influence of cell size on volume calculation using digital terrain models a case of coastal dune fields abstract in this work we analyze how variation in cell size influences the volume calculated from digital terrain models dtms derived from a lidar light detection and ranging survey in two coastal late holocene dune fields in southern brazil cell size varied from 1 to 100 m rmse root mean square error of the resampled dtms from the original lidar with 0 5 m resolution increases linearly with cell size while r 2 coefficient of determination decreases following a second order trend the volume does not show simple linear or exponential behavior but fluctuates with positive and negative deviations from the original dtm this can be explained by a random factor in the position of the cell with regard to landforms and a relationship between cell and landform size wherein a small change in cell size can lead to an under or overestimation of volume the aster gdem global digital elevation model and x sar srtm shuttle radar topography mission 1 digital elevation models dems were not considered viable volume sources due to large deviations from the reference data either as a consequence of noise in the srtm x sar data or lack of bias elevation correction to a common reference base in the gdem processing chain volumes from a 3 arcsec sir c srtm deviated around 5 from the reference data and are considered suitable input for numerical simulations of quaternary dune field evolution models because these values should be within the expected range of sediment volume changes over hundreds to millions of years

luminescence dating of recent dunes on inch spit dingle bay southwest ireland fifteen samples of dune sand and three samples from a core taken in the beach face were collected from a sand spit which protrudes into dingle bay in southwest ireland the potassium rich feldspar grains from the samples were dated using a single aliquot luminescence protocol for infrared stimulated luminescence irsl signals no ages over 600 years were obtained which demonstrates the youth of the dune forms currently observed the youngest ages were about 150 years old but for these samples the scatter in the equivalent dose obtained as the mean of 18 measurements was higher than for the older samples

holocene aeolian activity in the southwestern kalahari desert southern africa significance and relationships to late pleistocene dune building events little is known about the timing of dune building episodes in the southwestern kalahari desert previously arid phases when dune activity occurred have been inferred from gaps in chronologies derived from information that attests to former humid periods to redress this optically stimulated luminescence osl dating was applied to sediment samples taken from a range of aeolian landforms in the sw kalahari four periods of dune building are identified in the late pleistocene and holocene holocene aeolian activity at 6 ka and 1 2 ka led to the construction of localised dune forms in contrast to late pleistocene times when the extensive field of linear dunes that dominates the region was emplaced late holocene aridity was however sufficient to allow rapid emplacement of the lunette dune at witpan the record of aeolian activity is evaluated in the context of humid chronologies and an ocean atmosphere model of holocene climate change with good agreement obtained it is concluded that the application of

comparison of equivalent doses determined by thermoluminescence and infrared stimulated luminescence for dune sands in new zealand abstract a comparison is made between the use of thermoluminescence and infrared stimulated luminescence for determining the equivalent dose of sedimentary potassium feldspars results are presented for a suite of dune sands from raised marine terraces in south west north island new zealand with the exception of a modern dune sand the two methods yield very similar results in spite of the differences in the nature of the signals measured by the two methods

thermoluminescence dating of the middle pleistocene raised beach of sangatte northern france abstract tl dating of both quartz and potassium feldspar grains from the pleistocene beach of sangatte at the southern limit of the north sea basin give self consistent ages of 200 000 45 000 205 000 14 000 and 229 000 18 000 years respectively these results allow the beach deposits to be correlated with oxygen isotope stage 7 244 000 190 000 yr martinson et al 1987 the existence of a fossil beach cliff line at 10 m above french o d demonstrates that the strait of dover was open during the penultimate interglaciation

thermoluminescence dating of the chelford interstadial abstract the sediments at chelford constitute one of the key devensian sequences in britain previous radiometric dating attempts using wood and peat from the interstadial deposits per se suggest its age is likely to be beyond the limits of resolution by radiocarbon using tl dating of feldspar and quartz mineral fractions from the host succesion of chelford sands a sequence of internally consistent dates is derived which accords with the existing litho and biostratigraphic evidence these suggest that the absolute age of the chelford interstadial is in the range 90 100 ka the chelford sands appear to be the product of at least two cold stages

infrared stimulated luminescence irsl dating of late holocene aeolian sands in the mojave desert california usa a new method of dating potassium feldspar grains from aeolian sands is demonstrated a luminescence signal is measured whilst the grains are stimulated in the near infrared at 880 nm a surface sand sample gave an age of 40 15 years showing that this method is able to provide ages for very young samples since the measurement of an infrared stimulated luminescence irsl signal can take place with a short infrared exposure the irsl signal of the grains is not depleted thus growth curves can be obtained for 5 mg sample aliquots this procedure was exploited in this paper dates were obtained for 10 samples from the kelso dune field as a demonstration of the applicability of the method in a desert environment where there is no material suitable for radiocarbon dating although the number of dates are limited sand from an area at the eastern end of the dune field with crescentic dunes showing a different wind direction from that of today had an age of 4115 335 years similar to the 3960 385 years fo

geochronologies and environmental records of quaternary fluvial sequences in the guadalope basin northeast spain based on luminescence dating

thermoluminescence dating of the orkutsay loess section in tashkent region uzbekistan central asia abstract the chronology of loess in central asia was investigated by means of thermoluminescence dating tl in the 1970s when age estimates ranging from 20 ka to over 800 ka were taken as providing an absolute chronology this has caused major misinterpretation of central asian loess stratigraphy and palaeoclimatic reconstruction we present a new tl study of a loess section at orkutsay in the tashkent region uzbekistan nine samples spreading over a large stratigraphic interval yield apparent tl ages ranging from 20 ka to 134 ka we interpret our tl results with reference to recent tl dating studies of loess from other regions we consider most of our tl age estimates obtained by the regeneration method to be underestimated a single tl date of 92 8 ka obtained by the total bleach method for loess just below the first pedocomplex pc 1 of the last interglacial is also significantly younger than expected we attribute the underestimation to sensitivity change induced by the laboratory optical bleach and instability of the tl signal we conclude that the current tl techniques as employed in this study cannot provide a reliable absolute chronology for the sequence below pc 1 and cannot provide even a relative chronology for the loess below pc2 for the orkutsay section the dating limit is around 130 ka the results of this study suggest that the previous central asian loess chronology based on early tl studies is not valid

response of eolian geomorphic systems to minor climate change examples from the southern californian deserts abstract eolian processes and landforms are sensitive to changes in atmospheric parameters and surface conditions that affect sediment supply and mobility the response of eolian geomorphic systems to minor climate change can be examined through process response models based on a combination of relations between short term changes in climatic variables and eolian activity and the geologic and geomorphic record of holocene eolian activity at both time scales eolian activity in southern californian deserts is strongly controlled by variations in precipitation wind energy is not a limiting factor in this region formation of eolian deposits is a product of climatic changes that increase sediment supply from fluvial and lacustrine sources and may therefore be closely tied to periods of channel cutting and geomorphic instability during intervening periods eolian deposits migrate away from sediment source areas and are reworked modified and degraded remobilization of existing dormant dunes is a product of reduced vegetation cover and soil moisture in periods of drier climates the major control on these processes is decadal to annual changes in rainfall that determine vegetation cover and soil moisture content

optical dating preliminary results on the anomalous fading of luminescence from feldspars abstract luminescence emitted from various beta dosed alkali feldspars and plagioclase feldspars has been measured under optical stimulation the luminescence sensitivities were compared as the initial stage of an on going study of short term anomalous fading of the optically stimulated luminescence osl signal anomalous fading was observed in the luminescence stimulated by both green light 514 5 nm and ir 880 80 nm from samples representing each of the major compositional regimes of the feldspar series means of alleviating the influence of this fading in luminescence dating applications are under investigation particularly the effect of isothermal storage at 100 c initial findings show that anomalous fading in these samples does not lead to a stable remanent level within the storage times used a practical consequence is that use of a fading monitoring procedure is strongly recommended in optical dating

event stratigraphy paleoenvironment and chronology of se arabian deserts the geological record of the se arabian desert is exhibited in a variety of geomorphic features and their characteristic sediments ranging from alluvial fans to inland and coastal dunes and sabkhas together they suggest a large range of environmental and climatic variability between periods of relative aridity and humidity sedimentary events in the emirates appear to correlate broadly with high latitude glaciations which affected both the shamal winds and the extent of exposure of the arabian gulf in general the aeolian sands in the rub al khali responded to glacial events as a consequence of exposure of the floor of the arabian gulf during glacials when global sea level was low quartz sands from across the exposed floor of the arabian gulf were transported by the shamal winds south eastwards to the emirates and then south to the rub al khali the supply of shamal transported sand from the floor of the arabian gulf was cut off by high stands of sea level during interglacial periods the new coastal dunes miliolite rich in foraminifera and other cement assisting calcareous shell fragments were deflated down to the water table as their sand was transported further to the south leading to the creation of coastal sabkhas studies on aeolianites and the lacustrine deposits provide evidence of phases of enhanced humidity prior to the last glacial maximum and during the holocene in contrast the bedding attitudes of miliolites in se oman suggest that the wahiba sands were transported from south to north by a branch of the sw monsoon the depositional ages of these dunes indicate a close connection between the winds and coeval fluctuations of the sw monsoon the interdunal lakes and underlying dune sands reflect an active sw monsoon during the holocene this is also indicated by the aeolian and lacustrine records of the thar desert in india which likewise are controlled by the sw monsoon south and west of the oman mountains is a broad alluvial fan bajada that is mostly inactive today the oldest fluvial sediments are undated but preliminary age estimates suggest that some correlate with more humid earlier interglacials

optical dating of aeolian dynamism on the west african sahelian margin abstract the sahelian margin of west africa is widely recognised as an area of recent environmental catastrophe and human suffering arising from food shortage and land degradation associated with prolonged drought the propensity of this region to suffer drought has been related using environmental data collected during the period of instrumental records to a combination of low mean annual rainfall levels and a high degree of rainfall variability which relates to sea surface temperature anomalies in the adjacent tropical atlantic ocean despite the significant environmental and human consequences of such droughts there is a paucity of long term environmental data for the west african sahel aeolian dune reactivations in this area are a potentially highly useful environmental archive of past periods of extended drought conditions which may have resulted in localised or widespread dune reactivation here we describe the initial results from an ongoing programme of research which seeks to develop a detailed record of past dune reactivations in mali we find evidence for repeated holocene dune reactivation events and a significant number of reactivations which commenced at the time of onset of the last major drought cycle in the early 1970s we obtain ages as young as 20 30 years for some significant dune units thickness up to 1 m and describe the results of experiments which test the performance of our dating exercise we specifically test for the significance of preheat temperature on single aliquot regeneration sar equivalent dose determinations and recycling ratios neither are found vary significantly as a function of preheating optical dating of sand sized quartz could provide a useful tool for palaeogeographical mapping of ancient and historical dune reactivations in this region and elsewhere

thermoluminescence chronology of sand profiles in the thar desert and their implications thermoluminescence chronology of three sand profiles in western rajasthan indicates a peak in sand accretion rate at ca 14 ka and a period of dormancy during 13 6 ka bp this observation shows a general correlation with pollen and geochemical records from lakes in thar and demonstrates the potential of desert sands in paleoclimatic reconstruction thermoluminescence ages of 36 ka and 40 ka on two samples suggest that the aeolian sand mobilization activity in this regions is at least as old

thermoluminescence dating of sediments older than 100 ka abstract for several years attempts have been made to establish reliable procedures for thermoluminescence tl dating of sediments older than 100 ka disagreement persists among tl workers about which procedures are reliable for which sediments two recent reports have demonstrated that tl ages up to 800 ka for polymineral fine silt loess and up to 600 ka for quartz from beach dune sands agree well with expected ages several factors that apparently have influeneed negatively the accuracy of other results are use of ultraviolet tl emissions use of the regeneration tl procedures for feldspar bearing samples use of a single preheating procedure and use of a peak integration procedure rather than an equivalent dose plateau test consideration of published data suggests that more attention should be paid to the variable emissions intensity glow curve shapes signal lifetimes from discrete grains within subsamples the effects of such variability would probably account for the failure of peak integration and single preheating procedures to yield expected equivalent dose values single grain or micro tl studies of feldspar and quartz tl both spectral emission and glow curve measurements are recommended as aids to further understanding of current tl sediment dating practices

thermoluminescence dating of sand dunes in rajasthan india we report here a new application of thermoluminescence tl for dating sand dunes this application assumes that exposure to sunlight causes bleaching of the geological tl of a sediment to a residual value and that tl accumulation starts again when the sediment is buried under fresh deposit and is thus shielded from the sun although the tl method has been applied to loess1 2 and ocean sediments3 4 the application of this technique to sand dunes provides the first reliable dating control for dune dynamics palaeoclimatology and spread of deserts

thermoluminescence dates and palaeoenvironmental information of the late quaternary sand deposits tierra de pinares central spain abstract a large amount of quaternary palaeo environmental evidence lies within the terrestrial aeolian sediments filling the duero basin in central spain previous work has identified a number of stratigraphical units although the absolute age and origin of some of these is equivocal the uppermost unit the focus of this paper is a widely distributed sand which covers most of the tierra de pinares north of segovia detailed investigations of an exposure at burgomillodo reveal over 35 m of laminated and cross bedded sand from which seven thermoluminescence dates were obtained the bedding structures indicate a northwesterly palaeowind direction different from the present dominating westerly winds two phases of sand deposition are identified at the site with evidence of erosion and reactivation phases an upper unit of ca 7 ka during the warm aridity of the atlantic period and a lower unit between 12 5 11 ka coinciding with the cold aridity of the younger dryas event the latter in which at least 25 m of sand were deposited at the site is the dominant phase and is coincident with what has been identified elsewhere in spain from biological data as a period which was both cold and dry the burgomillodos site therefore represents the first sedimentological evidence for this arid phase in the younger dryas in central spain

filling the gap osl data expanding 14c chronologies of late quaternary environmental change in the libyan desert several decades of geomorphological and archaeological research in the libyan desert conducted by the cologne projects b o s and acacia have yielded a wealth of radiocarbon data from archaeological sites and over the last decade also 48 osl ages mainly from aeolian deposits this paper focuses on the combination of both data sets in order to obtain a synthesis of late quaternary occupational and environmental history in this region case studies demonstrate that despite a poorer time resolution of osl chronologies compared to 14 c data osl ages can be more consistent with the archaeological context particularly if the dating of charcoals poses problems due to poor quality or re deposition comparison of data sets from the egyptian sand seas and from the wadi howar sudan shows that in both cases osl and 14 c data cover complementary time slices on the regional scale however contradictory intervals of aeolian accumulation are documented which can be explained by the different environmental histories the results accentuate that interpretation of osl data has to be done in the context of the entire environmental systems including the effective geomorphological processes r 2007 elsevier ltd and inqua all rights reserved

stratigraphic evidence for late quaternary dune activity near hudson on the piedmont of northern colorado stabilized dune fields are common features near hudson on the piedmont of northern colorado exposures in dune and interdune sites expose a sequence of eolian sediments and paleosols that record a complex history of eolian activity during the late quaternary radiocarbon and thermoluminescence age estimates on a horizons buried by eolian sand indicate that dunes were reactivated sometime between 7 and 9 ka on the basis of morphology of surface soils the dunes were most recently stabilized 3 ka at present there are no data to indicate if there were multiple periods of dune movement and stabilization during the holocene the penultimate pre holocene dune forming episode probably terminated ca 13 ka and may be coincident with the pinedale glaciation the stratigraphy at interdune sites shows at least two eolian depositional events prior to the penultimate event they were separated by periods of pedogenesis one of which may have exceeded 40 ka this analysis indicates that dunes in northern colorado were active during both cold arid and warm arid periods in the late quaternary

alternative chronologies for late quaternary last interglacial holocene deep sea sediments via optical dating of silt sized quartz abstract we summarize the results of a test on the potential of optical dating for the age assessment of late quaternary deep sea sediments our approach combines a single aliquot regeneration sar protocol for equivalent dose d e estimation on fine silt sized quartz with a time dependent evaluation of supported and unsupported long lived radioisotopes within the deposited sediment matrix for this purpose nine samples from two independently dated deep sea cores from the indian ocean were obtained the sar analysis resulted in mean d e estimates with precisions ranging from 0 9 to 3 7 combination of these data with measured radioisotope concentrations resulted in stratigraphically sensible ages ranging from ca 7 to 120 ka these ages exhibit good agreement with existing chronologies for the cores based on radiocarbon age determinations and correlation of key volcanic palaeoecological and isotopic events optical dating may provide an important additional dating method for late quaternary deep sea sediments

combining ground penetrating radar surveys and optical dating to determine dune migration in namibia ground penetrating radar gpr profiles across a complex linear dune in the namib sand sea have been used to image sets of cross stratification and their bounding surfaces a combination of radar facies analysis and radar stratigraphy has been used to interpret the radar profiles and define a relative chronology thick sets of cross stratification indicate when the dune was most active whereas thin sets of cross stratification are interpreted to indicate the increased prevalence of wind reversals and lower rates of dune migration with bounding surfaces formed during periods of stabilization non deposition or erosion a drilling and dating campaign was designed on the basis of the dune stratigraphy as defined by the gpr survey sampling was targeted at large sets of cross stratification formed when the dunes were most active and avoiding bounding surfaces formed when the dune was stable or even eroded the results from optical dating give ages between 0 34 0 02 ka and 1 57 0 07 ka indicating a time averaged dune migration rate of 0 12 m a 1 over the past 1600 years

new chronological evidence for the nature and timing of linear dune development in the southwest kalahari desert abstract the age of the linear dunes in the southwest kalahari desert has not previously been directly established by applying the optical dating method to samples from the dunefield a number of questions relating to the timing and nature of linear dune development are addressed the last major period of simple linear dune development occurred 17 000 10 000 years ago probably from the reworking of earlier aeolian sediments dune emplacement occurred under more arid probably windier conditions than those prevailing today which are only responsible for episodic surficial dune sand movement as well as simple linear dunes the dunefield also contains more complex linear dune patterns samples from one area in the eastern dunefield demonstrate that multi phase development is more probable for complex dune patterns as opposed to single phase evolution under a complex wind regime

neotectonic fault activity in hong kong evidence from seismic events and thermoluminescence dating of fault gouge hong kong lies within a major ne trending fault zone that has been reactivated during several tectonic episodes since the palaeozoic three main faults sets are recognized in hong kong a dominant ne trending set an ene varying to e trending set and a subordinate nw trending set over the last 1000 years within a distance of 350 km of hong kong there have been about 40 earthquakes with magnitudes of over 4 75 and of these 11 had magnitudes of over 6 0 microseismic events in the last ten years are diffuse but may be associated with a major ne trending fault and a fault intersection thermoluminescence tl dates of fault gouge suggest that there have been three episodes of recent fault activity in hong kong these occurred at approximately at 100 000 190 000 and 270 000 years bp tl dating of alluvial sediments also indicates fault activity in the late pleistocene

dune activity as a record of late quaternary aridity in the northern kalahari new evidence from northern namibia interpreted in the context of regional arid and humid chronologies abstract sediments from presently vegetated linear dune ridges in the caprivi strip of northern namibia are optically dated to assess the timing of dune building phases and aridity in the late quaternary the dunes have been constructed from sediments likely to have been initially transported into the area by fluvial processes dune sediments do not preserve obvious evidence of hiatuses in deposition in the dated period 48 121 ka but continuous deposition and therefore continuous aridity is considered unlikely given differences in dated phases compared with chronologies from western zimbabwe to the southeast and western zambia to the north that include ages derived from the same equivalent sampling depths laboratory experiments provide evidence that dune sediments have not been bioturbated since deposition such that sample palaeodoses determined from different sampling depths are a true reflection of the duration of sediment burial independent chronologies from cave sediments provide evidence that humid episodes have occurred in the region within the dated range of dune construction it is concluded that dune construction in the late quaternary has been punctuated that the preserved record reflects the attributes of the aeolian processes that affect linear dune development and that the late quaternary record of dune building in the middle and northern kalahari was spatially complex

optical dating of dune sands in the northeastern deserts of china abstract optical dating has been used to obtain the ages of fossil stabilized sand dunes from four sections in the northeastern deserts of china our results indicate that the optically stimulated luminescence ages of the four sections correlate well even though the samples were collected from different deserts about 600 km apart our results also indicate that active dune formation in this region lasted from the last glacial maximum to about 10 ka and that the warm climate of the holocene was interrupted by a cold dry dune formation episode about 3 5 1 7 ka the holocene optimum in this region is between 10 and 3 6 ka and a later warm humid dune stabilization phase lasted from at least 1 6 to 1 0 ka the youngest age on the uppermost sand unit yielded an age of only 40 yr supporting the previous argument that the existence of modern active eolian sands in the regions with a mean annual precipitation of up to 450 mm is not mainly due to drought but to extensive land cultivation over historic time from the luminescence properties of the quartz grains it is hypothesized that the sands in most of the sections are probably derived from more than one source with a minor source of quartz having a different thermal history before deposition

thermoluminescence age determinations for the mungo iii human burial lake mungo southeastern australia abstract thermoluminescence dating work was carried out on quartz from unburnt sediment associated with the mungo iii human burial site in southeastern australia using selective bleach and total bleach methods a comparison of the techniques showed that in some cases incomplete removal of the thermoluminescence tl signal used for dating sediments had occurred and in these cases selective bleach was the more reliable of the two methods the selective bleach results indicate the age of the burial to be older than 24 6 2 4 ka and younger than 43 3 3 8 ka while the total bleach results give ages for the burial between 34 0 3 9 ka and 43 1 6 7 ka the ages place the mungo iii human remains with the same population or older than the previously discovered human remains of mungo i

coseismic underground rupture geometry historical surface deformations and seismic potentials of the 28 march 2019 mw 5 04 mangya earthquake fault the march 28 2019 mw 5 04 mangya earthquake damaged eight ongoing drilling boreholes in the oil production yingxiong ling yxl area southwestern qaidam of northern tibet the borehole damages provide an opportunity to measure directly the coseismic slips the rupture area and the seismic moment the damages reveal the underground rupture area of 45 30 10 24 km2 the maximum slip of 400 13 mm and the seismogenic fault dip of 38 6 these parameters generate a seismic moment of 1 81 0 47 1017 nm and a moment magnitude of 5 47 0 16 seismic exploration reveals that the geometry of the szg ramp the uppermost part of the multi bend yingxiong ling thrust system agrees primarily with the rupture plane derived from the borehole damages and one plane of the focal mechanism solution this suggests that this earthquake resulted from slipping on the ramp the hanging wall of the yxl thrust system forms the complex fault bend fold yxl anticlinorium active thrusting and folding along both edges of yxl attest to the southwestern vergence of this thrust system growth strata demonstrate average slip rates of the thrust system ranging from 0 2 mm yr to 0 3 mm yr the thrusted and folded recent alluviums along the southwestern edge indicate two thrusting events with coseismic slips of 1 7 0 15 m and 3 5 0 15 m at 6 16 0 52 ka and 35 91 ka respectively the entire rupturing of the thrust system can produce mw 7 65 0 03 earthquakes

late quaternary earthquake chronology from luminescence dating of colluvial and alluvial deposits of the arava valley israel abstract luminescence ages help provide a time scale for recurrent surface ruptures on a normal fault in the southern arava israel the dated samples come from alluvium and colluvium along a fault scarp north of elat the ages obtained mainly by infrared stimulation of sand size potassium feldspar grains accord with geomorphic age estimates from soils and degraded scarps four large earthquakes occurred between 37 000 and 14 000 yr ago five smaller earthquakes occurred thereafter continuing until recent times the mean recurrence interval for earthquakes of magnitudes greater than 6 is about 4000 yr

evaluation of luminescence dating procedures applied to late holocene colluvium near st paul s mission natal south africa colluvial deposits provide an interesting challenge for luminescence dating techniques because of the short and varied light exposure histories of the grains prior to deposition results of thermoluminescence tl and infrared stimulated luminescence irsl measurements are presented for two stacked colluvial deposits from natal a radiocarbon date for bulk organic matter in the a horizon of the soil formed within the surface of the lower unit provides a means of assessing the suitability of various luminescence procedures for such material the overlying colluvium contains grains bleached to varying extents as shown by the range of eds for the coarse grain feldspar separate obtained using the single aliquot irsl method for this sample all age estimates either by irsl or tl are too large compared with the radiocarbon age indicating that even the irsl signal was not zeroed in all grains before they were buried the underlying colluvium contains grains bleached more uniformly resulting in a smaller ra

the timing of coversand deposition in northwest norfolk uk a cautionary tale abstract coversand deposits consisting largely of reworked fluvial and glaciofluvial sediments blanket the landscape in discrete areas of northern and eastern england a newly discovered zone of coversand deposits has been found in northwest norfolk which shows stratigraphic evidence of episodic sand accretion the presence of involutions within the coversand at leziate signifies the occurrence of post depositional periglacial activity infra red stimulated luminescence irsl dating of feldspars has been undertaken on five samples from four sites within the new coversand zone three of the samples were insufficiently zeroed at deposition to provide accurate dates for deposition of the sand sheets challenging the assumption that coversands are all well bleached with consequent implications for existing thermoluminescence tl dates on uk coversands an irsl age of 12 825 1910 yr for well bleached sands at leziate shows that sand accretion occurred during the period of rapid climate transition at the end of the last glacial late holocene aeolian activity resulted in sand emplacement at ling common

stratigraphy and thermoluminescence dating of late glacial cover sand in denmark in western jutland deposits with a texture and structure similar to dutch cover sands have been found investigations have been carried out on the lithology and the lithostratigraphic sequences pollen analysis is used for biostratigraphic correlation and ages have been obtained by the radiocarbon method as well as by thermoluminescence techniques using both quartz and eldspar the five sites are presented separately and the data are integrated into a general stratigraphic outline of the late glacial cover sand sequence in jutland during the latest part of the upper pleniglacial and the earliest late glacial older cover sand type was deposited locally this sediment was also deposited during the later parts of the late glacial younger cover sand type was deposited primarily during the early dryas and late dryas but some sand of this type was also laid down during the allerod and the earliest holocene the palaeobotanical records are discontinuous but plant growth was probably present throughout the late glacial only during the altered did the deposition of sand decrease long enough to allow a relatively stable vegetational development the investigation shows that the sequence of events in jutland is similar to the dutch record

optical dating of tsunami laid sands abstract the ages of some tsunami deposits can be determined by optical dating a key requirement being that the deposits are derived from sediment that was reworked and exposed to daylight by tidal currents waves wind or bioturbation during the last years before the tsunami measurements have been made using 1 4 ev infrared excitation of k feldspar grains separated from samples of prehistoric tsunami sand sheets and modern analogs of tsunami source sediments at four sites in washington state and british columbia source sands gave equivalent doses indicative of recent exposure to daylight tsunami sand at cultus bay washington yielded an optical age of 1285 95 yr calendric years before a d 1995 1 at 2 this age overlaps the range of from 1030 to 1100 yr determined through a combination of high precision radiocarbon dating and stratigraphic correlation tsunami sands at three sites near tofino and port alberni on vancouver island british columbia have optical ages of 260 20 325 25 and 335 45 yr historical records and radiocarbon dating show that the sand at each of the three sites is between 150 and 400 yr old these optical ages support the hypothesis that the vancouver island sands were deposited by a tsunami generated by a large earthquake on the cascadia subduction zone about 300 yr ago

environmental controls on coastal dune formation skallingen spit denmark abstract many coastal dune systems in western europe were emplaced during the little ice age lia the formation of such dune fields has generally been ascribed to a combination of low sea level and strong winds during that time period providing a supply of sand from the exposed shoreface and sufficient wind energy to transport this sand landward however little information exists on the processes that controlled sediment supply to the beach and why this onshore supply was initiated at all in this contribution we consider the origin and development of older dune fields on a barrier spit complex skallingen located in the northern part of the danish wadden sea maps and new data on dune litho and chrono stratigraphy the latter based on osl dating allow a precise estimate of the initiation and termination of dune emplacement dune formation at skallingen started at a relatively late stage of the lia and it can be temporally correlated with a phase of relative sea level rise in north western europe and with a high frequency of storm surges along the danish west coast these are the conditions during which nearshore bars currently migrate onshore across the shoreface off skallingen the bars eventually merge with the beach and constitute a source of sand for modern foredune accretion it is probable that the onshore bar migration occurred under similar conditions in the past and the migration was triggered or enhanced by the sea level recovery from the mid lia low stand and the associated frequent storm surge activity consequently at skallingen onshore sand supply was caused by marine rather than aeolian agents this supply provided the basis for subsequent dune formation indications are however that the sediment supply to the beach dunes was a factor of 2 3 larger in the past dune aggradation eventually ceased around 1900ad because of dyke construction hence the association between dune formation and sea level surge variation at skallingen is somewhat contrary to other statements of coastal dune development during the lia in north western europe

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

late wisconsinan erosion and eolian deposition summer island area pleistocene mackenzie delta northwest territories optical dating and implications for glacial chronology the summer island area of the pleistocene mackenzie delta western canadian arctic is thought to have been last glaciated during the early wisconsinan 35 ka with a suggested late wisconsinan 13 ka glacial limit located 80 100 km to the south cryostratigraphic observations in the summer island area identify eolian and fluvial sediments overlying an erosion surface on summer island eolian sand occurs within sand wedges the tops of which are contiguous with an eolian sand sheet deposited on a formerly bare ice surface this paleo ice surface is attributed to fluvial erosion and that in turn is attributed to proglacial meltwater activity the age of erosion is inferred to be shortly before 14 ka determined by optical dating using infrared stimulation of luminescence from feldspar of the eolian sand wedges this 14 ka meltwater erosion is significantly north of the generally accepted limit of late wisconsinan glaciation in this coastal area suggesting that ice last covered the whole of rich

middle to upper pleistocene morphostructural evolution of the nw coast of sicily thermoluminescence dating and palaeontological stratigraphical evaluations of littoral deposits abstract infralittoral and terrigenous middle to upper pleistocene deposits outcropping at the nw coast of sicily gulf of castellammare and peninsula of capo san vito were investigated in order to recognise glacio eustatically caused sea level highstands and the interference between tectonics eustasy and local conditions of the coast the results originating from a stratigraphically important area were obtained by palaeontological stratigraphical analyses physical age determination with the thermoluminescence method and by detailed morphostructural studies the marine deposits situated at 3 40 m a s l mainly provide an oligotypic molluscan fauna referable to modern sgcf sfhn and sfbc biocoenoses of the infralittoral zone which live on various substrates in water of moderate to strong energy the senegalese molluscan forms providing the palaeocommunity of tyrrhenian age oxygen isotope substage 5e is comparable with the modern ap biocoenose which live on hard substrates in water of moderate energy the age determinations and estimates of the terraces indicate at most four glacio eustatic sea level highstands one perhaps two highstands between 800 ka and 250 ka isotope stages 24 8 a further event between 250 ka and 190 ka stage 7 and the youngest highstand event between 140 ka and 75 ka stage 5 the last glaciation stage 4 2 is represented by a terrigenous sequence which suggests rapid alternation of morphodynamically stable and unstable intervals as well as changes in moisture and seasonality of climate the terraces are affected by ne sw orientated faults causing brittle deformation and uplifting in rates of approximately 0 14 0 25 m ka with increasing intensity towards the east the oxygen isotope stratigraphy indicates 7 warming events during the past 800 ka the morphostructural pattern of the nw coast of sicily gives evidence for the sensible interference between local coastal conditions like sediment drift sea water currents and sediment supply on the one hand the absolute rise of eustatic sea level and the absolute uplift rate on the other hand it is obvious that eustatic oscillations deduced from deep sea sediment values does not automatically coincide with those recorded in the inner shelf area

thermoluminescence dating of aeolian sands from polycyclic soil profiles in the southern netherlands abstract an aeolian cover sand section with excellent 14c control on bolling peat and other sections with 14c dates on humic acid extracts from holocene polycyclic soil profiles in the southern netherlands have been tl dated using k feldspar separates the 14c dates indicated two periods of weichselian cover sand deposition and three periods of holocene drift sand accumulation bronze age medieval time and post medieval time alternating with periods in which the landscape was stabilized as conventional tl methods proved unsatisfactory a new approach has been applied to establish the equivalent dose ed of the samples using the formula ed d 1 f d is the dose value determined for a specific bleaching time and f is the fraction of the radiation induced tl signal that remains after this bleaching time as determined by additional laboratory measurements on irradiated material in spite of the new approach to determine the ed the tl ages of the weichselian cover sands are underestimated as has been noted before on similar material however the tl ages of the holocene drift sand samples indicate that tl can be used to distinguish these aeolian sands when soil profiles are lacking an example of this is provided

expansion and contraction of hulun buir dunefield in north eastern china in the last late glacial and holocene as revealed by osl dating optical stimulated luminescence osl study on sand and fossil soils from hulun buir dunefield in eastern china is reported in this paper aeolian dune sequences responded to the climate change by alternations of aeolian sand and dark sandy soils which corresponded to arid and humid conditions respectively optical dating using the single aliquot regeneration technique with quartz was applied to the deposits the results indicate that the soils and underlying aeolian sand correspond to the holocene optimum ho and the last late glacial respectively combined with studies of osl dating of 13 profiles and grain size magnetic susceptibility total organic carbon sediment color and scanning electron microscopy measurements for two representative sections indicate the expansion in the last late glacial sand was 10 times that of today the dune field was not totally stabilized by vegetation cover until ho 10 5 ka bp

chronological separation of interglacial raised beaches from northwestern europe using thermoluminescence thermoluminescence tl age estimates have been obtained on coarse grained detrital feldspar from eemian beach sand substage 5e early weichselian dune sands substages 5d and 5b and pre eemian beach sand the past radiation dose is obtained using the additive dose method even for the oldest samples which date to 300 000 yr b p by other methods the tl signal is not in saturation and can be doubled by the addition of laboratory radiation doses without saturation being achieved this is contrasted with the behavior of polymineral silt sized grains from loess in the adjacent area the tl age estimates are systematically underestimated by about 40 when compared with the expected geological ages however they are in correct stratigraphic order and demonstrate that stage 5 beach deposits can be distinguished from those resulting from earlier high sea levels using tl signals from potassium feldspars

late quaternary stratigraphy and geochronology of the western killpecker dunes wyoming usa abstract new stratigraphic and geochronologic data from the killpecker dunes in southwestern wyoming facilitate a more precise understanding of the dune field s history prior investigations suggested that evidence for late pleistocene eolian activity in the dune field was lacking however luminescence ages from eolian sand of 15 000 yr as well as folsom 12 950 11 950 cal yr b p and agate basin 12 600 10 700 cal yr artifacts overlying eolian sand indicate the dune field existed at least during the latest pleistocene with initial eolian sedimentation probably occurring under a dry periglacial climate the period between 13 000 and 8900 cal yr b p was characterized by relatively slow eolian sedimentation concomitant with soil formation erosion occurred between 8182 and 6600 cal yr b p on the upwind region of the dune field followed by relative stability and soil formation between 5900 and 2700 cal yr b p the first of at least two latest holocene episodes of eolian sedimentation occurred between 2000 and 1500 yr followed by a brief 500 yr episode of soil formation a second episode of sedimentation occurring by at least 700 yr may coincide with a hypothesized medieval warm period recent stabilization of the western killpecker dunes likely occurred during the little ice age 350 100 yr b p the eolian chronology of the western killpecker dunes correlates reasonably well with those of other major dune fields in the wyoming basin suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late quaternary similar to dune fields on the central great plains dune fields in the wyoming basin have been active under a periglacial climate during the late pleistocene as well as under near modern conditions during the latest holocene

changes in holocene paleoseismic activity in the hula pull apart basin dead sea rift northern israel abstract paleoseismic analysis of the azaz fault segment of the dead sea fault northern israel indicates that this region was subjected to intermittent periods of strong seismicity and quiescence during the latest pleistocene and the holocene the azaz fault forms the eastern margin of the hula valley a pull apart basin between two left stepping segments of the dead sea fault the fault is currently inactive but it displaces a 25 30 ka travertine in the northeastern corner of the hula valley and near surface marsh sediments inside the valley two trenches excavated across a 15 20 m high fault scarp near kefar szold expose fluvial and colluvial sequences showing clear evidence of recent tectonics one trench exposes well sorted bedded alluvial sediments comprising two upward fining units each capped by a weakly developed paleosol the sediments were deposited on the down faulted block and are bounded in the east by the fault scarp the second trench uncovers fine colluvial sediments cross cut by a wide fault parallel fissure filled by collapsed sediments in both trenches the lower sedimentary unit is capped by a coarse colluvium containing boulders up to 1 5 m in size the colluvium shows no clear bedding and has a weakly developed paleosol on top optically stimulated luminescence dating of the lower fluvial sequence shows that its age ranges between 12 ka at the base to 6 ka at the top while the middle part of the overlying colluvium is ca 4 8 ka the relation between the lower fluvial units and the fault indicates that at least two large scale earthquakes occurred in the early holocene each one resulting in a 1 1 5 m high fault scarp during this seismically active period no coarse colluvial sediments were deposited along the fault trace and thus the region must have had low tectonic relief the clear contact with the overlying coarse colluvium reflects a middle holocene rapid change to the present high steep relief this change was achieved by frequent strong seismic events which triggered colluvial processes and prevented stratification and soil formation on the slope the soil on the present slope reflects a quiescent period that has lasted at least several hundred years during which stress has accumulated and seismic risk increased

testing the potential of k feldspar pir irsl and quartz esr for dating coastal alluvial fan complexes in arid environments abstract coastal alluvial fans caf are important geo archives due to their sensitivity to both tectonic activity and climatic changes thus they can give key insights for geomorphic and sedimentary processes in this study we test the potential of k feldspar post infrared infrared stimulated luminescence pir irsl and quartz electron spin resonance esr methods for dating alluvial fan complexes in arid environments the existing chronological data from marine terraces that interact with caf make the atacama desert in northern chile an excellent setting for this research samples have been collected from alluvial marine and aeolian sediments embedded in the caf complexes allowing evaluation of the different signal properties and bleaching characteristics of the pir irsl and esr signals over late pleistocene time scales pir irsl dose distributions of clast rich alluvial fan samples are characterised by higher scatter and demonstrate heterogeneous bleaching while matrix rich alluvial fan deposits show rather homogeneous poor bleaching in the dose dispersion as indicated by a modern analogue sample in contrast marine and aeolian deposits are homogeneously well bleached supported by a modern littoral sample following the quartz multiple centre mc esr dating approach al and ti centres bleaching of the different centres prior to deposition has been achieved while the ti h centre provides mostly lower doses than the ti li centre in most cases the al centre provides the highest dose values this pattern is consistent with their respective bleaching kinetics and suggests that the ti centre signals most likely provide the closest estimate to the true burial dose for samples with doses 200 gy esr and pir irsl ages are consistent at 2 for the marine aeolian and clast rich debris flow deposits which is in agreement with existing chronological data in this area it appears that the mode of sediment transport on alluvial fans either as matrix or clast rich flows plays an important role in sediment bleaching while clast rich alluvial fan deposits are likely better bleached we cannot exclude insufficient bleaching during matrix rich alluvial fan flows our dating results suggest that both pir irsl and esr dating overestimate the true burial age the combination of pir irsl and mc esr dating can be considered as a promising tool for deciphering alluvial fan formation over late pleistocene time scales

thermoluminescence dating study of quartz in aeolian sediments from southeastern australia abstract using 90 125 m grains of quartz extracted from sediments the equivalent dose absorbed since burial was derived by exposing aliquots of quartz to a sunlamp regenerating the tl growth curve by artificial irradiation and comparing the natural tl of the sample being dated as well as that of an adjacent surface sample to this curve the age can then be calculated once the dose rate is known the method is tested successfully on known age aeolian sediments retaining their original bedding but reveals some difficulties in trying to use tl to date aeolian sediments for which the original bedding has been destroyed anomalous fading of tl in quartz is reported this latter difficulty was circumvented by using a delay of several weeks between the irradiation and heating of the quartz

a luminescence dating study of open air palaeolithic sites in western epirus greece we report results of a preliminary luminescence dating study of middle to late pleistocene red beds and early holocene dune deposits from prehistoric sites in northwest greece the wide range in age estimates contradicts the impression that all the red sediments of the region are as old as the pliocene or early pleistocene and that artefacts found in them are late intrusions and hence worthless in a stratigraphic context our data provide support for a recently proposed chronological framework of the palaeolithic in the region tl irsl comparisons confirm the irsl as a more appropriate means for dating water laid deposits while both methods appear to be equally useful for aeolian sediments the study cautions that the effect of various laboratory procedures used to obtain tl or irsl dates in a context of complex depositional histories precludes a simple prima facie interpretation of the ages a proper evaluation of luminescence dates requires a full account of the laboratory procedures employed and an understanding of the depositional history of the sediments

luminescence dating applications in geomorphological research abstract chronological control remains critical to the interpretation of environmental change and to establishing long term rates of geomorphological processes radiocarbon dating will continue to be the central technique for age assessment of carbon bearing sediments deposited in the last ca 40 ka but alternative absolute dating strategies are required for older or non carbon bearing sediments they include uranium series dating of precipitated sediments k ar and ar ar dating of primary volcanic materials and cosmogenic isotopic dating of surface exposure ages an additional family of methods collectively termed luminescence techniques is increasingly providing a basis for the age assessment of detrital sedimentary deposits these methods directly date the deposition of detrital mineral grains typically quartz and feldspar and have been demonstrated to provide accurate deposition chronologies for up to 800 ka although 150 ka is more typical in the past decade a subset of luminescence techniques which employ optical sample stimulation methods called optical dating has made it possible to date samples from a much wider range of depositional systems given that the methods directly date sedimentation they allow direct assessment of depositional dynamism in numerous terrestrial and subaqueous including marine sedimentary systems and have demonstrated particular potential in the elucidation of chronologies from aeolian dune and loess fluvial colluvial coastal and volcaniclastic environments this paper provides a summary of the principles of the luminescence especially optical dating methods and shows how recent developments specifically single aliquot dating procedures have dramatically enhanced the scope and potential of the method the luminescence techniques are increasingly being incorporated into a wide range of geomorphological studies which seek to establish the nature of landscape changes over the past interglacial glacial cycle and beyond

optical dating of young modern sediments using quartz results from a selection of depositional environments abstract equivalent dose ed evaluations for quartz grains extracted from a number of modern or young samples collected from a range of depositional environments are reported the signal used was optically stimulated luminescence osl with an argon ion laser tuned to 514 nm as a light source typical equivalent dose values were 0 05 0 3 gy for the given samples which is substantially less than equivalent doses expected for similar sediments by conventional thermoluminescence tl the non zero equivalent dose exhibited by the samples may be a product of relict osl from incompletely bleached traps sample pre treatment procedures or due to signal recuperation following bleaching during antiquity the potential significance of each are discussed a number of modifications to sample pre treatment and processing are also described

the blue emission of k feldspar coarse grains and its potential for overcoming tl age underestimation abstract this paper presents preliminary tl ages on k feldspar coarse grains from raised shallow marine sediments of nw europe and southern italy comparisons between tl ages using different optical filters suggest the use of the blue transmitting corning 7 59 filter allows measurement of an apparently stable tl component in k feldspar which could overcome the problem of age underestimation in the 75 300 ka range

dunes in southeastern namibia evidence for holocene environmental changes in the southwestern kalahari based on thermoluminescence data abstract linear dunes in the southwestern kalahari provide evidence of the nature of paleoclimates they have special significance because their alignments indicate a previous circulation pattern with prevailing northwesterly winds at present the bases of the dunes are fixed by vegetation and only the dune crests are active in contrast to previous suggestions final dune stabilization took place before about 9 8 ka this corresponds to reduced wind velocities accompanied by more humid conditions this seems to be the last important environmental change recorded by significant landforms in the southwestern kalahari since about 8 ka the region remained more or less semi arid the long distance to seasonal south shifting humid tropic air masses innertropical convergence zone itcz and the climatic barrier of the namib and the karas mountains against atlantic influences allowed only minor fluctuations the holocene is a period of reduced pan development the pans are partly buried by the early holocene linear dunes as well as by young sand fields at pan 1073 southeast of grootpan intra pan dunes have formed during the last 1000 years

quality assurance in luminescence dating recent advances in luminescence dating have led to increasing application of the technique to sediments from a wide range of depositional environments many of which are characterised by rapid transport and deposition under turbid conditions the complete zeroing of the luminescence signal by exposure to light is critical to obtaining an accurate age for deposition of the sediment before any geomorphological or palaeoenvironmental reconstructions can be undertaken based on this chronology comparison of luminescence dates with independent age control is rare due to a lack of suitable material in natural contexts and thus the accuracy of the luminescence dating technique has yet to be proven in many depositional environments there is therefore a clear need for both quality assurance in luminescence dating and a method for assessing the accuracy of each date this paper describes and demonstrates a quality assurance method that can be used as part of a routine dating programme and which can discriminate against samples which would give inaccurate dates

reconnaissance thermoluminescence dating of northern australian coastal dune systems abstract quaternary lithostratigraphic units in coastal dunes have been dated at three locations in northern australia cobourg peninsula shelburne bay and cape flattery by both radiocarbon dating of shell and organic carbon and thermoluminescence tl sediment dating both coarse fraction and fine fraction tl methods were used seventeen tl dates were measured none of the tl dates contradict the ages given by radiocarbon where multiple tl dates were taken from a unit they overlap within 2 standard deviation giving added confidence in the results a phase of dune emplacement during the late holocene ca 2700 1800 yr b p was identified in two of the dune fields an early holocene phase of dune emplacement ca 8600 7500 yr b p in two of the dune fields and a late pleistocene episode ca 24 000 17 000 yr b p in both the cape york dunefields three older units gave dates of about 29 000 81 000 and 171 000 yr b p but these must be treated with caution

dating the lower paleolithic open air site of holon israel by luminescence and esr techniques abstract the open air acheulian site in holon israel was dated by the luminescence methods and by electron spin resonance esr situated in the coastal plain quaternary kurkar group the holon site was first excavated in the late 1960s when typical lower paleolithic lithics and middle pleistocene fauna were found in order to date the site new test pits were dug adjacent to the earlier excavations and the archaeological bed was exposed in a section comprising a series of paleosols and aeolianites alkali feldspars separated from the sediments were dated using the infrared stimulated luminescence and thermoluminescence signals and quartz was dated using the optically stimulated luminescence signal the age of the archaeological bed is constrained by two samples to 198 000 22 000 201 000 17 000 yr the age of the base of the section is 240 000 29 000 yr and the age of the top is 81 000 8000 yr two teeth from the archaeological bed recovered from the original excavation collection yielded an average esr age of 204 000 16 000 yr calculated using the linear uptake model which is in a very good agreement with the luminescence ages these dates place holon within the range of other late acheulian and acheulo yabrudian sites in this region such as tabun e younger chronology yabrud i archaeological level 18 and berekhat ram

a comparison of tl age estimates from different mineral fractions of sands abstract although tl dating of sediments aims to produce accurate dates some recent attempts to date both fine grain polymineral mixtures and large grain feldspars have resulted in age estimates that appear to underestimate the true geological age of the material tl age estimates reported for different mineral fractions quartz and feldspar from the same large grain sand samples have also proved unexpectedly different the possible reasons for underestimation of large grain feldspar ages are reviewed in the context of an exercise designed to look for internal consistency in tl age estimates from quartz and feldspar fractions of sand samples from chelford u k the analyses of the chelford material show internally consistent age estimates over the range 20 100 ka bp that are also in agreement with the independent age control that is available for the site

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

immediate profile and planform evolution of a beach nourishment project with hurricane influences abstract in this study planform adjustment began during a period of calm weather immediately after nourishment and then the passage of one strong storm caused a substantial portion of the total profile equilibration weekly beach profiles shoreline surveys and nearshore wave measurements were conducted before during and immediately after construction of the 1100 m long upham beach nourishment project on the low energy west coast of florida this project was constructed in three segments the wide north segment the central segment and the narrow south segment with the exception of the relatively distant passage of hurricane charley calm weather prevailed for 45 days following completion of the south and central segments construction of the wide north segment was completed on august 27 2004 substantial planform diffusion occurred prior to construction completion via formation of a 300 m long spit extending from the wide north segment the shoreline orientation was changed abruptly due to this diffusion spit formation as opposed to the gradual adjustment predicted by most long term models planform adjustment was initiated prior to profile equilibration and it did not require high energy conditions a simple vector sum model for determining the orientation of a potential diffusion spit was developed this study recommends designing end transitions at the predicted diffusion spit orientation to avoid post nourishment spit formation during future projects profile equilibration occurred rapidly due to the passage of three hurricanes soon after nourishment was complete nine days after completion hurricane frances passed by the project area generating high wave conditions h sig 1 7 m for this region the steep post nourishment beach slope of 0 078 was reduced to 0 036 nearly to the equilibrium slope 0 034 due to this storm hurricanes ivan and jeanne which were nearly as energetic passed by the project area within 1 month after frances and resulted in much less profile slope change examination of the ratio of total volume to plan area remaining in the project area also suggested that a substantial portion of the total profile equilibration occurred as a result of hurricane frances this study indicates that profile equilibration can be an event driven process which contradicts the concept of longer term gradual profile equilibration both profile and planform adjustment can occur rapidly given the appropriate site conditions and energy levels

methodological considerations in the optical dating of quartz abstract the optically stimulated luminescence from quartz grains extracted from sediments at two archaeological sites has been studied the sites were the upper palaeolithic site at hengistbury head dorset u k and the upper aterian site at chaperon rouge morocco problems associated with the technique of optical dating are discussed particularly the thermal treatment that is necessary to remove thermally unstable charge following artificial irradiation and the extrapolation of growth curves to estimate the equivalent dose the technique used is described and some preliminary dates are presented

thermoluminescence dating tests for lacustrine glaciomarine and floodplain sediments from western washington and british columbia to help further develop reliable procedures for accurate thermoluminescence tl dating of quaternary waterlaid sediments we tested tl dating procedures on sediment types rarely examined six glaciolacustrine samples three samples of glaciomarine drift and eight samples of floodplain deposits we used the partial bleach r beta gamma technique applied to fine silt polymineral grains results from our younger known age glaciolacustrine sediments confirm earlier observations that only the clayey laminae are generally suitable for tl dating a clayey lamina older than ca 140 150 ka produced no age underestimation and this result ca 300 ka suggests that such older lake sediments are probably suitable for tl dating two proximal samples of glaciomarine drift produced large tl age overestimates whereas the single distal glaciomarine drift sample yielded an expected age 177 38 ka suggesting that follow up studies are warranted our results for eight flood plain samples confirm that zeroing of li

glacial interglacial changes in dust deposition on the chinese loess plateau the chinese loess plateau clp contains an extensive record of aeolian deposition through multiple glacial interglacial cycles independent chronologies based on pedostratigraphy magnetic susceptibility radiocarbon and luminescence dating were developed for 79 sites and used to estimate aeolian mass accumulation rates mars for marine isotope stages 1 5 the regional median value of mar for stage 2 is 310 g m2 yr compared to an estimate of 65 g m2 yr for stage 5 estimated mars from individual sites for stage 2 are approximately 4 3 times greater than mars for stage 5 and 2 1 times greater than for stage 1 mar values at individual sites are consistently highest in the northwest and lowest in the southwest of the clp during all marine isotope stages mars estimated on sections through loess terraces are consistently higher than mar estimates at other sites indicating that local recycling of loess material from exposed river valley deposits has been significant throughout the last 130 kyr although the spatial and temporal patterns in mar are robust there are uncertainties about the magnitude of these changes due to a lack of bulk density measurements and uncertainties in the chronologies for individual sites b site and chronological biases in the sampling used to derive regional estimates and c the unquantified nature of human impact on accumulation rates during the late holocene nevertheless the records from the clp pose a number of challenges which could be addressed by numerical models of the palaeo dust cycle

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples