age and origin of clayey silt brickearth in west london england the loamy brickearth deposits overlying coarse cold climate kempton park lynch hill and taplow gravels of the r thames in west london are dated by thermoluminescence and mineralogical comparisons with loesses of three known ages although much of the brickearth resembles loess it often contains more sand or clay than typical loess and the mineralogical studies suggest that even the coarse silt 16 63 m fraction is rarely similar in composition to any known english loess the thermoluminescence measurements suggest that most of the brickearth on the taplow and lynch hill gravels was deposited in the late devensian whereas that on the park gravel is mainly flandrian it is suggested that the latter is mainly floodloam whereas the earlier brickearth is a mixed aeolian sediment derived from various local sources in and close to the thames valley

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

loess in europe mass accumulation rates during the last glacial period abstract upper pleistocene loess palaeosol sequences provide excellent high resolution terrestrial archives of climate forcing due to improvements in numerical age determinations especially in luminescence dating methods a more reliable time based reconstruction of the past climate and environmental change has become available for the loess record in europe chronological information was collected from 43 sites along a northwest to southeast transect in europe thirty three of these sites had sufficient age information to allow estimation of mass accumulation rates and it was possible to isolate the mass accumulation rates of primary loess during the last glacial period 28 13 ka bp at 21 of these locations these sites fall along a coarse climatic gradient from the relatively coastal climate of belgium and france to the drier more continental climate of central europe interpreting mass accumulation rates of loess in terms of this climatic gradient is not straightforward as these deposits are dominated by sources in floodplains and large river systems thus accumulation rates are influenced strongly by regional wind and precipitation patterns but mostly by the availability of glacially derived material from the alps and the periglacial terrains that characterized european fluvial systems during and immediately following glaciation

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 applied to a thin winter varve of the late glacial south thompson silt south central british columbia the partial bleach r procedure of thermoluminescence tl dating of unheated sediments has been applied to the 2 4 m sized feldspar dominated grains from two components of a 10 11 ka bp glaciolacustrine silt a previous tl study of the 4 11 m sized feldspars from a 12 cm thick summer layer of this varved deposit did not produce the correct age here it is shown that the 2 4 m feldspar grains from a contiguous 5 mm thick clay rich winter varve give a satisfactory tl apparent age of 14 2 2 3 ka on the other hand and consistent with the previous results the 2 4 m feldspar grains from the thicker summer layer yield an incorrect high apparent age of 55 13 ka these results have implications for general tl dating of waterlaid sediments

the geochemistry of loess asian and north american deposits compared abstract loess is widely distributed over asia and north america and constitutes one of the most important surficial deposits that serve as terrestrial records of the quaternary the oldest pleistocene loess in china is likely 2 6 ma thus spanning much or all of the pleistocene in north america most loess is no older than the penultimate glacial period with the exception of alaska where the record may go back to 3 0 ma on both continents loess deposits date primarily to glacial periods and interglacial or interstadial periods are represented by paleosols both glacial and non glacial sources of silts that comprise the bulk of loess deposits are found on both continents although loess has been considered to be representative of the average upper continental crust there are regionally distinctive compositions of loess in both asia and north america loess deposits in asia from yakutia tajikistan and china have compositionally distinct major element compositions due to varying abundances of silicate minerals carbonate minerals and clay minerals in north america loess in the mississippi river valley the great plains and alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments trace element geochemistry sc th zr and the rare earth elements also shows regional diversity of loess bodies in both asia and north america on both continents most loess bodies show significant contributions from later cycle altered sedimentary rocks as opposed to direct derivation from igneous rocks further some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average upper crustal felsic rocks intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials ratios of soluble to insoluble elements show depletions in paleosols due to chemical weathering losses of calcite dolomite plagioclase mica apatite and smectite in asia and north america the last interglacial paleosol is more weathered than equivalent modern soils which could be due either to a climate that was warmer and more humid a longer period of pedogenesis or both in asia early pleistocene loess and paleosols are both more weathered than those from the middle and late pleistocene forming prior to a mid pleistocene aridification of asia from uplift of the tibetan plateau understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation past temperature and moisture regimes and even tectonic processes

geochemical comparison between gas in fluid inclusions and gas produced from the upper triassic xujiahe formation sichuan basin sw china abstract natural gas in the xujiahe formation of the sichuan basin is dominated by hydrocarbon hc gas with 78 79 methane and 2 19 c2 hc its dryness coefficient c1 c1 5 is mostly

climatic reconstruction of the weichselian pleniglacial in northwestern and central europe a multiproxy approach is applied to reconstructing accurately the weichselian pleniglacial climate 72 13 ka in northwestern and central europe standardised translations are used to transform proxy data into climate parameter values for six characteristic time windows quantitative reconstructions of the temperature regime are derived from periglacial coleoptera and botanical evidence while aeolian and fluvial evidence provide qualitative information on wind activity and precipitation respectively the early pleniglacial 74 59 ka the cold period between 41 38 ka and the late pleniglacial 27 13 ka are characterised by a strong north to south climatic gradient over northwestern europe during the last glacial maximum discontinuous permafrost was established in northern france whereas the continuous permafrost zone extended from the uk belgium the netherlands germany and poland to the nordic ice sheets prominent wind activity and a relatively low precipitation typify these periods in contrast an indistinct west to east climate gradient was present in the relatively more temperate intervals e g 50 41 ka seasonally frozen ground conditions prevailed in northwestern europe whereas discontinuous permafrost may be suggested for central germany it appears that the climate conditions in northwest and central europe were controlled by three major factors the scandinavian ice sheet the north atlantic surface water circulation and the russian continent 1998 john wiley sons ltd

a comparison of different tl techniques on loess samples from rheindahlen f r g abstract 9 tl samples of the loess profile rheindahlen lower rhine area germany covering the time span of the last 300 ka were studied systematic investigation was carried out using different filters and preheating procedures ed determinations were done by the additive dose and the regeneration method the annual dose was determined by aas alpha counting naa and gamma spectrometry in the laboratory and in the field the results show that the weichselian loess is datable whereas no tl age differentiation between loesses of stage 6 and stage 8 is possible if the accumulated dose ed is in the 600 gy region every apparent tl age between 100 and 300 ka can be obtained this leads to the conclusion that in rheindahlen no reliable tl ages are available for loess deposits underneath the eemian soil stage 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

evidence of quaternary climatic variations in a sequence of loess and related deposits at birch creek alaska implications for the stage 5 climatic chronology abstract a 45 m outcrop of quaternary sediments on birch creek near circle alaska reveals a record of fluctuating environmental conditions that probably spans several glacial interglacial cycles from base to top the deposits are forested floodplain warm colluvium with ice wedges cold forest soil warm loess cold paleosol containing old crow tephra oct cool to warm loess cold lacustrine very warm loess cold and modern forest soil warm resolution of the paleoclimatic history associated with the oct event is critical to understanding the nature of stage 5 in the western north american arctic application of recent age estimates for the oct tephra ca 140 000 yr bp to the birch creek section would indicate that either i the tephra paleosol dates from the 6 5 5 transition a strongly developed glacial interval occurred within stage 5 and the overlying very warm interval occurred in 5 3 or 5 1 or ii the tephra was deposited during a non milankovitch warming event late in stage 6 a paleoclimate chronology provides an alternative interpretation iii in which the tephra paleosol corresponds to stage 6 or even stage 7 the overlying loess to stage 6 and the lake sediments to all or part of stage 5 but the oct is older than 140 000 yr bp chronologies ii and iii imply a very warm beginning to stage 5 consistent with paleoclimate model simulations and data from other regions

a younger dryas ash bed in western norway and its possible correlations with tephra in cores from the norwegian sea and the north atlantic abstract a bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western norway it is formally mamed the vedde ash bed and its age is approximately 10 600 yr b p i e mid younger dryas the bed consits of pure glass having a bimodal basaltic and rhyolitic somposition the geochemistry of the glass shards suggests an icelandic source by means of stratigraphic position and geochemistry the ash is correlated with ash zones found in cores from the continental shelf the norwegian sea and the north atlatic

test of thermoluminescence dating of buried soils from mt kenya kenya we have applied the partial bleach r gamma thermoluminescence tl dating method to four organic rich ab horizons of buried soils from mount kenya our objective was to test the feasibility of directly measuring the time of last exposure to sunlight of the fine grained silicate minerals within these horizons the resulting apparent ages for three samples of 1 2 0 3 6 2 and 10 2 ka 1 std dev are in general agreement with associated 14c age estimates from buried whole soil paleosol samples the fourth sample of an age though unknown presumed to lie beyond the 14c dating limit yielded a tl age estimate of 60 20 ka notwithstanding some limitations these results are encouraging and imply that with simple refinements this tl method is capable of directly dating accurately such buried soils probably to well beyond the 40 ka 14c dating limit

tl dating studies of tephra loess and lacustrine sediments abstract a brief review is presented of my efforts to improve the accuracy of dating unheated sediments by tl and of the development of a new tephrochronometer specific applications to known age deposits are outlined as are studies of the depositional environment of subaqueous sediments removal of anomalous fading in loess by storage at 75 c for 8 days is demostrated throughout for unheated sediments the preferential use of the partial bleach r gamma or r beta technique is emphasized especially in situations where the growth curves are sublinear contrary to a widespread misconception sublinearity does not invalidate the partial bleach method furthermore examples are given of tl sensitivity or efficiency changes occurring with the regeneration technique changes that are variable and seemingly sample dependent

ipswichian fauna of victoria cave and the marine palaeoclimatic record the lack of age dating methods which can be applied beyond the limit of radiocarbon dating makes the global correlation of continental climatic events and stratigraphic sequences with the continuous palaeoclimate record obtained by isotopic and faunal analysis of deep sea sediment cores1 3 a difficult task often only a relative time scale can be obtained using complex and perhaps tenuous litho and biostratigraphical data speleothems may assist in this correlation for embodied in their calcium carbonate structures are elemental and isotopic variations which indicate both their age and climatic conditions prevailing during their deposition speleothems may be reliably dated by the 230th 234u method to an age of 350 kyr bp providing they consist of non porous unrecrystallized calcite which is essentially free of clastic detrital sediments4 6 they may also provide palaeoclimatic information for previously glaciated areas 1 because their presence indicates that groundwater movement was not prevented by ice formation at the surface and co2 was produced in the soil zone by root respiration and plant decay limestone bedrock may then be dissolved and reprecipitated as speleothems in caves below the surface and 2 because of the variations in stable isotopic content and fluid inclusion waters contained therein4 7 8 additional climatic and chronological information may be obtained where speleothems are interstratified with deposits characteristic of a particular climatic regime and with deposits containing organic remains we describe here the results of dating speleothems encrusting the remains of mammals from victoria cave in northern england and discuss their significance in terms of the correlation between continental and oceanic palaeoclimatic records

late pleistocene and holocene aeolian dust deposition in north china and the northwest pacific ocean abstract rates of dust deposition in the north pacific and the central loess plateau of china show a poor correlation during the last 30 000 yr although in both cases the dust was derived from deserts in northern china loess accumulation rates were high at the time of the last glacial maximum while dust flux to the north pacific was low at this time maximum dust flux to the north pacific is recorded in the mid holocene but holocene rates of loess accumulation have been low these differences are shown to reflect the different nature of the wind conditions responsible for dust transport to the loess plateau and the north pacific dust transport responsible for formation of the loess occurred mainly in the lower 1 5 km of the atmosphere and was accomplished by cold low level northwesterly winds associated with cold waves emanating from the mongolian anticyclone at present such conditions occur quite frequently in winter but during the coldest phases of the pleistocene they probably also occurred in the spring and summer long range dust transport from northern china to the north pacific requires that the dust is lifted to high levels above 3 km where it can be incorporated into the strong mid latitude westerlies strong vertical motions of the atmosphere occur most frequently in the spring when the mongolian anticyclone begins to weaken and frontal depressions move across the deserts of northern china such frontal depressions were probably more frequent during the climatic optimum of the mid holocene and during previous interglacials changes in continental aridity have probably played a minor role in controlling the magnitude of the dust flux to the north pacific

tl stratigraphy of pre weichselian loess from nw europe using feldspar coarse grains abstract a new feldspar relative tl dating method is proposed that enables dating of pre weichselian loess older than 130 ka by applying the additive dose technique and the mejdahl s exponential extrapolation to alkali feldspar coarse grains the method is applied to loess deposits from various reference loessic sections of nw europe our relative tl age estimates are consistent with the information provided by the regional stratigraphy furthermore they lead to a clear separation of the pre weichselian periods of loess deposition in the time period 130 ka 300 ka

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

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

unprecedented last glacial mass accumulation rates determined by luminescence dating of loess from western nebraska abstract a high resolution chronology for peoria last glacial period loess from three sites in nebraska midcontinental north america is determined by applying optically stimulated luminescence osl dating to 35 50 m quartz at bignell hill nebraska an osl age of 25 000 yr near the contact of peoria loess with the underlying gilman canyon formation shows that dust accumulation occurred early during the last glacial maximum lgm whereas at devil s den and eustis nebraska basal osl ages are significantly younger 18 000 and 21 000 yr respectively at all three localities dust accumulation ended at some time after 14 000 yr ago mass accumulation rates mars for western nebraska calculated using the osl ages are extremely high from 18 000 to 14 000 yr much higher than those calculated for any other pre holocene location worldwide these unprecedented mars coincide with the timing of a mismatch between paleoenvironmental evidence from central north america and the paleoclimate simulations from atmospheric global circulation models agcms we infer that the high atmospheric dust loading implied by these mars may have played an important role through radiative forcing in maintaining a colder than present climate over central north america for several thousand years after summer insolation exceeded present day values

thermoluminescence properties and age estimates for quaternary raised marine sediments hudson bay lowland canada thermoluminescence tl analyses of quaternary nearshore marine sediments from the hudson bay lowland revealed relatively high light emissions and linear growth curves to at least 400 gy above the natural dose initial results indicate that anomalous fading may be circumvented by a preheating at 150 c for 16 h without substantial thermal draining of stable tl components both the total bleach method with unfiltered sunlamp light and the partial bleach method with light blocked below 400 nm resulted in overbleaching and thus overestimates of age a tl age estimate of 5 3 0 8 ka on the holocene control sample similar to the radiocarbon age was obtained using the partial bleach method with light blocked below 540 nm this same method yielded an average tl age estimate of 73 10 ka for a pleistocene unit which corresponds to the amino acid based age estimate of ca 76 ka the agreement of the two age estimates is encouraging since both methods rely on separate assumptions that have not been independen

thermoluminescence dating studies of rapidly deposited silts from south central british columbia to determine whether quaternary sediments from small lake and fan deposits can be dated by thermoluminescence tl methods i have applied recently proposed techniques for tl dating to known age rapidly deposited silts and have examined the sensitivity of the tl of fine grain feldspars and quartz to light these feldspar dominated silts exhibited little or no detectable anomalous fading the tl of quartz was observed to be very resistant to light with wavelengths above 400 nm whereas that of feldspars was sensitive to all visible wavelengths no significant resetting of the tl of the 11 ka old glaciolacustrine silt deposition rate could be detected with these techniques implying that silts deposited at such rates into small glacier bordered lakes cannot be dated by these methods however accurate equivalent doses were measured for the derivative 7 5 ka old mudflow silts 1 mm year but only with the use of the r technique applied to the feldspars

metamorphic ore remobilization in the hallefors district bergslagen sweden constraints from mineralogical and small scale sulphur isotope studies the marble and metavolcanic hosted pb zn ag sb as deposits of the hallefors district located in the palaeoproterozoic bergslagen ore province south central sweden comprise both stratabound sulphides and discordant ag rich sulphide sulphosalt veins the complex sulphide sulphosalt assemblages of the alfrida jan olof mines at hallefors were investigated by a combination of ore microscopy electron microprobe analysis and in situ laser sulphur isotope analysis the massive ore is characterized by positive and homoge neous d 34 s 1 4 to 2 7 v cdt whereas vein hosted sulphides and sulphosalts exhibit similar but generally less positive to slightly negative d 34 s 0 6 to 2 0 comparison of the observed ore mineral assemblages with calculated phase equilibria in the sys tem fe as s o h and isotopic fractionation as a function of temperature oxygen fugacity and ph indi cates that the vein type mineralization was formed from relatively reduced and rather alkaline hydrothermal fluids at these reduced conditions fractionation of d 34 s via changes of fo2 is insignificant and thus the isotopic signatures of the vein minerals directly reflect the com position of the sulphur source we therefore conclude that the vein type ore essentially inherited the sulphur isotope signature from the pre existing massive sulp hides via metamorphic remobilization at approximately 300 400c and 2 3 kbar scales of remobilization observable are on the order of about 5 mm to 30 cm overall the sulphide sulphosalt assemblages from the alfrida jan olof mines exhibit d 34 s values which are comparable to a majority of metasupracrustal hosted deposits in the bergslagen province thereby suggesting a common origin from ca 1 90 1 88 ga volcanic hydro thermal processes