and of volcanic lithoclasts at the deposition stage, despite a high degree of diagenetic alteration. Overbank sandstones (lateral to channels) from the deep marine Gres d'Annot Formation (Eocene-Oligocene, Alps) illustrates how apatite and monazite delivered by a dominantly granitic source generate covariations between Zr and P, Y, Cc and Th contents with characteristically steep slopes

Conditional simulation of random sets: Application to an argilaceous sandstone reservoir.

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Élaboration d’une méthodologie pour la modélisation géostatistique des corps sédimentaires. Cas des unités stratigraphiques de la marge du Golfe du Lion

Chihi Hayet, Ravenne Christian, Marsily Ghislain de, Galli Alain, Tesson Michel. Élaboration d’une méthodologie pour la modélisation géostatistique des corps sédimentaires. Cas des unités stratigraphiques de la marge du Golfe du Lion. In: Documents des Laboratoires de Géologie, Lyon, n°156, 2002. STRATI 2002. 3ème congrès français de stratigraphie. Lyon, 8-10 juillet 2002. pp. 73-74

Geostatistical characterization of Callovo-Oxfordian clay variability from high-resolution log data

http://www.sciencedirect.com/science/article/B6X1W-4TNCG9T-1/2/0237cb95f51234546c22d2610c694281International audienceThe aim of this paper is to outline a methodology to transform depth intervals into geological time intervals and thus to estimate duration; for example the duration of biostratigraphical units or of hiatuses. The latter point is particularly important because a continuous time recording is often assumed in geological modelling. Andra (National Radioactive Waste Management Agency) has conducted studies in its Meuse/Haute-Marne Underground Research Laboratory located at a depth of about 490 m in a 155-million-year-old argillaceous rock: the Callovo-Oxfordian argillite. The study of the variations of that clay layer can be conducted by the analysis of logs and particularly high-resolution logs. Working in a geochronological system helps to understand the physical properties of rocks and to make very precise well-to-well correlations. To transform the present coordinates, a high-resolution tool is necessary: the FMI® (Fullbore Formation MicroImager, Schlumberger). First, well-to-well correlations are established between seven wells at different scales. Relative variations of the sedimentation rate are observed locally. Second, FMI® data are studied in detail to extract as much information as possible. For example, the analysis of FMI® images reveals a clear carbonate-clay interbedding which displays cycles. Third, geostatistical tools are used to study these cycles. The variographic analysis of conventional log data shows one-metre cycles. With FMI® data, smaller periods can be detected. Variogram modelling and factorial kriging analysis suggest that three spatial periods exist. They vary vertically in the boreholes but cycle ratios are stable and similar to orbital cycle ratios (Milankovitch cycles). The three periods correspond to eccentricity, obliquity and precession. Since the duration of these orbital cycles is known, depth intervals can be converted into time intervals (duration) and thus give real sedimentation rates and a quantification of hiatus duratio

A methodology to rescale the vertical coordinate into geological time using a geostatistical analysis of log data

International audienceThe aim of this paper is to outline a methodology to transform depth intervals into geological time intervals. Working in a geochronological system aids in the understanding of the physical properties of rocks and to do very precise correlations between wells. To transform the present coordinates a high resolution tool is necessary : the FMI® (Fullbore Formation MicroImager, Schlumberger). First, well log correlations are established between seven wells at different scales. Relative variations of sedimentation rate are observed locally. Second, FMI® images analysis are used to reveal clear carbonate - clay interbedding which display cycles. Third, to study these cycles, geostatistical tools are used. The variographic analysis of conventional log data shows cycles of one meter. With FMI® data, smaller cyles can be detected. Variogram modelling and factorial kriging analysis suggest that three spatial periods exist. They vary vertically and laterally in wells but cycle ratios are stable and similar to orbital cycle (Milankovitch cycle) ratios. The three periods correspond to eccentricity, obliquity and precession. If orbital cycles are known, depth intervals can be converted into geological time intervals and thus give real sedimentation rates and quantification of hiatus duration

Geostatistical characterization of orbital cyclicity of clay properties from log data (Callovian-Oxfordian clay, Bure, Meuse, France)

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