precise single grain 40 ar 39 ar dating of a cold to warm climate transition in central europe recent advances in 40ar 39ar dating1 2 have made it possible to date individual k feldspar grains from pleistocene tephra a capability that greatly improves the reliability and temporal resolving power of the method here we apply these new techniques to the dating of a phonolite tephra from the east eifel volcanic field in west germany which is sandwiched between loess and palaeosol alfisol deposits and which was therefore erupted during the transition from a glacial to an interglacial period our age estimate for this transition is 215 4 kyr 1 which has important implications for the marine 18o timescale and for models of global climate change during the pleistocene the results show that single grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits this technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine 18o timescale for more rigorous fourier analysis testing of the milankovitch hypothesis

luminescence dating of the loess profile at dolni vestonice czech republic abstract thermoluminescence tl and infra red stimulated luminescence irsl studies were carried out on 21 samples from loess profiles at dolni vestonice the irsl measurements gave systematically lower equivalent doses eds than the tl measurements this could be due to inadequate preheat being applied to the former dose rate intercomparisons confirm the view that alpha counting should be carried out on finely ground material comparison of ed determination by regeneration and additive dose methods did not suggest sensitivity increases on bleaching but for the older samples the tl ages were underestimated compared with the expected ages based on the correlation of palaeosol stratigraphy with the framework provided by the deep sea oxygen isotope record using the hypothesis of luminescence decay with a lifetime of 150 ka suggests that the previous ages assigned to the palaeosols may not be correct

devolatilization or melting of carbonates at meteor crater az we have investigated the carbonates in the impact melts and in a monolithic clast of highly shocked coconino sandstone of meteor crater az to evaluate whether melting or devolatilization is the dominant response of carbonates during high speed meteorite impact both melt and clast carbonates are calcites that have identical crystal habits and that contain anomalously high sio2 and al2o3 also both calcite occurrences lack any meteoritic contamination such as fe or ni which is otherwise abundantly observed in all other impact melts and their crystallization products at meteor crater the carbon and oxygen isotope systematics for both calcite deposits suggest a low temperature environment 100 c for their precipitation from an aqueous solution consistent with caliche we furthermore subjected bulk melt beads to thermogravimetric analysis and monitored the evolving volatiles with a quadrupole mass spectrometer co2 yields were 5 wt with typical values in the 2 wt range also total co2 loss is positively correlated with h2o loss an indication that most of these volatiles derive from the secondary calcite also transparent glasses considered the most pristine impact melts yield 100 wt element totals by empa suggesting complete loss of co2 the target dolomite decomposed into mgo cao and co2 the co2 escaped and the cao and mgo combined with sio2 from coexisting quartz and feo from the impactor to produce the dominant impact melt at meteor crater although confined to meteor crater these findings are in stark contrast to osinski et al 2008 who proposed that melting of carbonates rather than devolatilization is the dominant process during hypervelocity impact into carbonate bearing targets including meteor crater

thermoluminescence dating of a 10 m loess profile in pakistan abstract thermoluminescence tl dates are reported for a 10 m section of loess in northern pakistan age determinations were contrasted using the additive dose n beta i 0 and signal regeneration methods tl dates increase monotonically with depth down the profile with the n beta i 0 approach up to a value of 135 ka for the deepest sample ages assessed by regeneration after optical bleaching tend towards a limiting age of 72 ka the failure of the regenerative approach appears to result from a sensitivity change on bleaching which is proportional to the natural tl signal this effect is modelled in terms of changes in tl efficiency

thermoluminescence dating of loess and palaeosols from the lantian section shaanxi province china abstract ten samples of loess and palaeosol collected from the upper part of lantian section shaanxi have been dated using the fine grain 4 11 m tl technique palaeodose values were determined by the regeneration method readhead 1982 the tl ages obtained ranged from 2 4 104 years for the upper malan loess l1 to 1 5 105 years for the upper part of loess l2 of the lishi loess fine grain tl dating does not seem to be suitable for the samples older than 150 ka the uncertainty of the tl age estimate especially for the palaeosol sample may be primarily an effect of disequilibrium of the 238u decay chain and of water content variations since deposition of sediments

age genesis and paleoclimatic interpretation of the sangamon loveland complex in the lower mississippi valley u s a for more than a century the sangamon paleosol the sangamon has been an integral part of geologic and pedologic investigations in the central united states including the upper mississippi and lower missouri river valleys compositional pedologic micromorphologic stratigraphic and age data indicate that the prominent reddish paleosol developed in silt rich deposits of the lower mississippi valley from southernmost illinois to northwestern mississippi represents multiple periods of soil formation and is wholly or in part time equivalent to the sangamon of the central united states thermoluminescence data for localities where the sangamon developed in loess indicate that the primary period of loess deposition was from 190 to 130 ka oxygen isotope stage ois6 that loess deposition continued intermittently from 130 to 74 ka ois5 and that deposition was wholly or in part coeval with loveland loess deposition in the central united states beryllium 10 chemical and pedologic data indicate that in the lower mississippi valley 1 the sangamon represents a minimum time period of 60 80 k y 2 there were at least two periods of soil formation ca 130 90 ka and 74 58 ka ois4 and 3 rates of weathering and pedogenesis equaled or exceeded the net loess accumulation rate until at least 46 ka ois3 and resulted in development of a paleosol in the overlying basal roxana silt along a n s transect from southern illinois to western mississippi sangamon macroscopic characteristics as well as the micromorphology chemistry and mineralogy suggest a regional paleoclimate during periods of soil formation that 1 was warm to hot with a wider range in temperature precipitation and evapotranspiration than present 2 had seasonal to decadal or longer periods of drought and 3 had down valley southward trends of increasing temperature and precipitation and decreasing seasonality and variation in annual to decadal precipitation

fission track ages of late cenozoic distal tephra beds in the yukon territory and alaska six distal tephra beds from the yukon territory and alaska have been dated by the fission track method zircon and glass ages were determined for the fort selkirk and lost chicken tephra beds but only glass ages for the others assuming that no track fading has occurred in the glass old crow and dawson tephra beds are younger than 120 000 and 52 000 years bp respectively mosquito gulch tephra is 1 22 ma old fort selkirk tephra is about 1 ma old the ester ash bed is 0 45 ma old and the best estimate of the age of lost chicken tephra is the range 1 7 2 6 ma it is evident from these results and from the known abundance of tephra beds within late cenozoic deposits of the yukon territory and alaska that application of the fission track method to distal tephra in conjunction with detailed characterization studies offers great potential for elucidation of the late cenozoic geologic history of alaska and the yukon territory

influence of orbital parameters on pleistocene loess deposition in central alaska few long proxy climatic records are available from terrestrial locations the isotope records of pleistocene climate change found in marine cores reflect worldwide ice volume and temperature changes forced by variations in the earth s orbital geometry comparable terrestrial records are rare loess wind deposited silt is perhaps the closest terrestrial analogue to marine sediments in that both result from more or less continuous deposition of fine grained sediment here we examine the hypothesis that mag netic susceptibility variations through loess sections reflect climate forcing we statistically tested cross correlations between high precision orbitally tuned marine oxygen isotope curves recording the past 250 000 yr bp and magnetic susceptibility profiles through a thick loess section in central alaska highly significant p 0 0001 correlations indicate strong thick palaeosols formed in arctic loess during early parts of interglacial periods correspond ing to isotope stages 7 and 5 thinner soils formed during interstadial events corresponding to early stage 7 and stage 3 autocorrelation and time series analysis of the loess data show spectral peaks at 125 000 41 000 and 23 000 yr bp showing for the first time that terrestrial orbital periodicities influenced and are recorded in proxy climatic data from terrestrial aeolian deposits at high latitudes

luminescence dating of loess palaeosol sequences and coversands methodological aspects and palaeoclimatic implications abstract of the terrestrial archives loess palaeosol sequences provide a most complete record of climatic change this may be compared with the marine oxygen isotope stratigraphy and may help in the reconstruction of past atmospheric circulation patterns numerical chronometry of loess palaeosol sequences has generally been based on correlation of variations in climatic proxies such as magnetic susceptibility and particle sizes with marine isotopic data such chronometric assignments involve implicit assumptions about the constancy of sedimentation rates and particle fluxes through time this review presents a brief survey of the present status methodology outstanding problems and interpretational aspects of luminescence techniques and discusses the import of luminescence ages on global land sea correlations statistical analysis of the ages suggests episodicity of loess accumulation with extended periods of quiescence recent luminescence dating studies on closely spaced samples also lead to a similar inference luminescence ages imply high variability in loess sedimentation rates this conflicts with the assumption made in some current attempts to correlate loess records with marine records of almost constant particle fluxes a review of source proximal coversand deposits of northwest europe is also presented evidence of the onset of coversand deposition at 15 ka with a peak in accretion during the younger dryas and subsequent minor reactivation episodes is discussed

freshwater outburst from lake superior as a trigger for the cold event 9300 years ago paleoclimate proxy records reveal a pervasive cooling event with a northern hemispheric extent approximately 9300 years ago coeval changes in the oceanic circulation of the north atlantic imply freshwater forcing however the source magnitude and routing of meltwater have remained unknown located in central north america lake superior is a key site for regulating the outflow of glacial meltwater to the oceans here we show evidence for an approximately 45 meter rapid lake level fall in this basin centered on 9300 calibrated years before the present due to the failure of a glacial drift dam on the southeast corner of the lake we ascribe the widespread climate anomaly approximately 9300 years ago to this freshwater outburst delivered to the north atlantic ocean through the lake huron north bay ottawa river st lawrence river valleys

the last interglaciation in alaska stratigraphy and paleoecology of potential sites at least 20 localities in alaska contain deposits that may provide information on the last interglaciation oxygen isotope substage 5e these widely dispersed localities include river bluffs coastal bluffs and terraces elevated marine shorelines lake basins and artificial excavations most of the inferred interglacial deposits contain macrofossils or pollen that are older than the range of radiocarbon dating and commonly indicate climate as warm as or warmer than the present at a few localities evidence for deep thaw of permafrost also indicates a warm paleoclimate at eight localities the old crow tephra occurs at or below organic deposits that may represent substage 5e the tephra occurs beneath conspicuous organic deposits at fairbanks the yukon palisades and holitna lowland and directly above a peat bed at hogatza mine at birch creek halfway house ky 11 and imuruk lake the tephra occurs within a paleosol or organic deposit but other organic horizons that more likely indicate interglacial conditions occur at higher stratigraphic levels the varied stratigraphic relations of the old crow tephra suggest that it may have been deposited close to the boundary between isotope substages 6 and 5 which is dated at about 130 ka in the marine record and between 132 and 140 ka on land these age relations suggests that the tephra may have been deposited about 135 5 ka validating the recent fission track age determination of 140 10 ka for this deposit six coastal localities contain deposits of probable interglacial age and these commonly are associated with evidence for eustatic sea levels higher than those of the present beach and sublittoral sediments of the pelukian transgression occur up to 12 m asl along the northwest coast of alaska and are correlative with barrier island and lagoonal sediments on the alaskan arctic coastal plain both sets of deposits commonly contain extralimital mollusks and microfauna that indicate marine water slightly warmer than present and suggest that seasonal sea ice did not extend south of bering strait during the last interglacial as it does today farther south elevated marine terrace deposits on amchitka island contain marine invertebrates that indicate a climate warmer than at present peat horizons in coastal exposure at goose bay and coastal terraces at lituya bay contain pollen spectra that suggest forests like those of the present day and spruce macrofossils exposed on baldwin peninsula indicate boreal forest more extensive than at present sediments from several lakes in northwestern alaska may contain continuous records of the last interglaciation a major warm interval possibly isotope substage 5e has been identified in a core from squirrel lake by a peak in picea pollen that indicates forest extension beyond present limits similar pollen records are potentially available from two maars which formed in the cape espenberg area more than 125 ka terrestrial organic deposits thought to record the last interglaciation occur interstratified with marine and glaciogenic sediments in the nushagak lowland of southwest alaska and on baldwin peninsula in kotzebue sound extensive exposures along the copper and nenana rivers may also contain organic deposits that record the last interglaciation

the upper pleistocene loess record at harmignies belgium high resolution terrestrial archive of climate forcing abstract the loess palaeosol sequence in a section at harmignies in belgium is one of the most important upper pleistocene sites in northwest europe an extensive luminescence dating study was carried out to get a reliable chronological framework and to understand the climate forcing in an area where continuous permafrost dominated during most of the last glaciations twenty eight samples were investigated by infrared optically stimulated luminescence irsl and thermoluminescence tl methods resulting in more than 100 luminescence age estimates the dating results on colluvial sediments are in good agreement with landscape destabilisation phases during ois 5 during the last glacial four major periods of loess accumulation were likely to have occurred in europe at the harmignies section the oldest loess was deposited between 67 000 to 60 000 yr the second one from 60 000 to 50 000 yr the third one from 50 000 to 40 000 yr and the youngest loess accumulation period started most likely after the heinrich 3 event and lasted until the heinrich 2 event 25 000 20 000 yr two main periods of permafrost occurred at approximately 60 000 and 28 000 yr bp

thermoluminescence dating of loess recent developments abstract thermoluminescence tl dating has developed into an important chronological method in loess research especially beyond the range of radiocarbon dating the principles and the present stage of the method applied to windborne sediments are summarized in this article advice to users is provided for appropriate sampling and handling of tl samples as well as for measuring the natural radioactivity in the field the potential and the limitation of loess tl dating are discussed in terms of various case studies from central europe in spite of the problem of age underestimation for old loess tl dating has already contributed greatly towards a better understanding of the loess stratigraphy and chronology thermoluminescence as a dating tool for archaeological samples has been established for 30 years but the application of tl dating to quaternary sediments is apart from some earlier attempts in the soviet union shelkoplyas and morozov 1965 dreimanis et al 1978 a more recent development essentially of the last decade wintle and huntley 1979 since several review papers have already appeared on this subject e g wintle and huntley 1982 mejdahl 1986 wintle 1987 singhvi and wagner 1986 berger 1988 the present contribution will only briefly mention the underlying tl principles and the dating techniques but will focus on the recent development in tl dating of loess

tl dating of partially bleached sediments by the regeneration method abstract thermoluminescence dating of sediments in the warsaw laboratory is based on blue to green emission the partial bleach regeneration method is proposed for dating sediments which have not been completely bleached at the time of burial correct tl ages are reported for sediments covering organic deposits of the eemian interglacial and also for glacial sediments of wurm and riss age we obtained good results for dating till using the partial bleach regeneration method the tl zeroing in till is explained by the rubbing or compression of grains beneath the glacier and by the freeze thaw activity occurring during glacial transport and deglaciation

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

thermoluminescence and new 14c age estimates for late quaternary loesses in southwestern nebraska abstract loess of late quaternary age mantles most of nebraska south of the platte river valley at least five late quaternary loesses are recognized from oldest to youngest one or more undifferentiated pre illinoian loesses the loveland loess the gilman canyon loess which exhibits a well developed soil and rests unconformably on the sangamon soil the peoria loess capped by the brady soil and the bignell loess which is distributed discontinuously previous research shows that the loveland loess is illinoian the gilman canyon loess and peoria loess are wisconsin and the bignell loess is holocene we present here the first thermoluminescence tl age estimates and new 14 c ages for these late quaternary loesses at two key sections in southwestern nebraska the eustis ash pit and the bignell hill road cut tl age estimates from all samples collected from eustis ash pit and bignell hill were internally consistent tl and 14 c age estimates from these two sections generally agree and support previous age determinations the tl age estimate on loveland loess indicates deposition at 163 ka tl and radiocarbon age estimates indicate that gilman canyon loess believed to be deposited during the farmdale interstade first began to accumulate at about 40 ka the lower part of the gilman canyon loess is 36 ka at eustis and the middle of the unit is 30 ka at bignell hill the lower and upper parts of the peoria loess give age estimates of 24 ka and 17 ka respectively tl age estimates for deposition of the bignell loess are 9 ka near the base in agreement with radiocarbon age estimates and 6 ka immediately below the modern soil substantiating its holocene age comparisons of tl age estimates with 18 o and insolation curves which show loess deposition during interglacial and interstadial as well as glacial periods indicate that loess deposition on the great plains can occur under a variety of climatic conditions

isothermal plateau fission track ages of hydrated glass shards from silicic tephra beds abstract the age of silicic tephra beds that have experienced a simple thermal history can be accurately and precisely determined by application of the isothermal plateau fission track technique to hydrated glass shards age estimates obtained by this means compare very well with those based on co existing mineral phases using the k ar 40ar 39ar external detector fission track and thermoluminescence techniques this concordance contradicts the popular belief that hydrated glass shards give unreliable ages distal tephra beds many of which are difficult to date because of their fine grainsize low abundance of crystals and common presence of detrital grains are readily dated by the isothermal plateau glass fission track method this new advance should greatly facilitate the development of detailed chronologies of tephra bearing sedimentary sequences located far from volcanic centres

amino acid geochronology applied to the correlation and dating of central european loess deposits abstract numerous localities in the czech republic slovakia and austria have been sampled for fossil gastropod shells for the purpose of an aminostratigraphic evaluation of loess sequences in all three regions alloisoleucine isoleucine aile ile ratios are observed to be significantly higher in shells from loess deposited during the penultimate glacial period cycle c relative to samples from loess of the last glaciation cycle b the difference in aile ile ratio reflects both difference in age of the samples plus the impact on the older samples of the relatively high effective temperature of the last interglacial period amino acid data support the previous correlation suggested between pk ii iii in the czech republic and slovakia and the stillfried a in austria samples have also been recovered from older loess units and previously published correlations within the czech and slovak republics are tested aiie ile ratios appear to distinguish between samples from loess of the last four glacial cycles beyond cycle e 18o stages 10 and 11 the increase in alle ile ratio is relatively small from cycle to cycle in addition shells tend to be poorly preserved and are absent at many localities nevertheless amino acid geochronology offers a means of resolving ages of loess units in the critical time period that is beyond the range of radiocarbon and thermoluminescence methods but post dates the brunhes matuyama paleomagnetic reversal

thermoluminescence dating of the pleistocene old crow tephra and adjacent loess near fairbanks alaska two different thermoluminescence tl techniques have produced an average age of 109 14 ka for the widespread pleistocene old crown tephra previously of uncertain age a deposit of the tephra from the halfway house site at fairbanks alaska was dated directly at 110 12 ka by analyses of 4 11 m glass using the additive dose tl technique a lower age limit of 108 16 ka for this tephra was obtained indirectly by analysis of 4 11 m grains of loess just above it using the partial bleach tl technique for this partial bleach technique the assumptions of zeroing of tl and of the saturating exponential form of the tl growth curves were checked by analyses of a surface loess deposited within the last century also most or all of an unstable anomalous fading tl component was eliminated from the older polymineralic loess in only a few days by storing irradiated subsamples at elevated temperatures in contrast several months storage was required to achieve the same effect at room temperature for thi

a global view of the stability of luminescence signals from loess abstract loess samples from different parts of the world were used to evaluate the thermal stability of their ir stimulated luminescence irsl signals storage at different temperatures shows that the irsl signals have similar thermal stability identical laboratory experiments on coarse grain k feldspar show higher stability for its irsl signal mineral separation is suggested as a way of selecting the most stable luminescence signal to permit dating of older samples

age of sheep creek tephra pleistocene in central alaska from thermoluminescence dating of bracketing loess the age of the sheep creek tephra sct a widespread marker ash bed in eastern alaska and western yukon territory has been ambiguous and controversial we have obtained three reliable thermoluminescence age estimates from bracketing loess near fairbanks that imply a deposition age of about 190 000 20 000 yr for sct three of six loess samples near and closely bracketing the sct beds near fairbanks yielded younger age estimates 117 000 and 135 000 yr most likely based on field aspects because of reworking and contamination by translocated grains the new reliable age assignment of 190 000 yr confirms independent stratigraphic evidence of a pre last interglaciation age and stratigraphic evidence from one site upper eva creek that sct is older than the more widespread 140 000 yr old old crow tephra the sct age also has implications for regional correlations of glacial and nonglacial deposits in particular it supports the stratigraphic and geomorphic interpretation that the delta glaciation in the east central alaska range and the reid glaciation in western yukon territory are older than the last interglaciation isotope substage 5e

a review of current research on tl dating of loess abstract the thick loess deposits of china central europe and north america are particularly suitable for the application of the thermoluminescence tl dating method because individual grains are likely to have travelled large distances and thus been well exposed to light before deposition wind blown silt grains collected close to glacial rivers in alaska have been shown to give a zero age of not more than 2 ka demonstrating the efficiency of the zeroing mechanism differences in laboratory procedures can cause differences in the tl ages reported particularly for loess over 100 ka tl ages for interstadial soils in europe are in agreement with the very few radiocarbon dates on reliable material such as charcoal on the other hand tl dates from sites in belgium and north western germany indicate that the previously accepted chronology which was based on two radiocarbon dates on humic rich sediments is incorrect the use of the last interglacial palaeosol for assessing the tl dates on loess above and below it is limited by the uncertainty in the timing of termination of soil forming processes 107 and 71 ka are the limits suggested by the astronomically derived time scale results on deposits from china north america alaska and europe are discussed in this context

an evaluation of thermoluminescence dating of paleoearthquakes on the american fork segment wasatch fault zone utah the accuracy of the thermoluminescence tl method for dating holocene paleoearthquakes was tested on fine grained sediments from three trenches excavated across the american fork segment of the wasatch fault zone utah sediments exposed in the trenches targeted for tl dating include a horizons of buried soils loessial silts and sag pond muds this study indicates that these sediments were fully light bleached prior to deposition and are suitable for tl dating equivalent dose estimates by the regeneration total and partial bleach methods are in general agreement and mean tl age estimates are concordant with radiocarbon ages combined radiocarbon and tl age estimates indicate three major episodes of faulting at 5 3 0 3 2 6 0 3 and 0 5 0 2 kyr ago

applications and limitations of thermoluminescence to date quaternary sediments abstract the thermoluminescence tl method dates sediment by quantifying time dependent dosimetric properties of mineral grains sunlight exposure of the sediment during transportation and deposition or heating resets the tl clock to time zero after burial of the mineral grains ionizing radiation from the decay of radioisotopes imparts a tl signal this accumulated tl signal is proportional to the equivalent dose ed which is a measure of radiation exposure during the burial period a tl age estimate is determined from the ratio of the ed to the environmental radiation dose rate the calculation of an ed is influenced by the susceptibility of sediments to optical bleaching the emission spectra of minerals and possible long and short term fading there are three basic methods for determining an ed regeneration total and partial bleach the regeneration technique may yield under estimates because of sensitivity changes with laboratory bleaching the latter two techniques are most useful for well and partially light bleached sediments respectively a number of sediments can be dated by the tl method eolian and a variety of terrestrial sediments yield apparently accurate tl age estimates though there are possible complications associated with pedogenesis it appears that some fluvial sediment can be accurately dated by tl but little is known about the efficiency of optical bleaching for fluvial depositional systems till and glacier proximal deposits are inadequately light bleached to be dated by tl sediments deposited distal from the glacier margin which are at least partially bleached are preferred for dating future research is needed to understand better the relationship between sedimentary environments and the extent of light bleaching also studies should concentrate on dating feldspar extracts from well dated sequences to more fully ascertain the temporal limitations of the method only by understanding the interplay of sedimentology tl dosimetry and environmental radiation can the tl method be effectively applied to the myriad of depositional environments spanning the late to middle pleistocene

thermoluminescence dating of the malan loess at zhaitang china although the widespread loess deposits of north china have been well described there has been limited information on the absolute age of the various layers loess a wind carried deposit exposed to sunlight and subsequently buried should be amenable to dating by thermoluminescence through use of the fine grain technique ages from 18 to 84 ka have been obtained for a sequence in the malan loess exposed in the zhaitang section near beijing the dates are consistent with the evidence from geology and magnetostratigraphy and provide a chronology for the zhaitang section

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

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

thermoluminescence dating of late devensian loesses in southern england scattered across southern england are many isolated deposits of loess like material1 a few such as that at pegwell bay in kent are highly calcareous and unweathered but most have been reworked by fluvial or colluvial processes there is good stratigraphical evidence for a few pre devensian loesses also in kent but dating of more recent loess has so far been based on indirect evidence much work has been done on the pegwell bay loess as it is the most extensive truly aeolian loessic deposit in britain kerney2 compared the late devensian deposits in the isle of thanet and at pegwell bay with similar deposits in holland and belgium where radiocarbon dates have been obtained for interstadial deposits correlation of the east kent deposits with these in northern europe indicates that the loesses in kent were formed between 30 000 and 14 000 yr ago i report here dates for six of the more recent deposits in southern britain from the scilly isles to kent the dates have been obtained on the loess itself using a recently developed thermoluminescence tl dating technique3 4 and confirm the ages as being late devensian

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

isotope stage 5 130 74 ka in greenland a review abstract marine and glacigene deposits dated with varying degrees of certainty to isotope stage 5 130 74 ka are exposed in coastal cliffs in 18 areas and localities in northern and eastern greenland dating methods include thermoluminescence tl u th methods and correlation with the deep sea record amino acid parameters are used for correlation between localities deposits from the last interglaciation isotope substage 5e are rare and have been found only at three localities in both west and east greenland their mollusc and foraminifer faunas indicate more vigorous sea surface circulation and sea surface temperatures some degrees higher than known from the holocene during this warm period ice sheet growth began in northwest greenland the ice sheet reached its maximum for the last ice age during the succeeding phase provisionally correlated with isotope substage 5d this was followed by a new warm period with increased influx of warm subarctic water and high summer temperatures on land provisionally correlated with isotope substage 5a in east greenland the observations indicate a more complex ice sheet history the record from greenland is very similar to that obtained in adjacent coastal areas of the high arctic implying that the rapid shifts from warm to cold during isotope stage 5 were especially conducive to the formation of the embryonic north american and scandinavian ice sheets at high northern latitudes probably because the pulses of warm water were required to advect sufficient moisture into these areas to allow the growth of continental ice sheets

thermoluminescence dating of loess deposits at paudorf austria abstract the fine grain thermoluminescence tl dating method was applied to an upper palaeosol from a loess deposit in paudorf lower austria this site is of special interest as there is some controversy about the time of formation of this soil horizon the results of the present study strongly indicate that the soil formed during the wurm i ii interstadial deep sea 18 o isotope stage 3 although age underestimation due to a long term instability of luminescence centres in general cannot be ruled out arguments are given for the presented tl age which is also corroborated by the radiocarbon age of charcoal from the top part of the correlated palaeosol in aigen lower austria

thermoluminescence age of old crow tephra in alaska thermoluminescence dates for the loess deposits above and below the old crow tephra at the halfway house site near fairbanks limit the age of the tephra to 86 8 ka this is in excellent agreement with other estimates already in the literature the dating was performed using additive dose procedures and optical selection of the potassium feldspar signal from a polymineral mixture of fine grains

northwest european palaeoclimate as indicated by growth frequency variations of secondary calcite deposits a compilationn for the northwest of europe of over 500 uranium series speleothen and travertine dates is presented using a cumulative distributed error frequency approach these secondary carbonate deposits require both significant groundwater supply and a biogenic soil carbon dioxide source for their growth during glacial periods soil co2 production is inhibited and the water supply is ice locked therefore growth is slowed significantly if not stopped thus deposits can be used on a chronological basis to give a signal of glacial and non glacial periods however sensitivity to the groundwater supply modifies this signal with growth also limited in times of high aridity the palaeoclimatic signal is thus complex the compilation presented is used both as a chronology for comparison with the orbitally tuned marine oxygen isotope record and as a palaeoclimatic indicator attention is focused on two periods of the last glacial interglacial cycle where the record provides a significantly different palaeoclimatic record to other terrestrial and oceanic records these are the isotope stages 5 4 transition for which a relatively low cumulative growth frequency indicates an earlier increase in aridity than observed elsewhere and isotope stage 3 the pleniglacial where both statistically significant high 49 62 ka and low 22 35 44 46 ka levels of growth are observed and can be used to constrain the timing of many of the interstadial events within this period

distribution stratigraphy petrochemistry and palaeomagnetism of the late pleistocene old crow tephra in alaska and the yukon revision accepted january l i 1985 the late quaternary old crow tephra is a two pyroxene calc alkaline dacite whose known areal extent is broadly delimited by a triangle with apices at the seward peninsula the wrangell mountains and the old crow basin in the northern yukon everywhere the tephra is fine grained mdu 5 33 2 0 32 and moderately to poorly sorted 6u 1 33 0 29 samples from the extremities of the fall out zone have similarity coefficients of 0 95 a palaeomagnetic excursion is recorded in sediments just below old crow tephra in the fairbanks area and at imuruk lake on the seward peninsula a short full reversal of the magnetic field has been preserved at the corresponding stratigraphic level near old crow in the northern yukon chronological controls based on i4c and fission track dates and sedimentation rates show that these palaeornagnetic features are almost certainly partial records of the complex geomagnetic blake event which occurred 100 120 ka ago new petrochemical data demonstrate that the source of old crow tephra is in the eastern aleutian arc

stratigraphy geochemistry and thermoluminescence ages of lower mississippi valley loess four periods of loess deposition in the lower mississippi valley can be identified on the basis of geochemical and mineralogical criteria radiocarbon dating and thermoluminescence dating these are designated loess units 1 2 3 and 4 in order of increasing age carbonate rich unit 1 loess comprises more than 70 per cent of the thickness of the loess profiles 14c and tl dates indicate this loess was deposited between 9 000 and 20 000 years ago a maximum sedimentation rate of 2 17 mm yr 1 has been recorded near vicksburg just after the last laurentide glacial maximum between 17 190 and 15 580 years ago the unit 2 loess which is thin and partly decalcified was deposited slowly between about 25 000 and 20 000 years ago the unit 3 and unit 4 loess formations which are both highly weathered have yielded tl ages of 76 000 85 000 years and 119 000 132 000 years suggesting they were deposited during the altonian substage of the early wisconsinan and the illinoian glacial stage respectively the four loess units are stratigraphically equivalent to the peoria farmdale roxana and loveland loess formations previously recognized in illinois the source of dust in both areas was glacial outwash in the mississippi valley during interglacials and interstadials when the supply of glacial debris was reduced and the mississippi river changed from a braided to a meandering regime dust sedimentation in southern mississippi virtually ceased allowing weathering and pedogenesis to proceed

thermoluminescence dating applied to paleosols abstract thermoluminescence tl dating of quaternary sediments has developed rapidly in the last few years as paleosols often prove to be useful stratigraphic marker horizons it is of great interest to obtain absolute ages for them a technique is proposed which increases the range of tl dating of loess to some 300 ka special problems associated with paleosol tl dating such as sampling and dose rate evaluation are discussed three examples for paleosols from west german loess regions are presented the intra wurmian lohner boden soil 28 30 ka lower wurmian chernozem like soils ca 70 ka and the penultimate interglacial soil karlich interglacial between 230 and 170 ka

thermoluminescence ages for three sections in hungary abstract samples were collected from sections at mende paks and tapiosuly ages for the loess above the mf1 soil at mende were in agreement with the radiocarbon dates on charcoal fragments from the soil ages for loess from tapiosuly were also in agreement with radiocarbon ages for younger soils however tl age estimates for loess above or below the mf2 soil at each of the three sites suggested that this soil had an age of around 76 ka it has not been confirmed whether these ages are underestimated however they are older than previously thought on the basis of other tl studies they imply that the underlying mb soil is much older than the last interglacial

thermoluminescence dating of sediments abstract the potential for using the thermoluminescence behaviour of sediments for dating them was first recognized by soviet scientists g v morozov and v n shelkoplyas and for over a decade their tl dates obtained from a variety of sediments have appeared in the soviet literature since 1977 tl sediment dates have been published by six additional groups using a variety of methods in this review we describe the principles of tl dating the various methods used and contrast tl dating of sediments with the now well accepted tl dating of pottery we conclude that while tl dating has the potential to solve many sedimentary problems more fundamental research needs to be carried out before such dates should be accepted a set of criteria for acceptable dates is proposed

the potential of using thermoluminescence to date buried soils developed on colluvial and fluvial sediments from utah and colorado u s a preliminary results the natural tl intensity for surface and buried holocene and pleistocene a horizons developed on flood plain silts near denver colorado exponentially decreases with time this signal is approaching saturation by ca 130 ka the a horizon of the modern flood plain soil is not fully light bleached the tl properties and age estimates are presented for radiocarbon dated eolian enriched buried a horizons developed on fault derived colluvium from the american fork segment of the wasatch fault zone utah dating of these buried soils provide a close age estimate on paleoearthquake events mean tl age estimates by regeneration and total bleach techniques for buried a horizons are 0 5 0 1 ka and 2 7 0 4 ka which are in agreement with corresponding radiocarbon dates of 980 70 years bp and 2620 70 years bp a surface sag pond mud formed within an antithetic grabben is well light bleached and yielded a tl age estimate by the total bleach method of 240 60 years bp in agreement with its known age of 300 years bp this study indicates that relatively brief periods of pedogenesis are not sufficient to light bleach sediment and that eolian additions enhance the reduction of tl in soils

the loess profile at albertirsa hungary improvements in loess stratigraphy by luminescence dating abstract a very detailed upper pleistocene record is exposed in a loess palaeosol sequence at the section at albertirsa in hungary luminescence dating was carried out to establish a more reliable chronological framework for the hungarian loess record the lowermost palaeosol of the section probably an equivalent of the mf2 horizon at the mende key section is superimposed on penultimate glacial loess an irsl age estimate of about 65 ka bp was determined for the lower part of this palaeosol indicating soil formation late in oxygen isotope stage ois 5 or early in ois 3 a significant hiatus most likely occurs in the lower part of the lower fossil soil the loess between the upper and and lower palaeosol yielded a mean luminescence age of about 50 ka bp the upper palaeosol is probably an equivalent of the mf1 horizon at the mende type section formed between 37 and 25 ka bp and so this palaeosol represents the hengelo and or denekamp interstadial of northwestern european stratigraphy the loess is intercalated by a humic horizon which yielded a mean luminescence age estimate between 21 and 19 ka at the albertirsa section

thermoluminescence dating of late pleistocene loess and tephra from eastern washington and southern oregon and implications for the eruptive history of mount st helens the first numeric dating of late pleistocene loess from the palouse region of eastern washington is reported this loess is interbedded with thin distal tephra layers some identified as mount st helens products both the interbedded tephra layers and thick paleosols that have developed in the loess have previously been correlated across the region a thicker correlative of one of these tephra layers mount st helens set c was collected from summer lake oregon for direct dating by thermoluminescence tl polymineral fine grain tl ages for loess from three chosen sections in washington range from 17 to 83 ka these imply ages for some tephra beds that are significantly older than implied by earlier radiocarbon 14c dating for example tl ages of 17 21 ka for loess bracketing a tephra layer correlated to mount st helens set s suggests a somewhat older age for this ash than the previously accepted 14c age of 15 5 0 5 ka cal yr corrected to calendar years tl ages of 46 6 1 ka and 57 7 ka for loess above and of 53 7 ka and 75 6 ka below a tephra bed correlated to a mount st helens set cw layer along with a tl age of 46 5 ka for fine silt sized glass from a mount st helens set cy bed in oregon revise upward from 38 ka cal yr 14c age is 36 ka b p to 50 ka the age of this regionally important marker ash set several tl ages taken together imply a much longer eruptive history for mount st helens than previously thought a tl age of 83 8 ka just below a previously undated tephra layer from mount st helens emsh ash suggests that the eruptive history of the mountain extends back to at least 80 ka furthermore age depth extrapolation through our sections to an ash wa 5c probably correlated to mount st helens suggests an eruptive history of at least 120 ka

chronology and the upper dating limit for loess samples from luochuan section in the chinese loess plateau using quartz osl sar protocol abstract luminescence dating of loess older than 100 ka has long been a challenge it has been recently reported that using optically stimulated luminescence osl of fine grained quartz 4 11 m extracted from loess the range of luminescence dating could be pushed to 0 6 ma with osl ages being in agreement with independent ages watanuki t murray a s tsukamoto s 2005 quartz and polymineral luminescence dating of japanese loess over the last 0 6 ma comparison with an independent chronology earth and planetary science letters 240 774 789 the aim of this study is to provide a luminescence chronology 20 samples for the standard luochuan loess section and to further examine the upper limit of quartz osl dating for chinese loess the growth curve does not saturate at 700 gy and should allow reliable equivalent dose d e determination up to at least 400 gy however when compared with independent chronological control the d e that could be treated as reliable is less than 230 gy corresponding to 70 ka in age for chinese loess and the d e larger than 230 gy should be underestimated ages for samples from the lower part of palaeosol s1 are severely underestimated with the maximum age of 95 ka for a sample from the bottom of this palaeosol much younger than the expected age of 128 ka the maximum d e obtained for sample l9 m collected from loess layer l9 which is below the matuyama brunhes b m boundary whose age is 780 ka is only 403 gy which corresponds to an age of 107 ka the cause of underestimation is not yet clear the previous results by watunuki et al 2005 on the extension of osl dating of loess to 0 6 ma is not confirmed when evaluating the validity of osl ages in s1 another possibility is to question the already established chronological frame for luochuan section which is based on the hypothesis of continuous dust deposition the assumption of an erosion hiatus between l2 and s1 could make the osl ages look reasonable however if this is the case then it is difficult to explain why the age of sample l9 m is only 107 ka which could be treated as a saturation age while the osl can provide a correct age for loess as old as 94 9 ka for sample lc22 collected from the bottom of s1 much work is required to clarify these confusions

thermoluminescence dating of coarse grain quartz from the malan loess at zhaitang section china thermoluminescence tl ages were obtained for five loess samples taken from the zhaitang section near beijing china using the coarse grain quartz technique the paleodose values have been determined by the method of total sample bleaching and regeneration of the tl growth curve the method appears to be suitable for the age determination of loess samples up to about 150 000 yr where the annual dose rate values are of the order 3 4 mgy yr this limit is a function of the total accumulated dose the ages are in good agreement with those obtained by a fine grain tl technique and are consistent with geological and geomagnetostratigraphic evidence

isothermal plateau fission track age of the late pleistocene old crow tephra alaska hydrated glass shards of the widespread old crow tephra in alaska have been dated by the isothermal plateau fission track method which corrects for partial track fading if present the weighted mean age of 149 13 ka is older than previous estimates which range from 86 to 109 ka these new data support the view that old crow tephra was deposited during the cold interval that immediately preceded the last interglacial which is dated in the marine record at 125 ka b p it is likely therefore that the buried forest beds and numerous ice wedge pseudomorphs preserved in sediments just above old crow tephra in interior alaska relate to the last interglacial and not a younger warm event of early wisconsin age

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

thermoluminescence dating of periods of loess deposition and soil formation in normandy the least incomplete records of pleistocene climate change come from the study of deep sea sediments in which the stratigraphic record of oxygen isotope variations reflecting terrestrial ice volume is the primary correlation medium on continents the available record is far less complete because many of the characteristics of glaciation are erosional rather than depositional the areas of loess deposition may provide the best deposits in which to develop relatively complete regional stratigraphies that may be compared with the deep sea record1 2 in this study we use thermoluminescence tl dating of loess and of soil developed on loess to test this model we have confined ourselves to the last complete glacial cycle within which the reproducibility of the age determinations is similar to the time resolution of most deep sea core records