late quaternary tephrochronology of sweden a review abstract studies of late quaternary sediments in south and central sweden have yielded a detailed tephrochronology for the last glacial interglacial transition lgit ca 15 000 10 000 cal yr bp and the holocene more than ten tephra layers have been detected and geochemically characterised the most widespread tephra from the lgit is the rhyolitic phase of the vedde ash ca 12 000 cal yr bp which has been found in lacustrine sediments and marine clays south of the younger dryas moraines in south sweden other horizons from the lgit identified to date include the borrobol tephra ca 14 400 cal yr bp the hasseldalen tephra ca 11 500 cal yr bp the 10 ka askja tephra ca 11 300 cal yr bp and the hogstorpsmossen tephra ca 10 200 cal yr bp the most significant holocene isochrones are hekla 4 ca 4260 cal yr bp hekla selsund kebister ca 3750 cal yr bp hekla 3 ca 3000 cal yr bp and askja 1875 two new late holocene tephra horizons the stomyren tephra ca 2100 cal yr bp and the gullbergby tephra ca 2700 cal yr bp were identified in single sites and are so far less valuable as marker horizons but are potentially important for the future

racemization of amino acids in fossil bones and teeth from the olduvai gorge region tanzania east africa abstract investigation of amino acid racemization in fossil bones and teeth from the olduvai gorge region tanzania indicates that aspartic acid racemization can be used to date samples which are less than 80 000 100 000 years old in this area in older samples significant secondary aspartic acid is apparently present and thus these samples have lower than expectedd l aspartic acid ratios isoleucine in older samples however is apparently syngenetic with the samples so the epimerization of isoleucine to alloisoleucine can be used with certain limitations to date fossil bones and teeth from the older stratigraphic sections in the olduvai region

dates of holocene icelandic volcanic eruptions from tephra layers in irish peats tephra from historic and prehistoric eruptions of oraefajokull and hekla iceland have been found in irish peats using a series of stratigraphically related high precision radiocarbon measure ments the date of a known age eruption has been satisfactorily estimated based on the same techniques the calendrical date of the hekla 4 eruption has been estimated as 2310 20 bc

a 200 300 year cyclicity in sediment deposition in the gotland basin baltic sea as deduced from geochemical evidence abstract during the eu funded project basys baltic sea system study short niemisto type and long box and piston cores sediment cores were taken which cover sedimentation during the past 8 ka the uppermost part of the sedimentary sequence was chosen for a detailed geochemical study and freeze dried samples were analysed for about 20 elements but only the elements mn and ca are discussed an age model was constructed using radiometric dating results by 210 pb 137 cs and 14 c ams significant correlation exists along the cores between very high mn and moderately high ca due to occrrences of the mineral rhodochrosite kuthnahorite a complex mn ca carbonate this mineral is thought to be produced when salt water meets the pool of dissolved mn at the bottom of the gotland basin during favourable hydrographic conditions e g strong northwesterly winds salt water from the north sea invades even the deepest parts of the central baltic mn 2 which is produced mainly by the dissolution of ferromanganse oxides oxyhydroxides in the water colum and in the course of destruction of organic matter in the sediments combines with hco 3 2 and ca 2 in the seawater to form rhodochrosite after burial this mineral stays in the sediment and is seen as light coloured layers a certain cyclicity in the upper 1 5 m of the cores was observed in that about 200 300 a periods of elevated mn ca are followed by periods with lower mn ca of similar duration an explanation for the observed cyclicity may be sea level variations during rising sea level transgression more and more saline water is pushed into the deep basin of the baltic sea and if conditions are favourable high dissolved mn the mineral rhodochrosite is precipitated

assessing the impact of volcanic activity on mid holocene climate in ireland the need for replicate data analyses of pollen tephra mineral input and degree of peat humification from three neighbouring raised peat profiles at corlea central ireland covering the period of the deposition of a tephra

seven tephra isochrones in scotland this paper reports the presence and geochemical characteristics of seven separate tephras in scotland that fell in ad 1510 and about 450 bp 2100 bp 3600 bp 3830 bp 5600 bp and around 6000 bp the results come from 14 peat bogs spread throughout the highlands and islands where 26 tephra deposits have been characterized using over 400 grain discrete electron probe micro analysis firstly tephras are identified and defined by major element characteristics at a reference site secondly tephras are linked between sites on the basis of geochemistry and dated informal names based on british sites are suggested for tephras not yet linked to precise sources in iceland despite some apparent variation in colour all analysed grains in these seven deposits are silicic or intermediate in composition sio2 57 this phenomenon does not appear to be an artifact of preservation for two reasons first small 40 m basic glass shards in peat bogs in northern iceland are found to have undergone minimal alte

mire development pathways and palaeoclimatic records from a full holocene peat archive at walton moss cumbria england plant macrofossil data have been used to identify the successive mire communities occupying both central and marginal locations in the walton moss peatland complex during the last 10 500 years the reconstructed pathways of mire development indicate that early holocene fen and fen carr communities were succeeded by species indicative of deep mire water tables and oligotrophic conditions the character of the fen bog transition fbt is compared with similar records of peatland development from britain and scandinavia and with independent climate data for the early holocene the pseudohochmoor of central europe is suggested as an approximate modern analogue for the dry pioneer oligotrophic mire type and alternative explanations for its presence are explored the first major increase in ombrotrophic sphagna occurred at c 7800 cal bp overlying sphagnum peats provide a continuous record of climate change inferred from fluctuations in raised mire surface wetness the proxy palaeoclimate record reconstr

calendar year ages of three mid holocene tephra layers identified in varved lake sediments in west central sweden three intermediate to rhyolitic icelandic holocene tephra horizons hekla 3 kebister and hekla 4 have been identified in annually laminated varved lake sediments in the province of varmland west central sweden calendar year ages were obtained from varve counts and are supported by additional c 14 dating based on terrestrial plant macrofossils the varve ages of the three tephras are 3295 95 cal bp hekla 3 4030 103 cal bp kebister and 4390 107 cal bp hekla 4 the varve age of hekla 3 refines the former calibrated 14 c age based on studies in the british isles and germany considering the age error estimates associated with the varve chronology and calibrated c 14 ages the ages of kebister and hekla 4 are in agreement with former studies thus the age difference between kebister and hekla 4 is estimated to be ca 400 40 varve years formally estimated to ca 200 c 14 years between hekla 3 and hekla 4 to ca 1135 55 varve years formally estimated to ca 1100 calibrated c 14 years and between hekla 3 and kebister 708 20 varve years less

dating the naisiusiu beds olduvai gorge by electron spin resonance abstract the lower beds at olduvai gorge are well known for containing early hominid fossils and oldowan stone tools and their ages have been established by 40ar 39ar dating and paleomagnetic stratigraphy ages are generally less certain for the upper deposits at olduvai gorge because of the scarcity of datable tuffs the youngest archaeologically significant site at olduvai is microlithic lsa which lies in the type section of the naisiusiu beds the age for the site is controversial with 14c dates of 17 000 17 550 hay r l 1976 geology of olduvai gorge university of california press berkeley and 42 000 bp manega p c 1993 geochronology geochemistry and isotopic study of the plio pleistocene hominid sites and the ngorongoro volcanic highland in northern tanzania unpublished ph d thesis university of colorado boulder co the tuff bed in the zone with artifacts does not contain materials datable by 40ar 39ar and some other dating method was needed in the summer of 2001 five equid teeth were collected from the type naisiusiu site another tooth had previously been collected esr ages have been determined for three teeth from the archaeological level and their ages cluster around 62 5 ka assuming linear uranium uptake another tooth from a level without artifacts and believed to be significantly younger dated to 39 5 ka again assuming lu these dates are considerably older than previous estimates and suggest that the east african msa lsa transition occurred very early

calibration of the speleothem delta function an absolute temperature record for the holocene in northern norway the speleothem delta function sdf provides a new transfer function between the d18o signal of speleothem calcite and surface ground temperature the function is based on physical principles relating d18o of the calcite to thermodynamic fractionation and to the dripwater function which in turn relates d18o of dripwaters to that of the local precipitation and thus to the modification of source water in relationship to the geographical position of the site the sdf must be calibrated against at least two reliable and well dated palaeotemperature points the end product is a reconstruction of absolute cave and surface temperatures the technique is tested using a holocene speleothem from north norway sg93 dated by 12 tims u th dates the reconstructed temperature curve is presented and compared with the gisp2 ice core record and with the historic record in both cases the correlation with sg93 is impressive indicating the validity of the technique

linking the north atlantic to central europe a high resolution holocene tephrochronological record from northern germany a high resolution holocene tephrochronology for northern germany has been established based on systematic tephrostratigraphical analysis of three peat bogs microscopic volcanic ash layers have been traced and characterised petrographically and by the chemical composition of the glass shards at least 37 ash horizons representing 16 different explosive volcanic eruptions have been identified and many can be correlated between the three sites up to 100 km apart the tephra layers can be related to icelandic volcanic sources and some correlated to the eruptions of askja 1875 hekla 3 hekla selsund hekla 4 and hekla 5 as well as to unspecified eruptions of icelandic volcanic systems e g torfajokull the source volcanoes for some tephra layers remain unidentified some tephra layers were known previously from the north atlantic region e g sluggan glen garry others have not been recorded previously in the literature e g microlite tephra this study provides the first comprehensive holocene tephrostratigraphical record for northern germany complementing the north atlantic tephrostratigraphical dating framework effectively extending it into central europe the study shows that icelandic ash layers are even more widespread than hitherto thought copyright 2002 john wiley sons ltd

esr in the 21st century from buried valleys and deserts to the deep ocean and tectonic uplift abstract electron spin resonance esr dating can date many materials including hydroxyapatite in enamel and some fish scales aragonite and calcite in corals molluscs some travertine and calcrete and quartz from ash fluvial deposits and some flint dating studies using these materials have numerous potential applications in many varied quaternary settings esr dating uses signals resulting from trapped charges created by radiation in crystalline solids ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation when compared to other dating techniques age agreement has been excellent for teeth corals molluscs and quartz recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment new chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift using tooth and mollusc dates to assess water availability in deserts and using isochron data to assess u uptake processes into teeth when coupled with other geochemical and geomorphological techniques esr can provide the chronometric control to build paleoclimatic and other paleoenvironmental records many other applications are possible from heating studies for artefacts to dating sulphates and other minerals on distant planets

a sensitive high resolution record of late holocene climatic change from a raised bog in northern england proxy climatic data in the form of plant macrofossils have been analysed from a 5 m core from bolton fell moss cumbria uk detailed analysis of peat from the upper 50 cm of this core is used to demonstrate a strong correlation between changes in the relative proportion of taxa and known climatic changes over the last 1000 years the record of changes in bog vegetation contained within the peat profile is used to reconstruct changes in bog surface wetness for the latter half of the holocene as bog surface wetness is directly controlled by the prevailing climatic conditions this reconstruction can be viewed as a proxy climate record twelve radiocarbon age estimates on the 5m core suggest that between 50 and 500 cm peat accumulated at a relatively constant rate of 12 4 yr cm 1 the regular sampling intervals thus provide a time series of past bog surface wetness spectral analyses of this series indicates that wetness changes are cyclic with a ca 800 year periodicity

holocene climate variability and periodicities in south central sweden as interpreted from peat humification analysis analysis of the decomposition of peat has been used to identify climatic shifts over the last 10 000 years in two raised bogs stomyren and kortlandamossen south central sweden age depth curves have been constructed using radiocarbon dates and tephra layers peat humification data have been subjected to spectral analyses using the lomb scargle fourier method and reveal a periodicity of c 250 years in both records cycles of c 200 yr and c 400 yr were found at stomyren and at kortlandamossen respectively these periodicities could correspond to changes in solar activity levels a test estimating the possible level of noise has been applied to the spectral analyses the humification indices indicate prominent shifts to wetter conditions at c 7500 4300 4200 3700 3500 and 2800 2400 cal yr bp the most distinct drier phases start at c 4500 and 3250 cal yr bp

a first order model for temperature rise for uniform and differential compression of sediments in basins we deduce algebraic expressions for temperature rise for ideal cases of uniform and spatially varying compression of sediments of single mineralogy according to the results of the present work the temperature rise is related to the coefficient of volume expansion isothermal compressibility dimension bulk density and specific heat of the sediment columns rise of temperature due to compression of sediment is effectively inversely proportional to the volume coefficient of expansion or contraction of sediments compression related temperature rise is expected to augment diagenesis a more realistic model of temperature rise dealing with the rate of compression of sediments that of the pore fluid s and the vacant pore space individually would be required

amino acid racemization dating of quaternary deposits of central and southern italy abstract results are discussed of amino acid racemization dating of numerous samples of bones teeth tooth enamel and fossil shells racemization dating proved to be a very useful tool to date non marine and marine deposits which are a few hundred thousand years old as well as to correlate and chronologically classify even more ancient marine deposits aspartic acid racemization was used to date samples aged less than 80 000 100 000 yr for more ancient samples isoleucine epimerization instead was resorted to in this work dates were established for some important fragments of human bones and of large mammalian fauna weighing a few grams which would have been impossible to date with the 14 c technique requiring a large amount of bone material the extent of isoleucine epimerization was measured in glycymeris genera to estimate the age of numerous marine deposits of the tyrrhenian coast of centra southern italy and of sardinia in the tarquinia area latium three marine terraces were identified which were estimated to be approx 120 000 200 000 and 350 000 yr old in sardinia five marine horizons were identified the youngest deposit neotyrrhenian proved to be present at punta tramontana and santa reparata while at riola and stagno di sassu the most ancient marine deposits of sardinia were found in the rome area the monte mario formation was estimated to be coeval with monte delle piche formation finally from the terraced coastal deposits of capo milaazzo sicily panarea eolian archipelago archi calabria and gallipoli apulia a tyrrhenian age range of 100 000 120 000 yr was obtained

aspartic acid geochronology of sediments from the ocean margin off of india abstract aspartic acid racemization was studied in the clay and coarse fractions of sediments from southwestern bay of bengal core 1 in order to understand the role of terrestrial organic matter in the amino acid geochronology of indian marginal sediments conventional radiocarbon ages were determined for the coarse carbonate fraction 25 m of sediments the core covering an age back to 40 kyr bp aspartic acid racemization rate constants k asp were calculated for clay and coarse fractions of bulk sediments using a first order kinetic model and three horizons with constant k asp values were identified corresponding to the periods from 0 to 5 5 kyr 5 5 to 19 kyr and 19 kyr best fit models of high significance were derived from the relationship between aspartic acid d l ratio and calibrated radiocarbon ages as an alternative to racemization rate constants to test the applicability of these first order kinetic and logarithmic models derived for core 1 they were used to calculate ages for another sediment core core 2 calculated aspartic acid ages being consistent with radiocarbon ages however the logarithmic model gave better results than the first order kinetic model for older samples suggesting that the logarithmic model is a better choice for the amino acid geochronology of indian margin sediments for both sediment fractions aspartic acid ages based on the logarithmic model gave similar ages consistent with radiocarbon ages and suggesting that there is no significant difference in aspartic acid racemization between both fractions of bulk sediment as a result the clay fraction can also be used for amino acid dating of indian margin sediments

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

a proxy record of late holocene climate change from may moss northeast england quantitative reconstruction of changes in mire surface wetness has been used to reconstruct proxy climate from an upland ombrotrophic blanket mire on the north york moors in northeast england may moss testate amoebae plant macrofossil and humification analyses were carried out for six peat profiles transfer functions are used to generate estimates of water table levels from the testate amoebae stratigraphy which complement the semi quantitative indications of changing surface wetness provided by plant macrofossil and humification analysis 14c dates provide the chronology for the stratigraphy differences were encountered between ams 14c dates on pure sphagnum remains and radiometric dates on bulk peat from the same horizon which perhaps arise from the heterogeneity of peat replicate palaeoecological analysis of adjacent cores identifies consistency within testate amoebae and plant macrofossil stratigraphies and reveals a strong agreement between the water table level proxies the record of hydrological changes at sites across may moss are in synchrony and so climate change is the most likely cause of the moisture fluctuations changes to a wetter or cooler climate were identified cal ad 260 540 ca ad 550 650 cal ad 670 980 ca ad 1350 1450 cal ad 1400 1620 and ca ad 1700 1800 periods with a drier or warmer climate precede all of these wet shifts with particularly dry periods between cal ad 650 860 and 690 980 and between cal ad 1290 1410 and 1400 1620 copyright 2001 john wiley sons ltd

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

provenience age and associations of archaic homo sapiens crania from lake eyasi tanzania abstract fifty years ago an ethnographic expedition found primitive human fossils at lake eyasi tanzania subsequent emphasis has centered almost exclusively on cranial morphology neglecting the discovery site and associated finds fauna has been deemed essentially modern and racemization dates suggest a late pleistocene age for the hominid remains these assessments have been advanced as consistent with a terminal middle stone age antiquity based on recent observations at the site and new sediment analyses a provisional sequence is now proposed an earlier formation the eyasi beds is distinguished from later pleistocene deposits the mumba beds the latter being partially calibrated by uranium series and radiocarbon dates this evidence indicates that the eyasi beds the probable source of the human fossils are older than 130 000 years and the fauna may include seven extinct large mammal species documented eyasi beds artifacts are mostly unspecialized middle stone age types no typological or technical features suggest later msa specializations or innovations foreshadowing later stone age industries a series of core tools from the lakeshore suggests an industry of sangoan aspect all lines of evidence from the locality contradict the young amino acid racemization dates artifacts and fauna including archaic homo sapiens remains are of probable middle pleistocene age

two tephra layers bracketing late holocene paleoecological changes in northern germany paleoecological records from two holocene peat bogs in northern germany are linked by two microscopic volcanic ash layers correlated by petrology and geochemistry to explosive volcanism on iceland the younger microlite tephra cannot be correlated to any known eruption while the older tephra layer is identified as a deposit of the hekla 3 eruption the tephra layers are dated by an age depth regression of accelerator mass spectrometry 14c ages that have been calibrated and combined in probability distributions this procedure gives an age of 730 664 cal yr b c for the microlite tephra event and 1087 1006 cal yr b c for the hekla 3 event accordingly the tephra layers were deposited during the late bronze age at this time human settlement slowly increased pressure on the environment as indicated by changes in woodland pollen composition at the two bogs the tephra marker horizons further show that the palynologically defined transition from the subboreal to the subatlantic period is synchronous in the investigated area however the macroscopic visible marker in peat the change from fibrous to sapric peat the schwarztorf weistorf kontakt is asynchronous bog vegetation did not immediately react in unison to a climatic change at this pollen zone boundary instead the timing of vegetation change depended on the location within the bog

geochemistry dispersal volumes and chronology of holocene silicic tephra layers from the katla volcanic system iceland at least 12 silicic tephra layers silk tephras erupted between ca 6600 and ca 1675 yr bp from the katla volcanic system have been identified in southern iceland in addition to providing significant new knowledge on the holocene volcanism of the katla system which typically produces basaltic tephra the silk tephras form distinct and precise isochronous marker horizons in a climatically sensitive location close to both the atmospheric and marine polar fronts with one exception the silk tephras have a narrow compositional range with sio2 between 63 and 67 geochemically they are indistinguishable from ocean transported pumice found on beaches in the north atlantic region although they differ significantly from the silicic component of the north atlantic ash zone one naazo volumes of airborne silk tephra range from 0 05 to 0 3 km3 we present new isopach maps of the six largest layers and demonstrate that they originate within the katla caldera the apparently stable magma system conditions that produced the silk tephras may have been established as a consequence of the eruption of the silicic component of naazo ca 10 3 ka and disrupted by another large scale event the tenth century ad eldgja eruption ca 1 ka despite the current long repose silicic activity of this type may occur again in the future presenting hitherto unknown hazards copyright 2001 john wiley sons ltd

a 7500 year peat based palaeoclimatic reconstruction and evidence for an 1100 year cyclicity in bog surface wetness from temple hill moss pentland hills southeast scotland analyses of plant macrofossils peat humification and testate amoebae were used to reconstruct a proxy climate record spanning the last 7500 years from an ombrotrophic bog temple hill moss in southeast scotland the plant macrofossil data were subjected to detrended correspondence analysis dca which modelled effectively the significant wet shifts within the record a mean water table depth transfer function was applied to the testate amoebae data to provide quantifiable changes the three proxy records show coherent phase changes which are interpreted as variability in past effective precipitation two tephra horizons glen garry and lairg a were used in conjunction with radiocarbon dates to construct an age depth model producing a robust geochronology from which a time series was calculated the palaeoclimatic reconstruction identified major wet shifts throughout the holocene with specific events occurring around cal 6650 5850 5300 4500 3850 3400 2800 2450 1450 1350 and 250 150 bp spectral analysis of the plant macrofossil dca and colorimetric humification data produced a millennial scale periodicity of 1100 years the same periodicity has also been found in a palaeoclimatic reconstruction from a site in cumbria walton moss and may be linked with millennial scale periodicities found in oceanic palaeoclimatic records