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Caractérisation faciologique des sédiments récifaux de l'île Maurice par l'analyse factorielle des correspondances
| Content Provider | Semantic Scholar |
|---|---|
| Author | Montaggioni, Lucien F. Mahe, Jean-Claude |
| Copyright Year | 1980 |
| Abstract | L. Montaggioni", J. Mahéb a Université Française de l'Océan Indien, 97400 Saint-Denis-de-La-Réunion, et Laboratoire de Géologie Marine, Université d'Aix-Marseille Il, 13288 Marseille Cedex 02. b Laboratoire de Géologie, Centre Universitaire d'Avignon, 84000 Avignon. Reçu le 26/12/79, révisé le 29/4/80, accepté le 6/5/80. L'analyse factorielle des correspondances a été appliquée à l'étude de sédiments des récifs coralliens de l'île Maurice (Océan Indien occidental). Chaque échantillon et les variables qui le déterminent (14 constituants sédimentaires et 7 paramètres gr.anulométriques), sont projetés simultanément sur des diagr!lmmes à deux dimensions définis par des axes de variation maximale. Cette méthode permet d'analyser les associations et les oppositions entre échantillons et variables, d'identifier et de choisir les variables et les représentations graphiques les plus intéressantes pour caractériser les diverses unités morphosédimentaires récifales, et de définir les principaux facteurs régissant la sédimentation sur ces récifs (hydrodynamique, distribution des communautés biologiques benthiques, comportement hydraulique des particules sédimentaires). A la lumière des données de la bionomie benthique, on a pu mettre en évidence trois grandes zones récifales, relativement autonomes sur le plan de la production biodétritique et caractérisées par leurs biofaciès et le mode de déplacement des particules : zone externe à Alcyonaires, Bryozoaires et Foraminifères (prédominance de la saltation); zone intermédiaire à Coraux, Échinodermes, Serpules et Mélobésiées (prédominance de la traction); zone interne à Mollusques, Crustacés et Spongiaires (prédominance de la suspension). Oceanol. Acta, 1980, 3, 4, 409-420. Facies characterization of reefal sediments from Mauritius Island (Western lndian Ocean) by correspondence factor analysis. Correspondence factor analysis has been applied to the study of reef depositional environments from Mauritius Island (Western lndian Ocean). In order of decreasing water depth, the following reef units have been identified: an outer zone including outer sandy spreads, lower sloping platforms and spur-and-groove systems; narrow reef flats; and backreef zones comprising boulder-and-shingle spreads, sandy bottoms locally colonized by coral buildups and sea grasses, channels and pools, littoral muddy shoals and mangrove swamps or sandy beaches. Each sediment sample is determined by the relative (percentage) abundance of 14 components (Foraminifera, Alcyonarians, Bryozoans, Corals, Echinoderms, Serpulids, Coralline algae, Molluscs, Crustaceans, Sponges, Halimeda, aggregates, oxidized and reduced particles), and the values of7 grainsize parameters (mean size, sorting, skewness, kurtosis, percentages of traction, saltation . and suspension sub-populations). The samples and variables are simultaneously projected in two-dimensional diagrams defined by axes of maximum variation. The use of · éürrespondence analysis permitted the analysis of associations and oppositions, the 0399-1784/1980/409/$5.00/ e> Gauthier-Villars 409 L. MONTAGGIONI. J. MAHÉ identification and selection of the most interesting variables and graphie representations for the recognition of different reef environments, and the definition of the main sedimentation-controlling factors (wave energy; distribution of sediment-producing organisms; hydraulic properties of particles). The first of these factors is large! y related to the physiographical and hydrodynamical gradient, which controls the chemical state, depositional process and sorting of sedimentary particles, and the skeletal production of reef-associated organisms. Similarly, the second factor is partly a reflection of water energy conditions and of the distribution of sediment producers. The third factor is expected to account for relationships between the percentage abundance of particular sediment components and the mean size and kurtosis values. Three main reef zones may be distinguished on the basis of the distribution of sediment-producing organisms and related sedimentary facies; each of these zones is relatively autonomous as a skeletal producer, and is characterized by its biofacies and the mode of sediment transport: the outer zone displays Alcyonarian, Bryozoan and Foraminifera facies, mainly removed by saltation; the intermcdiatc ("rccf:d") zone displays Coral, Echinoid, Serpulid and Coralline algal facies, m tinly remov..:d by traction; and the inner zone displays Molluscan, Crustacean and Sponge facies, chiefly related to suspension. Oceanol. Acta, 1980, 3, 4, 409-420. |
| Starting Page | 409 |
| Ending Page | 420 |
| Page Count | 12 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://archimer.ifremer.fr/doc/00122/23320/21144.pdf |
| Volume Number | 3 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
