optically stimulated luminescence dating of late quaternary loess deposits in the coastal region of north china provenance and paleoclimatic implications abstract the aeolian deposits in the coastal region of north china are important for reconstructing paleoclimate in this paper chronology climatic proxies and chemical compositions of four loess sections were studied optically stimulated luminescence osl dating results indicate that the coastal loess was accumulated during late quaternary with ages ranging from the penultimate glacial period to the latest holocene both granulometric characteristics and geochemical properties indicate that the dust provenance of the coastal loess is partially different from that of the chinese loess plateau characterized by more proximal contributions except distal dust transported by northwesterly winter winds from the inland gobi and sand deserts the coastal loess also contains proximal local coarse particles which were derived from the exposed shelf as well as neighboring hills multiple climatic proxies including color magnetic susceptibility and particle size parameters correlate well with the marine specmap 18o record indicating that climatic changes in the coastal region of north china during the late quaternary was mainly controlled by variations of the east asian monsoon driven by changes in global ice volumes

testing optically stimulated luminescence dating of sand sized quartz and feldspar from fluvial deposits abstract we apply single aliquot optically stimulated luminescence osl dating to quartz and feldspar rich extracts from fluvial channel deposits of the rhine meuse system in the netherlands the time of deposition of these deposits is tightly constrained by radiocarbon dating or historical sources this allows us to compare osl ages obtained on quartz and infrared osl ir osl ages obtained on potassium rich feldspar with independent ages over the range of 0 3 13 ka we show that the quartz osl ages are in good agreement with the expected age using ir osl dating of feldspar we find a slight age overestimate for the youngest sample whereas for older samples the age is significantly underestimated we also apply osl dating to older fluvial and estuarine channel deposits with limited independent chronological constraints comparison of feldspar ir osl ages with the quartz osl ages up to 200 ka shows a clear trend where the former severely underestimates the latter this trend is similar to that found for the samples with independent age control indicating that the feldspar ir osl ages are erroneously young for the entire age range in the youngest samples incomplete resetting of the ir osl signal prior to deposition probably masks the age underestimation we show that the ir osl age underestimation is partly caused by changes in trapping probability due to preheating correction for this phenomenon improves the ir osl ages slightly but does not provide a complete solution to the discrepancy we suggest that in the light of the problems encountered in the ir osl dating of feldspar quartz is the mineral of choice for osl dating of these deposits however feldspar dating should continue to be investigated because it has potential application to longer time scales

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

kinematics and microphysics of the transition zone of the 10 11 june 1985 squall line abstract a high resolution composite analysis covering the entire breadth of the northern portion of a mature leading line trailing stratiform squall line system reveals that mean subsidence observed in the transition zone consisted of two different types of average downdraft one at upper levels that was mechanically forced and one at lower levels that was microphysically forced both the upper level and lower level mean downdrafts in the transition zone appeared to be the average effect of convective scale vertical drafts associated with convective structures that moved relative to the front edge of the convective line the structure of individual upper level convective scale downdrafts suggested that they may have been partially composed of gravity waves excited by the interaction of the penetrative convective updrafts of the mature and dissipating convective cells with the stable ambient flow the lower level mean downdraft extended from midlevels to near the surface but was maximum near the melting

origin of eolian sand mobilization during the past 2300 years in the mu us desert china abstract eolian sand dunes and sand sheets are extensive in the semiarid regions of northern central china previous studies indicated that these eolian sands mainly formed during historical times however the sand sources and their reworking processes have not been well studied and even the reasons for their occurrence are still controversial field investigation and sedimentary evidence indicate that both the inner mu us desert and its southern marginal region both sources of modern eolian sand are largely associated with reworking of sands of the last glaciation based on geological documentary and archaeological data three phases of land cultivation during the past 2300 years together with historical droughts high wind energy and the easily reworked sand sources largely account for the occurrence of active sand dunes and sand sheets in the mu us desert

climate change in arid central asia since mis 2 revealed from a loess sequence in yili basin xinjiang china abstract k feldspar pirir dating was used to establish a chronological framework for the ks15 05 loess section in the yili basin northern xinjiang province china in arid central asia the reliability of the dating results was verified from the luminescence characteristics and internal checks the chronology was used to calculate mass accumulation rates mars for the section and the paleoclimatic proxies of grain size and magnetic susceptibility were also analyzed the high dust accumulation patterns during the last glacial maximum in yili basin are consistent with those of the chinese loess plateau clp on a millennial scale the bolling allerod b a interstadial is clearly reflected in the ks15 05 section by the variation of the 2 10 m grain size fraction suggesting the influence of the westerlies which dominate the modern atmospheric circulation of the region however the b a interstadial is poorly recorded in grain size records of the clp and this disparity may provide additional information about the nature of the transmission of climate signals from the north atlantic region to asia specifically the zonal transmission of the b a warm signal to the clp may have been obscured by the cooling effect of high latitude cold air to the north of the clp

ubiquity of anomalous fading in k feldspars and the measurement and correction for it in optical dating anomalous fading rates were measured in k feldspars separated from 49 sediment samples mainly from north america the intensity of the optically stimulated luminescence was found to decrease linea

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

580 000 year environmental reconstruction from aeolian deposits at the mu us desert margin china abstract a 76 7 m thick section of aeolian sediment is exposed in the transition zone between the mu us desert and the loess plateau of northern china the aeolian sediments contain sand beds loess layers and palaeosols the particle size distribution data and the sem examination of quartz grains suggest the sand beds are wind blown origin palaeomagnetic measuring combined with thermoluminescence tl dating and pedostratigraphic correlation suggests the studied aeolian sequences were deposited within about 580 kyr the sand layers appear to reflect the episodic extensions of mu us desert during phases of active dune formation and intensified winter monsoon both the stratigraphy and the proxy climatic curves such as bulk magnetic susceptibility and grain size indicate that large amplitude second order climatic oscillations occur during both glacial and interglacial periods it is worth noting that nearly all the interglacial soils can be sub divided by the intercalated sand or loess beds this second order climatic oscillations are on the order of 10 000 of years which may reflect the precession scale variations of southeast summer monsoon driven by the orbital pacing of insolation in low latitudes

optical dating of holocene dune sands from the hulun buir desert northeastern china aeolian deposits from the hulun buir desert of northeastern china are studied with optically stimulated luminescence dating methods to establish the chronology of dune building phases and climatic changes since the last deglaciation our results indicate that wet climate marked by dune stabilization and soil development in the hulun buir desert commenced at 11 ka ago and this early episode of dune stabilization lasted until 4 4 ka ago this optimum climate between 11 and 4 4 ka ago is mostly the response to the strengthened monsoon circulation and increased precipitation in the northern hemisphere the environment generally became arid after 4 4 ka ago but the dry climate was interrupted by three phases of weak soil development occurring at 1 8 1 4 1 2 1 0 and 0 84 0 5 ka ago respectively such short events of dune stabilization were associated with the warm and humid climate in historical time however the present dune mobilization in the hulun buir desert is mainly the result of poor la

revisiting the palaeolithic site of kulbulak uzbekistan first results from luminescence dating abstract kulbulak has been considered as a key site for the palaeolithic archaeology in central asia its significance however is under debate our analysis of the lithics provides no evidence for a lower palaeolithic industry and challenges the existence of the denticulate mousterian as a particular middle palaeolithic facies in western central asia one limitation to interpreting the record preserved at kulbulak has been the lack of a chronological framework in this paper we report on the first age results that we have obtained for the sedimentary sequence using luminescence signals from potassium feldspar we applied a conventional approach which consists of stimulating single aliquots of feldspar with infrared at 50 c after a preheat of 250 c for 60 s the characteristics of this luminescence signal are documented and it is shown to suffer from anomalous fading the fading rates measured in the laboratory are used for correcting the ages in general the fading corrected ages are stratigraphically consistent and agree with the archaeological evidence they bracket the upper 6 m of the sequence in between 39 4 ka and 82 9 ka these are among the first dates for human occupation during the upper and middle palaeolithic in the region but should be interpreted with caution owing to the limitations of the fading correction model

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

optical dating in archaeology thirty years in retrospect and grand challenges for the future in 1982 when richard klein first became one of the editors of this journal the luminescence dating community was embarking on a new phase of exploratory research attention was turning from the use of thermoluminescence tl dating to estimate the time of last heating of archaeological objects such as pottery and burnt flint to the tl dating of unheated sediments that had been transported by wind and then deposited on the landscape this revolutionary development enabled the extension of tl dating to sedimentary deposits in a variety of environmental settings and to the multitude of archaeological sites that lack suitably heated artefacts in sediment dating the age of most interest is usually the time elapsed since grains of quartz or feldspar were last exposed to sunlight as the energy of the sun s rays is sufficient to evict electrons from their light sensitive traps these traps are steadily refilled after sediment deposition and the longer the grains remain buried the more tl they will emit when measured in 1985 huntley and colleagues proposed optical dating as a simpler and superior means of stimulating the light sensitive traps in quaternary sediments and this is now the principal luminescence based method of dating geological and archaeological deposits optical dating is an umbrella term for an armada of acronyms the most common in archaeological contexts being osl optically stimulated luminescence tt osl thermally transferred osl irsl infrared stimulated luminescence and pirir post infrared irsl all of these variants are founded on the same basic tenet measurement of a light sensitive signal to determine typically the last time that sediment grains were sun bleached but each approach has its virtues and vices in this paper we review this family of luminescence dating techniques and look back on 30 years of optical dating in archaeology some of the more interesting and important achievements are highlighted including the critical insights gained in the last two decades from osl measurements of individual grains of quartz we also look to the future of optical dating in archaeological contexts efforts to extend the age limits of optical dating to older hominin and archaeological sites will remain a key goal and understanding how archaeological sites of all ages form and evolve over time could be improved greatly by combining micromorphology analysis with optical dating of undisturbed intact sediments the latter poses a series of particularly formidable technical challenges but if the past is any guide to the future then we can expect optical dating to illuminate much more of human history before celebrating its golden jubilee

some observations on tunnelling of trapped electrons in feldspars and their implications for optical dating abstract anomalous fading in feldspars is now understood to be caused by the tunnelling of electrons from one defect site to another here we present some experimental observations concerning the phenomenon the fading rates of a variety of feldspar crystals and k feldspar separates from sediments are reported it is found that 1 the fading rates of 77 k feldspar extracts from sediments range from 1 to 10 decade with an average value of about 5 decade 2 the fading rates of k feldspars extracted from sediments derived largely from volcanic bedrock are not higher than those from non volcanic bedrock as is widely thought 3 the fading rates of 31 individual feldspars range from 1 to 35 decade 4 in plagioclase feldspars the fading rate increases with increasing ca and or fe content 5 the fading rate increases with laboratory radiation dose at large doses 6 for samples for which the time elapsed since burial is long enough for their luminescence to be in saturation the fading rate is correlated with the ratio of the field saturation intensity to the laboratory saturation intensity extrapolation to zero fading rate shows that trap emptying as a result of thermal eviction is not significant and that the mean thermal lifetime in temperate environments of electrons in traps relevant to dating is 4 ma and 7 different aliquots of a sample can have fading rates that differ by a factor as large as two even if the aliquots contain several thousands of grains thus it is necessary to ensure when correcting ages for anomalous fading that the fading rate used is that applicable to the aliquots on which the equivalent dose is measured

a radiometric calibration of the specmap timescale the astronomical theory of climate change asserts that earth s climate is affected by changes in its orbit which vary the seasonal and latitudinal distribution of solar radiation this theory is the basis of the orbitally tuned specmap timescale a key constraint for this important chronology was the mid point of the penultimate deglaciation initially dated to 127 000 years ago recent work suggests this event may be considerably older casting doubt on the astronomical theory the specmap timescale and the accuracy of orbitally tuned chronologies difficulties with u th coral dating of sea level events have impeded progress on this problem because most corals are not closed systems here we use a new approach to u th dating that corrects for open system behavior and produces a sea level curve of sufficient resolution to confidently correlate with specmap over the last 240 000 years permitting a reassessment of both this critical chronology and a central tenet of climate change theory high precision ages for 24 oxygen isotope events provide a 240 000 year chronology for marine 18o records that is independent of orbital tuning assumptions although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the marine isotope stage 7 6 boundary a comparison of radiometric and specmap ages for identical isotope events suggest that the specmap timescale is quite accurate and that its errors were in general overestimated despite suborbital complexity orbital cyclicity is clearly evident in our record high amplitude sea level oscillations at periods greater than 20 000 years are very close in phase to summer insolation in the northern hemisphere although sea level changes cannot be uniquely tied to a specific season or latitude of insolation forcing the simplest explanation is that long period high amplitude sea level change is linked to northern hemisphere insolation forcing these results validate the principles of orbital tuning and suggest such timescales are generally robust

thermoluminescence chronology of sand profiles in the mu us desert china abstract thermoluminescence tl is used to calculate the ages of two sand loess profiles in the marginal zone of the mu us desert china alternating units of dune sand and loess with palaeosols in the two profiles imply episodes of dune formation separated by periods of loess accumulation and pedogenesis our results indicate that there are three layers of dune sand intercalated in sediments of the last full glacial cycle suggesting the occurrence of three arid episodes during this time the first arid episode within this period occurred between

a solution to anomalous fading and age shortfalls in optical dating of feldspar minerals abstract recent reports of age underestimations for events of interest in both palaeoclimatology and archaeology have led to questioning the validity of using luminescence for dating sediments the commonly designated culprit is anomalous fading of feldspar luminescence we investigated the differential fading rates of single feldspar grains in sediment samples from different geological domains of north america and deduced how one could extrapolate to zero fading this is shown to resolve an extreme case of optical age underestimation documented for the late pleistocene norfolk formation a key palaeoclimate stratigraphic unit exposed along the north american atlantic coast

optical dating reveals that the height of earth s tallest megadunes in the badain jaran desert of nw china is increasing abstract the badain jaran desert bjd in nw china is well known for its unique landscape of megadunes coexisting with permanent lakes the megadunes are already the tallest sand dunes on earth and some of them are up to 400 m high however it is unclear whether or not the height of the megadunes is continuing to increase under present climatic and environmental conditions in order to determine the growth status of the megadunes we collected 26 samples from the windward slopes of two megadunes for optically stimulated and infrared stimulated luminescence dating the results show that the thickness of the modern eolian sand layers increases from the lower part of the windward slopes with a thickness of less than 1 m to more than 2 m in the middle and to 9 m in the upper part this indicates that the height of the megadunes is continuing to increase under modern conditions the surface sediments from the base of the windward slope and the adjacent lake basin have relatively old ages of 6 7 ka indicating that these areas are eroding the recent eolian sands of the upper part of the megadunes likely originated from the base of the dunes or from the lake basin the megadunes in the bjd are currently becoming increasingly high and steep due to the upward migration and accumulation of sand particles increased humidity and a weakened wind regime in northern china related to ongoing climatic warming are likely the main factors in maintaining the growth of the megadunes

a fluvial terrace record of late quaternary folding rate of the anjihai anticline in the northern piedmont of tian shan china abstract crustal shortening of the tian shan range in northwest china has largely been accommodated by fold and thrust belts that mark the northern and southern mountain boundaries which were formed during the basinward propagation of the deformation front of tian shan investigating the deformation rates of active folds anticlines in the mountain piedmonts within different timescales is important for understanding the mountain building and front propagation processes of the tian shan in this study we investigate the late quaternary folding rate of the anjihai anticline one of the major anticlines in the northern piedmont of tian shan our study is based on optically stimulated luminescence osl dating and topographic measurements of folded river terraces three well preserved fluvial terraces across the anjihai anticline were identified and dated to be 3 6 0 1 ka 9 0 0 6 ka and 53 3 2 2 ka respectively these terrace ages are combined with shortening and uplift of the terraces estimated using an area conservation method and the terrace height profiles to evaluate the average shortening and uplift rates our results show that the minimum shortening rate of the anjihai anticline is 0 4 mm a between 53 ka and 9 ka and 1 1 mm a over the past 9 ka and the corresponding minimum uplift rates are 0 5 mm a and 1 4 mm a respectively if a local sedimentation rate of 0 3 mm a is taken into consideration the shortening rate is 0 7 mm a between 53 ka and 9 ka and 1 3 mm a since 9 ka and the corresponding uplift rates are 0 8 mm a and 1 5 mm a respectively these data suggest that the anjihai anticline has accommodated 20 25 of the total shortening across the whole eastern tian shan 5 mm a in the holocene our results suggest that the holocene is a relatively tectonically active time interval since the late pleistocene the late quaternary shortening rate of the anjihai anticline is much higher than its long term average shortening rate 0 2 mm a since its formation at 7 4 ma a similar situation has also been observed for other active folds in the northern and southern piedmonts of tian shan the higher late quaternary folding rate is possibly attributed to the gradual propagation of the tian shan towards its northern and southern foreland basins in the quaternary

isochron dating of sediments using luminescence of k feldspar grains sponsorship research grant council of the hong kong special administrative region china project 7106 02p 7032 05 and 7035 06

optical dating of pottery burnt stones and sediments from selected quebec archaeological sites recent developments in luminescence technologies applied to sediment dating is used to better constrain the age of archaeological events suitable geoarchaeological material includes sediments and fired objects such as pottery and burnt stones the assessment of archaeological ages illustrated here are based on single aliquot regeneration sar with both infrared and blue stimulation on the same fine grained aliquot being detected these new approaches in optical dating were tested on polymineralic extracts of an archaic burnt stone a woodland ceramic and a soil containing plano artefacts the results demonstrate that whether or not these sites had yielded datable radiocarbon material luminescence would have provided a reliable chronological framework given that the appropriate procedures to correct anomalous fading are incorporated

optical dating of dune sand for the study of sea level change a new widely applicable method to obtain well constrained relative sea level records presented here relies on optical dating of inorganic coastal landforms and sediments eighteen optical ages of basal dune sand from a barrier in massachusetts united states indicate that local relative sea level rose 8 m during the past 5 5 k y a sea level curve drawn from these optical ages shows good agreement with independent evidence from salt marsh peat sampled behind the barrier demonstrating the reliability of the method optical dating will be particularly useful in analyzing coastal records that contain too few organic indicators to allow high resolution 14 c based analyses