multiple dating approaches applied to the recent sediments in the yangtze river changjiang subaqueous delta the accumulation rate of recent deposits in a delta environment is critical to the study of delta dynamics and their sustainable management the most commonly used dating approach for recent 100

spatial and temporal patterns of aeolian activities in the desert belt of northern china revealed by dune chronologies abstract as a part of the inqua project a global digital database and atlas of quaternary dune field and sand seas 337 age records from the desert dunes of china and 20 from mongolian dune fields have been compiled in the database this has opened the possibility of exploring and synthesizing the quaternary environmental changes in the asian mid latitudes dune fields directly from the on site aeolian sand archives this paper assessed the sand dune chronologies in terms of geographical distribution data quality and their implications for late quaternary palaeoenvironmental reconstructions the available ages are concentrated mainly in the last 20 ka and many are from the fields of stabilized dunes in the eastern portion of the desert belt in northern china the number of records and the ratio between the records of stable state and the total records could act as a proxy for the palaeoenvironmental interpretation the aeolian sand activities deciphered from the chronological data in the eastern portion of the desert belt in northern china show a reasonable correlation with the general global climatic curves at the glacial interglacial timescales the limited aeolian sand records from the glacial period however hamper the understanding of the detailed features e g forms and processes of the dune fields during glacial times in the last two millennia however there has not been any meaningful correlation between aeolian dune activity and climatic variation at the centennial time scales probably due to the complexity of the aeolian sand systems and human interventions extending the coverage of dune chronology both temporally and spatially is urgently needed for a full understanding of the environmental changes in the dune fields

a record of holocene climate change in the guanzhong basin china based on optical dating of a loess palaeosol sequence optical dating was used to obtain a chronology for a loess palaeosol sequence in the guanzhong basin on the loess plateau in china the sedimentary sequence recorded two dry episodes 3 7 2 4 ka and 1 2 0 8 ka ago in the holocene as shown by the presence of two layers of loess within the holocene deposits these two arid events are consistent with records of global climate change in the holocene and also coincident with major historic events in china this finding suggests that loess paleosol sequences in china can record global climate changes and implies that rapid climate change affected the progress of human civilization in addition changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation

luminescence sensitivities of quartz grains from eolian deposits in northern china and their implications for provenance article i nfo the thermoluminescence tl and optically stimulated luminescence osl sensitivities of quartz grains from desertsand loess redclaysequencesare usedtotrace eolianprovenancesinnorthern china our results indicate that the 110 c tl peak and osl sensitivities of quartz grains show differences among chinese deserts which can be subdivided into four groups according to the spatial variations of luminescence sensitivities such differences are related mostly to the regional difference in rock types of mountains surrounding or adjacent to the deserts wealsoexaminethepossibleprovenancechangesbetweenthequaternaryloessandthetertiaryeolianredclay and the results indicate that the luminescence sensitivity of tertiary red clay is higher than that of quaternary loess l1 l15 and l33 implying source materials of the eolian deposits changed relative to those of the quaternary

holocene climatic changes revealed by aeolian deposits from the qinghai lake area northeastern qinghai tibetan plateau and possible forcing mechanisms previous palaeoclimatic studies in the northeastern qinghai tibetan plateau netp during the holocene mainly using lake sediments have deepened our understanding of the climatic system in this remote region the timing and forcing mechanisms of climatic change in this region are still controversial however aeolian sand and silt deposits which are widely distributed in the netp can be readily dated by optically stimulated luminescence osl techniques and reveal the sensitive response of the landscape to climatic change in this study aeolian sand and loess at six sites around qinghai lake were studied to reconstruct millennial scale climatic changes during the holocene multiproxy data along with 24 osl age determinations show that low effective moisture and aeolian activity occurred at c 13 ka 10 9 1 ka and 8 9 7 8 ka periods of greater effective moisture may have occurred at 11 ka and 9 ka and there is evidence for a previously undocumented wet climate at 4 3 ka these results show that mi

geochemical characteristics of water dissolved gases and implications on gas origin of sinian to cambrian reservoirs of anyue gas field in sichuan basin china abstract the anyue gas field is a supergiant gas field which was discovered recently in the sichuan basin china where the sinian dengying formation and the cambrian longwangmiao formation are principal gas reservoirs gas in the anyue field contains mainly methane 98 and a low content of heavy hydrocarbons with minor h 2 s component reservoirs commonly contain bitumen and produce formation water it is currently suggested that natural gas in the anyue field is derived from the secondary cracking of crude oil however carbon isotopic ratio of methane is significantly less negative than that of bitumen which contradicts the isotopic signature oil cracking process would predict besides this phenomenon also cannot be explained by the process of thermochemical sulphate reduction tsr because there is no remarkable correlation between the 13 c 1 values and h 2 s contents as suggested in previous studies both free gas and water dissolved gas from the anyue gas field were analyzed in this study for their stable isotopes results show that the 13 c 1 of the gas derived from the formation water is much less negative than that of free gas therefore it is inferred that the less negative 13 c 1 values in the free gas reservoir are attributable to addition of natural gas that is previously dissolved in formation water geological setting of the gas reservoirs in dengying and longwangmiao formations of the anyue gas field is favorable for the formation and preservation of water dissolved gas in addition both formations had experienced significant structural uplifting before the gas reservoirs were formed reduced temperature and pressure in the formations by geological uplifting could cause super saturation of methane in the formation water and as a consequence water dissolved methane gas could exsolve from water phase into gas phase therefore it is concluded that natural gas in the anyue field is a mixture of free gas and gas exsolved from the formation water as a result the carbon isotope of methane gas in the anyue field became less negative than that of a single free gas component would predict

late quaternary aeolian activity in the mu us and otindag dune fields north china and lagged response to insolation forcing 1 dune fields in parts of northern china contain important stratigraphic records of late quaternary change in the east asian monsoon in this study 33 new optically stimulated luminescence osl ages and other measurements from aeolian sediment sections are used to reconstruct the timing of wet dry climate variation in the mu us and otindag dune fields of north china the results indicate dune activity and dry climate in the last few hundred years 14 ka to about 7 8 ka and 50 ka to 60 ka the dunes were mainly stable implying a wetter climate between about 7 8 ka and 2 4 ka these results imply a lag of several thousand years between peak summer insolation at 10 11 ka and high summer monsoon rainfall after 7 8 ka in the investigated regions the monsoon climate may not respond directly to orbital forcing over millennial time scales land surface feedbacks may account for lagged dune field response

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

osl chronology and possible forcing mechanisms of dune evolution in the horqin dunefield in northern china since the last glacial maximum the evolution processes and forcing mechanisms of the horqin dunefield in northern china are poorly understood in this study systematic osl dating of multiple sites is used together with pollen analysis of a representative section in order to reconstruct the evolution of the dunefield since the last glacial maximum lgm our results show that there was extensive dune mobilization 25 10 ka transition to stabilization 10 8 ka considerable dune stabilization 8 3 ka and multiple episodes of stabilization and mobilization after 3 ka comparison of dune evolution of the dunefields in northern china during the holocene showed that asian monsoon and resultant effective moisture have played an important role in the evolution of dunefields at the millennial time scale further analysis indicated that the dune evolution in the horqin dunefield before 3 ka was synchronous with climatic changes however increasing human activity has impacted dune evolution during the last 3 ka c 2012 university of washington published by elsevier inc all rights reserved the evolution processes and forcing mechanisms of the horqin dunefield in northern china are poorly understood in this study systematic osl dating of multiple sites is used together with pollen analysis of a representative section in order to reconstruct the evolution of the dunefield since the last glacial maximum lgm our results show that there was extensive dune mobilization 25 10 ka transition to stabilization 10 8 ka considerable dune stabilization 8 3 ka and multiple episodes of stabilization and mobilization after 3 ka comparison of dune evolution of the dunefields in northern china during the holocene showed that asian monsoon and resultant effective moisture have played an important role in the evolution of dunefields at the millennial time scale further analysis indicated that the dune evolution in the horqin dunefield before 3 ka was synchronous with climatic changes however increasing human activity has impacted dune evolution during the last 3 ka c 2012 university of washington published by elsevier inc all rights reserved

holocene environment changes around the sara us river northern china revealed by optical dating of lacustrine aeolian sediments abstract the sara us river is located along the boundary of the mu us desert and the chinese loess plateau in northern china the river has cut down through quaternary sediments creating 70 80 m deep valleys with thick lacustrine aeolian sequences exposed we applied optical stimulated luminescence on sediments from a holocene section of aeolian sand lacustrine deposits in the top of the river valley the dating results show that a humid period existed from 7 1 to 2 0 ka ago as evidenced by two layers of peat and lacustrine sediments however compared to other published holocene sections in the sara us river valleys close to the section under studying the local environment experienced very complicated changes during the holocene all of the sections recorded a period with drought and or cold before the holocene at around 13 ka and an episode of aridity after about 2 ka ago as evidenced by the layers of aeolian sand however the ages of the lacustrine and peat layers in these sections are substantially different geomorphological analysis by digital elevation models does not support the existence of a mega lake covering the study area at 2 ka the intricate environmental changes may have been caused by the meandering of the sara us river environmental changes also strongly affected human migration in this area which is documented by chinese historical records

environmental changes in hunshandake otindag sandy land revealed by optical dating and multi proxy study of dune sands abstract a stabilized sand dune from the southern hunshandake otindag sandy land in northeastern china was studied for reconstructing past environmental changes by optically stimulated luminescence osl dating magnetic susceptibility and particle size analysis the osl dating results indicate that the sandy deposits at the bottom of the section formed at 11 8 ka ago corresponding to low magnetic susceptibility and low fractions of fine particles

osl chronology of sand deposits and climate change of last 18 ka in gurbantunggut desert northwest china the development of the gurbantunggut desert is mainly controlled by the westerly wind and at present has little influence from indian and southeast asian monsoons a combined study using optically stimulated luminescence osl dating ground penetrating radar gpr surveys and climatic proxies analysis was carried out in the southern part of the desert the chronology extends back to 18 ka and is constructed based on 16 osl ages from boreholes in the linear dune body and the inter dune area the chronology suggests that sand deposition in the last 18 ka experienced two rapid accumulation phases at 11 and 2 5 ka ago which were also evident from the gpr surveys these periods relate to increased aridity in the region five climate phases are identified from the last 18 ka based on the osl chronology and climatic proxy analysis with grain size and magnetic susceptibility measurements the deglacial period 18 3 10 4 ka is characterized by climate instability and possible glacial melting events the holocene optimum peaked 8 5 ka and terminated 3 6 ka ago when the regional climate became arid osl samples from the dune body cluster around 2 5 ka which indicates rapid advance extension of dune bodies at this time copyright 2011 john wiley sons ltd

identification of well bleached grains in the optical dating of quartz abstract a simple means of identifying poorly bleached samples is proposed for the dating of quartz using the single aliquot additive dose optically stimulated luminescence osl protocol for a well bleached sample it is shown that the equivalent dose d e does not change with the ratio of the natural osl from a brief 0 1 s stimulation to the 110 c thermoluminescence from a subsequent small test dose in contrast in a poorly bleached sample the d e increases strongly at higher values of the ratio these observations suggest that this ratio can be used as an indicator of whether or not a sample is well bleached the osl tl ratio is also likely to be sensitive to such factors as thermal history and feldspar contamination

lateglacial and holocene dune evolution in the horqin dunefield of northeastern china based on luminescence dating abstract the horqin dunefield is located in the northern frontier of east asian monsoon eam zone and its activation and stabilization is sensitive to the ebb and flow of the eam however the activity of dunes in the horqin dunefield is still poorly understood due to limited numerical dating the purpose of the present study is to establish the chronology using luminescence dating in order to understand dune evolution of the horqin dunefield and to explore the relative role of climate and human activity eighteen samples were collected from seven sections following a southwest northeast transect through the dunefield and dated using quartz optically stimulated luminescence osl combining evidence from stratigraphy and the luminescence chronology dune evolution within the horqin dunefield since the lateglacial can be summarized as before 9 6 ka aeolian sand dunes were mobilized during the period 9 6 3 ka dunes were stabilized at around 3 ka dunes were mobilized again abruptly since 3 ka there were multiple phases of dune stabilization mobilization dune activity was dominated by climate before 3 ka however since 3 ka both climate variability and human impact have influenced dune evolution in the horqin dunefield

age dependence of luminescence signals from granitic and mylonitic quartz abstract granite and mylonitic samples with an age range of 11 3300 ma were collected from different regions of china several luminescence signals were measured from the extracted quartz age dependence has been observed in their luminescence signals including the sensitivity of the 110 c tl peak the temperature of the high temperature tl peak and the regenerated tl with dose other luminescence signals show little age dependence the tl reaches maximum at about 160 c in the quartz samples which is significantly different from signals from sediments it is concluded that the luminescence signals may lead to the establishment of a new geochronological method for the whole earth history

climate driven changes to dune activity during the last glacial maximum and deglaciation in the mu us dune field north central china one significant change of terrestrial landscapes in response to past climate change has been the transformation between activity and stability of extensively distributed wind blown sand dunes the relations between the dynamics of the aeolian landscape and its drivers are not yet completely understood however evidence of aeolian sand deposition during the last glacial maximum lgm is scarce in many mid latitude dune fields whereas abundant evidence exists for aeolian sand accumulation during the deglaciation i e after about 15 ka whether this contrast actually reflects changes in dune activity is still unclear making paleoclimatic interpretation uncertain comprehensive field investigation and luminescence dating in the mu us dune field north central china demonstrates that aeolian sands deposited during the lgm are preserved as fills in periglacial sand wedges and beneath loess deposits near the downwind dune field margin the scarcity of lgm dune sand elsewhere in the dune field is interpreted as the result of intensive aeolian activity without substantial net sand accumulation increasing sand accumulation after 15 ka reflected by much more extensive preservation signals a change in sand supply relative to sand transportation through the dune field reduced wind strength and other environmental changes including regional permafrost degradation after 15 ka transformed the dune field state from net erosion to net accumulation the dunes however remained largely mobile as they were in the lgm similar diverging patterns of dune sand accumulation and preservation before and after 15 ka in many mid latitude dune fields imply broad climatic controls linked to the changes in high northern latitude forcing

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

osl dating of past lake levels for a large dammed lake in southern tibet and determination of possible controls on lake evolution fluvio lacustrine terraces along phung chu river on the central southern tibetan plateau indicate that a large palaeo dammed lake formerly existed in this area based on landscape survey optically stimulated luminescence osl dating and sedimentary analyses this research shows that the phung chu was blocked and a dammed lake over 2500 km in size formed before 30 ka ago osl dating analysis suggests the fluvio lacustrine sediments were well bleached and yield accurate age estimates for two lake drainage events the first drainage event took place after 30 ka resulted in river incision and formed a high terrace at 50 m height from the present river level the second drainage happened after 3 7 ka resulted in further river incision and formed the second terrace at 25 m height from the present river level according to the distribution of the fluvio lacustrine sediments active normal faults particularly the kharta fault in this region and the high gradient slopes after phung chu enters the yo ri gorge seismically induced landsliding is regarded as highly likely to have been the cause of river blockage and associated formation of a dammed lake although glacial damming is also a possible cause the volume of drainages from this dammed lake may have led to catastrophic flooding and analogous modern lakes represent significant geo hazard risks to down river human settlements as dammed lakes are special phases in fluvial evolution often involving river blockage breakthrough and drastic catchment change these processes can reveal how tectonic or climatic events modify landforms however such tectonic derived landform changes can also impact palaeo climate of the region thus this study has added new evidence regarding the evolutionary history of a dammed lake including its formation duration extent and final drainage which is crucial for understanding its general landscape process mechanisms and for better assessing geo hazard risks

holocene lake level history of the tangra yumco lake system southern central tibetan plateau massive carbonate banks representing ancient lacustrine deposits are exposed in the catchment of the lake tangra yumco southern central tibetan plateau and nearby lake xuru co nine sediment samples were taken below and above these lacustrine deposits to determine periods of changing lake level using optically stimulated luminescence osl applying a multiple aliquot regeneration mar protocol according to facies and stratigraphy samples below the carbonate banks indicate a rising and samples from above a falling lake level the results indicate that the rising lake level of tangra yumco passed the sampling location at 10 5 and 2 1 ka while a falling lake level passed the sampling location at 0 9 ka the rising lake level of xuru co passed the sampling location at 7 9 and 1 7 ka and a falling lake level at 0 5 ka showing a similar trend as at tangra yumco combining these results with recalculated cosmogenic nuclide ages and previously published feldspar luminescence data allows the establishment of

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

post glacial entrenchment and knickpoint migration of the yarlung tsangpo gorge southeastern tibetan plateau abstract the formation of the yarlung tsangpo river system is commonly thought to be controlled by tectonic processes initiated several million years ago however climate change may also play an important role in guiding drainage evolution here we reconstruct the drainage history of the yarlung tsangpo gorge using field observations age constraints from optically stimulated luminescence and radiocarbon dating paleosalinity reconstruction and grain size analysis of lacustrine deposits and river valley characteristics field observations clay boron derived paleosalinity reconstruction and grain size analysis of lacustrine deposits demonstrate that a closed inland saline lake existed upstream of the yarlung tsangpo gorge implying that cutting of the gorge postdated this paleolake optically stimulated luminescence and radiocarbon dating suggest that the paleolake formed at least 51 ka and terminated after 13 ka with a shift in global climate following the last glacial maximum the paleolake drained by river capture and the gorge entrenchment commenced at the village of jiala northwest of the namche barwa peak approximately 13 10 ka ago the evolution of the yarlung tsangpo occurred on a remarkably short timescale of just tens of thousands of years in response to drainage system reorganization the yarlung tsangpo incised at an average rate of at least 26 mm yr the rapid fluvial incision initiated at jiala 13 ka ago propagated rapidly upstream at 2 12 m yr the yarlung tsangpo knickpoint has not stabilized but will likely continue to migrate upstream

luminescence dating of sand loess sequences and response of mu us and otindag sand fields north china to climatic changes the sand loess transition zone in north china is sensitive to climate change and is an ideal place to investigate past environmental changes however past climate change at millennial centennial timescales in this region has not been well reconstructed because of limited numerical dating alternations of sandy loam soils with aeolian sand layers in the mu us and otindag sand fields which lie along the sand loess transition zone indicate multiple intervals of dune activity and stability this change is probably a response to variations of the east asian monsoon climate during the late quaternary the single aliquot regeneration sar optically stimulated luminescence osl dating protocol which has been successfully applied to aeolian deposits worldwide is applied to these two sand fields in this study the osl ages provide reliable constraints for reconstruction of past climate changes at suborbital timescale sections in both sand fields contain aeolian sand beds recording millennial scale episodes of dry climate and widespread dune activation including episodes at about the same time as heinrich event 5 and the younger dryas in the north atlantic region these results demonstrate the potential of aeolian sediments in semi arid north china to record millennial scale climatic events and also suggest that dry wet climate variation at the desert margin in china may be linked to climatic change elsewhere in the northern hemisphere through atmospheric circulation this article was published online on 27 november 2008 an error was subsequently identified this notice is included in the online and print versions to indicate that both have been corrected 16 december 2008 copyright 2008 john wiley sons ltd

late pleistocene to present day eruptive history of the changbaishan tianchi volcano china dprk new field geochronological and chemical constraints abstract volcanic unrest during 2002 2006 renewed attention on changbaishan tianchi volcano as the source of the powerful explosive eruption vei 6 to 7 millennium eruption of 946 ce common era however progress in understanding the potential risk is complicated by discordant accounts of the most recent explosive eruptive history several eruptions since the late pleistocene such as the tianwenfeng twf qixiangzhan qxz millennium me baguamiao bgm liuhaojie lhj 1403 ce event 1403 and even a 1903 ce event have been proposed but the stratigraphic order ages distributions and even the very existence of some of these are still not fully ratified based on recent detailed stratigraphic logs of over 100 surface exposures and three deep trenches coupled with new geochronologic and petrochemical data including trace elements on glass and pyroxene we can now clarify these relationships herein we propose that the 946 ce millennium eruption be formally re named the generalized millennium eruption gme to avoid entrenched confusion and to formally acknowledge the composite comendite trachyte nature of the eruption thus three eruptions the twf qxz and the gme are confirmed the twf eruption is the first powerful explosive eruption at changbaishan tianchi and we find evidence that this eruption may have initiated the tianchi caldera it produced an extensive fallout pumice deposit that on the basis of new optically stimulated luminescence osl and radiocarbon 14c ages of overlying sedimentary strata indicates an eruption age 42 ka this new age constraint coupled with geochemical fingerprints confirms a correlation to the 50 6 kyr b j ash in japan sea the next eruption was the predominately effusive qxz that produced a clastogenic lava flow down the north slope of the edifice an age of 4 8 ka is proposed based on new radiocarbon 14c ages of charcoal at the base and from overlying sediment although the age of the gme is well established as late 946 ce there are some intriguing details in historical records of ash falls in japan that indicate two separate events on nov 3 946 ce and feb 7 947 ce we speculate that these correspond to the comendite and trachyte stages of the gme respectively subsequent to the gme no evidence of any post gme eruptions have been found these findings clarify and refine the history of the explosive stage of the changbaishan tianchi volcano that began 51 kyr this improved understanding should serve as a basis for further studies at changbaishan tianchi and inform a better constrained assessment of volcano hazard

osl chronology and palaeoclimatic implications of aeolian sediments in the eastern qaidam basin of the northeastern qinghai tibetan plateau abstract aeolian sediments are widely distributed in the hyper arid qaidam basin and are good palaeoclimatic records due to limited age control aeolian processes and their relevance to palaeoclimatic change are poorly understood in this study we present 28 optically stimulated luminescence osl ages for both loess 14 samples and aeolian sand 14 samples from 8 profiles in eastern qaidam basin eqb in order to provide a detailed chronology for understanding the timing of aeolian processes and associated environmental conditions we reconstructed the history of aeolian activity in the eqb since deglaciation by combining osl chronologies lithologic stratigraphy and grain size analysis the results indicate that 1 aeolian sand underlying the loess accumulated at ca 12 4 11 5 ka and 10 8 ka but not during the last glacial maximum 2 loess accumulation started at 10 ka and lasted to 0 45 ka at least while most of the loess was deposited during 8 4 5 ka 3 palaeoclimates in the eqb are inferred to be arid during 12 4 11 5 ka relatively humid during 10 8 ka humid during 8 4 5 ka and relatively arid during 4 5 0 45 ka and 4 evolution of aeolian sediments were mainly controlled by effective moisture and also affected by local topography

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

optical dating of holocene sediments from the yangtze river changjiang delta china abstract establishing a reliable chronology is essential for understanding delta evolution which is normally performed using radiocarbon 14c dating and the recently emerging technique of optically stimulated luminescence osl the application of the latter one to the holocene yangtze river changjiang delta deposit is still quite limited in this study two 60 9 m long cores were collected from taizhou tz and nantong nt within the paleo incised valley of the yangtze river and a total of seven and nine osl samples were collected from the tz and nt cores respectively in addition ten accelerator mass spectrometry ams 14c ages of the tz core were presented with eight ams 14c ages that were previously obtained from the nt core the single aliquot regenerative dose sar protocol was applied to coarse silt sized 45 63 m and fine sand sized 90 125 m quartz the results showed that the grains in the 45 63 m size fractions appeared to be better bleached than those in the 90 125 m size fractions and the detection of insufficiently bleached sediments is required in order to obtain accurate age estimates the ages adopted for the samples range from 3 ka to 9 ka for the tz core and from 1 ka to 14 ka for the nt core which were in general internally coherent within the limits of experimental errors and with respect to their stratigraphic order the ams 14c age of the tz core were significantly older than their osl ages while those from the nt core generally showed good agreement with their osl ages one should be cautious when using ams 14c to date deltatic deposits based on the osl ages two periods of rapid accumulation rates can be found in both cores which are linked to the rapid sea level rise in early holocene and migration of delta front facies in late holocene these investigations indicate that osl technique is an effective method with which to date holocene deltaic deposits especially in coarse sedimentary layers where organic carbon material is sparse

dune mobility and aridity at the desert margin of northern china at a time of peak monsoon strength wind blown sands were mobile at many sites along the desert margin in northern china during the early holocene 11 5 8 ka ago based on extensive new numerical dating this mobility implies low effective moisture at the desert margin in contrast to growing evidence for greater than modern monsoon precipitation at the same time in central and southern china dry conditions in the early holocene at the desert margin can be explained through a dynamic link between enhanced diabatic heating in the core region of the strengthened monsoon and increased subsidence in drylands to the north combined with high evapotranspiration rates due to high summer temperatures after 8 ka ago as the monsoon weakened and lower temperatures reduced evapotranspiration eolian sands were stabilized by vegetation aridity and dune mobility at the desert margin and a strengthened monsoon can both be explained as responses to high summer insolation in the early holocene

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

shrinking lakes in tibet linked to the weakening asian monsoon in the past 8 2 ka expansion or shrinkage of closed lakes is a natural response to fluctuations in precipitation and evaporation linked closely to changes in strength or position of atmospheric circulation in tibet there are many such lakes with paleo shorelines that can be used for reconstructions of climate history despite the fact that many paleo shorelines are well preserved in tibet dating them has been seriously hindered by various difficulties here we present the first optical dating chronology for a series of paleo shorelines in zhari namco the third largest inland lake in central tibet our results indicate that the lake level has dropped 128m over the past 8 2ka younger shorelines are found at lower altitudes indicating that the shorelines follow a geomorphic chronological order and a broadly continuous trend of stepwise shrinkage the surface area of zhari namco has shrunk in size from 4605km2 at 8 2ka ago to 996km2 at present 300km3 of water has been lost from this lake such a loss in water implies a significant reduction in precipitation over the past 8 2ka a likely result of a weakening asian monsoon following the decreasing precipitation since the early holocene this area has become increasingly arid

limited change in dune mobility in response to a large decrease in wind power in semi arid northern china since the 1970s abstract the climatic controls on dune mobility especially the relative importance of wind strength remain incompletely understood this is a key research problem in semi arid northern china both for interpreting past dune activity as evidence of paleoclimate and for predicting future environmental change potential eolian sand transport which is approximately proportional to wind power above the threshold for sand entrainment has decreased across much of northern china since the 1970s over the same period effective moisture ratio of precipitation to potential evapotranspiration has not changed significantly this natural experiment provides insight on the relative importance of wind power as a control on dune mobility in three dunefields of northern china mu us otindag and horqin although poorly understood and potentially large effects of human land use complicate interpretation dune forms in these three regions are consistent with sand transport vectors inferred from weather station data suggesting that wind directions have remained stable and the stations adequately represent winds that shaped the dunes the predicted effect of weaker winds since the 1970s would be dune stabilization with lower sand transport rates allowing vegetation cover to expand large portions of all three dunefields remained stabilized by vegetation in the 1970s despite high wind power since the 1970s trends in remotely sensed vegetation greenness and change in mobile dune area inferred from sequential landsat images do indicate widespread dune stabilization in the eastern mu us region on the other hand expansion of active dunes took place farther west in the mu us dunefield and especially in the central otindag dunefield with little overall change in two parts of the horqin dunes better ground truth is needed to validate the remote sensing analyses but results presented here place limits on the relative importance of wind strength as a control on dune mobility in the study areas high wind power alone does not completely destabilize these dunes a large decrease in wind power either has little short term effect on the dunes or more likely its effect is sufficiently small that it is obscured by human impacts on dune stability in many parts of the study areas

geochemical evidence for an eolian sand dam across the north and south platte rivers in nebraska abstract geochemical and geomorphic data from dune fields in southwestern nebraska provide new evidence that the nebraska sand hills once migrated across the north and south platte rivers and dammed the largest tributary system to the missouri river the lincoln county and imperial dune fields which lie downwind of the south platte river have compositions intermediate between the nebraska sand hills quartz rich and northeastern colorado dunes k feldspar rich the most likely explanation for the intermediate composition is that the lincoln county and imperial dunes are derived in part from the nebraska sand hills and in part from the south platte river the only mechanism by which the nebraska sand hills could have migrated this far south is by complete infilling of what were probably perennially dry north platte and south platte river valleys such a series of events would have required an extended drought both for activation of eolian sand and decreased discharges in the platte river system a nearby major tributary of the north platte river is postulated to have been blocked by eolian sand about 12 000 14c yr b p we propose that an eolian sand dam across the plattes was constructed at about this same time

geochronology and paleoenvironment of the taoshan site northeastern china and archaeological implications abstract the taoshan archaeological site located in northeastern china was found in 2011 and an area of 36 m 2 was excavated in 2013 and 2014 2908 stone artifacts 71 pottery fragments and five ornaments were excavated from three cultural layers similar sites with both stone artifact and pottery at least in heilongjiang province of china have not been reported the dating results showed that the optically stimulated luminescence technique is of great utility for such archaeological deposits and the three cultural layers were dated to 16 5 13 4 ka 13 4 8 7 ka and 8 7 5 6 ka respectively the climate proxies magnetic susceptibility total organic content and pollen indicate that the local climate was cold and dry for the period of 16 5 13 4 ka warm and wet for the period of 13 4 8 7 ka and warm and dry for the period of 8 7 5 6 ka respectively the types and amount of archaeological findings from each layer period reflect the human response to the past climate change implying that the human related processes identified at taoshan are associated with climatic and environmental changes the investigations of the site are very important for developing a better understanding of the colonization of this region by humans the transmission of technologies and the processes of economic and social change the local societies underwent the presence of microblades and pottery is the most significant for our reconstructing of the archaeology of the northernmost parts of northeast china

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

response of surface processes to climatic change in the dunefields and loess plateau of north china during the late quaternary this paper draws on recent optically stimulated luminescence osl dating to evaluate the long held assumption that dust accumulation rates in the loess plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time because both are controlled by the strength of the asian monsoons and also possibly because the dunefields are proximal loess sources the results show there is little evidence that high rates of loess accumulation coincided with well dated episodes of extensive dune activity in the mu us otindag and horqin dunefields at 11 8 ka and 1 0 ka explanations for the apparent lack of coupling include local variation in the trapping of dust and post depositional preservation of the loess and dune sediments in response to varying local environmental conditions in addition a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields the results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale the dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale but the timing of late quaternary dune activity along with a variety of other evidence indicates that moisture changes in many of the drylands of northern china may not be in phase with precipitation in core regions of the asian monsoons copyright 2011 john wiley sons ltd

refining the late holocene coastline and delta development of the northern yangtze river delta combining historical archives and osl dating historical documents provide a general chronological overview of the environmental evolution of the yangtze river delta yrd during the last ca 2000 years however absolute dating of the region

optical dating of an offset river terrace sequence across the karakax fault and its implication for the late quaternary left lateral slip rate abstract the karakax fault is one of the largest left lateral strike slip faults at the rim of the northwestern tibetan plateau in this study the optical dating techniques were applied to the taersayijilega river terraces which were transversely cut and offset by the karakax fault six fluvial sand samples from the river terraces were collected and dated the results show that the terraces t2 t5 have ages of 14 5 1 0 ka 21 2 1 2 ka 28 5 1 7 ka and 39 7 2 5 ka respectively by interpreting high resolution satellite images the horizontal displacements of the four river terraces are estimated at 160 m 235 m 260 m and 365 m respectively based on the ages and offsets of the terraces the average left lateral slip rate of the karakax fault was estimated at 7 8 1 6 mm a during the late quaternary such rate of the karakax fault is significantly higher than that of the longmu gozha co fault suggesting that the karakax fault plays an important role in accommodating eastward movement of the tibetan plateau at the northwest during the late quaternary

linkage between c4 vegetation expansion and dune stabilization in the deserts of ne china during the late quaternary abstract knowledge of the role of c4 vegetation expansion in regulating dune stabilization during the late quaternary is important for understanding the evolution of the environment and climate in the climatically sensitive margin of the east asian summer monsoon however due to the lack of both reliable vegetation records and chronological control during episodes of dune activity the relationship between c4 vegetation expansion and dune stabilization in the deserts of ne china during the late quaternary remains unclear here we present a new regional compilation of late quaternary stable carbon isotopic data from organic matter together with dated records from sub aerial sedimentary deposits in the region our compilation of vegetation development and dune activity in these deserts suggests that c4 vegetation expansion with a main contribution from chenopodiaceae and a secondary contribution from poaceae and cyperaceae may have played a critical role in dune semi stabilization with a northwestward trend from 13 to 9 ka and dune stabilization throughout the entire study region from 9 to 5 ka in addition during the late holocene intensified millet cultivation or overgrazing and or climatic deterioration at 1 5 ka likely caused an increase in c4 vegetation abundance in the deserts of ne china which is associated with a dune mobilization episode in contrast after 2 5 ka decreased vegetation cover and dune mobilization in the mu us and hobq deserts were likely caused by poor land use practices and historically documented droughts overall c4 vegetation expansion was the main cause of dune stabilization in these deserts during the late quaternary

late cenozoic seismic stratigraphy and glacial geological development of the east greenland and svalbard barents sea continental margins abstract the european program on the late cenozoic evolution of the polar north atlantic margins ponam running from 1990 to 1994 resulted in a wealth of seismic data and sediment cores particularly from the svalbard and barents sea continental margin but also from areas of the east greenland margin deep sediment coring was undertaken on both margins during odp legs 152 and 162 this paper uses the ponam generated information as well as previous and subsequent seismic and core data to review our present understanding of the glacial geological development of these regions four main depositional facies have been identified these are represented by hemipelagic glaciomarine sediments sandy silty debris flows diamictic debris flows and tills deposited directly beneath grounded ice the temporal and spatial distribution of these four facies determines the architecture and seismic character of the two continental margins the two regions show significant differences with regard to both the timing of initial glaciation and the response of the ice sheets to climatic variability glacial deposition has taken place on the east greenland margin at least since 7 ma but apparently only since 2 5 ma on the svalbard barents sea margin significant glacial expansion across the continental shelf probably occurred in the early and late pliocene in east greenland whereas the glaciers on svalbard and the barents sea did not reach the shelf edge until the early pleistocene despite a shorter glacial period average glacial sedimentation rates are 2 3 times higher on the svalbard barents sea margin than on the studied parts of the east greenland margin the svalbard barents sea ice sheet has advanced and retreated much more frequently during the plio pleistocene than the greenland ice sheet glacial regime polar on greenland and polythermal to temperate in svalbard and the barents sea and the more easily erodible preglacial bedrock of svalbard and the barents sea are thought to be main factors responsible for the differences in ice sheet behavior and consequently glacial sediment production

multiple episodes of aridity in southern africa since the last interglacial period there is generally a dearth of evidence of the nature of quaternary climate change within desert systems which has limited previous interpretations of past environmental change at low latitudes the last glacial maximum has previously been identified as the peak of late quaternary aridity when desert systems expanded to five times their present extent1 2 3 and low latitude aridity has been described for previous glaciations4 but little evidence has been derived directly for large desert basins particularly southern africa here we report new chronological optical dating evidence of arid episodes recorded in aeolian sediments from the mega kalahari sand sea episodic aeolian activity is recorded at the northeastern desert margin whereas more sustained activity is evident from the southwestern desert core several significant arid events are apparent since the last interglacial period with dune building arid phases at 95 115 41 46 20 26 and 9 16 kyr before present existing atmospheric general circulation model simulations and independent palaeoclimate data indicate that the changes in aridity are related to changes in the northeast southwest summer rainfall gradient which are in turn related to sea surface temperatures in the southeastern atlantic ocean

geomorphological and palaeoclimate dynamics recorded by the formation of aeolian archives on the tibetan plateau abstract aeolian sediments are an important archive for palaeoclimate reconstructions on the tibetan plateau the accumulation of aeolian sediments and the formation of palaeosols are used as a proxy for dry and wet phases respectively during the last decade the number of osl optically stimulated luminescence ages of aeolian sediments has been rapidly increasing this study summarises the results from more than 300 individual osl ages despite the widespread occurrence of aeolian sediments on the tibetan plateau nearly all osl samples are located on the northeastern and the southern part in most regions the strongest accumulation occurred during the late glacial and in the early holocene this coincides with the strengthening of the asian summer monsoon on the tibetan plateau and wetter climate conditions after the relatively dry glacial times the development of a sufficient vegetation cover acting as a sediment trap seems to be an important requirement for the preservation of aeolian archives short dry periods like the younger dryas led to a more enhanced aeolian accumulation without destruction of previously formed archives in some regions the formation of palaeosols occurred mainly during the wet early and mid holocene but the number of ages is relatively small in contrast a second phase of aeolian accumulation during the late holocene was related to the weakening of the asian summer monsoon and drier climate conditions this indicates that the reaction of aeolian accumulation on the tibetan plateau depends on the previous climate state a comparison between the osl ages from aeolian sands and loess deposits yields a different timing of deposition of these two sediment types while the sand deposits in different basins resemble wet and dry phases loess deposits show no common signal between the analysed areas this indicates an influence of local factors such as varying source areas and erosive processes on the slopes in general the aeolian archives in the high mountain environment are governed by numerous factors besides the climatic influence

late pleistocene and holocene aeolian sedimentation in gonghe basin northeastern qinghai tibetan plateau variability processes and climatic implications abstract although stratigraphic sequences of aeolian deposits in dryland areas have long been recognized as providing information about past environments the exact nature of the environmental processes they reflect remains unclear here we report the results of a detailed investigation of eight outcrop sections in the gonghe basin northeastern qinghai tibetan plateau measurements of sediment grain size and chemical composition indicate that the deposits are primarily of aeolian origin consisting of interbedded well sorted sand silty sand loess and or palaeosol however their occurrence varies from site to site fossil dune sands mainly occur in or close to the currently stabilized or semi stabilized dune fields whereas loess is distributed along the downwind marginal areas this pattern of basin scale differentiation was controlled mainly by spatial variability of sediment supply due to the antecedent sedimentary patterns within the basin together with previously published optically stimulated luminescence osl ages 24 new osl dates are used to elucidate the history of aeolian activity and its relationship to climatic changes there is no apparent relationship between past dune activity and downwind loess deposits deposition of silty sand probably occurred during past phases of windy dry and cold climate in the late pleistocene however climatic factors alone cannot explain the occurrence of silty sand deposition this is because the deposition of silty sand was always preceded by episodes of fluvial deposition prior to river incision thereby indicating the importance of an activated sediment supply associated with fluvial processes deposition of well sorted sand occurred episodically not only during the late pleistocene but also during the early to mid holocene vegetation conditions controlled either by the occurrence of intervals of moisture deficit during the late pleistocene or by changes in the balance between precipitation and evapotranspiration at a local scale played an important role in sand mobility and deposition the effect of vegetation on sand mobility is also suggested by independent evidence of aeolian activity from genggahai lake in the gonghe basin here the deposition of aeolian sand in the basin during the early to mid holocene indicates a low level of effective moisture caused by high evaporation induced by higher summer insolation despite the coeval increased regional precipitation recorded by lacustrine sediments in contrast late holocene palaeosols represent a high level of effective moisture and their formation did not necessarily require increased regional precipitation overall our results suggest that the relationship between aeolian activity and regional climate change is complex and that sand accumulations do not represent the consistent action of surface processes that are related to climatic changes

luminescence dated aeolian deposits of late quaternary age in the southern tibetan plateau and their implications for landscape history abstract aeolian deposits are widely distributed in the interior of the tibetan plateau and their chronology is poorly known it is not yet clear whether they accumulated only after the last deglaciation or over a longer time we applied quartz osl dating to aeolian samples from the lhasa area with osl ages ranging from 2 9 0 2 to at least 118 11 ka the probability density frequency pdf distribution of 24 ages reveals age clusters at about 3 8 16 21 33 and 79 83 ka indicating enhanced sediment accumulation then the results show that aeolian deposition occurred throughout most of the last 100 ka this implies that 1 an ice sheet covering the whole tibetan plateau during the last glacial maximum lgm could not have existed and 2 erosion during the last deglaciation was not as strong as previously proposed such that not all pre holocene loess was removed the age distribution shown in the pdf indicates that aeolian accumulation is episodic sand formation events revealed by age clusters at 3 8 and 16 21 ka imply roughly synchronous environmental responses to corresponding global scale arid events

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

luminescence dating of late holocene dunes showing remnants of early settlement in cuddalore and evidence of monsoon activity in south east india abstract in this study dunes from south east india were dated using optically stimulated luminescence osl to reconstruct the depositional history a belt of dunes has developed parallel to the coast between pondicherry and karikal in tamil nadu south east india in the area between cuddalore and porto novo the dune belt is 5 km wide a transect from the coast to the most western dune inland was investigated changes in the environmental conditions are recorded in the dunes they show features including unconformities changes in the direction of bedding erosional features water escape structures and remnants of human settlements the osl results show that strong changes in the environmental conditions occurred about 100 and 300 years ago the latter event marks also the termination of settlement in this place the settlement period started about 1500 years previously the periods of sand mobility and stabilisation of the land surface by soil formation correlate with changes in the precipitation record of india the investigated dunes very likely reflect fluctuations in the monsoon activity during the last 3500 years in south east india

quaternary environmental changes in the drylands of china a critical review abstract this paper reviews our current understanding of quaternary climate and landscape changes in the desert areas of northern china a key portion of the middle latitude drylands on earth combining earlier studies with our recent research and experience we offer a comprehensive picture of the state of chinese deserts during the quaternary and in the interest of enhancing future research identify knowledge gaps and areas of uncertainty lacustrine deposits found over an area ranging from china s western taklamakan desert to the eastern hunshandake sandy lands suggest that extensive lakes occurred in china s deserts during the pleistocene analysis of digital elevation models from srtm shuttle radar topography mission data supports this interpretation and shows the significant extent of these former lakes new estimates of mean annual evaporation of ca 1000 mm from lake surfaces and ca 100 mm from land surfaces confirms that local and regional rainfall is critical for maintenance of desert lakes in this temperate zone especially during intervals when the mean annual rainfall is more than 100 mm rapid shifts between sand seas and lakes in geologically and environmentally diverse settings suggest that the drylands of china are very sensitive ephemeral systems and not long lasting as previously thought available chronologies suggest that there were large lakes in the western taklamakan desert and the chadamu basin during mis marine isotope stage 3 at 30 ka probably related to a period of strong influence of northern hemispheric westerly winds channels and elevation models revealed by srtm data and remains of lacustrine sediments also indicate that there was a large lake in the hunshandake sandy lands in the eastern portion of the desert belt during the quaternary there is significant evidence that during the middle holocene strong summer monsoons led to a relatively large increase in moisture availability in the entire desert belt of northern china lacustrine records from the badain jaran desert in western inner mongolia suggest that it was generally dry before 10 cal ka becoming wetter from 10 to 4 cal ka and dry again afterwards study of palaeosols widely occurring in dune stratigraphy in the eastern portion of the desert belt suggests that there was a period of wet and warm climate in this region during the mid holocene optimum at a minimum between 6 ka and 4 ka but possibly lasting longer recent observations dealing with the generation and transport of dust from central asia indicate that the causal relationship between sand seas and loess sequences is not as close as previously assumed these results suggest that there is an urgent need to examine whether the frequency and amplitude of climatic variation in chinese deserts are somehow similar to that having occurred in the sahara desert of north africa deserts in northern china were also important focal regions for neolithic cultures during intervals when environmental conditions supported a denser vegetative cover there is evidence that some areas of woody vegetation to the west of badain jaran desert were deforested by humans by ca 4000 yr b p although it is still debatable whether humans have had a significant impact in other areas at that time opinions on the severity of desertification vary and are sometimes contradictory due to the lack of long term field based investigations

holocene climate variability and vegetation dynamics inferred from the 11700 cal yr bp laguna rabadilla de vaca sediment record southeastern ecuadorian andes palaeoenvironmental changes inferred from a 492 cm long lake sediment core from laguna rabadilla de vaca 3312 m in podocarpus national park southeastern ecuadorian andes were investigated usin

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

timing and spatial distribution of loess and loess like sediments in the mountain areas of the northeastern tibetan plateau abstract most studies on landscape evolution on the tibetan plateau during the late quaternary have mainly focused on using lacustrine records however mantles of sandy silt and paleosols also provide valuable archives for reconstructing holocene paleoenvironmental change yet little is known about the distribution and timing of these late quaternary aeolian sediments to enhance understanding and knowledge of aeolian sediments in tibet and to help reconstruct the nature of late glacial through mid holocene landscape development a loess paleosol sequence the suohuduo section located at the eastern margin of the tibetan plateau at about 4000 m above sea level is examined using sedimentological geochemical and geochronological methods a chronostratigraphy is established using nine optically stimulated luminescence and one radiocarbon ages sedimentation increased during the late glacial and the early holocene with an upwards fining of sediments in the lower part of the section two mid holocene paleosols that date to about 8 5 ka to 7 ka and 5 5 ka to 4 ka reflect more humid climate conditions during the mid holocene than earlier times the upper part of the section is mainly silt which reflects a more open landscape with higher aridity since 4 to 3 ka this time these data support evidence for similar climate paleoenvironmental change in adjacent regions on the tibetan plateau

holocene environmental changes in central inner mongolia revealed by luminescence dating of sediments from the sala us river valley luminescence dating of the fluvial and lacustrine sediments from the sala us river valley at the south edge of the mu us desert central inner mongolia is reported the study region lies in the northwestern marginal zone of the east asian summer monsoon and is sensitive to climate change the dating results combined with environmental proxies indicate that the holocene climate optimum period took place from 8 5 to 5 ka ago and was marked by lake development after 5 ka ago the region became arid as inferred from lake regression and fluvial activity deposition of fluvial sediments lasted from 5 ka to 2 ka ago at about 2 ka ago incision of the sala us river was initiated into the underlying sediments with a down cutting rate of 3 4 cm yr since 2 ka ago human activities also played an important role in causing environmental change in the region

large scale controls on the development of sand seas in northern china abstract although sand seas are located in arid regions given that the proportions of dune areas vary greatly from region to region they are clearly influenced by other factors as well as aridity this paper discusses the distribution pattern and major features of sand seas and large fields of stabilized dunes in northern china and demonstrates the main influences on their development it appears that the availability of onsite loose sediments not wind strength is critical to the occurrence of the sand seas on a regional scale tectonic endorheic basins or areas of alluvial fans or forelands of mountain ranges are advantageous to the accumulation of fluvial sediments and thus are ideal locations of large sand seas in an arid climate the large dune fields currently stabilized by vegetation were active sand seas during the drier periods of the late pleistocene and early holocene the distribution patterns of chinese sand seas suggest that the height or size of the dunes in the sand seas are determined more by the availability of sands than any other potential factors as the sand seas in china account for a large portion of deserts in the middle latitudes of the northern hemisphere taklamakan is the second largest sand sea on earth knowledge of these sand seas past changes is important for understanding climatic changes in the terrestrial regions of mid latitudes

initiation and variation of the dune fields in semi arid china with a special reference to the hunshandake sandy land inner mongolia sedimentary sequences occurring in desert dunes reflect changes in desert systems and as such may contain signals useful for recognizing spatial and temporal changes of deserts and their response to regional or even global climate fluctuations geomorphological and palaeoenvironmental studies within the dune fields of the asian middle latitudes have provided some solid evidence for interpreting the history of these sand seas using the hunshandake otindag sandy land a sandy area covered primarily by stabilized dunes and located in the semi arid zone of eastern inner mongolia china fig 1 as an example we studied the initiation and variation in the dune landscape in the eastern portion of the desert belt in northern china on the basis of physical and biochemical indicators in the sediments and osl chronology we herein argue that this dune system in the middle latitudes of eastern asia is much younger than previously assumed and that it has responded sensitively to climate change during the late quaternary geological evidence from the sandy land suggests that most of the current dunes are of late pleistocene or even holocene age palaeosols intercalated in the aeolian sequences and their osl chronology show that the climate of the hunshandake was much wetter than today between 9 6 ka and 3 ka this resulted in stabilization of the dunes in the eastern and central portions of the sandy land epochs of reworking or stabilization of the dunes are broadly consistent with the fluctuations in northern hemisphere solar radiation although with an obvious time lag because the increase rate of annual precipitation was not sufficient to fully stabilize the dunes in more arid part of the region some active dunes persisted even during this long lasting wetter epoch we conclude that periods of holocene dune stabilization due to palaeosol formation varied along the climate gradients across the various sandy lands of northern china and in general it began earlier and lasted longer in the east than in the west the general nature of the sandy lands and their counterparts in the western portion of the desert belt during the lgm and mid holocene climate optimum is discussed in comparison with their current states

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

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

aeolian activity in the south margin of the tengger desert in northern china since the late glacial period revealed by luminescence chronology abstract aeolian sediments from deserts in northern china have been widely used in the study of aeolian sedimentology and its dynamic association with past climate conditions the tengger desert the fourth largest desert in china is sensitive to the waxing and waning of the asian monsoonal system previous attempts to date aeolian deposits in the tengger desert concentrated solely on local scales and only a limited number of dates have subsequently been made available accordingly past sand dune activity in this desert remains poorly understood the aim of this study was to conduct a detailed historical investigation of aeolian activity in this region since the late glacial period and potential forcing mechanisms that governed the desert s evolution for this purpose we collected and dated eighteen samples from different geological sections along a west east transect in the desert s southern margin using optically stimulated luminescence osl our results in combination with previous aeolian sediment chronologies show that sand dune accumulation occurred before 10 ka sandy loess developed between 10 and 6 ka when sand dunes stabilized as a result of increased effective moisture levels and sand dunes again mobilized from 3 ka onwards as a result of increased aridity findings indicate that aeolian activity at the southern margin of the tengger desert was closely associated with asian monsoon circulation moreover the transition between mobilization and stabilization of sand dunes demonstrates the significance of effective moisture which is influenced by both monsoon precipitation and local convection and evaporation effects interacting together to control aeolian activity

holocene environmental changes in the central inner mongolia based on single aliquot quartz optical dating and multi proxy study of dune sands abstract alternating units of dune sands and paleosols in the central inner mongolia imply multiple episodes of dune building and stabilization in response to the waxing and waning of the east asian monsoon such eolian deposits were dated by using the single aliquot quartz optical dating method combined with the multi proxy study on the deposits the past environmental changes during the holocene have been reconstructed our results indicate that widespread eolian sand mobilization occurred in the studied region during the beginning of the early holocene from 11 5 ka to 9 ka the climate became warm and humid during the period between 9 ka and 5 6 ka holocene optimum after 5 6 ka the region again became arid as inferred from dune building however the environmental changes during the late holocene have been affected by both climate and human impacts and the presence of desert environment in such semiarid region is not only the result of climatic drought of the late holocene but also related to poor land use practices

late quaternary faulting on the manas and hutubi reverse faults in the northern foreland basin of tian shan china abstract the tian shan range lies in the actively deforming part of the india asia collision zone in the northern foreland basin of tian shan the strata were intensively deformed by cenozoic folding and faulting slip rate studies along these faults are important for understanding the dynamics of crustal deformation and evaluating the seismic hazards in the region two reverse faults the manas and hutubi faults in the northern foreland basin were investigated due to past faulting events along these faults the terrace treads along the manas river were ruptured forming fault scarps several meters in height loess deposits were trapped and preserved at the surface ruptures along these scarps the thickness of the trapped loess is dependent on the size of the ruptures the minimum and maximum ages of these scarps are constrained by dating the loess preserved at the surface ruptures and the terrace treads respectively using the quartz optically stimulated luminescence osl dating technique our dating results suggest that the loess trapped at the ruptures was deposited from the early to mid holocene at the hutubi fault and from the mid to late holocene at the manas fault the vertical displacements of the faults were evaluated by measuring the topographic profiles across the investigated fault scarps using the differential global position system dgps our results suggest that during the late quaternary in the studied region the vertical slip rates of the manas fault were between 0 74 mm yr and 1 6 mm yr while the hutubi fault had a much lower vertical slip rate between 0 34 mm yr and 0 40 mm yr the tectonic implications of our results are discussed

palaeoclimatic and palaeoenvironmental implications of late pleistocene aeolian sand in the jin shaan gorges of the yellow river valley revealed by luminescence chronology river valleys are critical water gas rock interactions zone where close interaction between fluvial and aeolian deposition are a pronounced feature in arid semi arid and semi humid environments

the evolution of a terrace sequence along the manas river in the northern foreland basin of tian shan china as inferred from optical dating abstract the tian shan range lies in the actively deforming part of the india asia collision zone the uplift rate and deformation pattern of the tian shan are important for understanding the dynamics of crustal deformation in the region the river terraces in northern tian shan provide key records of past changes in climate and or regional tectonics in this study a terrace sequence along the manas river in a tectonically active zone in the northern foreland basin of tian shan is investigated six river terraces were identified and dated using optically stimulated luminescence osl the results show that the six terraces were abandoned at 0 5 ka 1 4 ka 3 1 ka 4 0 ka 12 4 ka and 19 9 ka respectively together with high resolution global positioning system gps measurements on the terrace treads the fluvial history of manas river is reconstructed from 20 ka to 4 8 ka the height of the fluvial bed of manas river decreased at an average rate of 2 2 0 6 mm yr from 4 8 ka to the present the height of the fluvial bed decreased at an average rate of 13 5 0 6 mm yr corresponding to intensified incision of manas river during the late holocene this accelerated incision is very likely caused by the tectonic forces rather than climatic influences alone suggesting that the tectonic uplift activity was significantly intensified since 4 8 ka in the northern piedmont of tian shan other controlling factors on the incision of manas river are also discussed

osl dating of offset streams across the altyn tagh fault channel deflection loess deposition and implication for the slip rate abstract two deflected streams flowing across the altyn tagh fault atf were investigated at the aksay segment nw china due to strike of the atf stream channels are deflected and elongated by adding new sections along the fault line after subsequent water erosion and fluvial refreshment banks of these deflected streams are overlain by aeolian loess geomorphological features suggest that stream deflections along the fault were developed as a result of faulting activities and displacements were progressively accumulated from multiple faulting cycles each faulting cycle is composed of faulting event triggered elongation of channels creation of stream banks or risers and subsequent aeolian loess deposition on the banks a model is proposed to illustrate the relationship between fault movement and loess deposition which is supported by osl dating of the loess on the offset stream channels our results demonstrated that 1 loess deposits along deflected streams can be used to trace fault slip history given specific geomorphic assumptions discussed in the text and 2 based on stream channel offsets and loess ages the holocene slip rate of the atf is estimated to be 11 2 mm year along the aksay segment

hydrological and climatic changes in deserts of china since the late pleistocene article i nfo article history large areas in western china were wetlands or less arid between 40 and 30 ka corresponding to the greatest lake period on the adjacent tibetan plateau during the last glacial maximum some of these western chinese deserts again experienced wetter conditions however at the same time the sandy lands in the eastern chinese desert belt experienced an activation of aeolian dunes while interpretations of the mid holocene environment in the deserts of china are controversial it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems as well as other paleoenvironmental proxies such as the artemisia chenopodiaceae ratio should be interpreted with greater caution facing the highlighted uncertainties in our understanding of climate changes in chinese deserts it is hoped that this special issue will improve our knowledge considerably

late quaternary aeolian activity in gonghe basin northeastern qinghai tibetan plateau china abstract aeolian deposits at four sites in the gonghe basin were used to reconstruct the history of aeolian activity over the late quaternary these deposits include well sorted aeolian sand paleosols and or loess aeolian sand represents dune field expansion and or dune buildup whereas paleosols indicate stabilization of dunes accompanying ameliorated vegetation cover on the basis of 25 dates by optically stimulated luminescence osl it appears that aeolian activities occurred episodically at 33 5 20 3 13 9 11 8 11 0 9 4 7 8 and 5 7 5 5 ka which is largely consistent with the recent findings from the adjacent semi arid areas aeolian sand mobility occurring during the early to mid holocene conflicts with a climatic optimum inferred from lacustrine records in the northeastern qinghai tibetan plateau this inconsistency may be resolved by interpreting aeolian activity as a response to decreased effective moisture due to enhanced evaporation induced by higher summer insolation at that time together with local terrain and its effects on moisture our results suggest that aeolian sand and paleosol cannot be simply ascribed to regional dry and wet climates respectively and they most likely reflect changes in effective moisture

chronology of holocene sediments from the archaeological salawusu site in the mu us desert in china and its palaeoenvironmental implications the archaeological salawusu site is located at the southeast margin of the mu us desert and in the northern marginal area of the east asian monsoon therefore its environment is sensitive to the changes of the east asian monsoon at the palaeolithic salawusu site most of the previous studies are concerned with the age of the palaeoanthropic fossils ages ranging from 30 to 120 ka and the climate change in the last glaciation period while studies on the chronology and climate change since the late glacial are very limited in the current study eight luminescence samples were collected from dishaogouwan dsg section and dated using quartz optically stimulated luminescence osl radiocarbon samples were also collected and the past environmental changes since the late glacial have been reconstructed based on stratigraphical and chronological data the results show that 1 the ams age of modern weed living under water is about 1550 35 a which is the current reservoir effect age and after reservoir effect subtraction the radiocarbon age of the shells is in agreement with the osl age while the radiocarbon age of the bulk sample is younger 2 aeolian sand mobilization occurred in the studied region before similar to 12 ka 3 within the holocene the wettest climate occurred during the onset of the holocene when an extensive palaolake existed in the study area marked by the development of lacustrine sediments at around similar to 12 ka 4 after similar to 12 ka the climate showed a trend of increasing aridity which led to a continuous shrinkage of the palaolake and its ultimate desiccation between 1 8 and 1 0 ka evidenced by the shift from lacustrine sediments to peat and finally to palaeosol 5 the dating results also show an enormous incision of about 60 m in about 1 75 ka by the salawusu river c 2011 elsevier ltd all rights reserved the archaeological salawusu site is located at the southeast margin of the mu us desert and in the northern marginal area of the east asian monsoon therefore its environment is sensitive to the changes of the east asian monsoon at the palaeolithic salawusu site most of the previous studies are concerned with the age of the palaeoanthropic fossils ages ranging from 30 to 120 ka and the climate change in the last glaciation period while studies on the chronology and climate change since the late glacial are very limited in the current study eight luminescence samples were collected from dishaogouwan dsg section and dated using quartz optically stimulated luminescence osl radiocarbon samples were also collected and the past environmental changes since the late glacial have been reconstructed based on stratigraphical and chronological data the results show that 1 the ams age of modern weed living under water is about 1550 35 a which is the current reservoir effect age and after reservoir effect subtraction the radiocarbon age of the shells is in agreement with the osl age while the radiocarbon age of the bulk sample is younger 2 aeolian sand mobilization occurred in the studied region before similar to 12 ka 3 within the holocene the wettest climate occurred during the onset of the holocene when an extensive palaolake existed in the study area marked by the development of lacustrine sediments at around similar to 12 ka 4 after similar to 12 ka the climate showed a trend of increasing aridity which led to a continuous shrinkage of the palaolake and its ultimate desiccation between 1 8 and 1 0 ka evidenced by the shift from lacustrine sediments to peat and finally to palaeosol 5 the dating results also show an enormous incision of about 60 m in about 1 75 ka by the salawusu river c 2011 elsevier ltd all rights reserved

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

optical dating of holocene dune sands in the ferris dune field wyoming abstract optical dating of late quaternary quartz dune sands from the clear creek portion of ferris dune field wyoming demonstrates the considerable potential of the technique as a chronostratigraphic tool a sequence of radiocarbon dated holocene interdune strata permit optical dating of the intercalated dune sand to be tested the concordance is good the optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at clear creek peaked during two relatively short phases at ca 8500 and 4000 yr b p the dates indicate that aeolian accumulation maxima at least in the clear creek area may not be synchronous with previously defined phases of marked aridity

optical dating of eolian deposits since the last interglacial along the northern margin of the chinese loess plateau abstract understanding the chronology of eolian sand loess paleosol sequences along the northern margin of the chinese loess plateau clp is crucial for comprehending climate change and the advance and retreat of the adjacent mu us desert in this study a sand loess soil sequence from the northern margin of the clp was studied by applying the single aliquot regenerative sar protocol to quartz grains and the multi elevated temperature post ir irsl met pirir protocol to k feldspar grains for equivalent dose de determination 63 90 m quartz and k feldspar grains were used our results indicate that the met pirir ages of k feldspar grains in this sequence range from 94 4 7 0 ka to 148 3 13 3 ka for the last interglacial paleosol s1 for the upper part of the section quartz based sar osl dating was used yielding ages spanning from 5 8 0 4 ka to 35 9 4 1 ka after cross checking these results with previously reported isochron osl and tl ages the reliability of the met pirir protocol when applied to the last interglacial paleosol was confirmed based on a new osl chronology of the shimao profile the studied eolian deposits can be broadly correlated with the last glacial interglacial cycle but their dating also points to sedimentary hiatuses occurring at 94 4 ka 35 9 ka and 5 8 ka due most probably to strong wind erosion caused by intensified cold dry winter monsoonal circulations during the last glacial maxima

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

loess deposits in beijing and their paleoclimatic implications during the last interglacial glacial cycle abstract loess paleosol sequences are important terrestrial paleoclimatic archives in the semi arid region of north central china compared with the numerous studies on the loess of the chinese loess plateau the eolian deposits near beijing have not been well studied a new loess section in the northeast suburb of beijing provides an opportunity for reconstructing paleoenvironmental changes in this region an optically stimulated luminescence osl chronology yields ages of 145 1 to 20 5 ka demonstrating that the loess deposits accumulated during the last interglacial glacial cycle high resolution climatic proxies including color index particle size and magnetic parameters reveal orbital scale climatic cycles corresponding to marine oxygen isotope stages mis 6 to mis 2 in contrast to the loess deposits of the central loess plateau loess near beijing is a mixture of distal dust materials from gobi and sand deserts in the arid part of northwestern china and proximal local alluvial sediments climatic change in beijing during the last interglacial glacial cycle was controlled primarily by the changing strength of the east asian monsoon paleosols developed during the last interglacial complex between 144 0 and 73 0 ka and the interstadial of the last glaciation between 44 6 and 36 2 ka being associated with an enhanced summer monsoon in response to increased low latitude insolation and a weakened siberia high loess accumulation occurred during cold dry stages of the last glaciation in response to the intensified winter monsoon driven by the strengthened siberia high and its longer residence time

the timing and environmental significance of late quaternary linear dune development in western zambia optical luminescence dates for 19 samples from the degraded linear dune field of western zambia indicate multiple periods of regional dune building for the late quaternary 32 000 27 000 16 000 13 000 10 000 8000 and 5000 4000 yr ago these dates show that the last glacial maximum was not the only time when dune construction commonly linked to marked aridity occurred in central southern africa during the late quaternary whereas rainfall significantly less than today s ca 1400 mm yr 1 is a prerequisite for dune construction in the area adequate sediment supply also determines dune construction and preservation so that dune building cannot be simply and singularly linked to marked aridity the zambezi river system is proposed as an important source of dune sediments with the nature of linear dune activity explaining why stacked sediments preserve several phases of dune formation chronologies of dune construction in western zimbabwe and the southwest kalahari are in broad agreement with our zambian chronology and support a model of rainfall shifts along a sw ne gradient with some notable disparities these are probably a function of interregional sediment supply differences the number of samples used to delimit constructional periods and the multicausal nature of forcing mechanisms

optically stimulated luminescence dating of sand dune formed within the little ice age abstract optically stimulated luminescence osl dating has been intensively used to date the late quaternary deposits the single aliquot regenerative dose sar protocol was applied to measure coarse quartz grains extracted from dali sand dunes central china it was found that this popular method could not accurately date sand dunes activities that recently happened this is due to the low osl sensitivity of quartz grains leading to a failure in osl dating that has also been met in other sediments before to overcome this limitation quartz grains were heated to 500 c to increase the osl output for one magnitude sensitivity changes could also be corrected by the following test dose osl responses and has no influence on osl ages thus it is suggested to carry out the sar protocol for dim and young quartz osl samples with additional annealing step e g 500 c after the measurements of natural cycle the resultant osl ages proved that the last sand dune activities happened during the little ice age 400 years ago which was further supported by independent age control 1600 ad from historical documents

14 kyr of atmospheric mineral dust deposition in north eastern china a record of palaeoclimatic and palaeoenvironmental changes in the chinese dust source regions a multi proxy record of holocene and late pleistocene aeolian mineral dust is reconstructed using a combination of geochemical trace elements mineralogical and grain size analyses on cores from