Cruise Report 87042: Css Dawson Operations On Inner Scotian Shelf and Sable Island Bank

Forbes, Donald L.; Boyd, R.; Shaw, John; Johnston, L; Heffler, D. E.; McLaren, Shirley A.

doi:10.4095/130697

Cited by 1 publication

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“…Fluctuations du niveau marin relatif à l'intérieur du plateau Scotian depuis 10 ka fondées sur des datations au radiocarbone publiées ou nouvelles (Forbes et al, 1988(Forbes et al, , 1991aScott, 1977a;Hall, 1985;Honig, 1987 together with data from other sources (Scott, 1977;Hall, 1985;Honig, 1987). Information on the index points is contained in Appendix I.…”

Section: Long-term Relative Sea-level Trendsunclassified

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Impact of the Holocene Transgression on the Atlantic Coastline of Nova Scotia

Shaw¹,

Taylor²,

Forbes³

2007

gpq

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As analogs for impact of a future sea-level rise on the coast of Nova Scotia (eastern Canada), geological data and information on relative sea-level changes are examined at three different time scales. Relative sea level rose swiftly during the early Holocene, at a maximum rate of 11 m/ka at 7500 radiocarbon years BP. Freshwater, salt-marsh, and estuarine sediments that formed during this period have been located on the inner shelf. After 5000 BP the rate slackened to about 2 m/ka. Despite overall submergence and coastal retreat since that time, gravel barriers have persisted where large amounts of sediment have been added to the littoral system by erosion of glacial deposits. The barriers often display evidence of early progradational phases in the form of gravel beach ridges, partly or wholly submerged in lagoons behind contemporary storm beaches. Tide-gauge data from the past century show submergence rates averaging 3.5 mm/a, well in excess of the longterm trend. The response of the coastline to this rapid rise is complex. Unconsolidated cliffs (bluffs) retreat at up to 5 m/a during initial exposure to wave attack and during extreme storm events, but at lesser rates (<0.5 m/a) as protective beaches, lag shoals or boulder frames accumulate at the base of the cliffs. Beach retreat rates are sometimes very high (>8 m/a) in some locations, but low elsewhere, in some cases showing almost no movement over the past 10 years, and neighbouring beaches are sometimes observed to behave in completely different ways. Sediment released by coastal erosion finds its way into nearby estuaries, causing growth of flood-tidal deltas and marsh aggradation. If a global rise in sea level occurs, the processes of erosion and sedimentation operating along the coast of Nova Scotia during the Holocene are expected to continue in a similar fashion, but rates of change will increase at many locations.Les données géologiques et les connaissances sur les changements du niveau marin relatif sont étudiées à trois échelles temporelles en tant qu'analogues des conséquences d'une future hausse du niveau marin sur la côte de la Nouvelle-Écosse. Le niveau marin relatif s'est rapidement élevé au cours de l'Holocène inférieur, jusqu'au taux maximal de 11 m/ka à 7500 BP. Des sédiments estuariens ou issus de marais salants et d'eau douce datant de cette période ont été localisés sur le plateau continental intérieur. Après 5000 BP le taux a diminué jusqu'à 2 m/ka. En dépit de la submersion de la région côtière et de son dégagement subséquent, les cordons littoraux de gravier ont persisté là où de grandes quantités de sédiments ont été mis en place sur le littoral par érosion des dépôts glaciaires. Les cordons montrent souvent des indices de phases de progression sous la forme de crêtes de graviers, partiellement ou entièrement submergés dans les lagunes situées derrière les plages de tempêtes contemporaines. Les données marégraphiques du siècle dernier font ressortir un taux de submersion d'environ 3,5 mm/a, taux nettement plus élevé que celui de la te...

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Section: Long-term Relative Sea-level Trendsunclassified

“…In the 1940s, the barrier was situated much farther seaward and linked Story Head to a now-vanished drumlin. Between 1954 Forbes et al, 1988).…”

Section: Schéma De L'évolution Du Cordon Littoral De Fancys Point: A)mentioning

confidence: 99%