luminescence dating of sediments from buctouche spit new brunswick in this paper we describe our efforts to determine the formation chronology of a sequence of dunes on buctouche spit a holocene deposit on the northeast coast of new brunswick optical dating using infrared stimulation of k feldspar grains yielded ages ranging from 5 30 a for an embryo dune to 765 45 a for the oldest dune thermoluminescence ages although less precise support the recent formation of the dunes the ages exhibit the expected sedation from youngest to oldest and are consistent with historical evidence coupled with an assumed constant sediment aggradation rate the age resolution obtained was very good and we conclude that the optical dating method used here shows great promise

reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk roberts helen plater a j 2007 reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk the holocene 17 4 pp 495 505 rae2008

widespread middle holocene dune formation in the eastern upper peninsula of michigan and the relationship to climate and outlet controlled lake level dating of five widely spaced noncoastal dunes in eastern upper michigan by optically stimulated luminescence of quartz establishes that eolian sand was last mobilized between ca 7 and 5 5 ka in the region although this interval corresponds to the drier altithermal hypsithermal period climate alone may not have been sufficiently arid to cause dune formation in this area instead it appears that dune formation may also be linked to depressed water tables associated with outlet controlled low levels in lakes michigan and superior following dune stabilization peat began to accumulate in interdune areas ca 4 4 ka

late pleistocene coastal evolution of san giovanni di sinis west sardinia western mediterranean abstract the upper pleistocene succession of coastal deposits outcropping at san giovanni di sinis west sardinia has been studied since the 1960s however the absence of consistent radiometric ages has allowed the production of competing stratigraphic subdivisions of these deposits with different isotopic stage ois mis attributions the succession is composed of sandy to gravelly shallow marine coastal aeolian and alluvial fan plain deposits facies analysis and log correlations show the presence of three unconformities t1 t2 t3 always overlain by shallow marine deposits cutting through the substrate alluvial fan or aeolian sediments we have collected three samples for optically stimulated luminescence osl dating at the top of each shallow marine deposit the succession is composed of four unconformity bounded units u1 u2 u3 u4 and the new osl dates indicate the presence of three different sea level highstands the first unit u1 which is composed of shallow marine to aeolian deposits and overlies transgressive surface t1 is related to a marine transgression during ois 7 186 13 ky unit 2 is composed of continental deposits and formed during ois 6 unit 3 represents ois 5 and overlies a transgressive surface t2 more precisely subunit u3a is related to ois 5e 120 10 ky eu tyrrhenian or eemian sensu strictu and is characterized by shallow marine to aeolian deposits developed during both transgressive and highstand phases the following bay deposits of subunit 3b are associated with ois 5c 100 5 ky and record a second transgressive event t3 and highstand phase occurred during the neo tyrrhenian the succession of san giovanni di sinis ends with continental deposits of unit 4 associated to a sea level fall that took place at the beginning of the last glacial phase ois 4

origin and evolution of lunettes on the high plains of texas and new mexico lunettes isolated dunes on the lee side of playa basins are common landforms on the southern high plains of northwest texas and eastern new mexico the dunes contain calcareous 15 40 caco3 sandy loam or loamy sand with minor amounts of sepiolite deposited 25 000 800014c yr b p and derived by deflation of lacustrine carbonate in the basins the dunes also contain low carbonate 0 15 caco3 sand or loamy sand that was deposited 25 000 15 000 yr b p and 8000 5000 yr b p and was derived by deflation that created the basins or deflated from sand deposited in the basins buried soils are common in the lunettes a bk profiles characterize soils formed in the calcareous sandy loam the sandy low carbonate sediments contain a bt profiles in the oldest sand of some dunes and a bw a bt or a btk in the early and middle holocene sand the dune stratigraphy combined with carbon isotope data derived from dated a horizons in lunettes suggests the following scenario for the southern high plains the lunettes began forming as low carbonate sand dunes in the late pleistocene as playa basins were formed or deepened by wind erosion the erosion repeatedly alternated with stability the environment probably was cool and dry but one or more cool and wet intervals 25 000 15 000 yr b p resulted in a rise in the water table and deposition of lacustrine carbonate in the deepest basins there may have been short departures toward warmer and probably toward drier conditions throughout this time episodically dry conditions 15 000 8 000 yr b p resulted in deflation of the carbonate and further dune construction by repeated accretion of calcareous sandy loam or loamy sand the low carbonate sand was deposited during widespread drought and deflation 8000 5000 yr b p the dunes have been largely stable in the late holocene

a 250 000 year record of lunette dune accumulation on the southern high plains usa and implications for past climates abstract a concentration of lake playa basins occurs on the southern high plains shp of northwest texas and eastern new mexico associated with these lake playas are lee side lunettes positioned on their southeast margins ranging in height from 1 5 to 10 m an osl dating program was applied to 30 samples from lunettes associated with large lakes and small playa basins samples were extracted from trenched dune sections or from deep cores earlier shp lunette investigations show depositional ages primarily in the late wisconsin and holocene this research extends the timing of lunette accretion to the middle pleistocene the earliest recorded deposition for these features the expanded chronology permitted investigation into dune morphology on nested lunettes built on contracting lake margins outer lunettes formed prior to inner dunes but simultaneous deposition occurred on downwind ridges as younger lee side dunes were constructed large lake lunettes were inactive during discreet shp pluvial episodes from early wisconsin to lgm conversely these lunettes accreted when climatic conditions promoted basin desiccation and aeolian deflation this suggests their mode of formation contrasts with lunette models recognized for other regions from post lgm to earliest holocene active lunette accretion occurred from 16 to 11 ka followed by a significant period of lunette construction during the mid holocene late holocene lunette deposition was interrupted by intervals of landscape stability lunette deposition between 1300s and 1700s corresponds with drought intervals recognized in tree ring records from adjacent regions recent lunette activity on the plateau is contemporary with the 1930 s dust bowl further insight into shp response to changing climatic conditions was given by comparing lunette depositional events with previous investigations on sedimentation intervals for draws lake playa basins and sand sheets

influence of vegetation on aeolian sand transport rate from a backshore to a foredune at hasaki japan the influence of vegetation on aeolian sediment transport rate in the region from a backshore to a foredune was investigated at the hasaki coast in japan where an onshore wind was predominant and the creeping beach grasses carex kobomugi and calystegia soldanella were major species the comparison of cross shore distributions of the cross shore component of aeolian sand transport rate with and without vegetation which were estimated on the basis of the beach profile changes and a mass conservation equation showed that the creeping grasses influenced the aeolian sand transport rate the landward aeolian sand transport rate rapidly decreased landward from the seaward limit of vegetation when the grasses grew the aeolian sand transport rate reduced by 95 with a vegetation cover of 28 on the other hand when the grasses were absent the landward aeolian sand transport rate did not decrease near the seaward vegetation limit but near the foot of the foredune

optical dating of a fimic anthrosol in the southern netherlands plaggen agriculture was the dominant land use system in the pleistocene cover sand area of northwest europe before the introduction of chemical fertilisers in today s landscape fimic horizons and driftsand deposits are characteristic survivors of plaggen agriculture the age and accumulation rate of these phenomena cannot be satisfactorily determined by conventional methods like pollen analysis and radiocarbon dating the results of optical dating applied to a fimic horizon of a plaggen soil near weert netherlands are compared with those from conventional methods

late holocene aeolian sedimentation in the tottori coastal dune field japan sea affected by the east asian winter monsoon many dune fields that have formed along the southern coast of the japan sea are influenced by the north westerly winter monsoon which transports beach sand landwards the tottori coastal dune field of the japan sea has not been disturbed much by human activities until the 20th century and thus is expected to provide a continuous record of the relationships between the winter monsoon and aeolian sedimentation we examined new ground penetrating radar profiles and optically stimulated luminescence osl ages of quartz sand from transverse dune ridges in the western part of the dune field in addition to existing data in the eastern part this allowed us to extend the study period to cover the past 1000 years and to effectively compare the sedimentary record with other coastal dune fields in east asia and other palaeoenvironmental proxies osl ages from older dune sediments suggest considerable aeolian activity from the 10th to 12th century ad whereas a hiatus of dune sediment record between the 12th and 15th centuries was detected these results suggest that during the medieval period aeolian activity was low or that extensive erosion removed most of the deposits since the late 15th century dune sedimentation has apparently been broadly continuous though with periods of higher and lower activity in both of the eastern and western parts most of the dune ridges accreted landwards but clear seaward accretion occurred during the 18th century possibly reflecting a decrease in wind strength that restricted sand transport in contrast two significant landward accretion events are inferred to have occurred from the late 15th to 17th centuries and around 1840 corresponding to periods of increased dust fall in china which suggests an enhanced winter monsoon and to cold periods suggested by the decline of the sunspot number the timing of periods of inactive and active dune sedimentation inferred from alternations of organic soil and aeolian sand in other coastal dune fields of east asia appears to be concordant with corresponding periods in the tottori dune field we thus propose that other japan sea dune fields may also provide a valuable record of east asian winter monsoon fluctuations

isotope paleoecology of episodic mid to late holocene bison population expansions in the southern plains u s a abstract we used a xad purified ams radiocarbon method to date 62 bison specimens from different contexts on the very southern extent of the great plains of north america to produce a precise chronology of bison population expansions spanning the last 6000 years sixty one of these samples provide stable carbon and nitrogen isotope data indicating relative temperature and moisture conditions during intervals defined by the presence of bison within this time span this chronology indicates climatic conditions favorable to bison were present in the greater central texas area including the uplifted edwards plateau and extending to the coastal plain during periods from 5955 to 5815 3290 to 3130 2700 to 2150 and 650 to 530 cal bp however isotope results suggest climatic conditions differed for each period the earliest calf creek period was characterized by cool but dry conditions the later late archaic 1 2 periods were increasingly warmer and wetter and the latest toyah period was cooler and drier than the late archaic periods but warmer and wetter than calf creek both the calf creek and toyah periods had higher variability within these overall trends comparison with regional records suggests that these periods represent variation within generally cool dry climates human adaptive response to increased bison availability resulted in significant cultural changes across all four periods

optical dating of young coastal dunes on a decadal time scale we explore the use of quartz optically stimulated luminescence osl dating for reconstructing coastal evolution on a time scale of decades to a few hundred years samples are taken from the accretionary south west coast of texel a barrier island just offshore of the northern netherlands the ages of dune ridges are known from historical sources an excellent chronology with a decadal accuracy exists for the past 260 years osl ages of less than 10 years on the youngest samples indicate that the osl signal of the quartz grains is very well zeroed prior to deposition and burial osl ages of five samples from a 250 year old dune ridge are indistinguishable and the osl ages on 17 out of 20 samples are in excellent agreement with the well known independent age controls our results highlight the potential of osl dating for high resolution reconstruction of coastal evolution over the past few centuries

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

late holocene eolian activity in the mineralogically mature nebraska sand hills abstract the age of sand dunes in the nebraska sand hills has been controversial with some investigators suggesting a full glacial age and others suggesting that they were last active in the late holocene new accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic rich sediments suggest that eolian sand deposition occurred at least twice in the past 300014c yr b p in three widely separated localities and as many as three times in the past 80014c yr at three other localities these late holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s dust bowl period based on independent great plains climate records from lake sediments and tree rings however new geochemical data indicate that the nebraska sand hills are mineralogically mature eolian sands in nebraska have lower k feldspar and k2o rb and ba contents than most possible source sediments and lower k feldspar contents than dunes of similar age in colorado the most likely explanation for mineralogical maturity is reduction of sand sized k feldspar to silt sized particles via ballistic impacts due to strong winds over many cycles of eolian activity therefore dunes of the nebraska sand hills must have had a long history probably extending over more than one glacial interglacial cycle and the potential for reactivation is high with or without a future greenhouse warming

late holocene inland dune activity in the uk a case study from breckland east anglia inland dune fields found in breckland east anglia uk have previously been correlated with the widespread late devensian coversands of the region and a seventeenth century sandflood which is known to have inundated the village of santon downham a programme of optically stimulated luminescence and radiocarbon dating undertaken on the dunes at wangford warren and santon downham reveals that episodic aeolian activity has taken place during the last 7000 years five sand depositional phases on breckland dunes are identified c 6500 c 1600 1100 c 500 c 400 335 and from c 200 30 years before present between c 2120 1840 years ago and within the period 1100 300 years ago quiescent periods allowed the development of fen peat and soils local controlling factors on aeolian activity in breckland appear to be related to anthropogenic activities and livestock sheep and rabbits reducing vegetation cover and decreased precipitation and sea levels which led to lowering of water tables breckland aeolian activity when compared to the national and sub continental holocene aeolian activity record shows a high level of concordance the underlying forcing factor for late holocene dune activity in the uk and elsewhere in europe appears to be climatic instability in the north atlantic associated with both the little ice age and previous similar events which led to increased storminess climatic variability and lower temperatures

middle to late pleistocene coastal deposits of alghero northwest sardinia italy chronology and evolution the shallow marine to coastal deposits of alghero have been dated using the optically stimulated luminescence osl method and studied to define the palaeoenvironmental evolution of coastal areas in northwest sardinia dating coupled with sedimentological and stratigraphical analyses allowed the subdivision of the succession in four unconformity bounded units u2 u3a u3b u4 unit u2 of penultimate glacial stage mis 6 ca 150 ka is composed of dune deposits formed intermittently along rocky coastal areas under strong wind conditions subunit u3a is composed of cliff bounded gravelly dominated pocket beach deposits commonly highly fossiliferous and is assigned to the interglacial mis 5e ca 125 ka subunit u3b is characterized by sandy beach to coastal systems of the isotopic sub stage mis 5c ca 100 ka the unconformity between u3b and u4 marks the initiation of last glacial regression mis 5a 4 ca 77 ka during which shelf areas were exposed and small incised valleys developed along the valley flanks colluvial or sheetflood sediments were deposited and in the central part thick reddish paleosols formed valleys were eventually filled by thick aeolian dune deposits mis 4 3 indicating persistent inland sand transport around alghero coastal carbonate rich dunes preferentially formed and migrated inland during lowstand and falling stages when the climate is relatively cold vegetation is quite open winds are fairly strong and sediment supply from exposed shelf areas is high

effective integration of core and log data abstract the primary purpose of core to log data integration is to reduce the uncertainty associated with formation evaluation in so doing advantage is taken of both the higher precision of core data and the larger scale of investigation of log data it is particularly important that when tying logs back to core the calibration algorithm is as well defined as possible a basic requirement is the definiton of a common reference depth scale a second requirement is to reconcile the different vertical resolutions by the depth averaging of core data the signal enhancement of log data or both essential to this process is the adoption of key intervals as control zones for data integration these procedures can result in a reduced uncertainty which transmits through to reservoir appraisal through a better petrophysical definiton of constituent lithological units important new developments will facilitate the integration of core and log data where core recovery is incomplete these include the ultrasonic monitoring of core entry into the core barrel the multi sensor scanning of whole cores and the interactive display of both core and log data in interrogative workstation mode implementation of the optimum data integration strategy and of the new upcoming developments will require cross discipline collaboration between those responsible for core acquisition core analysis and wireline log interpretation a key factor will be the ability to develop interpretative algorithms for cross scale application

late holocene dune activity linked to hydrological drought nebraska sand hills usa dunee elds of the great plains contain stratigraphic records of episodic holocene aeolian activity potentially providing a valuable record of climatic change it has been dife cult to establish unambiguous links between activity at specie c sites and regional palaeoclimate however here we demonstrate that widespread late holocene aeolian activity in the nebraska sand hills the largest dunee eld on the great plains of north america occurred during a period of hydrological drought aeolian sand sheets are interbedded with peat that accumulated in interdunes throughout much of the holocene the youngest of these sand sheets was deposited between 950 and 650 cal bp about the same time as the most recent major episode of aeolian activity at upland sites up to 120 km apart sand sheets could only have advanced across the interdunes if the local groundwater e ow systems that maintain interdune wetlands were temporarily reduced or eliminated by a reduction in recharge both reduced recharge and upland aeolian activity are best explained by regional megadrought

deconstructing a polygenetic landscape using lidar and multi resolution analysis abstract it is difficult to deconstruct a complex polygenetic landscape into distinct process form regimes using digital elevation models dems and fundamental land surface parameters this study describes a multi resolution analysis approach for extracting geomorphological information from a lidar derived dem over a stabilized aeolian landscape in south texas that exhibits distinct process form regimes associated with different stages in landscape evolution multi resolution analysis was used to generate average altitudes using a gaussian filter with a maximum radius of 1 km at 20 m intervals resulting in 50 generated dems this multi resolution dataset was analyzed using principal components analysis pca to identify the dominant variance structure in the dataset the first 4 principal components pc account for 99 9 of the variation and classification of the variance structure reveals distinct multi scale topographic variation associated with different process form regimes and evolutionary stages our results suggest that this approach can be used to generate quantitatively rigorous morphometric maps to guide field based sedimentological and geophysical investigations which tend to use purposive sampling techniques resulting in bias and error

a 10 000 year record of dune activity dust storms and severe drought in the central great plains dune fi elds and loess deposits of the great plains of north america contain stratigraphic records of eolian activity that can be used to extend the short observational record of drought we present a 10 000 yr reconstruction of dune activity and dust production in the central great plains region based on 95 optically stimulated luminescence ages the integration of data from both eolian sand and loess is an important new aspect of this record clusters of ages defi ne episodes of extensive eolian activity which we interpret as a response to frequent severe drought at 1 0 0 7 ka and 2 3 4 5 ka with peaks centered on 2 5 and 3 8 ka sustained eolian activity occurred from 9 6 to 6 5 ka parts of this record may be consistent with hypotheses linking holocene drought to sea surface temperature anomalies in the pacifi c or atlantic oceans or to the el nino southern oscillation phenomenon but the record as a whole is diffi cult to reconcile with any of these hypotheses

aeolian sand depositional records from western nebraska landscape response to droughts in the past 1500 years the great plains is dominated by presently stabilized dune fields that are indicators of extreme drought in the late holocene this study focused on deciphering the timing of reactivation of dunes in western nebraska stratigraphy adjacent to dune dammed lakes reveals aeolian sand separated by palaeosols indicating mobilization of aeolian sand followed by landscape stability the chronology of aeolian sand depositional events is constrained using the luminescence based single aliquot regeneration method providing resolution to relate dune movement to tree ring and palaeolimnologic records of drought there are at least a six aeolian depositional events in the past 1500 years with apparent mean ages of 1390 130 670 70 470 40 240 40 140 20 and 70 10 yr all study sites show evidence for aeolian accumulation in the twentieth century potentially reflecting the 1930s drought significant aeolian activity is coincident with the tree ring identified sixteenth century megadrought indicating widespread landscape impacts

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

procedures used for luminescence dating of sediments abstract an account of the procedures for thermoluminescence tl and optically stimulated luminescence osl dating of sediments used at the nordic laboratory for luminescence dating is given the topics discussed include sampling sample preparation separation of quartz and feldspars using heavy liquids dose rate estimation and methods for estimating the equivalent dose special attention is paid to the partial bleach tl technique of mejdahl 1988 which appears to give reliable results for partially bleached sediments optically stimulated luminescence dating using stimulation by infra red ir and green light has been taken up and especially added dose methods using stimulation by ir or green light have been tried with some success some sources of error are discussed including the adverse effect of shallow traps

a chronology of hurricane landfalls at little sippewissett marsh massachusetts usa using optical dating abstract optical dating has been applied to sediments preserved in little sippewissett marsh massachusetts usa which are associated with overwashing of the beach barrier during hurricane strikes on the coast the aims were to determine the hurricane landfall frequency and make comparisons with independent age control and the historical record written sources of hurricane activity along the american east coast are only considered reliable back to the mid 19th century but the sedimentary record is potentially much longer optical dating was applied to quartz grains extracted from thirteen samples within a sediment core from the salt marsh variability in the luminescence characteristics between aliquots was observed and 33 of the measured aliquots were discarded based upon the ratio of the fast component to the medium component the majority of the samples gave normal dose distributions implying homogeneous resetting of the luminescence signal at the time of deposition but three of the samples required application of the minimum age model mam ages ranging between 20 2 and 594 38 years were obtained and are broadly in agreement with independent chronologies thus demonstrating the potential of optical dating in this setting the hurricane record based upon optical dating extends approximately 300 years further back in time than the official national oceanic atmospheric administration noaa record the localised nature of hurricane landfalls means that it will be necessary to collect multiple cores from a number of different sites in order to build up a complete hurricane record for this part of the coast

stratigraphy and geochronology of upper quaternary eolian sand on the southern high plains of texas and new mexico united states eolian sand in dune fields and sand sheets cover 10 000 km 2 10 of the southern high plains of northwestern texas and eastern new mexico these deposits are concentrated in three west east trending belts of dunes the muleshoe lea yoakum and andrews dune fields from north to south that appear to be eastern extensions of the mescalero monahans dune system in the pecos river valley and in the seminole sand sheet a discontinuous accumulation of sheet sands between the lea yoakum and monahans andrews dunes the most common landforms are parabolic dunes associated with blowouts coppice dunes and sand sheets all typical of sandy vegetated semiarid landscapes barchan dunes in keeping with a relatively limited sand supply and an underlying surface that is relatively hard blackwater draw formation pleistocene and fence row dunes historic dunes formed along field boundaries these eolian deposits accumulated episodically in the late pleistocene and holocene and provide clues to the history of regional drought and aridity the earliest phase of sedimentation occurred when sheet sands were deposited between 11 000 and 8000 14 c yr b p probably in several phases based on archaeological data as a result of episodic drought beginning between 11 000 and 10 000 yr b p eolian deposits dating between 8000 and 3000 yr b p are rare although eolian sediment 8000 4500 14 c yr b p is ubiquitous in the draws that cross the region and paleoenvironmental indicators show that the region was subjected to aridity throughout middle holocene time the middle holocene deposits most likely were remobilized in late holocene time most of the deposits and landforms of the dune fields and sand sheets are late holocene dating before 4000 14 c yr b p and mostly before 1500 14 c yr b p the muleshoe and lea yoakum dunes and the seminole sand sheet underwent substantial eastward expansion in late holocene time buried soils and radiocarbon ages show that the eolian sand accumulated in several stages probably in response to cyclic drought the muleshoe dunes accumulated after ca 1300 cal yr b p ca 1400 14 c yr b p after ca 750 670 cal yr b p ca 850 750 14 c yr b p just after ca 500 cal yr b p ca 450 14 c yr b p and during the nineteenth and twentieth centuries the lea yoakum dunes were active after ca 3400 cal yr b p ca 3200 14 c yr b p and historically the seminole sand sheet was active ca 430 330 cal yr b p ca 360 14 c yr b p and in the twentieth century the andrews dunes were subjected to at least two phases of eolian sedimentation after ca 2320 cal yr b p ca 2320 14 c yr b p comparisons with eolian chronologies from other regions on the great plains suggest that dune mobilization was a regional phenomenon after ca 2300 cal yr b p ca 2300 14 c yr b p after ca 1500 1400 cal yr b p ca 1650 1550 14 c yr b p after ca 700 cal yr b p ca 800 14 c yr b p between 500 and 300 cal yr b p ca 450 300 14 c yr b p and in the nineteenth century the climatic fluctuations responsible for mobilizing the dunes probably were relatively minor yet the landscape impacts were substantial resulting in widespread wind erosion and dune construction

variable response of coastal environments of the northwestern gulf of mexico to sea level rise and climate change implications for future change the results from nearly three decades of marine geological research in the northwestern gulf of mexico are compiled in an effort to understand those factors e g sea level rise sediment supply subsidence antecedent topography that influenced coastal evolution during the last eustatic cycle 120 ka to present armed with this information we evaluate coastal response to variable sea level rise of the holocene and accelerated rise during historical time to gain a better understanding of how the coast is likely to respond to future changes the early holocene evolution of northwestern gulf of mexico bays was punctuated by rapid and possibly synchronous flooding events that are interpreted as resulting from episodes of rapid sea level rise two of these events one between 8 4 and 8 0 ka and the other between 7 4 and 6 8 ka were associated with known episodes of ice sheet retreat in north america and antarctica respectively during the middle and late holocene the east texas and western louisiana coasts experienced episodes of stability and growth followed by rapid shoreline retreat while the central texas coast remained relatively stable this variability in coastal response to sea level rise resulted mainly from differences in sediment supply and the highly irregular antecedent topography on which coastal environments formed sand that nourished the evolving east and south texas as well as westernmost louisiana coasts was derived mainly from transgressive ravinement of deltas that were formed during the falling stage of sea level mis5e mis2 the loci of these deltas controlled the spatial variability of this offshore sand supply sand supply to the central texas coast has been dominated by converging longshore currents and throughout the middle to late holocene was large enough to keep pace with sea level rise moreover sand supply from rivers has varied considerably in response to climate change during the early holocene when the average rate of linear sea level rise was 4 2 mm yr the brazos colorado and rio grande rivers all formed deltas on the inner continental shelf today only the brazos contributes enough sediment to the gulf of mexico to form a delta but its sand delivery is minimal a reversal from late holocene growth of western louisiana east texas and south texas barrier islands and peninsulas to erosion occurred during the last 2 0 ka after the rate of sea level rise began to decelerate the actual timing of this reversal was diachronous across the coast and was caused by a decrease in sediment supply once offshore sand sources were bypassed by the landward advancing shoreface transgressive ravinement differences in the exact timing and rate of retreat also reflect variability in the offshore profiles of these barriers and their thickness which results from the underlying relief on the pleistocene surface the late holocene was also the time of chenier plain development in western louisiana and east texas that was marked by localized differences in growth and retreat the current rate of eustatic sea level rise in the northern gulf of mexico is in the range of 2 0 and 3 0 mm yr and is approaching rates of the early holocene this is on average about five times the long term rate of the past 4 0 ka this larger rate is associated with an increase in coastal erosion in historical time relative to long term rates current rates of gulf shoreline erosion are approaching rates of the early to mid holocene and the rate of retreat of some barriers is not sustainable core transects off central texas reflect a late holocene history of shoreface progradation but the modern shoreline is currently eroding albeit at slower rates than elsewhere along the coast overall the sand supply needed to sustain the gulf shoreline is lacking likewise baylines are experiencing erosion rates that are faster than the late holocene average and bayhead deltas are at the tipping point of catastrophic retreat spatial variability in erosion rates highlights the importance of factors such as sediment supply subsidence and anthropogenic influences on coastal evolution tropical storms and hurricanes while exerting the most noticeable coastal change merely exacerbate overall shoreline retreat and migration along the entire northwestern gulf coast the impact of human intervention to natural processes is particularly evident primarily due to alterations in river discharge and sediment supply to the coast interruptions in along shore and cross shore sand transport and increases in rates of subsidence through fluid withdrawal compared to natural changes that took place during the holocene the impacts of human activity have been virtually instantaneous the geological record indicates that the ongoing increase in the rate of sea level rise coupled with diminished sediment supply and human intervention will continue to severely impact the low gradient coastal environments of the northwestern gulf of mexico

holocene stratigraphy and chronology of the casper dune field casper wyoming usa activation chronologies of dune fields within the north american great plains are significant sources of paleoclimate information although many regional chronologies exist several dune fields have been understudied including the casper dune field of central wyoming this study investigated aeolian dune sediment and buried soils of the casper dune field complex parabolic and hairpin parabolic dunes dominate the eastern dune field while simple parabolic and linear dunes dominate the western dune field buried soils are found throughout the dune field though their distribution and degree of development varies buried soils in the eastern dune field are weakly developed with typical a c profiles whereas soils in the western dune field typically exhibit a bt c profiles optically stimulated luminescence osl and radiocarbon ages were used to provide a chronology of dune field activation that spans most of the holocene at the onset of the holocene alluvium was deposited first followed by widespread d

luminescence dating of holocene aeolian sand movement thy denmark abstract we report on the application of optically stimulated luminescence dating to an investigation of the frequency of periods of aeolian sand movement and dune formation on the coast of thy holocene aeolian sediments interleaved with peaty palaeosols form some of the most complete successions known in western denmark samples were taken from a coastal exposure and an inland archaeological site dosimetry was based on laboratory gamma spectrometry and quartz luminescence measurements used the single aliquot regenerative dose protocol and 470 30 nm stimulation the sand samples cover an age ranging from about 100 years to 4500 years the youngest dates give us confidence that the material was well bleached at deposition good agreement was obtained with the radiocarbon palaeosol ages we identify three main periods of aeolian sand movement starting at about 4200 2700 and 900 years ago at least during the latter two periods significant aeolian sand movement occurred all three phases of aeolian activity were separated by long periods of stability and soil formation a more recent episode of dune formation restricted to the coast and beginning less than 200 years ago may have been triggered by modern coastal erosion

identifying extreme pluvials in the last millennia using optical dating of single grains of quartz from shorelines on australia s largest lake the filling of kati thanda lake eyre kt le australia s inland sea has captured scientific and cultural interest for over a century and a half however despite the presence of multiple shoreli

optical and radiocarbon ages of stacked paleosols and dune sands in the nebraska sand hills usa abstract optical ages for eolian sands from the nebraska sand hills indicate periods of extensive eolian activity at ca 115 25 840 70 2300 240 and 3560 340 a activity was also noted at single sampling locations at ca 6180 370 8430 510 and 13110 800 a many of these ages are similar to those noted by earlier authors optical ages from samples collected within paleosols indicate shorter and possibly less extensive periods of eolian activity at approximately 1220 150 1590 110 and possibly 1950 150 a during which the paleosol sands accumulated what was originally interpreted as a single 1 2 m thick paleosol is shown by optical dating to consist of three or more welded soils developed within eolian sands with optical ages of ca 3800 240 2740 240 1560 110 and possibly 1930 140 a each of which match eolian pulses recognized elsewhere scatter in some optical ages is attributable to intersection of sand filled rodent burrows extending in outcrop 1 5 m below the contact between paleosol and overlying topset beds a 5310 360 a optical age for one probable intersected burrow provides evidence for upward or lateral transport of older sands

quaternary deformations along the engadine gruf tectonic system swiss italian alps the engadine line el is a seismically active fault in southeastern switzerland in the field we studied its western segment presently not affected by seismicity but characterised by features suggesting neotectonic motions and the coterminous gruf line uphill and downhill facing scarps offset rivers non equilibrium hydrological conditions and aligned deep seated gravitational slope deformations are dominant in the western sector of the el in the inn valley landform offsets and the most recent fault striations point to oblique left lateral strike slip close to the el at the maloja pass a huge collapse beheaded the inn valley trench excavation with palaeoseismic analysis stratigraphic correlations of quaternary deposits and optically stimulated luminescence dating indicate that the collapse and faulting mostly occurred in the late pleistocene in the bregaglia valley the gruf line stretches along the southwestern extension of the el six deep seated gravitational slope deformations developed along the gruf line and were dated to pre and post last glacial maximum times we suggest that the western sector of the el moved also in a pleistocene time interval during which tectonic forces in the area were probably larger than at present favouring local uplift widespread gravity deformation and retrogressive slope failure at the inn valley head copyright 2007 john wiley sons ltd

nebkha formation implications for reconstructing environmental changes over the past several centuries in the ala shan plateau china abstract sediments of chinese tamarisk tamarix chinensis lour nebkhas in china s arid ala shan plateau document both the formation processes of these vegetated dunes and the environmental changes and geomorphological evolution in this region dating of the nebkhas showed that after surface water disappeared the wadis and playas evolved into gobi deserts desert pavements within two centuries the 13c trends in the litter deposited within the nebkhas revealed three stages of fluctuating moisture conditions during the past five centuries before the 1580s between the 1580s and the late 1990s and from the early 2000s to the present however changes in the coarse fraction of the nebkha sediments show that this region experienced at least five phases of aeolian sediment transport during the same period the early stages of nebkha formation coincided with the initial stage when the wadis and playas evolved into gobi deserts and nebkha sizes increased rapidly due to the abundant sediment supply provided by the playas however after the playa surfaces stabilized the nebkha sediments documented environmental changes in adjacent regions our results also show that the formation of the tamarix nebkhas in this region was not controlled by the groundwater table because in most periods the water table depth remained above the depth that limits tamarix survival in the ala shan plateau nebkha formation was mainly controlled by aeolian processes and revealed the integrated effects of environmental changes thereby providing possibilities for climate and environment reconstructions with a relatively high resolution in extremely arid areas

sand deposition during the last millennium at aberffraw anglesey north wales as determined by osl dating of quartz abstract ground penetrating radar gpr was used to identify sediment units at the terminus of a small dune field at aberffraw nine samples were taken from boreholes sample locations were based on the stratigraphy established by gpr quartz grains were dated using a single aliquot regenerative dose protocol that allows for sensitivity changes sand deposition at llyn coron aberffraw occurred three times in the last 700 years with initial sand movement occurring around 1331 ad when historical documents record sand being mobilised in a strong storm

chronology and geochemistry of late holocene eolian deposits in the brandon sand hills manitoba canada abstract accelerator mass spectrometry and conventional radiocarbon age determinations of organic matter from paleosols indicate that the brandon sand hills area of southern manitoba has been subjected to recurrent intervals of eolian activity in the past 5000 years although precise regional correlations are precluded by dating uncertainties periods of most notable paleosol development occurred around 2300 to 2000 1400 to 1000 and 600 to 500 cal yr bp with eolian activity occurring before and after each of these periods episodes of eolian activity may correspond to periods of regional drought whereas paleosols mark periods of increased moisture availability and stabilization by vegetation the geochemistry of the eolian sands paleosols and source sediments indicates that partial leaching of carbonates occurs from pedogenesis during humid climatic phases and that this is probably the primary mechanism of carbonate depletion of eolian sands in this area recent trends in sand dune activity from historic aerial photography and early explorers accounts indicate that the few active dunes that presently exist have stabilized at a rate of 10 20 per decade despite several severe droughts in the 20th century this may be attributed to pre settlement droughts that were more severe than those in historic times although regional dune stabilization may also be related in part to the spread of forest cover in the past few hundred years

terrestrial gastropod succession in a late holocene stream deposit in south texas abstract investigation of snail bearing alluvium from the smyth crossing site in uvalde county texas indicates that the terrestrial gastropod fauna of this area has been stable for at least 3000 yr however relative proportions and presence absence variations indicate changes in the relative occurrence of preferred microhabitats of certain snails gastropods from an excavated soil column reveal a succession of gastropod associations in response to succession of the plant community of the site from a riverside gravel bar to an upland savannah grassland human impact on the gastropods is mostly contemporary with apparent local extirpations of some species having occurred the recovered paleofaunas provide no evidence for regional climatic change since 3000 yr b p

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

late holocene aeolian activity in the cimarron river valley of west central oklahoma abstract this investigation uses a multidisciplinary approach including geomorphic surface mapping soil stratigraphic analysis radiocarbon dating and optically stimulated luminescence osl dating to investigate the chronology of soil formation and aeolian activation periods recorded in ridge dune deposits as well as the spatial variability of aeolian processes during active aeolian episodes this study shows that aeolian landforms superimposed on fluvial terraces adjacent to the cimarron river in southeastern major county and northwestern kingfisher county oklahoma are the product of distinct late holocene climatic conditions in which periods of dune activity are episodic and accumulation of sediments is relatively rapid soil forming processes operated on the stabilized dunes during intervening periods we also demonstrate that the synthesis of geomorphic techniques soil stratigraphy 14c dating and osl dating can provide complimentary and high resolution data about aeolian activity in the southern plains

late holocene dune migration on the south texas sand sheet abstract there are a wide variety of vegetated eolian depositional landforms associated with the south texas sand sheet attesting to the past dominance of eolian processes mapping identified two sets of parabolic dunes elongating with winds from the southeast and the northwest parabolic dunes elongated by northwesterly winds are older than ca 200 years and may be associated with eolian depositional events ca 2700 and or 2000 years ago the latest dune migration event associated with southeasterly winds occurred ca 200 years ago and at one site is inset into northwesterly extended parabolic dunes this period of dune migration may be coincident with particularly severe drought identified in the tree ring record centered at ad 1790 when the palmer drought severity index was 4 a threshold of dune movement may have occurred ca in the 11th 15th and 20th centuries when there are two or more consecutive years with a palmer drought severity index of

importance of small block rotations in damage zones along transcurrent faults evidence from the chuquicamata open pit northern chile chuquicamata in northern chile is one of the largest porphyry copper deposits in the world the western side of its orebody is bounded by a major longitudinal fault the west fault we report paleomagnetic results from surface sites and drill cores from different geological units at chuquicamata especially within the late eocene fiesta granodiorite of the western block of the west fault characteristic remanent magnetizations chrm were determined after detailed thermal or alternating field demagnetization soft components carried by multidomain magnetite crystals in the fiesta granodiorite were removed by af demagnetization at 10 20 mt the chrms not demagnetized by alternating fields up to 100 mt have unblocking temperatures above 580 c with 75 of the magnetization removed in the temperature range of 580 590 c optical and sem mineralogical observations and microprobe data indicate the occurrence of multidomain magnetite formed during a late magmatic stage of alteration coeval with strong oxidation of primary titanomagnetite and formation of ilmenite hematite pseudobrookite and rutile the characteristic directions have negative inclinations and declinations 330 to 230 strongly deflected from the expected eocene direction anisotropy of magnetic susceptibility ams with degree up to 1 4 is carried by multidomain magnetite ams ellipsoids have subvertical foliations with azimuth varying strongly from n280 to n20 we show that both the chrms and the ams fabrics record the same apparent relative rotations between sites although the ams anisotropy is high there is no evidence for a solid state deformation and the apparent rotation of the magnetic fabric is interpreted to be the consequence of small block rotation the apparent large 100 counterclockwise rotations of small blocks within the fiesta granodiorite suggest a wide damaged zone related to sinistral displacement along the west fault this interpretation is consistent with previous models indicating that the fiesta granodiorite was sinistrally translated and brought in front of the early oligocene porphyry copper deposit during the oligocene early miocene this study shows that paleomagnetic markers are useful for improving the quantification and understanding of small scale deformation within plutons adjacent to major fault zones

mid to late holocene coastal dune event stratigraphy for the north coast of northern ireland an event stratigraphy of dune stability instability phases has been reconstructed using 22 radiocarbon and 13 luminescence dates for six dunefields along the north coast of northern ireland there is no evidence for dune development prior to 7000 cal years bp during the early holocene rapid rise in rsl and only limited evidence for sand accumulation in association with the rsl maximum dunefield dates correspond to either the subsequent regressive phase or later the gradual transgressive phase of rsl history in the mid and late holocene at these times accommodation space for dune development and sediment supply were maximized episodes of climatic deterioration particularly at 3100 2400 cal years bp and 650 50 cal years bp the little ice age were marked by widespread dune instability a similar coincidence in timing has been recorded for dune systems elsewhere in northwestern europe and is generally attributed to an increased frequency of storms and storm surges associated with the climat

relationship between copper tonnage of chilean base metal porphyry deposits and os isotope ratios re os isotopes in pyrite and chalcopyrite from early high temperature hypogene alteration assemblages in chilean porphyry copper deposits identify the source of os and by inference cu in these ore systems typical concentrations for os in both pyrite and chalcopyrite are between 7 and 30 ppt 10 12 g g and for re between 0 200 and 10 ppb 10 9 g g re os isochrons yield ages and initial 187 os 188 os ratios for the sulfides the isotopic data reflect the relative contributions of copper from the mantle and crust in chilean porphyry copper deposits seven ore deposits that reside in different tectonic terranes and represent distinct epochs of mineralization in chile were studied the initial osmium ratios of the first stage of mineralization at each of the deposits range from 0 15 to 5 these values are more radiogenic than the present chondritic mantle 0 13 and indicate significant crustal contributions of os to the magmatic and or hydrothermal systems there is a strong correspondence between the total copper content and initial os isotopic ratios in base metal porphyry deposits the larger deposits have lower initial os ratios than the smaller less significant deposits this relationship implies that larger deposits acquire a greater proportion of os from the mantle the initial os ratio of samples in the central segment of porphyry copper deposits of northern chile also decreases with decreasing age of the deposit a plausible interpretation of the re os data is that the later and larger deposits use regional tectonic and structural features that allow sampling of deeper more primitive magmatic sources

episodic flooding of estuarine environments in response to drying climate over the last 6000 years in baffin bay texas abstract recent studies along the northwestern gulf of mexico document rapid centennial scale landward retreat or back stepping of estuarine environments up to 20 km ca 8 0 ka 4 8 ka and 2 6 ka if such rapid changes in coastal environments occurred today along the urbanized coast of the gulf of mexico major economical and ecological loss would occur although the 8 0 ka event occurs at a time of increased rates of sea level rise the latter two do not leading to the hypothesis that they may be the result of past climate change in this study 121 cores 4 3 km of high resolution seismic profiles and 53 radiocarbon dates are utilized to characterize the stratigraphic architecture and constrain the timing of stratigraphic flooding surfaces in the estuarine fill of upper baffin bay texas over the last 6 ky five flooding surfaces which formed between 1 1 1 0 ka 2 7 2 1 ka 3 8 3 0 ka 5 2 4 9 ka and 6 5 5 7 ka occur within error of drying in southern texas driven by warming in the north atlantic and recorded in independent paleoclimate archives we suggest that these flooding surfaces which occurred when sea level in the gulf of mexico was rising

the osl chronology of eolian sand deposition in a perched dune field along the northwestern shore of lower michigan abstract extensive coastal dunes occur in the great lakes region of north america including northwestern michigan where some are perched on high 100 m bluffs this study focuses on such a system at arcadia dunes and is the first to systematically generate optical ages from stratigraphic sections containing buried soils dune growth began ca 4 5 ka during the nipissing high lake stand and continued episodically thereafter with periods of increased sand supply at ca 3 5 ka and ca 1 7 ka the most volumetrically dominant phase of dune growth began ca 1 0 ka and continued intermittently for about 500 years it may have begun due to the combined effects of a high lake phase potential changes in lake hydrodynamics with final isostatic separation of lake superior from lakes michigan and huron and increased drought and hydrologic variability associated with the medieval warm period thus this latest eolian phase likely reflects multiple processes associated with great lakes water level and climate variability that may also explain older eolian depositional events comparison of arcadia ages and calendar corrected 14c ages from previous studies indicate broad chronological agreement between events at all sites although it appears that dune growth began later at arcadia

luminescence dating of well sorted marine terrace sediments on the southeastern coast of korea abstract along the southeastern coastline of the korean peninsula well developed marine terraces are found at various elevations the ages of these terraces and the time of deposition of the terrace sediments are important to our understanding of the geological history of this area during the quaternary period and represent a unique record of the regional tectonic activity previous efforts to establish a chronology using optically stimulated luminescence osl methods have produced controversial results particularly because of stratigraphic inconsistency and poor reproducibility in this paper the application of osl dating based on the single aliquot regenerative dose sar protocol for quartz is investigated the dependence of equivalent dose on the preheat and cut heat temperatures thermal treatment of the regeneration and test doses respectively are examined linearly modulated luminescence signals from chemically cleaned quartz samples are used to identify the presence of a thermally unstable component with a large optical cross section component a which in part affects the ability to correct for sensitivity changes during measurements and thus the reliability of the equivalent dose estimates in some samples a higher heat treatment after the test dose is shown to improve our ability to measure a dose given in the laboratory before any heat treatment dose recovery test this higher temperature treatment effectively removes component a and hence improves sensitivity correction furthermore the samples were broadly divided into poorly sorted and well sorted based on field evidence the poorly sorted samples contain friable weathered gravel clasts which is a likely post depositional source of quartz grains in general these grains will not have been zeroed prior to deposition and so the poorly sorted samples are rejected from further age studies results obtained from the well sorted samples are reproducible at each sampling location and give ages grouping broadly into 50 70 and 110 120 ka but laterally discontinuous on a scale of tens of km our osl results for the younger group are supported by radiocarbon ages from overlying terrestrial deposits it is concluded that these results point to considerable tectonic activity in the southeast of korea during the late pleistocene

deconstructing aeolian landscapes abstract semi stabilized dune systems are important indicators of quaternary drought variability across central north america the south texas sand sheet stss is the southernmost relict dune system on the great plains and is exposed to higher evapotranspiration and moisture variability than similar landscapes farther north in this study a combination of surface and sub surface remote sensing is used to analyze the semi stabilized dune landscapes of the stss in order to delineate distinct aeolian sediments that can represent generations of sedimentation or particular climate conditions the combination of multi resolution analysis of a lidar dataset electromagnetic conductivity surveys and xrf scans of soil cores are shown to be useful tools for deconstructing and modeling the environmental history of the stss optically stimulated luminescence osl dating of identified surfaces suggests that the stss is older than previously thought since dune systems are excellent repositories of climate and biophysical data for a landscape and are also sensitive to changes in climate and ecology the methodology employed in this study can be used to characterize the vulnerability of other similar environments to climate change through the holocene and over the next century

middle and late holocene dune reactivation in the nebraska sand hills usa a combination of optical dating of aeolian sand and radiocarbon dating of palaeosols and interdune sediments has allowed some refinements to the chronostratigraphy of the nebraska sand hills our results directly confirm previous inferences that multiple phases of aeolian deposition including megabarchan dune reactivation occurred within the sand hills during the middle and late holocene optical dates on stratified aeolian barchan dune sediments from two localities provide ages ranging from c 6 ka to 300 years ago weakly developed palaeosols intercalated within the dune sediments and other forms of post depositional modification indicate periods of relative stability and reduced dune mobilization optical dates on the upper 12 15 m of two dune exposures indicate repeated possibly regionally correlative reactivations which occurred between c 400 500 and 200 300 years ago comparison of late holocene aeolian activity with local and regional palaeoclimatic proxy records suggests that dune reacti

holocene dune activity and environmental change in the prairie parki and and boreal forest central saskatchewan canada past aeolian activity was reconstructed at four dunefields in the prairie parkland and boreal forest of central saskatchewan to elucidate landscape response to environmental change optical ages from stabilized dunes in the boreal transition ecoregion indicate two episodes of activity the first at about 11 ka corresponds to a period of early holocene parkland and grassland cover following deglaciation and drainage after about 13 0 ka and brief establishment of boreal forest the second between about 7 5 and 5 ka corresponds to a period of mid holocene parkland grassland cover optical ages from dunefields in the prairie parkland primarily record mid holocene activity between about 7 5 and 4 7 ka corresponding to a period of grassland cover with some reworking continuing into the late holocene although this area was deglaciated by about 13 5 ka there is no evidence of early holocene dune activity suggesting that mid holocene activity may have reworked earlier deposits here consequently much of the morphology and stratigraphy observed in these dunefields are associated with mid holocene activity likely associated with increased aridity and reduced vegetation cover at that time this study provides the most northerly evidence of mid holocene dune reactivation on the great plains lending support to the assertion that aeolian activity was widespread at that time

the termination of the last major phase of aeolian sand movement coastal dunefields denmark optically stimulated luminescence osl dating of sand samples from stabilized or inactive coastal dunes in denmark provides information on the age of the termination phase of the last major aeolian activity period a total of 26 sand samples were taken from four different coastal dunefields around the north sea skagerrak and kattegat coasts of denmark the osl dates indicate that the last major phase of aeolian activity terminated between ad 1860 and 1905 most of the dunes examined in this study were active around 1820 during a period documented to have been very stormy a dune management scheme started around 1792 and this no doubt was a major cause of dunefield stabilization but an overall decline of storminess particularly spring and summer storminess around the end of the 19th century must also have contributed to the increasing inactivity of coastal dunes the new osl dates on aeolian sand movement agree well with historical data and data from topographic maps on dune movement this agreement supports the observation from earlier work that osl dating of recent aeolian sand movement is accurate over the last few decades to centuries copyright 2005 john wiley sons ltd

holocene eolian activation as a proxy for broad scale landscape change on the gila river indian community arizona abstract eolian sediments are common within the middle gila river valley southern arizona and reflect variability in eolian and fluvial processes during the late holocene this study focuses on deciphering the stratigraphic record of eolian deposition and associated luminescence dating of quartz extracts by single aliquot regeneration sar protocols stratigraphic assessment coupled with luminescence ages indicates that there are four broad eolian depositional events at ca 3145 220 yr 1950 1360 yr 800 100 yr and 690 315 yr this nascent chronology correlated with regional archeological evidence and paleoclimate proxy datasets leads to two general conclusions 1 loess deposits transverse dune formation and sand sheet deposition in the late holocene are probably linked to flow variability of the gila river though the last two events are concordant with regional megadroughts and 2 the stability of eolian landforms since the 19th century reflects the lack of eolian sediment supply during a period of fluvial incision resulting in entisol formation on dunes the prime catalyst of eolian activity during the late holocene is inferred to be sediment supply driven by climate periodicity and variable flow within the gila river catchment

soil genesis optical dating and geoarchaeological evaluation of two upland alfisol pedons within the tertiary gulf coastal plain abstract much of the gulf coastal plain is mantled by sandy a and e soil horizons overlying finer grained bt horizons researchers have applied optical stimulated luminescence osl dating to a variety of depositional settings such as hillslopes and terraces in an attempt to understand depositional versus pedogenic origins of the sandy horizons and archaeological burial processes these investigations have documented a range of integrity conditions from pristine to highly bioturbated however little work has been conducted in upland summits thus we integrated field morphological descriptions constituent mass balance reconstruction and optical dating to reconstruct the timing and pedogenic pathways of two summit alfisols on the tertiary gulf coastal plain in texas investigations reveal that the sandy a and e horizons and the bt horizons in each pedon are genetically related with textural contrasts resulting from pedogenic processes optical dating revealed highly complex age structures strongly influenced by bioturbation weathering and the presence of coarse clay plus total silt particle sizes pedogenic mixing is extensive in the a and e horizons which effect apparent osl ages

late quaternary eolian sand depositional record for southwestern kansas landscape sensitivity to droughts abstract eolian deposits and landforms are ubiquitous in western kansas particularly south of the arkansas river with the presence of a stabilized dune field stratigraphic studies and associated optical dating reveal a complex depositional history for this dune field spanning the late quaternary the oldest eolian deposits from ca 16 to 12 ka completely or partially bury high terraces with ages of ca 16 and 33 ka it is unknown whether these eolian deposits reflect regional aridity and or a change in sediment availability with the transition of the arkansas river from a single channel to a braided system there is pervasive evidence for episodic eolian erosion and deposition ca 9 8 to 6 3 ka generally coincident with loess deposition on upland surfaces olson c g nettleton w d porter d a brasher b r 1997 middle holocene aeolian activity on the high plains of west central kansas holocene 7 3 255 261 and thus it is inferred to reflect regional aridity sites within the dune field show a sequence of eolian sands and weak buried soils reflecting either dune migration or sand sheet accretion at ca 1490 430 380 320 180 and 70 yr ago which correspond well with continental scale droughts in the tree ring record eolian sand in the arkansas river dune field may be derived principally with variability in fluvial activity and in climate during the late pleistocene to the middle holocene with substantial reactivation of eolian systems during decadal scale drought variability in the past 2000 yr

episodic late holocene dune movements on the sand sheet area great sand dunes national park and preserve san luis valley colorado usa abstract the great sand dunes national park and preserve gsdnpp in the san luis valley colorado contains a variety of eolian landforms that reflect holocene drought variability the most spectacular is a dune mass banked against the sangre de cristo mountains which is fronted by an extensive sand sheet with stabilized parabolic dunes stratigraphic exposures of parabolic dunes and associated luminescence dating of quartz grains by single aliquot regeneration sar protocols indicate eolian deposition of unknown magnitude occurred ca 1290 940 715 80 320 30 and 200 120 yr ago and in the 20th century there are 11 drought intervals inferred from the tree ring record in the past 1300 yr at gsdnpp potentially associated with dune movement though only five eolian depositional events are currently recognized in the stratigraphic record there is evidence for eolian transport associated with dune movement in the 13th century which may coincide with the great drought a 26 yr long dry interval identified in the tree ring record and associated with migration of anasazi people from the four corners areas to wetter areas in southern new mexico this nascent chronology indicates that the transport of eolian sand across san luis valley was episodic in the late holocene with appreciable dune migration in the 8th 10 13th and 19th centuries which ultimately nourished the dune mass against the sangre de cristo mountains

laboratory measurements of porosity permeability resistivity and velocity on fontainebleau sandstones the relations among the resistivity elastic wave velocity porosity and permeability in fontainebleau sandstone samples from the ile de france region around paris france were experimentally revisited these samples followed a permeability porosity relation given by kozeny carman s equation for the resistivity measurements the samples were partially saturated with brine archie s equation was used to estimate resistivity at 100 water saturation assuming a saturation exponent n 2 using self consistent sc approximations modeling with grain aspect ratio 1 and pore aspect ratio between 0 02 and 0 10 the experimental data fall into this theoretical range the sc curve with the pore aspect ratio 0 05 appears to be close to the values measured in the entire porosity range the elastic wave velocity was measured on these dry samples for confining pressure between 0 and 40 mpa aloading and unloading cycle was used and did not produce any significant hysteresis in the velocity pressure behavior for the velocity data using the sc model with a grain aspect ratio 1 and pore aspect ratios 0 2 0 1 and 0 05 fit the data at 40 mpa pore aspect ratios ranging between 0 1 0 05 and 0 02 were a better fit for the data at 0 mpa both velocity and resistivity in clean sandstones can be modeled using the sc approximation in addition a linear fit was found between the p wave velocity and the decimal logarithm of the normalized resistivity with deviations that correlate with differences in permeability combining the stiff sand model and archie for cementation exponents between 1 6 and 2 1 resistivity was modeled as a function of p wave velocity for these clean sandstones

dating recent colluvial sequences with 210pb and 137cs along an active fault scarp the eliki fault gulf of corinth greece reliable dating is an essential element of palaeoseismological studies yet whilst a suite of geochronological methods can now provide late quaternary age control it remains very difficult to date modern events i e those occurring within the last 150 years this is significant because the starting point for many palaeoseismological investigations is a modern surface rupturing event whose geological effects need to be disentangled in trench stratigraphies from palaeoseismic ruptures two dating methods which in combination can provide robust dating control in recently deposited sediments are the 210pb and 137cs dating methods here we test the applicability of using 210pb and 137cs to date colluvial sediments exposed in three trenches excavated across an earthquake fault the eliki fault gulf of corinth greece which ruptured in an earthquake in 1861 the 210pb and 137cs profiles observed in these colluvial sequences are relatively erratic due to the mixed nature of the sediments i e their deposition in an environment where the supply of slope sediments is driven by seasonal rainfall causing non uniform sediment accretion and sediment reworking in one trench however 210pb dating corroborated by 137cs dating indicates that a proposed post 1861 surface colluvial unit has been deposited over the period 1950 ad present at a rate of ca 9 mm year and overlies a significantly older unit 120 years old the dating control provided here by 210pb and 137cs dating corroborates the published interpretation of the trench stratigraphy and refines the 14c based estimated dates for the upper unit at two other trenches 210pb and 137cs dating only provided minimum ages based on the presence or absence of 210pbexcess and 137cs such approximate ages however may still useful in corroborating interpretations made using the trench stratigraphy or at sites which have long earthquake recurrence intervals determining which earthquake event was responsible for a particular bed offset

optically stimulated luminescence dating of young sediments a review optically stimulated luminescence osl dating of young 1000 years sediments is used increasingly in a wide variety of late holocene studies as a mean of establishing contemporary sedimentation rates or the timing of sediment deposition this paper provides a summary of the basic principles of osl dating outlines the problems specific to the dating of young material and then uses recent applications to young sediments to illustrate the greatly increased scope and potential of the method in geomorphology and the geology of recent deposits the overall reliability of this new generation of osl ages is examined by comparing where possible osl ages with independent age control it is concluded that the osl ages are accurate in that there is no evidence for systematic over or under estimation it is our conclusion that osl dating should be regarded as a reliable chronological tool for determining the time of deposition of water lain sediments from the coastal zone and aeolian deposits from both coastal and inland environments our conclusion is supported by the growing popularity of osl dating in geomorphology and geology

reconstruction of holocene coastal foredune progradation using luminescence dating an example from the świna barrier southern baltic sea nw poland abstract two sandy spits on the wina barrier wolin and uznam provide a very detailed succession of holocene coastal foredunes and dunes and are regarded as key sites along the southern baltic sea coast optically stimulated luminescence osl dating is proven to be a powerful tool for the reconstruction of holocene coastal spit evolution and foredune accretion quartz extracted from the coastal sediments in the study area provides excellent properties for osl dating the osl age from the innermost dune indicates that spit development of the wina barrier started immediately after rapid sea level rise of the littorina transgression decelerated at 6 6 ka a significant change in the foredune progradation rate occurred during the late subatlantic transgression at 1 2 ka 800 ad when migration rates decreased from 2 6 0 7 m a 1 to 1 3 0 4 m a 1 progradation accelerated again during the little ice age between 1550 and 1850 ad the systematic dating of 28 samples reveals six hiatuses during foredune succession at 2100 bc 900 bc 200 bc 200 ad 600 ad 1000 ad and 1600 ad the timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area troszyn and wina and with phases of increased aeolian activity in other parts of north and west europe we conclude that four of these phases of foredune erosion instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at 2200 bc 900 bc 600 ad and at 1600 ad the latter corresponding to the little ice age the period of increased aeolian activity around 1000 ad is probably to a phase of intensive forest clearance in central europe in contrast the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget milder and calmer climate and an intact vegetation cover

origins of the 1988 north american drought the 1988 summer drought in the united states was the most extensive in many years because the drought developed in different places at different times not all regional effects can be traced to the same cause along the west coast and in the northwestern united states drought conditions developed during 1987 in association with the 1986 to 1987 el nino in the tropical pacific ocean record low rainfalls from april to june 1988 led to rapid development of drought in the north central united states strong anticyclonic conditions and a northward displaced jet stream in the upper atmosphere over north america throughout this period were only part of pronounced and distinctive wavetrain of anomalies in the atmospheric circulation that appeared to emanate from the tropical pacific below average sea surface temperatures along the equator in the pacific in the northern spring of 1988 combined with warmer than normal water from 10 degrees to 20 degrees n led to a northward displaced but still active intertropical convergence zone itcz southeast of hawaii results from a steady state planetarywave atmospheric model indicate that the atmospheric heating anomalies associated with the displaced itcz can force an anomalous wavetrain across north america similar to that observed land surface processes probably contributed to the severity and persistence of the drought however the large scale atmospheric circulation perturbations associated with natural variations in the coupled atmosphere ocean system in the tropical pacific were most likely the primary cause

optically stimulated luminescence dates for late pleistocene and holocene sediments from norre lyngby northern jutland denmark quartz from late pleistocene marine and freshwater deposits of known 14c age and from a historically dated aeolian deposit has been studied using multiple aliquot and single aliquot protocols comparisons are presented between equivalent doses derived using a multiple aliquot additive dose thermoluminescence approach and three osl protocols single aliquot regeneration and added dose sara mejdahl and botter jensen 1994 single aliquot additive dose murray et al 1997 and single aliquot regenerative dose murray and roberts 1998 dose rates determined by laboratory gamma spectrometry are compared with both field gamma scintillation measurements and laboratory beta thermoluminescence dosimetry measurements the agreement is satisfactory the resulting dates are discussed in terms of absolute chronology and bleaching environment

formation of linear and parabolic dunes on the eastern snake river plain idaho in the nineteenth century abstract geomorphic and stratigraphic evidence show periods of distinct hydrologic excess and deficit sometime in the past 500 years on the eastern snake river plain natural exposures at the current shore of mud lake contain a lacustrine silty sand beneath eolian sands the latter deposit is expressed at the surface as hairpin parabolic and linear dunes these dunes can be traced into and across lakes a clear sign of recent aridity two shallow water gastropods and two wood fragments from the lacustrine silty sand yield the respective ams 14 c ages of ca 705 and 988 year bp and 195 and 305 year bp the offset in ages indicates a lake hard water effect of aquatic gastropods with the wood ages providing the closest age constraint optically stimulated luminescence single aliquot regeneration ages of 150 30 and 120 20 year bp on quartz grains from the overlying eolian sands further constrains a drop in lake level and subsequent aridity to the 19th century this lacustrine dune sequence is probably the geomorphic expression of a distinct wet period followed by a severe drought between ad 1845 and 1856 which has been documented in the dendroclimatic records for the rocky mountains and the western great plains lake fluctuations and dune formation is associated with greater subdecadal variability in spring precipitation than recorded in the past 100 years

limits to resolving catastrophic events in the quaternary fluvial record a case study from the nene valley northamptonshire uk flood events within rivers are responsible for much erosion and deposition thus deposits laid down during floods could potentially comprise the bulk of the quaternary fluvial record however it is difficult to detect individual flood events as effectively illustrated by the middle devensian weichselian to holocene fluvial sequence from the nene valley northamptonshire described in this paper this is due to limits in the resolution of sedimentological palaeontological and geochronological techniques geochronological techniques have the highest resolution but error bars of c 50 years radiocarbon and up to 2 ka optically stimulated luminescence in the late glacial do not allow detection of floods lasting only a few weeks or less geochronology is however essential for linking periods of fluvial deposition to climatic phases at the marine isotope substage scale thus multiple age determinations show remnant middle devensian deposits within a facies association mainly of younger dryas age showing similar fluvial response to climate during both time periods palaeontological assemblages suggest that climate was also similar although with some subtle differences determining average fluvial activity in response to broad climate phases improves understanding of how rivers behave over long time periods even though determination of the role of flood events in the quaternary fluvial record remains elusive

optically stimulated luminescence dating of late holocene raised strandplain sequences adjacent to lakes michigan and superior upper peninsula michigan usa this study evaluates the accuracy of optically stimulated luminescence to date well preserved strandline sequences at manistique thompson bay lake michigan and tahquamenon and grand traverse bays lake superior that span the past 4500 yr the single aliquot regeneration sar method is applied to produce absolute ages for littoral and eolian sediments sar ages are compared against ams and conventional 14 c ages on swale organics modern littoral and eolian sediments yield sar ages b100 yr indicating near if not complete solar resetting of luminescence prior to deposition beach ridges that yield sar ages b2000 yr show general agreement with corresponding 14 c ages on swale organics significant variability in 14 c ages n2000 cal yr b p complicates comparison to sar ages at all sites however a sar age of 4280 f 390 yr uic913 on ridge77 at tahquamenon bay is consistent with regional regression from the high lake level of the nipissing ii phase ca 4500 cal yr b p sar ages indicate a decrease in ridge formation rate after 1500 yr ago likely reflecting separation of lake superior from lakes huron and michigan this study shows that sar is a credible alternative to 14 c methods for dating littoral and eolian landforms in great lakes and other coastal strandplains where 14 c methods prove problematic

climatic control on quaternary fluvial sedimentology of a fenland basin river england understanding and interpreting climate response from ancient fluvial deposits requires a combined approach of detailed sedimentological description and interpretation local climate proxies and the accurate comparison of these sequences with further independent climate records application of these multiple lines of evidence is particularly effective in the quaternary period where higher resolution and more detailed palaeoenvironmental reconstruction are possible this paper presents results from a devensian weichselian age sequence in northern fenland england that integrates these approaches detailed sedimentological description has identified three fluvial facies associations overlain by a period of ice wedge cast formation fossil plant and coleopteran material within these sediments have been studied to provide palaeoenvironmental reconstructions for the local landscape including quantitative temperature estimates using the mutual climatic range method on fossil coleoptera in addition joint application of radiocarbon and optically stimulated luminescence osl dating allows this sequence to be compared with the stacked marine isotope record although dates do not agree well at the limit of the radiocarbon technique sedimentological interpretations palaeoenvironments and global ice volume variations a proxy for climatic severity are all in agreement and show clearly how the river nene responded to subtle changes in climate and vegetation cover during the devensian weichselian stage the level of detail possible in this reconstruction shows the importance of this approach in understanding fluvial response to past climate changes

residual luminescence signals in modern coastal sediments abstract modern sediments from coastal and near coastal environments in england and wales had their equivalent doses eds determined using single aliquot additive dose infra red stimulated luminescence irsl certain samples were also investigated using multiple aliquot methods for irsl green light stimulated luminescence glsl and thermoluminescence tl and also single aliquot glsl only one modern sample had its irsl signal reduced to give a zero ed those which had been deposited through turbid water columns had significant signal remaining for all stimulation methods although the glsl and irsl eds were lower than the tl analogous buried samples were also dated and findings were compared with the available age control and the modern results where a tl as well as an irsl ed was obtained for one such sample it was found to be considerably higher suggesting that the bleaching environment had been poor an unbleached residual signal in these samples could not be detected however and the dates reflected the age control the selection of a water content for use in dating was found to be critical in environments with such naturally high and variable water contents

equivalent dose determinations for polymineralic fine grains using the sar protocol application to a holocene sequence of the chinese loess plateau abstract a single aliquot regenerative dose sar protocol involving stimulation of the same disc with an infra red laser diode followed by blue leds was applied to polymineralic fine grains infra red stimulated luminescence irsl and post ir optically stimulated luminescence osl ages are presented for a series of 19 fine grain 4 11 m samples taken from a loess section duowa in the western chinese loess plateau there are significant differences between the equivalent doses and thus the ages for the irsl and post ir osl measurements three potential explanations are investigated incomplete bleaching prior to deposition thermal transfer of charge and initial sensitivity change the question regarding which sequence of ages ir or post ir osl is correct if either is not resolved although the 19 post ir osl ages yield more consistent results it is proposed that the double sar protocol employed may not be correctly monitoring the sensitivity changes relating to either or both natural signals

an optical luminescence chronology for late pleistocene aeolian activity in the colombian and venezuelan llanos the lowland savannas llanos of colombia and venezuela are covered by extensive aeolian landforms for which little chronological information exists we present the first optically stimulated luminescence osl age constraints for dunes in the llanos orientales of lowland colombia and new ages for dunes in the venezuelan llanos the sampled dunes are fully vegetated and show evidence of post depositional erosion ages range from 4 5 0 4 to 66 4 ka with the majority dating to 27 10 ka marine isotope stage 2 some dunes accumulated quickly during the last glacial maximum although most were active 16 10 ka accretion largely ceased after 10 ka all dunes are elongated downwind from rivers parallel with dry season winds and are interpreted as source bordering features as they are presently isolated from fluvial sediments by gallery forest it is proposed that activity was associated with a more prolonged dry season which restricted gallery forest leading to greater sediment availability on river shorelines such variability in dry season duration was potentially mediated by the mean latitude of the itcz the cessation of most dune accretion after ca 10 ka suggests reduced seasonality and a more northerly itcz position consistent with evidence from the cariaco basin

twentieth century dune migration at the great sand dunes national park and preserve colorado relation to drought variability abstract the great sand dunes national park and preserve in southern colorado contains a large dune mass banked against the sangre de cristo mountains the dune mass is bounded for hundreds of kilometers by a vegetated low relief sand sheet with abundant active parabolic and barchanoid dunes the clear morphology of these dunes formed by winds mostly from the southwest and the unambiguous identification of these forms in remotely sensed images provide straightforward targets to assess temporal changes in dune position a digital database of georeferenced remote sensing images from 1936 to 1999 is used to quantify parabolic and barchan dune migration rates and surface reflectance an indicator of vegetation cover with evolving drought conditions in the twentieth century the total net migration of 13 parabolic dunes in 63 years is 0 31 to 0 66 km whereas 11 barchan dunes moved an average of 0 12 to 0 47 km compared to intervening wet year there is at least a three fold increase in average parabolic dune migration during well documented droughts in the 1930s 1950s and 1990s with a concomitant reduction in vegetation cover and surface water resources the landscape response to the most recent drought in the late twentieth century is documented by an average parabolic dune migration rate of 30 m year which is a six fold acceleration over prior wet years and similar to dune response during the 1930s a nonlinear threshold for parabolic dune migration is indicated with lower quartile palmer drought severity index values of