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TitleDifferential preservation of coastal structures on paraglacial shelves: Holocene deposits of southeastern Canada
AuthorForbes, D L; Shaw, J; Taylor, R G
SourceMarine Geology vol 124, 1995 p. 187-201,
Alt SeriesGeological Survey of Canada, Contribution Series 32494
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNova Scotia; Newfoundland and Labrador
NTS11; 12A; 12B; 12C; 12D
AreaChedabucto Bay; St. George's Bay; Halifax
Lat/Long WENS -64.0000 -56.0000 49.0000 44.0000
Subjectsmarine geology; surficial geology/geomorphology; coastal environment; coastal studies; coastal erosion; Holocene; continental shelf; littoral environment; postglacial deposits; transgressions; sea level changes; drumlins; glacial features; lithology; coastal barriers; Quaternary
Illustrationssketch maps; stratigraphic sections; seismic reflection profiles
AbstractRecent work has advanced our understanding of mixed sand-gravel littoral systems in glaciated regions. New insights include the nature and causes of coastal instability and conditions for preservation of Holocene barrier deposits on paraglacial shelves. The best-preserved relict barrier structures recognized on the inner shelf of southeastern Canada are interpreted as postglacial lowstand deposits, initiated under stable to slowly rising relative sea level in areas of substantial shelf relief. A largely intact early-Holocene gravel foreland survives at 38 m present water depth, its preservation attributed in part to sediment volume and a partially protected location. The mechanism by which this structure was abandoned and overstepped is unclear, but may be related to accelerating sea-level rise. In some cases, barriers keep pace with sea-level rise for some time before being overstepped or reworked landward. The duration and extent of preservation depend in part on the deposit volume, as smaller accumulations are consumed and reworked more quickly. Deposit volume is a function of sediment supply, accommodation space, and headland spacing, among other factors. Where barriers are small and thin, beach sediments, overtaken by the transgression, may be smeared across the shoreface in a thin post-transgressive veneer. In such settings, as along the Eastern Shore of Nova Scotia, the only coastal units preserved on the shelf are back-barrier estuarine facies in flooded-valley depressions. Differential preservation is governed by shelf relief and accommodation space, coastal alignment and compartmentalisation, sediment supply and barrier volume, rate and acceleration of sea-level rise, wave energy and potential for sediment reworking on the inner shelf.