| Titre | Tidal modulation of river-flood deposits: how low can you go? |
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| Auteur | Maselli, V; Normandeau, A ; Nones, M; Tesi, T; Langone, L; Trincardi, F; Bohacs, K M |
| Source | Geology 2020 p. 1-5, https://doi.org/10.1130/G47451.1 |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190549 |
| Éditeur | Geological Society of America |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/G47451.1 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Région | Po River |
| Lat/Long OENS | 11.6000 12.7000 45.2000 44.5000 |
| Sujets | systèmes fluviaux; marées; dépôts de marée; milieux de marée; deltas; dépôts fluviaux; processus fluviaux; taux de décharge; inondations; établissement de modèles; échantillons carrotés; granoclassement;
bioturbation; vitesses de fluage; cycles sédimentaires; dépôts de tempête; paléogéographie; ressources pétrolières; roches reservoirs; mudstones; milieu sédimentaire; hydrographie; transport des sediments; analyses stratigraphiques; sédiments
alluviaux; géologie des dépôts meubles/géomorphologie; sédimentologie; stratigraphie; combustibles fossiles; Nature et environnement; Sciences et technologie |
| Illustrations | cartes de localisation; images satellitaires; séries chronologiques; profils; images géophysiques; graphiques; modèles |
| Diffusé | 2020 04 17 |
| Résumé | (disponible en anglais seulement)
Quantification of the interaction between river discharge and tides is vital to characterize fluvio-deltaic systems, to identify diagnostic elements of tidal
signatures in the rock record, and to reconstruct paleogeographies. In modern systems, even microtides can significantly influence delta morphodynamics; yet, many fundamental processes, particularly in prodeltaic settings, remain elusive. Here, by
combining a unique process-product data set acquired during a flood event of the Po River (Italy) with numerical modeling, we show that tidal signatures are recorded in the open-water prodelta zone of a microtidal system. Based on the analyses of
box-cores collected before and after a flood off the main distributary channel, we interpreted storm beds, tide-modulated flood strata of alternating normal and inverse graded beds, and rapid bioturbation. Modeling of the river discharge indicates
that, at the peak of the flood, the steepening of the water-surface profile forced by 0.15 m lowering of sea level during low tides generated an 8% increase in river flow velocity. The alternation of profile steepness and associated cyclicity in flow
strength during consecutive tidal cycles controlled the sediment load of the plume and, consequently, led to the deposition of tidal-modulated strata. Formation of microtidal signals appears to be enhanced in fluvio-deltaic successions characterized
by multiple distributaries and in basins where river floods are out of phase with storm-wave activity. Bioturbation of sediment, which can start during the waning stage of the flow, and erosion by storm waves hamper the preservation of tidal signals,
unless rapid burial occurs. The recognition of tidal-modulated strata in river-dominated settings may facilitate the characterization of mudstone reservoirs and reconstruction of paleogeographic conditions during deposition. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Nous avons combiné un ensemble de données processus-produits unique acquis lors d'unecrue du fleuve Pô (Italie) avec une modélisation numérique.
Les marées basses |
| GEOSCAN ID | 321865 |
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