Cement stratigraphy: image probes of cathodoluminescent facies

Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum emission of cathodoluminescence digital images, it gives via crosscorrelation a measure of similarity (values scaled from minimum −1 to maximum 1) between two cathodoluminescence facies. Cementation events and diagenetic chronologies can thus be quickly correlated without the support of a full chronology, the model normally established on cement morphologies, petrological analyses and cathodoluminescence zonation sequences. A case study from two Upper Kimmeridgian Mount Salève outcrops (France) illustrates this methodology. Their diagenetic sequences recorded in cathodoluminescent cements are presented and being compared. The final statistical similarity between the two outcrops reaches an index of R=0.78. This result is sustained by petrological and geochemical analyses such as alizarine-ferricyanure stained thin sections, X microfluorescence mapping of elements, and microthermometry of fluid inclusion

Bio-Optical Environmental Assessments of Marginal Seas - Progress Report2

Algal blooms in the Mediterranean Sea have been studied by means of SeaWiFS derived (1998-2003) data on chlorophyll-like pigment concentration. Statistics of blooming anomalies, as well as comparisons with analogous data collected in situ, were used to address the relationship between local and regional phytoplankton dynamics, in both the (mesotrophic, sometimes eutrophic) western basin and the (oligotrophic) eastern basin. Intense (coastal) blooming appeared to be linked to local factors, and only occasionally affected by mesoscale features such as eddies or meanders, suggesting that the forcing functions of local (harmful) algal blooms and regional blooms are different, or overlap only marginally.JRC.H.5-Rural, water and ecosystem resource

A multipurpose software for stratigraphic signal analysis

Le signal peut se définir comme l'enregistrement des variations d'une grandeur physique dans le temps. Cette définition permet conceptuellement de considérer les enregistrements stratigraphiques comme des signaux et de les étudier comme tels en utilisant des méthodes provenant de disciplines plus spécialisées dans le traitement du signal. Le logiciel développé dans ce travail fournit les outils d'analyse du signal dans un contexte plus spécifique, plus adapté aux attentes du stratigraphe. Le signal stratigraphique n'est, à priori, pas accessible et doit être extrait. L'extraction manuelle peut s'avérer fastidieuse. Ce travail a permis sa semi-automatisation. Le signal stratigraphique est souvent corrompu par variation du taux de sédimentation, érosion ou hiatus. Une analyse directe sans prétraitement est déconseillée. Dans cette étude, nous proposons des protocoles pour contourner ces difficultés. Enfin, les méthodes développées ont été testées sur des cas pratiques très variés

A Computer-Assisted Method for Depositional Model Determination

A software has been developed to overcome the difficulties related to depositional model determination in Geosciences. The implemented methods, Walker, Harper and Turk methods, based on Markov process and Markov chain analysis, have been used in a case study. The results of the analysis are consistent with previous works. The analysis shows also that the results are accurate and do not rely on the used method. Therefore, the obtained depositional sequence is suitable to build a depositional model on which reliable sequence stratigraphic studies can be based

Algal blooming patterns and anomalies in the Mediterranean Sea as derived from the SeaWiFS data set (1998–2003)

Optical remote sensing allows to monitor the space and time heterogeneity of phytoplankton growth in marginal and enclosed seas, a factor critical to understanding their ecosystem dynamics. SeaWiFS-derived (1998–2003) data were used to monitor algal blooming patterns and anomalies in the Mediterranean basin. Yearly and monthly means of chlorophyll-like pigment concentration (chl) were computed for the 6 years available, and climatological means derived. The data set statistical variability was assessed by computing yearly and monthly chl anomalies, as the difference between each individual year/month and the corresponding climatological year/month. The space and time patterns of the chl field appear to concur with the Mediterranean general oceanographic climate, while the chl anomalies describe trends and “hotspots” of algal blooming. The analysis shows a general decrease of chl values in the yearly and monthly means, an increasing negative trend of chl anomalies over the basin interior, and the anticipation of the north-western spring bloom, in comparison to what seen in historical CZCS (1979–1985) data. These have been interpreted as symptoms of an increased nutrient-limitation, resulting from reduced vertical mixing due to a more stable stratification of the basin, in line with the general warming trend of the Mediterranean Sea in the last 25 years. The patterns of high chl, coupled to a positive trend of chl anomalies, recurring at near-coastal hotspots, appear to be linked to continental runoff and to a growing “biological dynamism” at these sites, i.e. to the intensification of noxious or harmful algal blooms, in the north-west, and of coastal fisheries, in the south-east

A Semi Automated Method for Laminated Sediments Analysis

We developed a software performing laminae counting, thickness measurements, spectral and wavelet analysis of lami-nated sediments embedded signal. We validated the software on varved sediments. Varved laminae are automatically counted using an image analysis classification method based on K-Nearest Neighbors (KNN) algorithm. In a next step, the signal corresponding to varved black laminae thickness variation is retrieved. The obtained signal is a good proxy to study the paleoclimatic constraints controlling sedimentation. Finally, the use of spectral and wavelet analysis methods on the variation of black laminae thickness revealed the existence of frequencies and periods which can be linked to known paleoclimatic events

Morphological variability of the baobab (Adansonia digitata L.) population in the city of Ziguinchor, Senegal

Le baobab, Adansonia digitata L., espèce emblématique du Sénégal est l’une des principales espèces ligneuses à usages multiples que l’on rencontre dans le paysage urbain et périurbain en Afrique inter-tropicale. Cet arbre, charismatique et souvent mystérieux, reste au cœur des politiques urbaines, car participant de façon significative à l’amélioration du cadre de vie de ses résidents et à l’écologie urbaine. Cette étude s’est fixée comme objectif de décrire la variabilité morphologique de sa population dans la ville de Ziguinchor et de caractériser les morphotypes éventuels. Pour ce faire, une description morphologique a été effectuée sur 67 individus répartis dans sept (7) quartiers de la ville. Grâce à la méthode d’optimisation des clusters et à une classification hiérarchique, deux morphotypes ont été identifiés. Le morphotypes 1 à gros fruits, lourds et majoritairement des formes ovales. Leurs feuilles sont petites contrairement au morphotype 2, caractérisé par des individus aux grandes feuilles avec des petits et légers fruits. L’analyse multivariée des variances par permutations (permanova) a montré que les variables qualitatives tels la déformation fruit, le bord côtelé ou non, la forme du sommet et de la base du fruit n’a pas d’effet significatif sur la variabilité des individus de la population de baobabs étudiée. Mots clés: Adansonia digitata L, diversité, caractérisation, morphotype, milieu urbain, clusteringThe baobab, Adansonia digitata L., an emblematic species of Senegal, is one of the main multipurpose woody species found in the urban and peri-urban landscape in inter-tropical Africa. This charismatic and often mysterious tree remains at the heart of urban policies, as it plays a significant role in improving the living environment of its residents and in urban ecology. The objective of this study was to describe the morphological variability of its population in the city of Ziguinchor and to characterize the possible morphotypes. To do this, a morphological description was carried out on 67 individuals distributed in seven (7) neighborhoods of the city. Using the cluster optimization method and a hierarchical classification, two morphotypes were identified. Morphotype 1 with large, heavy fruits and mostly oval shapes. Their leaves are small in contrast to morphotype 2, characterized by individuals with large leaves and small and light fruits. The multivariate analysis of variance by permutations (permanova) showed that qualitative variables such as fruit deformation, ribbed or not, shape of the top and base of the fruit have no significant effect on the variability of the individuals of the baobab population studied. Keywords: Adansonia digitata L, diversity, characterization, urban, morphotype, Ziguinchor, cluster&nbsp

Cement stratigraphy: image probes of cathodoluminescent facies

Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum emission of cathodoluminescence digital images, it gives via crosscorrelation a measure of similarity (values scaled from minimum -1 to maximum 1) between two cathodoluminescence facies. Cementation events and diagenetic chronologies can thus be quickly correlated without the support of a full chronology, the model normally established on cement morphologies, petrological analyses and cathodoluminescence zonation sequences. A case study from two Upper Kimmeridgian Mount Sale`ve outcrops (France) illustrates this methodology. Their diagenetic sequences recorded in cathodoluminescent cements are presented and being compared. The final statistical similarity between the two outcrops reaches an index of R = 0.78. This result is sustained by petrological and geochemical analyses such as alizarine–ferricyanure stained thin sections, X microfluorescence mapping of elements, and microthermometry of fluid inclusions

Bio-Optical Environmental Assessments of Marginal Seas: Progress Report 2

Algal blooms in the Mediterranean Sea have been studied by means of SeaWiFS derived (1998-2003) data on chlorophyll-like pigment concentration. Statistics of blooming anomalies, as well as comparisons with analogous data collected in situ, were used to address the relationship between local and regional phytoplankton dynamics, in both the (mesotrophic, sometimes eutrophic) western basin and the (oligotrophic) eastern basin. Intense (coastal) blooming appeared to be linked to local factors, and only occasionally affected by mesoscale features such as eddies or meanders, suggesting that the forcing functions of local (harmful) algal blooms and regional blooms are different, or overlap only marginally

Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

International audienceWe present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies