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Late Quaternary Evolution of Coastal Sand Barriers, Port Stephens-Myall Lakes Area, Central New South Wales, Australia
- B.G. Thom, G.M. Bowman, P.S. Roy
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- Journal:
- Quaternary Research / Volume 15 / Issue 3 / May 1981
- Published online by Cambridge University Press:
- 20 January 2017, pp. 345-364
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- Article
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The geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of Newcastle, New South Wales (N.S.W.), Australia, in order to determine modes of deposition, and the degree to which marine and estuarine deposits can be correlated and dated. Each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur. In four of the bays dual sand barriers, comprising an Inner Barrier and an Outer Barrier, provide the framework for correlation between embayments. Six stages are recognized in the deposition of late Quaternary sediments in this area: (i) Pre-Last Interglacial, involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes; (ii) Last Interglacial stage during which Inner Barriers were formed; (iii) Last Glacial reworking of barrier and dune sands by westerly winds; (iv) Postglacial Marine Transgression during which the Outer Barriers were initiated; (v) Mid-Holocene stage following cessation of sea-level rise ca. 6000–6500 yr B.P. on this coast, and involving progradation of Outer Barriers in some embayments; and (vi) Late Holocene episodic eolian reworking of dune complexes and Outer Barriers. The relatively high wave and wind energy as well as the tectonic setting of the central N.S.W. coast results in somewhat different geomorphic histories from barrier-island coasts in North America and Europe.
4 - Wave-dominated coasts
- Edited by R. W. G. Carter, University of Ulster, C. D. Woodroffe, University of Wollongong, New South Wales
- Foreword by Orson van de Plassche
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- Book:
- Coastal Evolution
- Published online:
- 06 July 2010
- Print publication:
- 05 January 1995, pp 121-186
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Summary
Introduction
Wave-dominated sedimentary coasts comprise accumulations of detrital sand and gravel-sized material which undergo high levels of physical reworking, interspersed with periods of burial before finally being deposited as the coastal deposits we see today (Davis & Hayes, 1984). Quite commonly sediments tend to be of clean sand and gravel, often quite well sorted and abraded, containing relatively high proportions of more resistant minerals and rock types such as quartz, chert and heavy minerals. Waves and wave-induced currents are the dominant mechanisms for moving and depositing sand on shorefaces and beaches of the open coast, although winds, river discharge, tidal currents and Ekman flows variously act as transporting agents landward of the beach, in estuaries and seaward of the shoreface. In relation to the shoreface and beach, open coastal types are determined by four factors: (i) substrate gradient, (ii) wave energy versus tidal range; (iii) sediment supply versus accommodation volume (Swift & Thome, 1991); and (iv) rates of sea-level change. At one extreme are steep, high-energy, sediment-deficient coasts that have bedrock cropping out as headlands, with negligible sand at their base and relatively deep water offshore (autochthonous, accommodation-dominated coast of Swift & Thorne, 1991). At the other extreme are low-gradient, low-energy coasts that are typically muddy with a coastal fringe of wetland vegetation. Here, incident wave action is dissipated over very shallow offshore gradients such as those associated with deltaic environments at river mouths (autochthonous, sediment-supply dominated coast of Swift & Thorne, 1991; see Chapter 3). But even here, rare high-energy events such as cyclones can cause episodes of wave reworking leading to the formation of cheniers.