GEOSCAN, résultats de la recherche


TitreMorphodynamic evolution, self-organisation, and instability of coarse-clastic barriers on paraglacial coasts
AuteurForbes, D L; Orford, J D; Carter, R W G; Shaw, J; Jennings, S C
SourceMarine Geology vol 126, 1995 p. 63-85,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 37894
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est; Nouvelle-Écosse
Lat/Long OENS -63.2500 -63.0000 44.7500 44.5833
Sujetsmilieu côtièr; études côtières; évolution postglaciaire; plages; barrages construits par la marée; dépôts glaciaires; antecedents glaciaires; morphologie; graviers; sedimentation; changements du niveau de la mer; sables; géologie marine; sédimentologie; géologie des dépôts meubles/géomorphologie; Quaternaire
Illustrationssketch maps; graphs; plots
Résumé(disponible en anglais seulement)
Beaches and barriers on many mid- to high-latitude coasts comprise mixtures of fine and coarse clastic materials forming a distinctive morphodynamic environment. In many cases, the sediments are derived primarily from limited glacigenic deposits and the coasts are considered paraglacial. Over relatively long time scales (decades to centuries), coarse-clastic barriers on such coasts show evidence of self-organisation through large-scale morphological evolution and facies differentiation. This process involves gradual reworking, partitioning, and textural sorting of material toward transport minima. Long intervals of slow evolution are punctuated by episodes of rapid reorganisation, involving breakdown of stable barrier structures and facies patterns, remixing of sediment, and accelerated migration of transgressive systems. Drift-aligned systems develop longshore cell structure, sometimes leading to breaching and segmentation, and may evolve toward progressively greater swash alignment under appropriate circumstances. Swash-aligned systems may experience catastrophic transformation when appropriate environmental triggers lead to threshold exceedance in the morphodynamics of the shore system. Adjacent barriers may show quite different behaviour, depending on the antecedent states of individual coastal cells. While appropriate parameterisations and sediment budget formulations allow us to model the long-term evolution of some barrier structures, the non-linear dynamics that appear to dominate large-scale behaviour may limit predictability. The identification of stability threshold criteria remains an important research priority.