Regional landform patterns in the Strzelecki Desert dunefield: dune migration and mobility at large scales
Fitzsimmons, K.E. (2006) Regional landform patterns in the Strzelecki Desert dunefield: dune migration and mobility at large scales. Regolith 2006 – Consolidation and dispersion of ideas. Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME), Perth, pp.95-99.
The Australian desert dunefields dominate the continent, forming a large anti-clockwise whorl across more than one... more
The Australian desert dunefields dominate the continent, forming a large anti-clockwise whorl across more than one third of the country (WASSON et al. 1988). The majority of these dunes are linear bedforms, forming parallel to the resultant vector of the sand shifting winds prevailing at the time of their formation (KING
1960). Despite being the most extensive landforms on the continent, studies of regional landform patterns relating these linear dunes with other landforms have been scarce. This work aims to make use of a new geomorphic mapping system designed for aeolian environments to identify regional landform patterns in the Strzelecki Desert (Figure 1), potentially shedding further light on dunefield formation at large scales.
Download (.pdf) Aridity in the monsoon zone as indicated by desert dune formation in the Gregory Lakes basin, northwestern Australia
Fitzsimmons, K.E., Miller, G.H., Spooner, N.A., Magee, J.W. (2012, in press) Aridity in the monsoon zone as indicated by desert dune formation in the Gregory Lakes basin, northwestern Australia. Australian Journal of Earth Sciences.
Desert dunes within the monsoon-fed Gregory Lakes basin form valuable archives for Quaternary paleoenvironments, in a... more Desert dunes within the monsoon-fed Gregory Lakes basin form valuable archives for Quaternary paleoenvironments, in a region where such records are scarce. Optically stimulated luminescence (OSL) chronologies from two dunes identify the timing of aeolian processes, interpreted as a complex response to aridification and increased sediment availability during lake transgressions and associated fluvial activity. The earliest aeolian deposition in our record occurred ca 91.5 ka, which postdates the last “mega-lake” phase but predates a smaller lake transgression during early MIS 3. Sand plain accretion took place around ca 47 ka during contemporaneous periodic high lake levels. This was followed by intermittent linear dune building, between ca 35 and 11.5 ka, which most likely took place during an interval of relative aridity. Close spacing of mid-Holocene ages within one dune indicates rapid sediment accumulation in a single arid event ca 5 ka. At no time in the last 50 ka have lake levels reached those of the last "mega-lake” phase prior to ca 91.5 ka, suggesting a substantially weakened present-day monsoon.
Seasonally active slipface avalanches in the north polar sand sea of Mars: Evidence for a wind-related origin
Geophysical Research Letters, in press, doi:10.1029/2012GL051329
Meter-scale MRO/HiRISE camera images of dune slipfaces in the north polar sand sea of Mars reveal the presence of deep... more Meter-scale MRO/HiRISE camera images of dune slipfaces in the north polar sand sea of Mars reveal the presence of deep alcoves above depositional fans. These features are apparently active under current climatic conditions, because they form between observations taken in subsequent Mars years. Recently, other workers have hypothesized that the alcoves form due to destabilization and mass-wasting during sublimation of CO2 frost in the spring. While there is evidence for springtime modification of these features, our analysis of early springtime images reveals that over 80% of the new alcoves are visible underneath the CO2 frost. Thus, we present an alternative hypothesis that formation of new alcoves and fans occurs prior to CO2 deposition. We propose that fans and alcoves form primarily by aeolian processes in the mid- to late summer, through a sequence of aeolian deposition on the slipface, over-steepening, failure, and dry granular flow. An aeolian origin is supported by the orientations of the alcoves, which are consistent with recent wind directions. Furthermore, morphologically similar but much smaller alcoves form on terrestrial dune slipfaces, and the size differences between the terrestrial and martian features may reflect cohesion in the near-subsurface of the martian features. The size and preservation of the largest alcoves on the martian slipfaces also support the presence of an indurated surface layer; thus, new alcoves might be sites of early spring CO2 sublimation and secondary mass-wasting because they act as a window to looser, less indurated materials that warm up more quickly in the spring.
Ice and sulfate induration in the martian north polar sand sea
Presented at the 2nd Planetary Dunes Workshop, 05/2010
Saltation has been a major erosional and depositional force on the surface of Mars, but the dynamics and timescales... more Saltation has been a major erosional and depositional force on the surface of Mars, but the dynamics and timescales that govern the movement of martian sand dunes are poorly understood. In particular, major insights are needed into the mechanisms that cause induration of sand dunes and how these mechanisms affect dune migration rates. Possible modes of induration include chemical (cementation by salts, ferricrete, etc.), physical (settling and compaction of sand and/or dust), and niveo-aeolian (cementation by pore or interbedded ice). This study aims to search for evdience of each of these processes and evaluate their relative influence by examining dunes within the north polar sand sea, which encircles and is sourced from within the north polar plateau (Planum Boreum) [4]. The north polar sand sea offers a unique opportunity to study all of the above processes in one location, as both ice and soluble sulfates are present in the dune fields.
Recent aeolian dune changes on Mars
by Ken Edgett
(2008)
M. C. Bourke, K. S. Edgett, and B. A. Cantor
Geomorphology, 94, 247–255. doi:10.1016/j.geomorph.2007.05.012
Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or... more Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated, or subject to infrequent episodes of movement.
Mars landscape evolution: Influence of stratigraphy on geomorphology in the north polar region
by Ken Edgett
(2003) **SELF ARCHIVED PDF AVAILABLE HERE**
K. S. Edgett, R. M. E. Williams, M. C. Malin, B. A. Cantor, and P. C. Thomas
Geomorphology, 52(3–4), 289–297. doi:10.1016/S0169-555X(02)00262-3
Lithology and physical properties of strata exposed at the Earth's surface have direct influence on the erosion and... more Lithology and physical properties of strata exposed at the Earth's surface have direct influence on the erosion and geomorphic expression of landforms. While this is well known on our planet, examples on Mars are just coming to light among the tens of thousands of airphoto-quality images (resolutions 1.5–12 m/pixel) acquired since 1997 by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). Specific examples occur among martian north polar layered materials, which MOC images reveal are divided into two distinct stratigraphic units: a lower, dark-toned layered unit and a younger, upper, lighter-toned layered unit. The lower unit is less resistant to wind erosion than the upper unit. The upper unit most likely consists of stratified dust and ice, while the lower unit contains abundant, poorly cemented sand. Sand is more easily mobilized by wind than dust; the lower resistance to erosion of the lower unit results from the presence of sand. Where wind erosion in polar troughs has penetrated to the lower unit, geomorphic change has proceeded more rapidly: sand has been liberated from the lower unit, and arcuate scarps have formed as the upper unit has been undermined. Wind erosion of the lower unit thus influences the geomorphology of the north polar region; this result likely explains the genesis of the large polar trough, Chasma Boreale, and the relations between dunes and arcuate scarps that have puzzled investigators for nearly three decades. The properties of the stratigraphic units suggest that the upper limit for the amount of water contained in the north polar layered materials may be 30–50% less than previously estimated.
Strengthening of North American dust sources during the late Pliocene (2.7 Ma)
by David Naafs
Published in Earth and Planetary Science Letters
Here we present orbitally-resolved records of terrestrial higher plant leaf wax input to the North Atlantic over the... more
Here we present orbitally-resolved records of terrestrial higher plant leaf wax input to the North Atlantic over the last 3.5 Ma, based on the accumulation of long-chain n-alkanes and n-alkanl-1-ols at IODP Site U1313. These lipids are a major component of dust, even in remote ocean areas, and have a predominantly aeolian origin in distal marine sediments. Our results demonstrate that around 2.7 million years ago (Ma), coinciding with the intensification of the Northern Hemisphere glaciation (NHG), the aeolian input of terrestrial material to the North Atlantic increased drastically. Since then, during every glacial the aeolian input of higher plant material was up to 30 times higher than during interglacials. The close correspondence between aeolian input to the North Atlantic and other dust records indicates a globally uniform response of dust
sources to Quaternary climate variability, although the amplitude of variation differs among areas. We argue that the increased aeolian input at Site U1313 during glacials is predominantly related to the episodic appearance of continental ice sheets in North America and the associated strengthening of glaciogenic dust sources. Evolutional spectral analyses of the n-alkane records were therefore used to determine the dominant
astronomical forcing in North American ice sheet advances. These results demonstrate that during the early Pleistocene North American ice sheet dynamics responded predominantly to variations in obliquity (41 ka), which argues against previous suggestions of precession-related variations in Northern Hemisphere ice sheets during the early Pleistocene.
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Short-lived and long-lived dust devil tracks in the coastal desert of southern Peru
by Ralf Hesse
Hesse, R. 2012. Short-lived and long-lived dust devil tracks in the coastal desert of southern Peru. Aeolian Research 5: 101-106. doi:10.1016/j.aeolia.2011.10.003
In the coastal desert of southern Peru, sequential high-resolution satellite images document the presence of... more In the coastal desert of southern Peru, sequential high-resolution satellite images document the presence of short-lived and long-lived dust devil tracks. Dust devil tracks in the study region remain visible for less than 6 months in one area and for more than 4 years in another area. Short-lived tracks are generally darker than the surrounding ground surface. The brightness of long-lived tracks is often equal to that of their surroundings; they become visible due to a brighter edge along their margins. Different modes of formation related to ground surface properties are suggested to explain the differences in persistence and appearance. Dark, short-lived dust devil tracks are ascribed to the removal of silt-sized material from largely sand-sized surface materials. Long-lived tracks with bright margins are ascribed to coarser surface materials and the fallout of sand-sized particles along the track edges. Locating suitable areas on Earth for the study of dust devil tracks and distinguishing between different types of dust devil tracks is expected to further promote terrestrial analogue studies for Martian dust devil streaks.
Late Pleistocene aeolian reactivation downwind of the Naracoorte East range, South Australia
Fitzsimmons, K.E., Barrows, T.T. (2012) Late Pleistocene aeolian reactivation downwind of the Naracoorte East range, South Australia. Zeitschrift für Geomorphologie 56(2), 225-237.
Southeastern South Australia, straddling the coastal zone and semi-arid desert margins of the lower Murray-Darling... more Southeastern South Australia, straddling the coastal zone and semi-arid desert margins of the lower Murray-Darling Basin, provides an important record of landscape response to past environmental change during the Pleistocene. Previous research in the region has focussed either on the coastal barrier systems, which formed during interglacial periods, or the sub-parabolic and linear dune systems downwind, which generally formed under arid conditions out of phase with the strandlines. However, the geomorphologic and chronological relationship between these two systems is poorly understood. This study provides the first constraints on the initation of dune development downwind of the Naracoorte East strandline. In this preliminary study we show that aeolian deposition at Naracoorte was constrained by sediment supply from the strandline upwind, and was most likely gradual, more or less continuous, and took place under relatively arid climatic regimes. We demonstrate a genetic link between strandlines and the dune fields in the region.
Do swarms of migrating barchan dunes record paleoenvironmental changes?--A case study spanning the middle to late Holocene in the Pampa de Jaguay, southern Peru
by Ralf Hesse
Hesse, R., 2009. Do swarms of migrating barchan dunes record paleoenvironmental changes? – A case study spanning the middle to late Holocene in the Pampa de Jaguay, southern Peru. Geomorphology, 104, 185-190.
Swarms of barchan dunes are common in arid environments. Unlike immobile or slowly moving dunes whose stratigraphy can... more Swarms of barchan dunes are common in arid environments. Unlike immobile or slowly moving dunes whose stratigraphy can be used to reconstruct paleoenvironmental changes, the high migration rate of barchans seems to prohibit their use as geoarchives. In this paper, a possible use of barchan swarms for paleoenvironmental reconstructions is presented. The approach is based on dune migration. In a case study based on 500 dunes in the Pampa de Jaguay aeolian transport corridor in coastal southern Peru, middle to late Holocene changes in the supply of aeolian material are inferred from calculating the time of dune initiation at the coastline. Limitations posed by the assumptions underlying this approach are discussed.
Late Quaternary environments and human occupation in the Murray River Valley of northwestern Victoria
Prendergast, A. L., Bowler, J. M. and Cupper, M. L., 2009. Late Quaternary environments and human occupation in the Murray River Valley of northwestern Victoria. In Fairbairn, A., O’Connor, S., and Marwick, B. (eds.) New Directions in Archaeological Science. Terra Australis 24. p. 55-74.
Using remote sensing to quantify aeolian transport and estimate the age of the terminal dune field Dunas Pampa Blanca in southern Peru
by Ralf Hesse
Hesse, R., 2009. Using remote sensing to estimate aeolian transport rates and the age of the Dunas Pampa Blanca dune field in southern Peru. Quaternary Research, 71, 426-436.
Aeolian dunes are widely used to reconstruct paleoenvironmental conditions. However, terminal dune fields (ergs) in... more Aeolian dunes are widely used to reconstruct paleoenvironmental conditions. However, terminal dune fields (ergs) in the coastal desert of southern Peru – where information regarding Quaternary paleoenvironmental conditions is very limited – have until now not been used for paleoenvironmental reconstructions and the time depth of their accumulation is unknown. Here, different estimates are derived to constrain the time depth recorded in the Dunas Pampa Blanca, a terminal dune field in coastal southern Peru. Dune field age is calculated using the volume of the Dunas Pampa Blanca and (i) recent aeolian transport rate in migrating transverse dunes feeding the Dunas Pampa Blanca (derived from digital processing of sequential Landsat and Quickbird images) and (ii) limitations posed by recent fluvial sediment supply to the source of aeolian transport. The resulting maximum age estimate of 70±8 ka (from aeolian transport) compares with a minimum age estimate of 4–75 ka (from sediment supply). However, a minimum age estimate of 110–450 ka is deduced from the tectonic and topographic evolution of the region. This discrepancy contradicts the hypothesis of late Quaternary stability in the Peruvian coastal desert and indicates that recent conditions of aeolian sediment supply and transport are not representative for the late Quaternary.
Geology and Geomorphology of Coral Pink Sand Dunes State Park, Utah
For a reprint copy, please contact: kathleen.nicoll@gmail.com
Citation: Richard L. Ford, Shari L. Gillman, David E. Wilkins, William P. Clement, and Kathleen Nicoll, 2010. "Geology and Geomorphology of Coral Pink Sand Dunes State Park, Utah," in Geology of Utah’s Parks and Monuments: 2010 Utah Geological Association Publication 28 (third editiion), D.A. Sprinkel, T.C. Chidsey, Jr., and P.B. Anderson, editors.
ABSTRACT Coral Pink Sand Dunes State Park, located in southwestern Kane County, Utah, contains a variety of geologic... more
ABSTRACT Coral Pink Sand Dunes State Park, located in southwestern Kane County, Utah, contains a variety of geologic features, including one of the largest areas of freely migrating dunes in the Colorado Plateau. The semiarid climate, strong prevailing southerly winds, sparse vegetation, and abundant supply of sand-sized sediment make this area susceptible to eolian processes. Picturesque exposures of Jurassic rocks are present within the park. The stratigraphic sequence ranges from the Triassic-Jurassic Moenave Formation to the Middle Jurassic Carmel Formation. The most widespread bedrock unit exposed within the park is the Navajo Sandstone (Lower Jurassic). The Navajo Sandstone is also widely exposed across the Moccasin Terrace southwest of the park and is the most likely source for the sand that comprises the dune field. The “coral pink” color of the dune sand is the result of iron-oxide stains on the surface of the sand grains inherited from the source sandstones.
Migrating dunes, whose morphology is primarily a function of wind characteristics, include transverse ridges, barchanoid ridges, and a solitary star dune. Dunes influenced or impeded by topographic obstacles or vegetation include climbing dunes, echo dunes, parabolic dunes, vegetated linear dunes, and nebkhas. We divide the dune field into major geomorphic units based on the dominant dune type. A largely stabilized (vegetated) sand sheet and partially stabilized, poorly organized dunes are present at the southern (upwind) end of the dune field. The active core of the dune field contains transverse ridges and barchanoid ridges. Barchanoid ridges at the northern (downwind) end of the active core grade into climbing dunes that ramp up the bedrock escarpment associated with the Sevier fault. The climbing dunes in turn grade into large parabolic dunes that dominate the downwind end of the dune field.
Coral Pink Sand Dunes lies within the structural transition zone between the Great Basin section of the Basin and Range province to the west, and the core of the Colorado Plateau to the east. The north-south-trending Sevier fault cuts through the length of the park. The fault trace is marked by a west-facing bedrock escarpment that divides the park into two topographic units (a forested plateau to the east and a relatively low-lying valley floor to the west) and acts as a major control over the accumulation of sand within the dune field.
Important events recorded in the geologic features of the park include the Triassic and Jurassic depositional history of the Glen Canyon Group, the Cretaceous to Cenozoic structural history of the Colorado Plateau, and the late Holocene history of the active dunes. Optically stimulated luminescence dates from the active core of the dune field indicate that Holocene eolian deposition began at least 4,000 years ago. Radiocarbon dating of organic materials from an exhumed soil surface suggests a period of landscape stability approximately 500-200 years ago, coincident with the Little Ice Age. Dendrochronologic data from the ponderosa pines in the park, along with historic photos, indicate the dunefield has experienced alternating wet periods and drought since the end of the Little Ice Age, which have influenced vegetation coverage and dune activity in the area.
Wind Regimes and Aeolian Transport in the Great Basin, U.S.A.
--> Citation Jewell, P. W. and Nicoll, K. 2011. Wind Regimes and Aeolian Transport in the Great Basin, U.S.A. Geomorphology 129: 1-13. doi: 10.1016/j.geomorph.2011.01.005
ABSTRACT The modern Great Basin of the interior western United States is characterized by surface winds with... more
ABSTRACT The modern Great Basin of the interior western United States is characterized by surface winds with considerable spatial and temporal variabilities. Wind records from the second half of the 20th century for 12 Great Basin localities, analyzed with standard aeolian-sediment transport methods developed elsewhere in the world, reflect this complexity. The drift potential (DP) for aeolian deposits is generally moderate (DP 200– 400) in the western Great Basin and weak (DP b 200) in the central Great Basin where winds are
predominantly west-southwesterly. DP is relatively high (DP N 300) at the eastern edge of the Great Basin where the dominant prevailing wind direction is south-southwesterly. Both DP and resultant drift direction (RDD) are consistent with synoptic meteorological observations of the evolution of cold fronts in the Great Basin. Meteorological observations show that effective winds to produce dunes are most commonly the result of late winter–early spring cyclogenesis. There has been considerable temporal variability of DP in the latter half of the 20th century. Most of the Great Basin has experienced decreasing wind strength since 1973, consistent with recent studies of wind strength in North America and elsewhere. Dune morphology matches both localized RDD and temporal variations in DP reasonably well in the Great Basin. The results demonstrate that local topography can have an important influence on wind directionality, thus providing a cautionary note on the interpretation of dune morphology in the paleoclimatic and stratigraphic record.
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Blowout evolution in a coastal dune: using GPR, aerial imagery and core records
R. González-Villanueva†, S. Costas ‡, H.Duarte‡, M.Pérez-Arlucea† and I. Alejo †
Journal of Coastal Research SI 64 278 - 282 ICS2011 (Proceedings) Poland ISSN 0749-0208
The aim of this work is to present the results of GPR surveys from a large trough blowout and a saucer blowout... more
The aim of this work is to present the results of GPR surveys from a large trough blowout and a saucer blowout associated to an energetic shoreline in a temperate- humid coastline (NW of Spain Traba sedimentary complex), cross-validated with core data and field exposures. Finally, to relate the sedimentological information obtained from the interpreted reflection profiles to the geomorphological development of the blowouts, as revealed by
aerial photographs and other evidences. GPR can provide i8nsights into the internal stratigraphy of a blowout dune; this linking with aerial imagery provides a suitable tool. The pre-blowout dunes, in which the blowouts are developed, presented a similar radar facies and corresponded with sequences of the accretionary state of the dune complex. They overlie older deposits consisting of gray sands with organic-rich humic horizons, showing wetter conditions. The combination of different factors, such as previous topography, winds and wave erosion of
foredunes and changes in vegetation cover, are the driving force to the initiation of blowouts. A detailed study of 2D/3D GPR surveys indicates that the internal sedimentary structure of the depositional lobe is more complicated than expected, and this pattern appears related mainly to changes in the vegetation cover. The results show how much the direction of blowouts migration is dependent on changes in near-surface wind flows
due to the presence/absence of vegetation
Roberts, D., Murray-Wallace, C.V., Bateman, M.D., Carr, A.S., Holmes, P.J. (2008) Fossil elephant trackways, sedimentation and diagenesis in OSL/AAR-dated Late Quaternary coastal aeolianites: Still Bay, South Africa. Palaeogeography Palaeoclimatology Palaeoecology 257, 261-279
by Andy Carr
The impressive Pleistocene coastal aeolianite exposures in sea cliffs east of Still Bay on the west–southern coast of... more
The impressive Pleistocene coastal aeolianite exposures in sea cliffs east of Still Bay on the west–southern coast of South Africa host a rich archive of fossil mammalian trackways, including the African elephant (Loxodonta africana). Neither the ichnofossils nor their host sediments have been described in any detail and chronologies remained uncertain. This paper presents a new optically stimulated luminescence (OSL) and amino acid racemisation (AAR) chronology (the first joint application of OSL/AAR dating in South Africa). This provides a temporal framework for assessing the palaeoenvironmental significance of dune sedimentation patterns, pedogenesis and ichnology.
The Pleistocene aeolianite exposures at Still Bay represent the recently eroded remnants of a dune cordon, mainly built by coalesced parabolic dune systems. Sedimentary facies are dominated by large-scale planar cross-stratification formed by foreset progradation in the nose and trailing arms of the dunes and low-angle bedding, chiefly representing sedimentation in low relief interdune terrain. The main dune building wind regime was westerly, associated with cyclonic polar frontal systems (as at the present time). The OSL and AAR dating demonstrate ages ranging from MIS 5e to 5b and termination of Pleistocene aeolian sedimentation at 90 ka. The Pleistocene aeolianite is separated from the overlying Holocene dunes (dated to 8 ka), by a major hiatus recorded by a horizon of intense pedogenesis.
Elephant footprints were seen in profile, as casts on the underside of beds and as natural impressions. The taphonomic processes controlling the morphology and preservation of these unique ichnofossils were found to be complex. The presence of Loxodonta africana at Still Bay represents the southernmost occurrence of this species recorded to date and possibly, a closer proximity of woodland during MIS 5. This and other observations may indicate a higher moisture regime than at present. There is no available evidence that the elephants were predated by contemporary Middle Stone Age people.
Carr, A.S., Bateman, M.D., Holmes, P.J. (2007) Developing a 150 ka luminescence chronology for the barrier dunes of the southern Cape, South Africa. Quaternary Geochronology 2, 110-116
by Andy Carr
The southern coastline of South Africa exhibits extensive aeolianites and spectacular barrier dunes; the ages and... more
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 De distributions. Results indicate that the SAR protocol is providing accurate and precise De 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 De's. Single grain De 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.
Bateman, M.D., Carr. A.S., Holmes, P.J., Dunajko, A., McLaren, S.J., Marker, M.E., Roberts, D.L, Murray-Wallace, C.V., Bryant, R.G. (2011) The evolution of barrier dune systems: A case study of the Middle-Late Pleistocene Wilderness barrier dunes, South Africa. Quaternary Science Reviews 30, 63-81
by Andy Carr
Barrier systems contain lengthy, but complex, records of long-term environmental fluctuations. The Wilderness... more Barrier systems contain lengthy, but complex, records of long-term environmental fluctuations. The Wilderness embayment, South Africa, contains a system of shore-parallel barriers reaching up to 200 m above modern sea level. This study reports the results of chronological, topographical (both on- and off-shore), sedimentological and micromorphological analyses within the Wilderness embayment. Sixty-one new luminescence ages from sixteen sites in unconsolidated dunes and three separate barriers are presented which, when combined with previously published luminescence ages from the area, provide a high-resolution chronological framework for the emplacement and evolution of the barrier system. The preserved barriers have been constructed within at least the last two glacial–interglacial cycles with notable phases between 241–221 ka, 159–143 ka, 130–120 ka, 92–87 ka and post 6 ka. Multiple phases of barrier construction occurred during sea-level highstands, with sediment deposition on each individual barrier occurring over at least two interglacials. Holocene evolution of the system sheds light on earlier events, with dune preservation occurring only during early regression from the Mid-Holocene highstand. Tectonic stability at Wilderness allowed glacio-eustatically formed shorelines to occupy similar positions on multiple occasions. This, in conjunction with a relatively humid climate and a well-vegetated landscape, enabled deflated sediment from beaches to form dunes which stacked upon each other to form an extensive and complex vertical accretionary sequence. Repeated erosion and recycling of pre-existing barriers as well as barrier construction on what is currently the off-shore platform during still-stands in sea-level regressional cycles, when sea levels dropped below ca −50 m from the present day, has added to the complexity of the preserved terrestrial barrier record. The Wilderness barrier system contrasts with barriers developed elsewhere in the world where higher rates of crustal uplift have allowed preservation of a more complete and more widely spaced palaeorecord. This research also shows the utility of integrating off-shore topography as revealed by bathymetry, with terrestrial topographic data for the better understanding of the evolution of palaeo-coastlines and the preserved dune record found on present-day coastal plains. Local variation in the topography of the continental shelf at Wilderness has generated spatial and temporal complexity within the sedimentary records of individual barriers as well as having a significant influence on preservation.
Relationships between desert dunes during the late Quaternary in the Lake Frome region, Strzelecki Desert, Australia
Fitzsimmons, K.E., Bowler, J., Rhodes, E., Magee, J. (2007) Relationships between desert dunes during the late Quaternary in the Lake Frome region, Strzelecki Desert, Australia. Journal of Quaternary Science 22(5), 549-558
Transverse and linear dunes near the ephemeral Lake Frome in the Strzelecki Desert of Australia provide evidence for a... more Transverse and linear dunes near the ephemeral Lake Frome in the Strzelecki Desert of Australia provide evidence for a genetic geomorphic relationship between desert dune types. Transverse dunes, overlying palaeoshorelines, lie upwind from linear dunes. The sedimentology of both dune types is similar, suggesting reworking or downwind transport of the same source material over time. Clay pellets from several horizons within the linear and transverse dunes provide evidence for fluctuating water tables and high evaporation rates during those periods of aeolian activity, along with salt influx associated with the deflation of Lake Frome. We conclude that the nature and initiation of dune activity is controlled not only by aridity, but by local hydrology. OSL ages from both transverse and linear dunes indicate aeolian activity at 66-57ka and 22-11ka. Transverse dune building took place around 106-111ka. Linear dune activity initiated at least 66ka ago, with reactivation around 43-28ka, followed by pedogenesis in response to humid conditions. Widespread dune reactivation from around 22ka correlates broadly with the Last Glacial Maximum and late glacial period, consistent with evidence of cold, arid conditions and dune activity in Australia.
Understanding linear dune chronologies: Insights from a simple accumulation model.
by Abi Stone
A co-author of this paper published in 2010 in Geomorphology 120(3-4), 195-208.
Authors are Telfer, M. W., Bailey, R. M., Burrough, S. Stone, A. E. C., Thomas, D. S. G., Wiggs, G. S. F.