humid to arid to subhumid vegetation shift on pilliga sandstone ulungra springs new south wales abstract the pilliga sandstone region of the northwest slope of new south wales has a natural vegetation cover of sclerophyllous relatively closed to open forests with a largely heathy understorey and a warm subhumid and continental climate pollen analysis of spring fed deposits gives a vegetation history extending from at least 30 000 yr b p to the late holocene tree pollen became scarce after about 25 000 yr b p and an assemblage dominated by chenopodiaceae liguliflorae tubuliflorae and probably poaceae developed no similar assemblage is known from present pollen rain studies carried out in australia however it clearly represents a treeless open shrub steppe formation and therefore an arid or semiarid environment the site thus provides evidence of an eastward late pleistocene extension of the arid zone in australia and is the first full glacial vegetation record between 20 and 35 latitude in australia the present vegetation cover did not become reestablished until the beginning of the holocene which raises questions about the form in which pilliga sandstone vegetation survived full glacial conditions

late pleistocene glaciation of the kosciuszko massif snowy mountains australia abstract late pleistocene glaciation of the australian mainland was restricted to a small area of the southeastern highlands geomorphic mapping of the area and exposure dating using the in situ produced cosmogenic isotope 10be provides evidence for at least two distinct glaciations the early kosciuszko glaciation consisted of a single glacier advance before 59 300 5400 years ago snowy river advance the late kosciuszko glaciation comprised three glacier advances 32 000 2500 headley tarn advance 19 100 1600 blue lake advance and 16 800 1400 years ago mt twynam advance the early kosciuszko glaciation was the most extensive and the late kosciuszko advances were progressively less extensive these periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern australia glacier advances on the kosciuszko massif correlate with advances in tasmania south america and new zealand and are broadly representative of hemispheric climate changes during the last glacial cycle

palaeoenvironmental change recorded in the palaeodunefields of the western murray basin south australia new data from single grain osl dating this study is concerned with the reconstruction of the palaeoenvironmental history of southeastern australia for the last 300 ka by establishing a luminescence chronology of dune sand deposition in the western murray basin south australia in the study area vast fields of palaeodunes stabilised by vegetation provide evidence of past environmental change in total 98 samples were collected from dune sand layers at 13 different dune sections the time of their deposition was determined using optically stimulated luminescence dating of single quartz grains accounting for the impact of post depositional mixing by the use of a finite mixture model the oldest depositional phase demonstrates that dune sand layers of great antiquity are preserved in the western murray basin ranging up to at least 380 ka phases of substantial dune sand deposition were identified for the periods 18 38 ka and 63 72 ka older depositional phases also exist but are poorly resolved due to relatively large errors of the luminescence ages aeolian deposition during the last termination and the holocene is relatively limited with a slight clustering of ages at the time of the antarctic cold reversal and from 5 8 ka two modern ages give evidence of very recent dune sand deposition comparison with other palaeoclimate records from the region suggests that phases with high aeolian sedimentation coincide with more arid conditions and breaks in the dune record with more humid phases thus although dune records are often discontinuous and their interpretation in palaeoclimatic terms is not always straightforward the palaeodunes of the western murray basin show a good preservation of phases of aeolian activity and provide useful information for palaeoenvironmental reconstruction

the effect of sparse vegetation on the transport of dune sand by wind the precise effect of a sparse plant cover on the transport of dune sand by wind is a critical factor in understanding the morphology evolution and global distribution of aeolian dunes1 3 it is also of considerable practical importance in sand stabilization rehabilitation and restoration ecology here i report the first detailed experimental quantification of this effect using living plants in patterns approximating natural vegetation for wind velocities v at 0 5 m elevation up to 15 m s 1 and plant covercup to 17 the rate of aeolian sand transport q g cm 1 s 1 is closely approximated by q b v 1 kc vt 3 where b is bagnold s constant4 vt is a threshold velocity and k is a constant dependent on plant geometry for typical small erect or spreading herbaceous dune plants k 0 018 for small rounded stemless plants k 0 046

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

a quantitative approach to understanding dated dune stratigraphies attempts to reconstruct past changes in climate related forcing of dryland landscapes are hampered by the lack of an adequate quantitative framework for understanding the production and interpretation of dated sedimentary records in drylands as in other environments information on past forcing conditions is progressively modified degraded and removed from the available stratigraphic record by a series of filters involving changes in the primary forcing factors themselves geomorphological processes and the sampling dating procedures in this paper we describe a quantitative model that includes these effects and use the model to examine the nature of preserved dryland sedimentary records and their relationships to primary forcing conditions thicker preserved sedimentary records reflect periods of more intense aeolian activity localized switching between erosion and deposition results in discontinuous and highly variable stratigraphic sequences a preservation bias towards younger deposits is observed potentially leading to a continuum of accumulation that decays approximately in proportion to time periods not represented by deposition can in some cases be interpreted as periods of higher precipitation and or lower wind energy an asymmetry exists between the efficiency with which past drier and wetter episodes can be identified which relates to the time separation of depositional periods and the correct distinction between hiatuses due to forcing conditions and those due to under sampling relevant to this is the effect of random dating errors statistical uncertainty which increasingly with age filter out higher frequency events from the record a new data treatment method termed accumulation rate variability provides an efficient proxy for accumulation rates and therefore the intensity of aeolian activity with significant improvements over existing date frequency methods the filtering problem discussed applies to all attempts at understanding the timing and nature of past events independent of the proxies and dating methods employed further explicit analysis of these issues would be beneficial copyright 2013 john wiley sons ltd

the fire human and climate nexus in the sydney basin eastern australia it is widely believed that australian aborigines utilized fire to manage many landscapes however to what extent this use of fire impacted on australia s ecosystems remains uncertain the late pleistocene holocene fire history from three sites within the sydney basin gooches swamp lake baraba and kings waterhole were compared with archaeological and palaeoclimatic data the gooches swamp record appeared to be most influenced by climate and there was an abrupt increase in fire activity from the mid holocene perhaps associated with the onset of modern el nino dominated conditions the kings waterhole site also displayed an abrupt increase at this time however there was a marked decrease in charcoal from 3 ka similarly lake baraba displayed low levels of charcoal in the late holocene at both kings waterhole and lake baraba archaeological evidence suggests intensified human activity in the late holocene during this period of lower and less variable charcoal it is hence possible that aboriginal people strongly influenced fire activity in some areas of the sydney basin during the late holocene perhaps in response to the increased risk of large intense fires as an enso dominated climate became more prevalent the fire his tory within the sydney basin varies both temporally and spatially and therefore it is inappropriate to apply a single fire regime to the entire region for landscape management this work also has implications for future fire incidence associated with climatic variability under an enhanced greenhouse effect

factors determining desert dune type while most observers recognize four elemental types of desert dunes longitudinal transverse barchan and star1 3 there is little agreement about which factors determine these types the angular relationships between the resultant of sand shifting winds and both the crest and principal slipfaces of the elemental types have been discussed qualitatively for many decades these relationships have been quantified but the wide range of dune types that combine the elemental forms and the juxtaposition of different dune types show that wind regime is not the only determinant for example sand availability has been considered important we have now quantified the importance of both wind regime and sand availability as determinants of dune type we show here that the four elemental types occur in areas uniquely defined by both the equivalent sand thickness of sediments held in the dunes and a measure of directional variability of sand moving winds wind strength does not appear to be important vegetation has an ambiguous role and the particle size of dune sediments is unimportant

is there evidence for global scale forcing of southern hemisphere quaternary desert dune accumulation a quantitative method for testing hypotheses of dune system development luminescence dating of desert dune sediments has generated many hundreds of ages many used in reconstructions of quaternary environmental changes others in attempts to elucidate dune processes environmental and climatic interpretations of these records have proved problematic and it remains challenging to test hypotheses of the systematic response of dunefields to changes in external forcing in the past and to make predictions of the future we use a method that quantifies dune sediment accumulation to interpret dune luminescence age datasets rather than simply using the ages themselves as proxies of change the accumulation intensity method allows periods of dune sediment accumulation here over the timescale 102 105 years to be identified from compilations of dated sand sea stratigraphic sequences we apply this approach to two of the largest dune age datasets from southern africa and australia testing whether or not dunefield accumulation has co varied in the late quaternary and whether systematic relationships to external drivers at global hemispheric regional and local scales can be identified

reconstructing palaeoenvironments on desert margins new perspectives from eurasian loess and australian dry lake shorelines abstract desert margins preserve evidence of more extensive arid conditions in the past and represent global hot spots with respect to climate change the balance of scientific evidence now suggests that dryland landscape reactivation did not correspond simply to ice age aridity peaks as previously assumed this paper provides a new perspective on and more nuanced understanding of desert marginal landscapes as palaeoenvironmental archives the two case studies represent ends of a sediment availability spectrum both environments experience substantial spatial and temporal variability in deposition with implications for reconstructing past environments at individual sites recently generated chronostratigraphic data from the dry subhumid dobrogea loess romania are synthesised to provide quantitative insights into the spatial and temporal organisation of loess plateaux loess accumulation peaks during the lgm and mis4 but not at all sites accumulation rates vary substantially between sites comparison of geographical context yields no clear driving mechanism for this variability secondly two transverse lunette dunes in semi arid willandra lakes australia yield comparable chronostratigraphies and distribution of stratigraphic units a first attempt is made to identify changes in wind regime through time on the australian desert margins and suggests that high latitude climate forcing may have acted upon semi arid australia over millennial scales the novel perspectives generated from the new datasets provide unprecedented insights into past climate circulation and land surface processes along desert margins these new perspectives coupled with the new geochronological and quantitative palaeoclimate proxy tools now available represent the next frontier for palaeoenvironmental research on desert margins

last glacial maximum dune activity in the kalahari desert of southern africa observations and simulations abstract it has long been understood that as ephemeral landscape features sand dunes are highly sensitive to environmental change and thus their distribution and the timing of their development may provide clues to past climate dynamics the relationship between climate and dune activity however is neither simple nor straightforward with a range of controls affecting the balance between erodibility the availability of sediment for deflation and erosivity the potential for sediment transport to explore such complex systems over large spatial and temporal scales a number of dune activity indices dai have been created that incorporate wind speed and moisture balances to calculate the potential for and degree of dune mobilisation using modern weather station data these indices have generally been shown to provide reasonable indications of dune activity potential until recently however the detailed quantitative data required to inform these equations has not been available for past climate scenarios and attempts to determine the relative importance of the various controls of dune activity have relied on rough estimations of climatic parameters this paper combines data from monthly general circulation model gcm outputs from the coupled ocean atmosphere gcms for 21 ka with the most detailed dai equation presently available to calculate the potential for dune reactivation in southern africa during the last glacial maximum lgm 18 24 ka based on these data and calculations it is indicated that there was significantly less potential for dune activity across southern africa at 21 ka when compared to the aeolian sediment records from the region this study poses serious and fundamental questions about 1 the reliability of the model outputs 2 the degree to which dais are able to account for the complexity and dynamics of aeolian systems and or 3 the interpretation of dune records as palaeoclimatic proxies at millennial time scales

last glacial coastal dunes in eastern australia and implications for landscape stability during the last glacial maximum abstract the last glacial maximum or lgm 25 000 15 000 yr b p has been recognized in australia as a period of increased dryness coolness continentality and windiness compared to earlier and later period enhanced aeolian activity during the lgm occurred in arid and semi arid regions of western central and eastern australia the east coast has been considered to have been better watered and vegetated however at a number of sites from tasmania to north queensland there is evidence for extensive aeolian instability of coastal sand deposits dating by radiocarbon and thermoluminiscence techniques has supported morphologic and stratigraphic evidence of dune formation during the lgm under the influence of westerly offshore winds in the southern sector of the east coast i e south of 31 s latitude and southeast winds to the north it is now apparent that vegetation cover on sandy surfaces was quite patchy during the lgm sand surface instability under conditions of strong west or southeast winds promoted linear and or parabolic dune development this suggests greater concentration of forests in more discrete protected sites along the eastern escarpment than was previously considered by palaeoecologists more widespread drier and cooler climatic conditions operated even in coastal regions on expanded continental shelves at this time stabilization of areas of active dunes became more likely as sea levels rose reduced windiness occurred and precipitation increased as sea surface temperatures began to rise in the holocene

last glacial maximum to early holocene wind strength in the mid latitudes of the southern hemisphere from aeolian dust in the tasman sea dust transported by southern hemisphere mid latitude westerly winds from australia and deposited in the tasman sea shows no evidence for stronger winds during the last glacial maximum lgm compared to the holocene features of the particle size distributions of the dust do however indicate enhanced dry deposition of dust in the lgm changing to rainfall scavenging during deglaciation and the early holocene as climate ameliorated from these results it appears that activation of desert dunefields over 40 of australia during the lgm was the result of a reduction in stabilizing vegetation and more frequent episodes of sand movement rather than of increased wind strength the lgm climate of inland australia must have been considerably more stressful for plants as a result of lower precipitation and or carbon dioxide stress to achieve the implied levels of surface destabilization enhanced atmospheric dust loads in the southern hemisphere and deposition over antarctica were most likely the result of greatly expanded source areas in the mid latitude southern continents and a weaker hydrological cycle rather than greater entrainment or more efficient transport by stronger winds during the lgm wind strength appears to have varied regionally and predominantly in high latitudes rather than uniformly for all zonal winds

slope aspect slope length and slope inclination controls of shallow soils vegetated by sclerophyllous heath links to long term landscape evolution abstract on upland triassic sandstone slopes of the western blue mountains nonswamp sclerophyllous heath shrub dominated vegetation on shallow soils is commonly found downslope and adjacent to sclerophyllous forest on deeper soils some consider heath and thus shallow soils as favouring west facing slopes which are expected to experience drier microclimates due to insolation strong and desiccating winds and severe summer fires however our analysis of extensive areas with heath on shallow soils based on vegetation and topographic maps and fieldwork of uplands with various degrees of dissection suggests that aspect is a poor predictor of shallow soils rather shallow soils and heath are found on short slopes and the lower segments of longer slopes with the latter significantly steeper than forested segments the shallow deep soil boundary marked by contrasting modern vegetation structures does not signify a catchment area threshold and correspondingly the vegetation patterns are not in balance with distributary catchment processes as short slopes are mantled exclusively by shallow soils instead the soil depth boundary represents the propagation of base level lowering signals which takes place not only by the headward retreat of knickpoints but also via increased lowering of slope segments adjacent to drainage lines this leads to steep slopes immediately adjacent to canyons narrow gorges and small steep valleys that are mantled by shallow discontinuous soils undergoing rapid erosion these steep slopes persist in the landscape for 10 my after upland stream rejuvenation until incision of more weatherable permian sediments underlying the triassic cliff forming sandstones triggers rapid lateral expansion of gorges once shallowly mantled and steeper slopes adjacent to streams are consumed by gorge widening slopes adjacent to wide gorge clifflines reflect former upland drainage patterns rather than the redirected flow to rapidly widening gorges hence modern vegetation patterns reflect a significant phase of landform development perhaps combined with enhanced erosion during the last glacial period that is compounded by a humped soil production function on bedrock

wind tunnel modelling of the influence of vegetation structure on saltation threshold the influence of vegetation structure on saltation threshold was investigated using uniformly spaced arrays of non erodible roughness elements on a bed of erodible sand in an wind tunnel structural variables tested using arrays of solid cylinders included element aspect ratio height diameter and lateral cover total frontal silhouette area per unit ground area in agreement with previous studies increase in saltation threshold above the value for bare sand was strongly related to lateral cover increasing aspect ratio from 0 25 to 4 tended to enhance the increase in saltation threshold at a given lateral cover an approximate fit to the results could be obtained using a relation proposed by raupach et al journal of geophysical research 1993 98d 3023 3029 porous elements were constructed as clusters of narrow vertically oriented cylinders model stems forming porous model plant bodies that were cylindrical in overall shape low porosity elements were found to be approximately 50 per cent more effective in increasing saltation threshold than either solid or high porosity elements the ratio of plant body frontal silhouette area based on overall dimensions to total stem frontal silhouette area was found to be a useful measure of plant body porosity for wind erosion studies some conventional measures of vegetation amount fail to account for changes in vegetation structural attributes that may strongly influence aeolian processes

the timing of linear dune activity in the strzelecki and tirari deserts australia abstract linear dunes occupy more than one third of the australian continent but the timing of their formation is poorly understood in this study we collected 82 samples from 26 sites across the strzelecki and tirari deserts in the driest part of central australia to provide an optically stimulated luminescence chronology for these dunefields the dunes preserve up to four stratigraphic horizons bounded by palaeosols which represent evidence for multiple periods of reactivation punctuated by episodes of increased environmental stability dune activity took place in episodes around 73 66 35 32 22 18 and 14 10 ka intermittent partial mobilisation persisted at other times throughout the last 75 ka and dune activity appears to have intensified during the late holocene dune construction occurred when sediment was available for aeolian transport in the strzelecki and tirari deserts this coincided with cold arid conditions during marine isotope stage mis 4 late mis 3 and mis 2 and the warm dry climates of the late pleistocene holocene transition period and late holocene localised influxes of sediment on active floodplains and lake floors during the relatively more humid periods of mis 5 also resulted in dune formation the timing of widespread dune reactivation coincided with glaciation in southeastern australia along with cooler temperatures in the adjacent oceans and antarctica

lateral migration thermoluminescence chronology and colour variation of longitudinal dunes near birdsville in the simpson desert central australia the longitudinal dunes of the simpson desert in the vicinity of birdsville have been reworked largely during the holocene from dunes deposited up to 80000 years ago or earlier the widespread asymmetry of these roughly northward trending dunes with steeper eastern faces and more gentle western faces supports wind rose data showing sand transporting winds from the southwest obliquely intersecting the dunes while this suggests a change in the wind pattern since the dune field was oriented it does not indicate that the dunes are necessarily shifting leeward eastward as a consequence it is hypothesized that the direction of migration is controlled by the extent to which the dunes are vegetated relatively well vegetated dunes can accrete sand on their gentle stoss slopes and erode on their lee slopes causing them to shift westward and hence obliquely into the wind a condition that probably prevails in wetter regions and during episodes of relatively humid climate in contrast in very dry areas or during arid phases sand can move unimpeded up a sparsely vegetated stoss face and over the crest to form an avalanche or slip face on the lee side thereby causing the dunes to shift eastward despite evidence that longitudinal dune crests can shift laterally to some extent the dunes in the western part of the simpson desert have not migrated either westward or eastward more than 100m or so from their pleistocene cores aeolian transport and partial or complete removal of iron cutans from around quartz grains results in dunes of widely varying colour yet of similar age

sr nd isotope and trace element geochemistry of late variscan volcanism in the pyrenees magmatism in post orogenic extension abstract we obtained sr nd isotope and trace element data on late variscan volcanic rocks in the pyrenees felsic lavas and andesites from the ossau and the serra de cadi massifs and calc alkaline andesites and alkali basalts from the la rhune and the anayet volcanic massifs the calc alkaline volcanic rocks have crustal trace element and sr nd isotopic characteristics the andesites probably originated from melting of pan african paragneisses with a limited contribution of mantle derived sources having lithospheric characteristics the andesitic lavas were more or less contaminated in magma chambers by palaeozoic sedimentary rocks which can be interpreted as a recycled proterozoic crust the felsic lavas are principally derived from anatexis of the palaeozoic products the rhyolites providing even peraluminous characteristics the anayet andesites show mantle derived characteristics and are interpreted as a mixture between a strongly undersaturated continental alkali basalt and a peraluminous end member however sr and nd contents rale out any simple process the late anayet alkali basalts show typical asthenospheric sr and nd isotopic characteristics the la rhune basalts exhibit sr and nd sub continental lithospheric isotopic characteristics very similar to those of the triassic pyrenean continental basalts it is thought that the granulite facies metamorphism dated at 310 ma was caused by the ascent of the asthenosphere inducing a thermal anomaly the mafic magmas ascending from the mantle are responsible for the crustal anatexis this results in the emplacement of both the pyrenean composite plutons such as the querigut massif and the ossau volcanic rocks the pyrenean late variscan volcanic rocks were emplaced in either pull apart basins opened by the reactivation of the major variscan pyrenean fault in a distensive setting or better in basins resulting from a post orogenic collapse both these models involve a thinning of the subcontinental lithosphere until its disappearance consequently the inferred mantle derived end member of the anayet lavas which occurs in a post variscan distensive setting clearly derives from the asthenosphere

palaeohydrology of lowland rivers in the murray darling basin australia abstract this study derives a new function describing the relationship of channel bankfull discharge qbf to channel width in modern rivers of the murray darling basin mdb of southeastern australia and applies this to dated palaeochannels of seven rivers to quantify late quaternary discharge history in this important basin all rivers show high mis3 and mis2 qbf declining in the holocene the qbf of modern mdb rivers is correlated with total catchment precipitation but comparison with palaeochannel qbf estimates shows that while enhanced runoff efficiency is necessary to account for much larger late pleistocene palaeochannels either lower or higher precipitation rates could have prevailed a strong association between relative palaeo qbf enhancement and temperature suggests a temperature mediated mechanism controlling river discharge such as the fraction of precipitation stored as snow and thawing in spring the enhancement of orographic rainfall or co2 feedbacks with vegetation cover significantly enhanced mis3 qbf requires an additional mechanism such as increased rainfall these findings are consistent with others that increased moisture availability was associated with past colder climates although this was not necessarily the result of enhanced precipitation

climate variability at the southern boundaries of the namib southwestern africa and atacama northern chile coastal deserts during the last 120 000 yr abstract in this study we present grain size distributions of the terrigenous fraction of two deep sea sediment cores from the se atlantic offshore namibia and from the se pacific offshore northern chile which we unmix into subpopulations and which are interpreted as coarse eolian dust fine eolian dust and fluvial mud the downcore ratios of the proportions of eolian dust and fluvial mud subsequently represent paleocontinental aridity records of southwestern africa and northern chile for the last 120 000 yr the two records show a relatively wet last glacial maximum lgm compared to a relatively dry holocene but different orbital variability on longer time scales generally the northern chilean aridity record shows higher frequency changes which are closely related to precessional variation in solar insolation compared to the southwestern african aridity record which shows a remarkable resemblance to the global ice volume record we relate the changes in continental aridity in southwestern africa and northern chile to changes in the latitudinal position of the moisture bearing southern westerlies potentially driven by the sea ice extent around antarctica and overprinted by tropical forcing in the equatorial pacific ocean

late quaternary linear dune accumulation and chronostratigraphy of the southwestern kalahari implications for aeolian palaeoclimatic reconstructions and predictions of future dynamics abstract the linear dunes of the kalahari now largely inactive have long been identified as having potential palaeoenvironmental significance the application of optically stimulated luminescence osl dating to these dunes in the 1990s provided the first chronology of aeolian accumulation in this region though field methodologies and time consuming multiple aliquot laboratory protocols limited both the depth of sampling in dune bodies and the total number of samples dated in order to permit a more thorough investigation of the potential of these dunes to preserve long chronological records this intensive study presents 71 osl ages from the linear dunes of the southwestern kalahari at witpan south africa sampled with coring equipment at regular and frequent intervals down to bedrock the earliest sand accumulation recorded at witpan is at 104 ka and in spatially discrete locations other evidence of dune activity is recorded at 77 76 57 52 and 35 27 ka although an inherently discontinuous archive the linear dunes of the southwestern kalahari have the potential to record multiple phases of dune construction following the last glacial maximum there is near continuous evidence of dune building with a peak of accumulation recorded from 15 to 9 ka at five individual sites this latter period is generally recognised from other proxy evidence as being unusually arid in this region and such periods of dune activity are likely to be related to intensification of the continental anticyclone during the holocene accumulation has continued at most sites sampled albeit at a lesser intensity this may imply that these dunes are presently not far from thresholds of activation

sticky dunes in a wet desert formation stabilisation and modification of the australian desert dunefields independent dating evidence and dune morphology indicate great stability of the australian dunefields most dunefields have seen only minor superficial modification since they were formed up to 1 million years ago despite quite large changes in climate conditions this stability may be partly due to the relatively dense vegetation cover on australian dunes under the marginally arid climate but new studies supported by many older observations suggest that sticky dunes where sand grains are bonded or cemented may form under a broader range of wind climates than widely thought and have greater resistance to reworking new mapping of the australian continental dunefields from satellite imagery shows a previously unrecognised diversity of dune morphologies dune orientation continuity connectedness crest planform crest sharpness spacing and setting all show patterns of variation over the continent these are consistent with the overall low sand supply and variable wind climate that contribute to the dominance of longitudinal dunes but also with only superficial modification of the dunes after their initial formation the longevity of the dunes is likely also partly due to the stabilisation of dune sand by pedogenesis the bonding of sand by pedogenic calcium carbonate gypsum silica and translocated clays the extremely low mobility of the sand dunes has led to preservation of dunes of great age with stacked accretionary units and multiple palaeosols

climate variability over the last 35 000 years recorded in marine and terrestrial archives in the australian region an oz intimate compilation abstract the australian region spans some 60 of latitude and 50 of longitude and displays considerable regional climate variability both today and during the late quaternary a synthesis of marine and terrestrial climate records combining findings from the southern ocean temperate tropical and arid zones identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35 000 years climate drivers include the seasonal timing of insolation greenhouse gas content of the atmosphere sea level rise and ocean and atmospheric circulation changes our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region limiting the usefulness of this approach instead we have taken a spatial approach looking to discern the patterns of change across the continent the data identify the clearest and most synchronous climatic response at the time of the last glacial maximum lgm 21 3 ka with unambiguous cooling recorded in the ocean and evidence of glaciation in the highlands of tropical new guinea southeast australia and tasmania many terrestrial records suggest drier conditions but with the timing of inferred snowmelt and changes to the rainfall runoff relationships driving higher river discharge at the lgm in contrast the deglaciation is a time of considerable south east to north west variation across the region warming was underway in all regions by 17 ka post glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north west of the continent in contrast to the southern latitudes no evidence for cooling during the younger dryas chronozone is evident in the region but the antarctic cold reversal clearly occurs south of australia the holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the holocene giving way to a weakened monsoon and an increasingly el nino dominated enso to the present the influence of enso is evident throughout the southeast of australia but not the southwest this climate history provides a template from which to assess the regionality of climate events across australia and make comparisons beyond our region

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

the australian desert dunefields formation and evolution in an old flat dry continent a new map the first based on interpretation of satellite imagery reveals both the complexityofaustralia sdunefieldsandtheirrelationshipswithtopography climateandsubstrate of the five main sand seas the mallee strzelecki and simpson in eastern australia cover quaternary sedimentary basins whereas the great victoria and great sandy dunefields in the west are formed by reworking of valley and piedmont sediments in a non basinal landscape of low relief ridge and valley topography these dunefields cover large areas of the arid zone and semi arid zone and small areas of dunes in sub humid areas around the margins of the continent reflecting past expansion of arid climates during glacial stages of the last several glacial cycles several areas of low relief stand out as being largely dune free the limestone nullarbor plain clay plains of the georgina basin and floodplains of rivers in the carpentaria lake eyre and murray darling drainage basins where sand is rare or not transported by diminished late quaternary rivers the yilgarn block of southwestern australia is also surprisingly free of dunes possibly as a result of long deep weathering everywhere the history of climate change is evident in dune morphology and distribution including large areas where the sand dune orientations are markedly divergent from modern sand moving wind directions

seasonal variation of crescentic dune morphology and morphometry strzelecki simpson desert australia the general absence of contemporary dune building in the australian arid zone finds the occurrence of crescentic dune genesis and evolution at gurra gurra waterhole a somewhat enigmatic event amongst prevalent inactive linear dunescapes crescentic dune construction is geographically restricted to areas of dominant unidirectional high windiness and minimal vegetation parameters that are generally uncommon in arid australia today the influence of seasonal multidirectional winds can see dune form undergo continual transition between quasi equilibrium and disequilibrium such dynamic antithesis is depicted in seasonal mathematical comparisons of the planimetric attributes length and width dimensional equilibrium is a transient feature at gurra gurra waterhole and not characteristic of this dunescape copyright 2001 john wiley sons ltd

relocating and orientating cores by the integration of electrical and optical images a case study from ocean drilling program hole 735b while the dip of structural features on recovered rotary drilled core can be accurately measured the azimuth of such features in a geographical reference frame is not known scribing techniques and analysis of magnetic signatures have been used in attempts to solve this problem but scribing has so far failed in deep sea drilling operations and magnetic signatures cannot always be easily resolved here we demonstrate a method for core reorientation and accurate location within a borehole using a comparison between borehole electrical images and whole core digital images odp hole 735b penetrates a 1500 m section of lower oceanic crustal gabbroic rocks with an average core recovery of 86 6 the absence of orientated core pieces severely restricts the interpretation of these data in this study the entire outer surface of individual core pieces was scanned using the dmt digital colour corescan system structural features on these unrolled digital images are correlated with images of the same features on formation microscanner logs obtained during the wireline logging programme using this approach it is possible to reorientate and accurately locate core pieces within the drilled section

ecogeomorphic state variables and phase space construction for quantifying the evolution of vegetated aeolian landscapes cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so a model that incorporates the effects of vegetation and its interactions with geomorphic landscape development the discrete ecogeomorphic aeolian landscapes decal model can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments a key challenge in this research area is the analysis and comparison of both simulated and real world vegetated dune landscapes using objective and quantifiable principles this study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes using a suite of mathematically defined landscape metrics to provide a rigorous and statistical evaluation of vegetated dune field evolution within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real world landscapes based on a simplified scenario of parabolic dunes developing out of blow outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types pioneer grass and successional woody shrub by establishing a typological phase diagram of different landscape classes the set of simulation outcomes furthermore defines a higher dimensional phase space whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics or state variables contribute to the data distribution principal component analysis can reduce this to a visual three dimensional 3d phase space where landscape evolution can be plotted as time trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario the use of landscape state variables and the construction of a 3d phase space presented here may provide a general template for quantifying many other eco geomorphic systems on the earth s surface

climatic and vegetation control on sediment dynamics during the last glacial cycle as climate is changing rapidly there is an increasing need to understand how water and soil resources respond to climate change soil and sediment dynamics are sensitive to several external factors such as climate vegetation type and distribution human activity and tectonic activity however the relationship between erosion and changes in these factors is difficult to constrain with current available approaches here we show that uranium isotopes in sediments from river paleochannels can be used to reconstruct variations in the residence time of sediments in a catchment over the past 100 k y we find that sediment residence times increase by an order of magnitude during interglacials compared to glacial periods this is interpreted as a change in sediment stores in the landscape that are tapped by catchment erosion young upland soils during glacial periods reworking of old alluvial sediments during interglacials a direct correlation is found between the sediment residence time and climatic parameters sea surface temperature atmospheric carbon dioxide content and paleorainfall estimates suggesting that during a glacial cycle sediment dynamics closely follow variations in climate however this relationship is not simple because there is no correlation between sediment residence time and paleodischarge estimates because sediment residence time variations correlate with changes in vegetation inferred from pollen data it is hypothesized that the influence of climate on erosion over a glacial cycle may be indirect and operates via the influence of climate on the type of plant ecosystems within a catchment if verified elsewhere this conclusion would emphasize the important role of biology in the physical evolution of earth s surface here observed over a 100 k y time scale

aeolian and fluvial evidence of changing climate and wind patterns during the past 100 ka in the western simpson desert australia abstract sediments near finke in central australia provide evidence of late quaternary evolution and the interaction of aeolian and fluvial systems in response to changing climate in the western simpson desert thermoluminescence tl dating is used to develop a chronology of aeolian and alluvial activity and to identify differences in sand provenance quaternary alluviation in the finke valley at this location occurred at or prior to c 90 ka and with no surviving evidence of subsequent activity until the holocene in contrast to rivers in the eastern part of the lake eyre basin substantial alluviation took place here in the early to mid holocene probably due to reactivation of the northern monsoon and its partial penetration into central australia the regional dunefield near finke consists of linear dunes largely reworked and aligned during the last glacial 30 12 ka as part of the great anticlockwise whorl of dunes in central australia the oldest dated source bordering dunes from the finke river are bright red in colour were deposited at c 100 ka and are now buried beneath paler source bordering dunes the latter consist of two exposed units a lower one of unknown orientation that dates at 17 9 ka and an upper unit aligned to the northwest and parallel to the prevailing winds that dates at 5 0 ka the tl signature and sediment texture of the oldest source bordering dunes show them to have probably been derived from weathered alluvial red beds of similar or greater age nearby and to have contributed abundant sand to the regional dunefield immediately north of the river in contrast sand from the younger paler source bordering dunes appears to be from a different source and to have only recently extended into the regional field the finke region would seem to be in a pivotal position for the study of palaeowind patterns that have created and modified australia s whorl of continental dunes the 30 18 ka regional linear dunes near finke are oriented almost due north their cross sectional asymmetry steeper eastern slopes suggests a response to southwesterly or westerly sand transporting winds between 18 and 10 ka these winds appear to have shifted to their present southeast orientation during the past 5 ka from dune ages alignments and asymmetry it is proposed here that there was a northward shift in the wind pattern at finke by about 100 150 km 1 1 5 of latitude during the last glacial but that through this period the regional dune pattern has remained remarkably stable

late quaternary palaeoenvironmental change in the australian drylands in this paper we synthesise existing palaeoenvironmental data from the arid and semi arid interior of the australian continent for the period 40 0 ka moisture is the predominant variable controlli

dynamics of a holocene cliff top dune along mountain river northwest territories canada abstract the dynamics of a cliff top dune system located at the foot of the mackenzie mountains was reconstructed by radiocarbon dating and tree ring analysis of forest paleosols in eolian sediments the first evidence of eolian activity dates to ca 3000 yr b p when the breaching of a bedrock sill initiated the erosion of glaciofluvial deposits that resulted in the exposure of a 75 m high cliff of erodible sediment sandy sediment eroded from the cliff by katabatic winds from the mackenzie mountains buried a mature forest growing on alluvial sediments despite a minor eolian event between 750 and 860 cal yr a d dune development began ca 1100 cal yr a d and has been marked by two major sedimentation periods between ca 1100 cal yr a d and 1460 a d and from 1865 to present detailed analysis of tree morbidity and mortality indicates that the dune progressed at an average rate of 78 cm yr for the last century dune dynamics are directly related to slope activity that controls the episodic nature of sediment availability and to the katabatic wind regime comparison of the dune dynamics and paleoclimatic data suggest a possible influence of warm climate on eolian activity

low latitude glacial cooling in the southern hemisphere from amino acid racemization in emu eggshells the record of natural climate variability over glacial interglacial timescales provides a framework from which a better mechanistic understanding of the climate system may be derived but this approach is limited by the number and distribution of well dated and reliable palaeoenvironmental archives particularly vexing is the conflicting evidence for low latitude cooling during the last glacial maximum and the apparent synchrony in glacial activity between the hemispheres despite out of phase insolation forcing1 4 here we utilize the temperature dependent amino acid racemization reaction in radiocarbon dated emu eggshell fragments from the continental interior of australia to reconstruct low altitude subtropical temperatures for the past 45 kyr racemization rate changes indicate that millennial scale average air temperatures were at least 9 c lower between 45 and 16 kyr bp than since 16 kyr bp a temperature change of this magnitude coupled with other low latitude palaeotemperature records that indicate substantial cooling3 4 must reflect global processes which we speculate involved glacial age reduction in atmospheric water vapour content

relationships between desert dunes during the late quaternary in the lake frome region strzelecki desert australia 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 saltinflux associatedwith thedeflation oflakefrome weconclude thatthe nature andinitiation 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 copyright 2007 john wiley sons ltd

coarse cliff top aeolian sedimentation in northern gaspesie quebec canada this paper deals with the effects of wind on rockwall dynamics on 5 and 6 january 1988 very strong northwest winds blizzard were blowing onto the rockwall of mount saint pierre alt 424 m gaspesie quebec canada the most violent recorded squall reached 99 4 km h 1 during this event the summit plateau received a large amount of aeolian sediments originating from the shale rockwall that forms the mountain s northwest side in the 15 to 20 m wide by 75 m long belt located along the top of the rockwall over a 1200 m2 area a continuous layer of debris completely covered the snow this layer of debris had a mean thickness of 11 4 mm which represents an accumulated volume in the order of 13 m3 largely dominated by sand and granules 2 4 mm the 28 samples collected for grain size analysis also contained numerous thin shale flakes many of which were longer than 10 mm the largest flake measured had a width of 134 mm and a weight of 164 3 g six available 14c dates provide information concerning mean cliff top aeolian sedimentation rate for the last thousand years c 1 8 mmyr 1

investigating parabolic and nebkha dune formation using a cellular automaton modelling approach vegetation plays an important role in shaping the morphology of aeolian dune landscapes in coastal and semi arid environments where ecogeomorphic interactions are complex and not well quantified we present a discrete ecogeomorphic aeolian landscape model decal capable of simulating realistic looking vegetated dune forms permitting exploration of relationships between ecological and morphological processes at different temporal and spatial scales the cellular automaton algorithm applies three simple rules that lead to self organization of complex dune environments including nebkhas with distinctive deposition tails that form in association with mesquite type shrubs and hairpin long walled parabolic dunes with trailing ridges that evolve from blowouts in association with vegetation succession changing the conditions of simulations produces differing landscapes that conform qualitatively to observations of real world dunes the model mimics the response of the morphology to changes in sediment supply vegetation distribution density and growth characteristics as well as initial disturbances the introduction of vegetation into the model links spatial and temporal scales previously dimensionless in bare sand cellular automata grid resolutions coarser than the representative size of the modelled vegetation elements yield similar morphologies but when cell size is reduced to much smaller dimensions the resultant landscape evolution is dramatically different the model furthermore demonstrates that the relative response characteristics of the multiple vegetation types and their mutual feedback with geomorphological processes impart a significant influence on landscape equilibria suggesting that vegetation induces a characteristic length scale in aeolian environments this simple vegetated dune model illustrates the power and versatility of a cellular automaton approach for exploring the effects of interactions between ecology and geomorphology in complex earth surface systems

how do longitudinal dunes respond to climate forcing insights from 25 years of luminescence dating of the australian desert dunefields abstract this paper presents a meta analysis of 689 luminescence age estimates of australian desert sand dunes this analysis had two aims to examine the hypothesis that quaternary climate changes have forced dune accumulation and to understand longitudinal dune behaviour from the age architecture of sand dunes for which stratigraphic information is often absent or poorly known a novel approach to the analysis of probability density curves of dune age frequency shows that in the mallee dunefield of southeastern australia only the period leading up to and including the last glacial maximum lgm 18 34 ka experienced marked dune growth which cannot be explained by random stochastic activity during the lgm most but not all mallee longitudinal dunes were accumulating more rapidly than before and after in the strzelecki dunefield source bordering sbd longitudinal dune tl n 61 and osl n 40 ages are more frequent at the pleistocene holocene transition but nearby non sbd longitudinal dunes n 21 ages were only active above background levels during the lgm however the strzelecki dune age data set suffers from being drawn from a small number of individual dunes 10 sbd dated using tl 12 sbd dated by osl 7 non sbd dated by osl with a marked bias away from surficial young and basal old depths even during the lgm many dunes do not record active growth and the dunefield was most likely a mosaic of stable dune surfaces and bare mobile patches supported by the scant pollen data from the arid zone hyper aridity has not been experienced in these dunefields these vegetated dunes exhibit conservative behaviour with limited response to the range of climate forcing experienced in the late pleistocene a more complete understanding of dunefield response to quaternary climates would require an intensive and structured dating program to overcome the noise from stochastic processes leading to small scale activity in these dunes and the simultaneous removal of parts of the sedimentary record

aeolian deposits on a scottish mountain summit characteristics provenance history and significance the summit plateau of the storr 719 m in northern skye is mantled by a sheet of aeolian sediment up to 2 9 m thick covering an area of 33 000 m2 with a volume of 41 000 m3 the deposits are of massive poorly sorted sand with significant components of silt and fine gravel and contain clasts up to 109 mm in length the thickness and coarseness of the deposits decline westwards and northwards away from the highest cliffs implying that the sediment comprises particles dislodged from rockwalls and blown upwards in an accelerating vertical or near vertical airflow settling through a lower velocity flow onto the plateau surface where they are trapped by vegetation radiocarbon dating of soils buried under and within the deposits suggests that accumulation began after 7 2 6 9 calendar ka bp but before 5 6 5 3 calendar ka bp and was probably initiated by exposure of the present rockwall by a massive landslide at c 6 5 0 5 calendar ka bp pollen analyses of buried organic horizons suggest that a vegetation mat dominated by grasses and sedges was present throughout the period of sediment deposition sediment accumulation over much of the plateau averaged 10 20 mm per century throughout the late holocene but reached c 60 mm per century in the area of the thickest deposits the volume of the deposits implies the removal of 420 480 mm of rock averaged over the face during the late holocene and suggests that small scale granular disaggregation and release of small clasts constitute a major component of rockwall retreat under present conditions the origin of the storr deposits suggests that plateau top aeolian sediments on other scottish mountains accumulated in a similar way but have been eroded and redeposited on lee slopes following breakage of vegetation cover 1998 john wiley sons ltd

late quaternary aeolian dunes on the presently humid blue mountains eastern australia abstract sand dunes on the newnes plateau 1000 m a s l west of sydney were active during the last glacial maximum the scattered sand dunes are forested under the modern humid temperate climate regime dune types range from parabolic to transverse lee dunes and sand sheets or patches all point to the presence of conditions marginal for aeolian activity made possible through wind acceleration on windward slopes ready sand supply from the weathered sandstone of the plateau and sparse vegetation cover modern climate envelopes of sand dune activity in australia predict that unrealistically drier conditions are necessary to allow wind transport at this site only additional impediments to plant growth such as lower temperature and lower atmospheric carbon dioxide concentrations appear to allow the necessary conditions for dune formation these observations and conclusions extend our understanding of the extremes of the lgm climate in humid eastern australia confirming that the widespread treeless vegetation was also sparse even in areas that today have annual rainfall above 1000 mm

evaluating the use of dune sediments as a proxy for palaeo aridity a southern african case study abstract the dominance of dryland environments in the southern hemisphere makes the study of these regions of critical importance for the development of regional hemispheric and global models of environmental change unfortunately the wetting and drying cycles associated with semi hyperarid climates are not conducive to the preservation of traditional organic proxy data sources the last decade however has seen the development of a number of alternative archives including the application of luminescence dating techniques to dunes and other aeolian deposits in continental situations the existence of relict dune fields has long been thought to be evidence of drier conditions during the pleistocene and direct ages from these features have been interpreted almost exclusively as indicating phases of aridity however an increasing number of ages from a broader range of environments are calling into question the assumption that aeolian activity can be simply equated with aridity presented here is a comparison of dune ages that have been obtained from across southern africa with a range of proxies from both terrestrial and marine records taken as a whole three primary phases of activity can be identified at 60 40 35 20 and 17 4 ka the frequent discordance with other terrestrial records indicating coeval increases in humidity and the close correlation of these phases with wind strength proxies suggest that aridity is unlikely to be the sole or even primary forcing mechanism for aeolian activity in the region and the palaeoclimatic significance of these sedimentary archives needs to be reassessed

vostok ice core provides 160 000 year record of atmospheric co2 direct evidence of past atmospheric co2 changes has been extended to the past 160 000 years from the vostok ice core these changes are most notably an inherent phenomenon of change between glacial and interglacial periods besides this major 100 000 year cycle the co2 record seems to exhibit a cyclic change with a period of some 21 000 years

understanding linear dune chronologies insights from a simple accumulation model abstract dunefields are today often found in regions where environmental conditions are no longer conducive to widespread aeolian transport and deposition and are thus seen as potential archives of palaeoenvironmental information some dune types are more suitable for this purpose than others and linear dunes used here synonymously with longitudinal dunes have been most frequently employed they are commonly found in dryland and dryland marginal regions and they are apparently less migratory than some other dune forms thereby offering the potential for longer environmental histories most recent studies have employed optical osl dating surveys which directly date the emplacement of dune sands to attempt to produce a representative history of aeolian accumulation at a dunefield scale yet such studies have not always given due consideration to the geomorphology of linear dune accumulation although linear dunes do not rework their sand as readily as say barchans dunes it is clear that sand deposited during an aeolian event is likely to have been removed from elsewhere on the dunefield s surface for this reason all dune archives must be assumed to be discontinuous over long timescales the effect of sediment redistribution on dune preservation and thus palaeoenvironmental interpretation is difficult to observe and poorly understood we present a simplified probabilistic model to replicate deposition erosion of sand at a linear dune crest thus simulating the type of profile sampled in many field studies in order to produce a local accumulation history the modelled sand flux incorporates various feedbacks and the simulations are run with varying boundary conditions in which the simulated surface is assumed to be in equilibrium over the multi millennial timescales of the model s duration periodic instabilities in the landscape are generally well recorded by the modelled dune accumulation history particularly when the events involve the system as a whole briefly functioning out of an equilibrium state i e the probabilities of deposition and reworking are not equal however under forcing conditions where the probabilities are unchanged throughout the duration of the model run the results can show apparent structure within the data when sample sizes are low although at large sample sizes the preservation potential decays with burial age according to a power law the model confirms the importance of rigorous sampling strategies for such studies but also suggests that if such precautions are taken the reworking inherent to linear dune aeolian systems does not preclude their use as a quaternary palaeoenvironmental archive of environmental change

synchrony of southern hemisphere late pleistocene arid episodes a review of luminescence chronologies from arid aeolian landscapes south of the equator abstract luminescence dating chronologies that have been reported in various studies of late pleistocene arid land aeolian sequences from australia southern africa and south america are reviewed with the objective of determining whether any pan hemispheric synchroneity existed in the timing of landscape responses to late quaternary climate changes south of the equator the results broadly show that contemporaneous regional arid land aeolian activity occurred in australia and southern africa during the periods ca 65 41 and 36 9 ka the relatively limited luminescence data from the south american subcontinent also point to recurrent arid land aeolian deposition between 63 and 8 ka with increasing frequency in the period ca 32 8 ka records from all three continents suggest a period of reduced aeolian activity between 41 and 36 ka overall the data are indicative of extensive landscape instability of the low to mid latitudes in the southern hemisphere during the last glacial period particularly at the last glacial maximum which accords with mainstream opinions aeolian activity during the holocene has generally been localised the rigour with which comparisons can be made between the different studies however is constrained by variations in practices between laboratories and changes that have occurred to luminescence dating procedures over the years

physiological significance of low atmospheric co2 for plant climate interactions abstract methods of palaeoclimate reconstruction from pollen are built upon the assumption that plant climate interactions remain the same through time or that these interactions are independent of changes in atmospheric co 2 the latter may be problematic because air trapped in polar ice caps indicates that atmospheric co 2 has fluctuated significantly over at least the past 400 000 yr and likely the last 1 6 million yr three other points indicate potential biases for vegetation based climate proxies first c 3 plant physiological research shows that the processes that determine growth optima in plants photosynthesis mitochondrial respiration photorespiration are all highly co 2 dependent and thus were likely affected by the lower co 2 levels of the last glacial maximum second the ratio of carbon assimilation per unit transpiration called water use efficiency is sensitive to changes in atmospheric co 2 through effects on stomatal conductance and may have altered c 3 plant responses to drought third leaf gas exchange experiments indicate that the response of plants to carbon depleting environmental stresses are strengthened under low co 2 relative to today this paper reviews the scope of research addressing the consequences of low atmospheric co 2 for plant and ecosystem processes and highlights why consideration of the physiological effects of low atmospheric co 2 on plant function is recommended for any future refinements to pollen based palaeoclimatic reconstructions

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

conditions favourable for the formation of warm climate aeolian sand sheets aeolian sand sheets are areas of aeolian sand where dunes with slipfaces are generally absent sand sheets are ubiquitous to modern warm climate sand seas generally occurring marginal to dune fields although they may exist within the interior of a sand sea or independent of a dune field sand sheet deposits are recognized in ancient aeolian sequences where they may account for significant accumulations of low angle aeolian stratification we suggest that the occurrence of sand sheets instead of dunes indicates that conditions are outside the range within which dunes form or that one or more factors interfere with dune development while also favouring the accumulation of sand sheets a study of six modern sand sheets in north america located at great sand dunes gran desierto dumont algodones padre island and colorado river delta indicates that the factors favourable for sand sheet development are 1 a high water table 2 surface cementation or binding 3 periodic flooding 4 a significant coarse grained sediment population and 5 vegetation these factors are reflected in the nature of stratification and the accessory features of sand sheet accumulations within the areas of modern sand sheets as well as in their ancient counterparts in the triassic dolores and pennsylvanian permian rico formations

soil production in heath and forest blue mountains australia influence of lithology and palaeoclimate an erratum has been published for this article in earth surfaces processes and landforms 25 13 2005 1683 1686 recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth this contrasts with a long held assumption that maximum soil production occurs under a soil cover of finite depth sites in the blue mountains australia show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath covered spurs and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil the substrate varies from hard ferruginized sandstone to soft saprolite in situ 10be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but in contrast to other studies these sites do not show significant depth dependence of apparent soil production the pattern reflects both hardness variation in the rock substrate and the effect of late quaternary climatic change optically stimulated luminescence osl dating indicates that soil 30 cm depth is of holocene age whereas the deeper soil is substantially older the age break coincides with a stone line interpreted as a former surface lag deposit assuming that pre holocene soil depths were 30 cm less than today recalculated soil production tends to decrease with increasing depth soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic in the long term average rates of erosion and soil production decrease with increasing soil depth copyright 2005 john wiley sons ltd

climate space bioclimatic envelopes and coexistence methods for the reconstruction of past climates a method using australian beetles and significance for quaternary reconstruction abstract if quaternary palaeoclimatic reconstructions are to be adequately contextualised it is vital that the nature of modern datasets and the limitations this places on interpreting quaternary climates are made explicit such issues are too infrequently considered this paper describes a coexistence method for the reconstruction of past temperature and precipitation parameters in australia using fossil beetles it presents the context for quaternary palaeoclimatic reconstruction in terms of climate space bioclimatic envelope data derived from modern beetle distributions and the palaeoclimatic limitations of bioclimatic envelope based reconstructions tests in modern climate space using bioclimatic envelope data for 734 beetle taxa and 54 site based assemblages from across the continent indicate that modern seasonal especially summer temperatures and precipitation are accurately and in the case of temperature precisely reconstructed the limitations of modern climate space especially in terms of the limited seasonal variation in thermal regimes and subsequent lack of cold winters in the australian region renders winter predictions potentially unreliable when applied to the quaternary record

palaeoenvironmental reconstructions from linear dunefields recent progress current challenges and future directions abstract this paper reviews recent progress in the use of linear dunes as geoproxies of late quaternary environmental change summarises the challenges facing their use and explores some potential solutions to these challenges large areas of the swathes of linear dunes which occupy the continental interior of southern africa australia and parts of central asia and southern america currently have limited or negligible aeolian activity they have been recognised as offering potential information about past environments for more than a century but only with the widespread application of luminescence dating during the 1990s did they realistically start to offer the prospect of being an extensive dateable proxy of late quaternary palaeoenvironments and possibly palaeoclimates dating aeolian dune sands with luminescence methods is generally although not always relatively straightforward over the past twenty years a large number 1000 of luminescence ages have been added to the global dataset yet there has also been significant criticism of some of the rationale underpinning much of the interpretation of the records derived at the landscape scale developments of arguably equal importance have come from improved geomorphological understanding based on the wider availability of remotely sensed data and the paradigm of dunefield evolution as a self organising complex system current challenges are identified in three key regions incomplete understanding of how the process geomorphology of linear dunes affect the accumulation and preservation of sediment a lack of clarity regarding the temporal and spatial scale of the response in a dynamic environmental setting and uncertainty surrounding the drivers of changing rates of net accumulation solutions to these challenges lie within diverse research methodologies certainly further field study is required with improvement required in understanding system responses to changing environmental stimuli at scales from sedimentological to landscape in parallel the full implications of complex systems approaches to aeolian geomorphology for linear dunes lag behind the adoption of the concept to some other dune forms e g barchans the relationship between observed dune complexity and age from field data complicates previous suggestions that dune patterning may be purely a function of development time parallel to this lies the need to improve interpretation of the results of dune geochronological studies a suggestion is offered which aims to test the statistical significance of dune accumulation time series by comparison with a modelled system with unchanging external forcing despite the initial promise of linear dune records as a revolutionary source of palaeoenvironmental information in drylands the outcomes to date have been coarse although still valuable in resolution perhaps the most valuable realization has been that geomorphological understanding of these widespread landforms is incomplete

last glacial maximum and last glacial interglacial transition pollen record from northern nsw australia evidence for a humid late last glacial maximum and dry deglaciation in parts of eastern australia this paper presents the results of a palynological investigation into the late last glacial maximum lgm and last deglaciation ca 20 000 9000 cal a bp from little llangothlin lagoon in the sub tropics of eastern australia the lagoon held permanent water during the late lgm and early deglaciation but was intermittently dry during the late deglaciation during the late lgm local vegetation was dominated by a sub alpine herbfield but the significant presence of rainforest taxa in the pollen record indicates the survival of rainforest rainforest margin or wet sclerophyll communities close to the site by ca 17 000 cal a bp open eucalyptus forest replaced the alpine herbfield vegetation indicating that warming had commenced rainforest taxa disappeared at this time but re appeared at the end of the deglaciation the lgm conditions are consistent with a dominant circulation system whereby persistent high pressure over eastern australia brings onshore easterlies to this region and maintains humid conditions along the east coast and highlands of the great dividing range this is similar to modern winter circulation but the persistence of rainforest and wet sclerophyll taxa suggests an increase in easterly flow over modern conditions during the lgm

dune mobility and vegetation cover in the southwest kalahari desert as part of a wider project investigating the palaeoenvironmental significance of partially vegetated linear dunes in the southwest kalahari data collected in the latter part of 1992 concerning dune movement and vegetation cover suggest that sediment transport is occurring on some dune surfaces and that the majority of surface activity occurs on the crests and upper slopes of the dunes the data suggest that the limiting variables on surface sediment movement vary on different parts of a dune on interdunes and lower dune slopes the primary limiting variable is available wind energy while on dune crests and upper slopes it is vegetation cover ground cover by litter has much greater importance in protecting the surface sediment from erosion than rooted vegetation from individual data points no evidence is found to support a threshold vegetation cover below which sediment movement occurs rather a gradient of activity is suggested whereby a reduction in vegetation cover increases the potential for sediment movement and surface change however dunes with differing amounts of mean vegetation cover display differing degrees of surface activity and at this scale a vegetation cover threshold in the region of 14 per cent may be recognized

chronology of murrumbidgee river palaeochannels on the riverine plain southeastern australia four major periods of palaeochannel activity have been identified on the murrumbidgee sector of the riverine plain of southeastern australia on the basis of stratigraphic information the channels reveal a picture of changing flow conditions during the last full glacial cycle the ages of the periods were determined from nearly 40 thermoluminescence dates on surficial fluvial and aeolian sediments these are named the coleambally phase which occurred from 105 to 80 ka the mid to latter part of oxygen isotope stage 5 the kerarbury phase from 55 to 35 ka stage 3 the gum creek phase from 35 to 25 ka late stage 3 to early stage 2 and the yanco phase from 20 to 13 ka late stage 2 the present flow regime was established by about 12 ka stage 1 the first two phases correlate with episodes of enhanced fluvial activity in northern and central australia and with reduced dust activity globally the phases in stage 2 appear to be associated with seasonal snow melt and increased peak flows in periods flanking the last glacial maximum source bordering aeolian dunes associated with the coleambally kerarbury and yanco phases were found however the tl dates show that some have undergone aeolian reworking thermoluminescence dating and fluvial stratigraphy have revealed a detailed picture of late quaternary climate and flow regime changes that has the potential to extend to identified deposits stratigraphically older than those described here

a 40 000 year vegetation history and climatic interpretations of burraga swamp barrington tops new south wales abstract burraga swamp a small basin surrounded by cool temperate rainforest at 985 m in the central new south wales highlands has provided a record of 40 000 years from 40 000 30 000 years bp the site was a lake with a very slow rate of deposition of fine grained sediments and flourishing aquatic swamp vegetation the dryland vegetation was an open or sparsely treed grassland herbfield from 30 000 21 000 years bp the dryland vegetation remained much the same but the aquatic vegetation disappeared from 21 000 17 500 years bp sandy sediments were deposited at an accelerated rate culminating in a layer of gravelly sand possibly the result of periglacial activity only one band of clay in this section contained sufficient pollen to study indicating treeless vegetation after 17 000 years bp the rate of sediment accumulation slowed or ceased and after 15 000 years some mesic elements started to return at 6500 years bp peat started forming and cool temperate rainforest was fully developed remaining on the site to the present this site extends the record of treeless condition at the last glacial maximum to more northerly localities than previously known