Transgressive Dune Research Articles

Le Pléistocène de la façade atlantique du Nord-Médoc (France) : état des connaissances sur la lithologie et la chronostratigraphie des « Argiles du Gurp » s.l [The Pleistocene of the atlantic side of the north-Medoc (France) : progress achieved with respect to the lithology and chronostratigraphy of the « Argiles du Gurp » s. 1.

The Pleistocene outcrops of the erosional cliffs of the North-Médoc coastline have been described since the last century as «Argiles du Gurp». They constitute two sedimentary sequences separated by a level of lignite older than 50000 years BP. The lower sequence has a lagoonal origin and the upper is continental. A synthesis of previous works and new field investigations allow us to detail the sequence lithology and to propose a new nomenclature and a palaeogeographical meaning for these deposits. The upper part of the lower sequence includes evidence of a former raised sea level near the present day one which could be attributed to the Eemian or Holsteinian interglacial. The upper continental sequence has a fluvial origin which could be contemporeneous with a glacial period. The entire outcrops was eroded and cryoturbated during the Würm IV glacial maximum and covered by the coastal transgressive dune systems during the Holocene.

Coastal dunes: sensitive or not?

This paper introduces a classification of coastal dune systems into two main morphodynamic classes, namely retentive and transgressive dune systems. Retentive systems include coastal dune types where sand accumulation within vegetation is dominant over other processes. In this category we include such morphological types as hummock dunes, foredunes, and retention ridges, including sub-environments such as precipitation ridges that form the landward boundary of transgressive dunefields. Transgressive systems include those coastal dune types where sand transport is dominant over other processes, and the dunes are unvegetated and mobile. In this category we include such morphological types as parabolic dunes, reversing transverse dunes, barchans, seif dunes, transgressive sheet dunefields and headland-bypass dunefields. Components of the two main morphodynamic types of coastal dune systems range in sensitivity from sensitive to robust. Retentive dune systems, being vegetated, are sensitive and fragile. Mobile dunes that form the major component of transgressive dune systems are robust and resilient. This morphodynamic classification is particularly useful because the two types of dune systems have diametrically opposed sensitivities and hence different management requirements.

Dune phases as time-transgressive phenomena, Manawatu, New Zealand

Abstract New Zealand's most extensive Holocene dunefield is situated in the Manawatu and adjoining regions. Evidence collected from the area, including 25 radiocarbon dates, suggests that the dunefield developed in phases, with the first probably initiated at the coast earlier than 6000 years ago. The first phase may have ceased near the coastline around 4500 years ago, but dunes continued to migrate until they reached 16 km inland ca. 1600 years ago. About 3500 years ago, dunes again began migrating inland from the coast with some still active 400 years ago. The time-transgressive nature of transgressive dune deposits and the possible causes of the dune phases are discussed.

Major phases of coastal erosion ca. 6700-6000 and ca. 3000-2000 BP between Cervantes and Dongara, western Australia

Abstract Relict foredune plains developed along parts of the coast between Cervantes and Cliff Head during Holocene time. Evidence for major episodes of marine erosion was provided by the presence of extensive erosional scarps or discontinuities within, or at the inner margin of, many of the plains. Such features often truncate older coastal landforms such as parabolic dunes. Shells within foreshore deposits immediately seaward of the erosional ‘cuts’ were dated to obtain an approximate age for the end of erosional episodes. At two locations dating suggests that erosion occurred ca. 6700-6000 BP. Dates from four other sites suggest that a major erosional episode occurred between ca. 2000 and 3000 BP. There was no evidence for the occurrence of major episodes of marine erosion at other times since the attainment of modern Holocene sea level. The first erosional episode is likely to have been associated with the final stages of the postglacial marine transgression. The second, which was also associated with the initiation of transgressive dunes, was probably caused by an increase in the occurrence and/or intensity of either tropical cyclones or winter cyclonic storms. However, the occurrence at that time of a minor marine transgression cannot be discounted.

Holocene alluviation and transgressive dune activity in the lower Manawatu Valley, New Zealand

Abstract Location of an estuarine bed near Opiki enabled the approximate mid Holocene limit of the Manawatu River estuary to be determined. Since about 6000 years B.P., flood-plain accretion in that area has averaged 1.5 mm/year, although accretion rates may have diminished with time. Two riverbank sections near Rangiotu provide evidence for the initial encroachment of Foxton Phase dunes. Thin sand horizons overlying the former flood-plain surface are identified as eolian veneer deposits, preserved at the rear of former migrating dunes, which constructed sand plains. Radiocarbon dates obtained from interbedded organic material reveal that dunes first entered the area c. 2300 years B.P. with further episodic encroachment until c. 1600 years B.P. As the Foxton Phase dunes had migrated c. 16 km inland there is no absolute date for the commencement of the phase but study of contemporary rates of dun~ advance suggests that the Foxton Phase may have been initiated at the coast about 550~6oo0 calendar years ago....

A review of coastal dunebuilding in Eastern Australia

SUMMARY The distribution of transgressive coastal sand dunes in eastern New South Wales and Queensland is summarised and the factors involved in transgressive dune initiation are reviewed. On the basis of radiocarbon and pedological evidence, it is suggested that episodes of transgressive dune instability have been synchronous over large areas. Widespread sand blowing appears to have taken place in the early Holocene between 9,000 and 7,000 years ago. Instability was also widespread between 3,500 and 2,000 years ago and within the last thousand years. Possible causes of dune instability are considered.

Wave, beach and dune interactions in southeastern Australia

A morphodynamic classification of surfzones, beaches and dunes of the microtidal, low- to high-energy southeast Australian coast is presented. The first section (A: Waves and beaches) briefly deals with the transformation of deep-water wave energy as it crosses the shelf, nearshore and surfzone. Depending on the deep-water wave characteristics and shelf and inshore morphology, resultant breaker wave energy may be high, moderate or low, and the accompanying beach surfzone morphodynamic state in fine to medium sand beaches either dissipative, intermediate or reflective. Dissipative beaches have wide surfzones with shore parallel bar(s) and channel(s) and predominantly shore-normal circulation; intermediate beaches are characterised by rip circulation, crescentic-transverse bars and megacusps; and reflective beaches by a barless surfzone and steep, cusped or bermed beach. Each beach form has a characteristic level of beach stability, zone of sediment storage and mode of beach and dune erosion. Landward aeolian sediment transport of swash-deposited sand (Section B) is dependent on the subaerial beach topography and the aerodynamic flow regime across that topography. Characteristic profile shapes are ascribed to each beach type (dissipative, intermediate and reflective). Aeolian sand transport rates are potentially highest on dissipative beaches, moderate on intermediate beaches and lowest on reflective beaches. These rates determine the potential size of foredunes which are correspondingly largest on dissipative beaches and smallest on reflective beaches. The combination of mode and frequency of beach/dune erosion, rates of aeolian sand transport, and foredune volume and morphology provide an explanation of the nature and morphology of landward-occurring, large-scale dune systems. Dissipative beaches are frequently characterised by large-scale transgressive dune sheets; intermediate, by a trend from large-scale parabolic dune systems (high-wave energy) to small-scale blowouts (low-wave energy); and reflective beaches by minimal dune development.

Late Quaternary Evolution of Coastal Sand Barriers, Port Stephens-Myall Lakes Area, Central New South Wales, Australia

AbstractThe 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.

WIND AND SEDIMENT MOVEMENT IN COASTAL DUNE AREAS

Little is known about how air-sediment interaction processes control the differential rates and direction of dune migration along the coast of South Australia. Information is needed on sand transport and dune formation in order to establish better guidelines for conservation and agricultural management programmes in areas that are undergoing erosion. The writers, with financial support from the Coast Protection Board, Department for the Environment, South Australia, have commenced a pilot research project to examine dunes in the lower Coorong and adjacent areas in the southeast of the State (Figure 1). The aims of the project are - To determine: (a) instantaneous surface stress values on the windward slopes of active transgressive dunes; (b) sand movement over the crestline as a function of surface stress on the windward slope in order to establish the life expectancy of stability of individual dunes; (c) the extent to which the local topography affects the wind regime in the dunal areas. To obtain: (a) air trajectories over and around transgressive dunes; (b) information on dune geometry (slope inclinations, crest heights, base lengths, etc.).

ANU Radiocarbon Date List VII

Along SE coast of Australia a variety of Holocene barriers composed of siliceous sand and shell detritus occur within bedrock-confined embayments. On basis of morphostratigraphy 4 barrier types are recognized: prograded, stationary, receded and episodic transgressive dunes. Several subtypes are also distinguished. Composite bay barriers involving partial eolian reworking of a prograded barrier constitute most complex examples of Holocene depositional sequences on this coast. The present list is a preliminary attempt at defining the age structure of a group of such barriers (excepting receded type). Ages are reported in conventional years bp. Text references to ages and age ranges are environmental effect corrected ages bp* and yr* (as recommended by Stuiver and Polach, 1977), using 450 ± 35 yr as postulated by Gillespie and Polach (in press) in order to relate Australian oceanic environment shells to terrestrial environment wood. δ13C errors, where based on measurement, are always ± 0.2% and are not shown in the text; when based on estimated values (Est) the error is given.

Rate of movement of transgressive sand dunes at Cronulla, New South Wales

Abstract Using radial line plots from aerial photographs taken between 1930 and 1965, the rate of movement of the transgressive dune sheet at Cronulla was measured. Over the 35 years, the dune sheet has advanced 291 m at the mean rate of approximately 8 m per year.

Rate of movement of transgressive sand dunes at Cronulla, New South Wales

Rate of movement of transgressive sand dunes at Cronulla, New South Wales