Barrier islands on bedrock; a new landform type demonstrating the role of antecedent topography on barrier form and evolution

Barrier islands commonly occur in coastal plain and deltaic settings, and a variety of behavioral and stratigraphic models exist. In this paper, a 90 km long barrier island system in the Outer Hebrides of Scotland is identified for the first time. Uniquely among barrier islands, the system rests dir...

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Bibliographic Details
Published in:Geology (Boulder) 2012-10, Vol.40 (10), p.923-926
Main Authors: Cooper, J. A. G, Jackson, D. W. T, Dawson, A. G, Dawson, S, Bates, C. R, Ritchie, W
Format: Article
Language:English
Subjects:
barrier islands
bedrock
carbonate sediments
characterization
Continental dynamics
controls
Europe
Evolution
geomorphology
gneisses
Great Britain
Hebrides
identification
Islands
landform description
landform evolution
landforms
Landscape ecology
metamorphic rocks
Outer Hebrides
Scotland
sea-level changes
sediment supply
Sediments
substrates
three-dimensional models
topography
transgression
United Kingdom
Western Europe
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Summary:Barrier islands commonly occur in coastal plain and deltaic settings, and a variety of behavioral and stratigraphic models exist. In this paper, a 90 km long barrier island system in the Outer Hebrides of Scotland is identified for the first time. Uniquely among barrier islands, the system rests directly on a planar bedrock (gneiss) surface (a strandflat). This bedrock surface has a profound influence on the morphology of the barrier island chain, and exerts the dominant influence on barrier island form and evolution during transgression. Topographical irregularities on the bedrock surface control both plan and profile morphology of the barrier islands. Under sea-level rise, by barrier migration, sediment is redistributed onshore and alongshore in a strongly three-dimensional manner, determined by topographic variability in the bedrock. The barrier islands represent an endpoint in transgressive barrier island geomorphology that is controlled by the bedrock surface: they are at the upper end of the recognized tidal amplitude for barrier islands; the offshore wave regime is very high-energy; they lack a shoreface; and neither ravinement surface nor transgressive sand sheet are developed. Sediment supply is dominated by offshore-derived skeletal carbonate.
ISSN:0091-7613
1943-2682
DOI:10.1130/G33296.1