Barrier Dune Research Articles

Habitat Preferences of the Australian Endangered Samphire Tecticornia Flabelliformis

Australia’s only federally listed endangered samphire, the fan or bead samphire Tecticornia flabelliformis (Paul G.Wilson) K.A.Sheph. & Paul G.Wilson, is a small deciduous forb up to twenty centimetres high that is generally found growing in monospecific patches on clay pans or sabkhas directly behind coastal barrier dunes or on salt lakes further inland. The habitat requirements that control the distribution of fan samphires are poorly understood.During September 2004, thirty-six soil samples were collected from within and surrounding three stands of fan samphires near Gulf St Vincent, South Australia. Analysis of the samples showed that pH had the strongest association with the presence of fan samphires, with field moist chlorinity also strongly associated. Oven dried chlorinity and percentage moisture were not significantly different between sites with fan samphires and those sites without, although the fan samphires occurred on soils with a wider range for these parameters than the surrounding areas displayed.Soil samples were also analysed for soil particle size. The species appears to prefer locations where the ‘within site’ mean clay content is between 31% and 37%. Field observations of a light-coloured subsurface hard pan under fan samphire stands were noted.

The luminescence chronology of dune development on the Maputaland coastal plain, southeast Africa

Geomorphological and lithostratigraphic mapping of dune systems on the Maputaland coastal plain of northeastern KwaZulu-Natal Province, South Africa has defined the relative-age relationships between the complex pattern of Quaternary parabolic and hummocky dunes, sand megaridges and the composite coastal barrier dune cordon. Here infra-red-stimulated luminescence (IRSL) ages are presented in the context of regional stratigraphic relationships and serve to bracket the period of accumulation of the main dune systems. The luminescence ages challenge the widely held belief that the north–south aligned dune pattern reflects a coastward-younging sequence. The framework of ages highlights the spatial variations in dune mobilization and long accretion history on some dune forms. Weathered dune and interdune wetland sediments spanning from prior to marine isotope stages (MIS) 11 and up to MIS 7 underlie the coastal plain. At least two generations of decalcified aeolianite of MIS 5 and 4 form the core of the complex coastal barrier dune. On the coastal plain, frequent sand mobilization events during MIS 3–2 resulted in the development of discrete complexes of highly extended, northward directed parabolic dune systems and reworking of the crest of the central sand megaridge. The luminescence-dated dune mobilization history brackets the period of formation of interdune and lacustrine peat and diatomite deposits. During the Holocene marine transgression at least four laterally extensive, complex transverse ridges of coalesced ascending parabolic dunes accreted against the aeolianite core of the coastal barrier. Polyphase dune formation and remobilization is discussed in the context of the regional groundwater and vegetation responses to global climatic changes, wind regimes and glacio-eustatic sea-level fluctuations.

Tsunami washover deposits, Tawharanui, New Zealand

Barrier dunes on the northern side of the Tawharanui Peninsula, north of Auckland, New Zealand, appear to have been overtopped by extreme waves that have deposited two large sand washover lobes in a back beach wetland. Present-day storm surges and storm waves are incapable of overtopping the barrier dunes. However, historical data and numerical models indicate tsunamis are amplified by resonance within the adjacent bay and Hauraki Gulf. Further, the location of nearshore reefs in close proximity to the washover lobes suggests that the interaction between tsunamis and the reefs further amplified the waves at those locations. The presence of a distinctive pumice (Loisels Pumice) within the washover deposits suggests that the deposits are associated with a 15th Century eruption from the submarine Mt Healy caldera located northeast of New Zealand.

Soil chronosequence development in dunes on the southeast African coastal plain, Maputaland, South Africa

Dunes have accreted on the southeast African coastal plain in coast-parallel patterns of degraded whaleback ridges, sand megaridges and extended parabolic dunes since the Pliocene. In the Maputaland dune field, relative dating is complicated by soil degradation, erosion and vegetation cover. This project assessed alternative relative and numeric dating techniques that can be used to differentiate dune systems and eolian sand bodies. Soil profile characteristics were used to calculate soil development indices (SDI) for soil horizons sampled from hand augered holes and rare exposures. Infrared stimulated luminescence (IRSL) dating of representative dunes and sand units helped define the pedogenesis achieved since deposition. The quartzose dune sands have weathered to form very deep soil profiles. Enhanced SDI values for horizons or sampled intervals down the profile reflect pH decrease, advanced rubification or distinct mottling, clay increase and harder consistency with depth. The youngest Holocene profiles exhibit decreasing horizon index values with depth below the A horizon whereas late Pleistocene profiles display SDI values increasing with depth within the upper 3 m of the profile. Within some Mid- to Late Pleistocene eolian sands greater profile-horizonation and catena complexity manifests as complex soil profiles or distinctly mottled, clay-enriched horizons, at depths of 2–5 m below the surface. The SDI profiles from specific dune systems or stratigraphic units cluster well and effectively characterize soil development in dune sand units of different ages. Depositional age plotted against sampled horizon index values makes it possible to determine generalized rates of soil profile development, and to compare pedogenic processes on the high-rainfall, coastal barrier dunes to those found in the drier interior. Sampled horizon index values distinguish buried soil profiles and highlight possible localized surficial reworking.

Developing a 150 ka luminescence chronology for the barrier dunes of the southern Cape, South Africa

The southern coastline of South Africa exhibits extensive aeolianites and spectacular barrier dunes; the ages and palaeoenvironmental significance of which have, until recently, received limited attention. We present preliminary results for samples taken from a single 6.5 m section in the seaward barrier dune near to the town of Wilderness. The reliability of these ages has been investigated using a series of dose recovery and pulsed irradiation experiments, as well as through analyses of single aliquot and single grain D e distributions. Results indicate that the SAR protocol is providing accurate and precise D e determinations and that adequate sensitivity correction is being made. The application of pulsed irradiations does not result in significant changes in the dose–response curves or averaged D e's. Single grain D e distributions are broad, with significant levels of overdispersion, which may reflect beta dose heterogeneity effects. Peaks in aeolian activity date to 157–154 and 140–125 ka, with a slower rate of deposition recorded from 115 to 85 ka. Brief phases at 40 and 21 ka are also identified. Some ages, notably those from OIS 3 and OIS 2, are surprising from a geomorphological perspective, given the likely distance of the dune from the shoreline at such times, although they are not inconsistent with evidence from the east coast of South Africa. The results reveal multiple phases of Late Quaternary barrier dune accumulation, and suggest that aeolian activity in this region has been episodic and potentially more complex than previously thought.

Land use and occupation characterization of Northern coast municipalities, Rio Grande do Sul, Brazil

A ocupação dos municípios litorâneos do Estado do Rio Grande do Sul vem se intensificando nasúltimas décadas por causa de dois vetores principais: o processo de urbanização e o processo de exploraçãoturística. A proximidade da Região Metropolitana de Porto Alegre (RMPA), a acessibilidadefacilitada pela confluência de uma série de rodovias e a diversidade de ambientes longitudinais à costaconferem à região uma situação ímpar. Esses ecossistemas de rara beleza (campos de dunas, banhados,cordão de lagoas e escarpa do planalto) vêm sofrendo uma ação antrópica significativa, mas carente dequalidade. O principal objetivo deste artigo é caracterizar os perfis dos municípios do Litoral Norte doEstado do Rio Grande do Sul, a partir da análise territorial dos processos de urbanização e de emancipação,do crescimento demográfico, das migrações e de indicadores econômicos, contribuindo, assim,com elementos para subsidiar a formulação de políticas públicas municipais e regionais. A regionalizaçãoadotada procura contemplar aspectos político-administrativos e físico-naturais, englobando vinte e ummunicípios. A caracterização empreendida delineou quatro perfis de municípios: urbanos com populaçãopermanente; urbanos para fins de segunda residência; urbanos agroindustriais; e municípios rurais.

Holocene sea-level changes and landscape evolution on the northern Carmel coast (Israel)

Archaeological, fluvial and morphological features are used to reconstruct sea-level changes and landscape evolution on the northern Carmel coast, Israel during the Holocene. Between 8900 BP and 7000 BP sea level lay between 35 m and 7 m below present, rising at an average rate of 12-14 mm/yr. This rate decreased to 2-4 mm/yr between 7000 BP and 4000 BP, with the sea between –7 m and present MSL. Since the Middle Bronze Age (4000 BP), sea level has been within ± 0.5 m. The landscape has evolved in five main stages, linked to the Holocene marine transgression and changes in the fluvial water regime. (1) Around 8900 BP, sea level lay around –35 m. The southern coastline between N. Megadim and N. Maharal was straight and sandy. North of N. Oren, the coastline was mostly rocky, with marshy clays embedded in the troughs between the coastal kurkar ridges. All southern wadis, from N. Megadim to N. Maharal, crossed the Carmel coast kurkar ridge through the N. Oren canyon. The northern wadis from N. Mitleh to N. Ahuza were blocked and flowed northward, crossing the Carmel coast ridge westward through N. Ovadia channel and at Kfar Samir. (2) Between 8200 BP and 7500 BP, sea level lay around –16 m. North of N. Oren the coastline was extensively indented, creating lagoons and shallow bays. To the south, the coast was straight and sandy. Alluvial sediments filled the eastern trough and water overflow allowed streams to flow directly to the sea. (3) Between 7000 BP and 6500 BP, the sea was around 9 m below present. A row of offshore islands was situated parallel to the coast from Atlit northward. (4) During the Chalcolithic period (6000-5700 BP) sand dune barriers interrupted natural drainage and a series of polyhaline lagoons was formed. (5) Between 5700 and the Middle Bronze Age, sea level has risen to its present position.

Holocene geoarchaeology of the Sixteen Mile Beach barrier dunes in the Western Cape, South Africa

Holocene evolution and human occupation of the Sixteen Mile Beach barrier dunes on the southwest coast of South Africa between Yzerfontein and Saldanha Bay are inferred from the radiocarbon ages of calcareous dune sand, limpet shell ( Patella spp.) manuports and gull-dropped white mussel shells ( Donax serra). A series of coast-parallel dunes have prograded seaward in response to an overall marine regression since the mid-Holocene with dated shell from relict foredunes indicating periods of shoreline progradation that correspond to drops in sea level at around 5900, 4500 and 2400 calibrated years before the present (cal yr B.P.). However, the active foredune, extensively covered by a layer of gull-dropped shell, has migrated 500 m inland by the recycling of eroded dune sand in response to an approximate 1 m sea level rise over the last 700 yr. Manuported limpet shells from relict blowouts on landward vegetated dunes indicate human occupation of coastal dune sites at 6200 and 6000 cal yr B.P. and help to fill the mid-Holocene gap in the regional archaeological record. Coastal midden shells associated with small hearth sites exposed in blowouts on the active foredune are contemporaneous (1600–500 cal yr B.P.) with large midden sites on the western margin of Langebaan Lagoon and suggest an increase in marine resource utilisation associated with the arrival of pastoralism in the Western Cape.

Aeolianite and barrier dune construction spanning the last two glacial–interglacial cycles from the southern Cape coast, South Africa

The southern Cape region of South Africa has extensive coastal aeolianites and barrier dunes. Whilst previously reported, limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea-level fluctuations that have taken place during the Late Quaternary. Sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial–interglacial cycles. Aeolianite deposition has occurred on the southern Cape coast at ca 67–80, 88–90, 104–128, 160–189 and >200 ka before the present. Using this and other published data coupled with a better understanding of Late Quaternary sea-level fluctuations and palaeocoastline configurations, it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea-level high stands. These marine transgressions and regressions allowed onshore carbonate-rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions. The lack of carbonates in more recent dunes (Oxygen Isotope Stages 1/2 and 4/5) is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and/or changes in the balance between the warm Agulhas and nutrient-rich Benguela ocean currents.

Aeolianite and barrier dune construction spanning the last two glacial?interglacial cycles from the southern Cape coast, South Africa

Aeolianite and barrier dune construction spanning the last two glacial?interglacial cycles from the southern Cape coast, South Africa

Developing sinks for CO 2 through forestation of temperate coastal barriers: an environmental business

Since the 1940s, some sectors of the sand dune barriers of Buenos Aires Province have been forested to fix the sand in the neighborhoods of resort villages. Man took advantage of the maritime climate and the shallow groundwater to introduce pine forests. Today, these forests reach more than 20 m in height and have developed soils of more than 0.05 m in thickness on former arid sands. Field data were referred to Landsat (TM) composite and Normalized Difference of Vegetation Index, NDVI, images to calculate forest density and covered area. Considering published tables of wood density for each species, the amount of total carbon storage was estimated on 318 t C ha-1 (Mg=106 g) in biomass and 86 t C ha-1 in soils. The three areas analyzed at Miramar, Necochea and Claromeco have captured 658,868 t of carbon in the last 50 years. It is estimated that 150,000,000 t C could be sequestered within temperate dune barriers of Argentina, Uruguay and Brazil. Besides this ecological point of view, there is an important socio-economic factor that cannot be excluded.

Transient geomorphic control of water table and hydraulic head reversals in a coastal freshwater peatland

Abstract We studied a Great Lakes peatland protected by a barrier dune system to test the hypothesis that changes in the morphology of a barrier beach alter the wetland surface-water and ground-water hydrology such that the plant rooting zone in the wetland interior might be affected. Hydraulic head measured in observation wells located on transects perpendicular to a flow-through channel, uplands, and Lake Ontario were compared to lake-level changes, weather patterns, and the temporal conditions of the barrier beach. Water-table elevations within the wetland complex always remained 0.35 to 0.84 m above Lake Ontario's water level (mean difference = 0.62 m) and did not fluctuate in parallel with changes in the lake's water level. Flooding events occurred when breaches closed and isolated the wetland complex from Lake Ontario; daily average water levels rose between 0.06 m and 0.27 m. When the barrier beach was breached naturally or by human activity, daily average water-table elevations in the wetland rece...

High-Resolution Subsurface (GPR) Imaging and Sedimentology of Coastal Ponds, Maine, U.S.A.: Implications for Holocene Back-Barrier Evolution

Ground-penetrating radar (GPR) transects and sediment cores have been used to examine the basement morphology, stratig- raphy, and environmental history of maritime ponds along the pen- insular coast of Maine. Silver Lake, Lily Pond, and North Pond are shallow ( , 3 m) water bodies bordered by steep bedrock ridges in the north, east, and west, and sandy barriers to the south. The bedrock basins of the ponds are formed in metasedimentary rocks surrounded by resistant pegmatitic intrusions. A dense network of GPR traverses obtained over the ice-covered Silver Lake reveals a series of prominent wavy-parallel and basin-fill reflector geometries terminating against the bedrock or grading into the barrier sediments and interpreted as organic lake-bottom facies. The transparent units represent sand-rich horizons, mostly eolian in origin. Convex-up structures found both on the surface and within the basin-fill sequence are interpreted as pre- served parts of coastal dunes. The present study indicates that fresh- water conditions prevailed since at least 4.6 ka, with an initial sedi- mentation rate of 1.7 mm/yr. The position of this unit below the con- temporary sea level suggests presence of a welded barrier by that time. Radar profiles taken along the shores of Lily Pond, a small water body behind the Sand Dune Barrier, indicate a significantly larger areal extent of the pond in the past. A succession of organic deposits over- lying a Pleistocene glaciomarine unit indicates progressive inundation of the paleo-lagoon by rising sea level. Saltwater peat seaward of Lily Pond was buried by washover sands about 1.2 ka, and a narrow pond existed here prior to dredging and artificial infilling of its eastern part in the 1950s-60s. The organic and eolian units are absent in the North Pond, where sedimentary fill consists of glaciomarine clay overlain by marine sands. A proposed three-stage model of pond evolution along an embayed coastline consists of: (1) organic accumulation in an up- land depression during lower sea level; (2) predominantly washover or tidal deposition in a lagoon (Stage 2a) or blocked coastal pond (Stage 2b) during initial transgression, and (3) mainly eolian and organic de- position behind a prograded or aggraded barrier. Future accelerated rise in relative sea level and inadequate sediment supply will cause many back-barrier ponds to reenter Stage 2 of the proposed model.

Evidence for dune reactivation from GPR profiles on the Maputaland coastal plain, South Africa

Abstract The Maputaland area of northeastern South Africa is characterized by extensive dunefields which developed during polyphase reworking of regional aeolian cover sand from the Mid-Pleistocene to the Holocene. Extended parabolic dunes, many preserved only as wind-rift trailing limbs, as well as areas of sinuous crested dunes, hummocky dune systems and the high, composite, accretionary coastal barrier dune cordon are the dominant dune forms. There are few natural sections exposing the stratigraphic succession and unequivocal relative age relationships between dune systems are uncommon. A ground penetrating radar (GPR) survey of dunes and representative aeolian sand stratigraphic units was undertaken in order to investigate the internal structure of the different dune forms and identify stratigraphic relationships between buried sedimentary units. The GPR profiles revealed that the trailing limbs of almost all the parabolic dunes that were surveyed comprise stacked sand units, separated by low-angle reflections interpreted as bounding surfaces, which accumulated through polyphase vertical accretion. Most extended parabolic dunes are aligned north-south and the upper parts of the dunes are characterized by inclined reflections in GPR profile interpreted as large-scale sets of cross-stratification with apparent dips toward the west. A hummocky dune revealed cross-stratified aeolian sand superimposed on a truncated dune form and probably formed through deflation of pre-existing dunes. Using 100 MHz and 200 MHz antennae, it is clear that GPR is capable of imaging very fine sedimentary structures and buried erosional surfaces in the homogeneous aeolian sand of Maputaland. At some of the sites investigated, the buried sand units identified were sampled by hand-augering for infrared-stimulated luminescence dating. The age determinations on these samples suggest that vertical accretion of up to 7 m of sand occurred intermittently over variable time scales up to 25 000 years on some parabolic dune limbs during the Late Pleistocene. In some complex dunefields, adjacent dunes were mobilized at different times, suggesting that remobilization was localized. The implications of the complex internal structure and vertical accretion of extended parabolic dunes are discussed in the context of changes in vegetation cover and water table due to seasonal and short-term cyclical climate variations as well as long-term climate change patterns during the last glacial cycle and the Holocene.

Evolution de la côte du Calvados depuis l'Eemien et découverte d'un squelette de cheval dans les tourbes holocènes

Among the fauna collected by J.Couvelard during the surveys carried out since several years at Graye-sur-Mer and Asnelles (Calvados) an almost complete skeleton of an Holocene horse {Equus caballus) was found. This horse is included in the upper part of the littoral peats. These peats and clays have been deposited since the Preboreal up to presently, behind a dune barrier progressively pushed towards the modern coast during the flandnan transgression In these marshes the marine influence is present only at the transition Subboreal-Subatlantic. The peats cover Weichselian heads and loess Below, a marine formation of the Late Eemian and peaty clays of the Early Weichselian fossilize an old marine platform. The skeleton is contemporaneous with pieces of pompean pottery (3rd-4th Century AD)

The late Cenozoic evolution of coastal water bodies in Northern Kwazulu-Natal, South Africa

Abstract Three large coastal water bodies (St Lucia, Sibaya and Kosi) of markedly different contemporary morphology occur on the eastern margin of the northern KwaZulu-Natal coastal plain, South Africa. This paper examines their Late Cenozoic evolution and investigates the controls on their evolution that have produced the observed differences in morphology. All three systems origins were due to Mio-Pliocene low sea-level still stands allowing rivers to scour channels into Cretaceous and Palaeocene sedimentary sequences. During the Last Interglacial (oxygen-isotope stage 5e), sea level was approximately 5 m above present level and the morphology of the three systems was similar. An offshore barrier archipelago partially isolated a back-barrier environment that comprised intertidal sand-flats, localised reefs and tidal channels. The area around Bazaruto Island, Mozambique, provides a modern analogy. River rejuvenation and associated incision up to and during the Last Glacial Maximum (16 000–18 000 BP) caused a minimum of −40 m scour which is still reflected in the bathymetry of Lake Sibaya and Kosi. Accumulation of barrier sands partly against pre-existing Interglacial barrier remnants during the Holocene marine transgression (16 000–4500 BP, Ramsay, P.J., 1995. 9000 Years of sea-level change along the South African coastline, Quaternary Int. 27, 1–5.) was responsible for lagoon isolation, although the extent and nature of separation from the sea varies markedly between the systems. The northern part of Lake St. Lucia was closed from the sea during the late Holocene, probably during a sea-level fall from a Holocene high stand of ca. 3 m, at 3000 BP. The Kosi system had a late Pleistocene to early Holocene outlet situated at Bhanga Nek, Lake Nhlange, but this inlet mouth closed approximately at 3000 BP. The present mouth was established by 1600 BP. Lagoonal conditions within Lake Sibaya terminated ca. 5000 BP when coastal barrier dune formation caused complete impoundment and enabled the lake water level to rise to 20 m above mean sea-level. Lake St. Lucia's large catchment has meant that fluvial sediment input has kept pace with the Holocene transgression, whereas the localised drainage associated with Sibaya and Kosi has resulted in a negligible fluvial sediment input allowing for deep lacustrine conditions to develop. Lagoonal segmentation is present to some extent in each system as a result of mobile coastal sediments and their reworking by short-period wind waves. The differential stages of lagoonal segmentation in the three systems can be explained by (a) the presence of cohesive sediment and bedrock around St Lucia which reduce shoreline mobility, and (b) the great water depths in Sibaya compared to Kosi which require longer periods of infilling before segmentation is complete

Erosion and recycling of aeolian dunes in a rapidly infilling macrotidal estuary: the Authie, Picardy, northern France

Abstract The Authie is a rapidly infilling macrotidal (mean estuary-mouth spring tidal range = 8.5m) estuary in Picardy, northern France, whose mouth is affected by strong tidal currents and wind waves generated in the English Channel. The estuary cuts across a major sand dune barrier and has been sourced by sand derived from offshore and alongshore, as well as from recycling of the aeolian dunes lining its north bank. Sand released by the severe erosion of these north bank dunes is temporarily stored on the beaches. A small fraction of the sand is back-cycled into the dunes via blowouts. The rest is transported towards the inner estuary where it forms longitudinal aeolian dune ridges and sand sheets that are ultimately recycled into sandy-muddy intertidal flats that develop into salt marshes. The erosion of the dunes lining the north bank of the estuary represents a morphodynamic adjustment to concentration of the tidal flux against this north bank by massive accretion and progradation of a south-bank sand platform. This erosion contributes in giving a funnel-shaped estuary mouth and probably in accommodating the tidal prism following large-scale reclamation of the inner estuary. The estuary-ward recycling of aeolian dune sand enhances overall accretion of the estuary whose ultimate fate is complete silting up in the decades to come.

Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of south-western Australia

When the estuaries of south-western Australia were first flooded by the Holocene marine transgression about 7000 years before present (BP), most were enclosed by limestone barrier dunes. Coastal sand drift built bars and flood-tide deltas in the narrow entrances, but until about 3500 years BP the estuaries remained tidal-dominated systems with a diverse marine–estuarine fauna. Now the bars/deltas so obstruct the small tides that estuary water is fresh in winter and marine to hypersaline in summer; the estuaries are river-flow-dominated systems and the ecosystems are characterised by a restricted euryhaline estuarine biota. Some estuaries are still permanently open, their bars/deltas never close, and some are seasonally open, their bars open with river flow in winter and close in summer. Other estuaries are normally closed, their bars remain closed for several years and break with episodic flood flow, or are permanently closed coastal salt lakes with bars that never or rarely break: they can become grossly hypersaline and may dry up altogether. An hypothesis to explain this Holocene transformation of the estuaries attributes it principally to sedimentary processes in an environment where river flow is highly seasonal, tides are microtidal, there was a fall in sea level, and there are differences in the volume and periodicity of flow and the degree of shelter to the entrances from the prevailing south-west winds and swell.

Vegetation of a Freshwater Dune Barrier Under High and Low Recreational Uses

BONANNO, S. E., D. J. LEOPOLD, AND L. R. ST. HILAIRE. Vegetation of a freshwater dune barrier under high and low recreational uses. J. Torrey Bot. Soc. 125:40-50. 1998.-The 27.4 km freshwater dune barrier on the eastern shore of Lake Ontario protects an extensive system of high quality wetlands. The vegetation was previously undescribed, and development pressures required management decisions for which data were needed. The objective of this study was to describe and compare the vegetation under high and low recreational use. We found four community types using hierarchical classification (TWINSPAN): (1) Ammophila breviligulata (beachgrass) (2) Toxicodendron radicans-Vitis riparia-Populus deltoides (brushland) (3) Quercus rubra-Acer rubrum (forest), and (4) Alnus incana (thicket). Reciprocal averaging ordination displayed communities along a first gradient of distance from the beach. A second gradient is likely related to disturbance. Species composition was similar in beachgrass and brushland communities under high and low recreational use. Under low use, forest and shrub thicket were present on the back of the barrier, but were absent under high use. Species richness and ground cover of vegetation, and density of colonizing species were lower on equivalent physiographic zones under high compared to low recreational use.

Fluvial deposition on the Shoalhaven deltaic plain, Southern New South Wales

Abstract New research from the Shoalhaven deltaic plain prompts revision of ideas on fluvial deposition in coastal New South Wales. Extensive remnants of Pleistocene alluvium occur on the surface and beneath Holocene sediments. Thermoluminescence (TL) analysis indicates that there were at least two and probably four phases of Pleistocene deposition spanning much of Last Interglacial and Glacial times. Deposition continued even when sea levels were low. Holocene infilling was faster than previously thought, for the Shoalhaven was feeding fluvial sand onto the shore and the adjacent barrier dune system by 6 ka. Away from the main channel, deposition occurred mainly as levee building along tributary and distributary channels. Claims for an initial southerly course of the Shoalhaven across the plain followed by avulsion northward to the present mouth are discounted. Channels flowing southward are too small to be former courses of the Shoalhaven, and are better explained as distributaries caused by crevassing ...