a diffusion adsorption model of uranium uptake by archaeological bone abstract an argument for the possibility of uranium uptake by buried bone taking place through the adsorption of uranyl species on bone mineral is advanced in the light of this a diffusion adsorption model for uranium uptake by buried bone is developed the necessary constants are evaluated from the literature and from laboratory measurements of the partition coefficient between solution and bone mineral the geochemical and hydrological parameters which control uptake are discussed the predictions of the model are shown to be in general accordance with the timescale magnitude and distribution of uranium uptake in archaeological bone using the model specific predictions of the variation of apparent uranium series ages in bone can be made and bone is shown clearly not to conform to the closed system assumption when the model is extended to tooth enamel it is found to be incompatible with the early uptake model used for esr dating but to fall between the early uptake and linear uptake models similarly it suggests that uranium series dates on enamel assuming a closed system are liable to underestimate the true age by at least one third

site specific equilibrium isotopic fractionation of oxygen carbon and calcium in apatite the stable isotope composition of biogenic apatite is an important geochemical marker that can record environmental parameters and is widely used to infer past climates biomineralization processes dietary preferences and habitat of vertebrates in this study theoretical equilibrium isotopic fractionation of oxygen carbon and calcium in hydroxyapatite and carbonate bearing hydroxyapatite is investigated using first principles methods based on density functional theory and compared to the theoretical isotopic fractionation properties of calcite co 2 and h 2 o considering the variability of apatite crystal chemistry special attention is given to specific contributions of crystal sites to isotopic fractionation significant internal fractionation is calculated for oxygen and carbon isotopes in co 3 between the different structural sites occupied by carbonate groups in apatite typically 7 for both 18 o 16 o and 13 c 12 c fractionation at 37 c compared with calcite water oxygen isotope fractionation occurrence of a type substitution in apatite structure in addition to the main b type substitution could explain the larger temperature dependence of oxygen isotope fractionation measured at low temperature between carbonate in apatite and water theoretical internal fractionation of oxygen isotopes between carbonate and phosphate in b type carbonated apatite 8 at 37 c is consistent with experimental values obtained from modern and well preserved fossil bio apatites concerning calcium theoretical results suggest a small fractionation between apatite and calcite a0 17 at 37 c internal fractionation reaching 0 8 at 37 c occurs between the two ca sites in hydroxyapatite furthermore the ca isotopic fractionation properties of apatite are affected by the occurrence of carbonate groups which could contribute to the variability observed on natural samples owing to the complexity of apatite crystal chemistry and in light of the theoretical results measurements of site specific isotopic fractionation properties could improve our understanding and the interpretation of isotopic records in apatites

a revised 10 4 c magnitude of the abrupt change in greenland temperature at the younger dryas termination using published gisp2 gas isotope data and air thermal diffusion constants abstract we revisit the portion of nature 391 1998 141 devoted to the abrupt temperature increase reconstruction at the younger dryas preboreal transition the original estimate of 5 to 10 c abrupt warming is revised to 10 4 c the gas isotope data from the original work were employed combined with recently measured precise air thermal diffusion constants geochim cosmochim acta 67 2003a 345 j phys chem 23a 2003b 4636 the new constants allow a robust interpretation of the gas isotope signal in terms of temperature change this was not possible at the time of the original work when no air constants were available three quasi independent approaches employed in this work all give the same result of a 10 c warming in several decades or less the new result provides a firm target for climate models that attempt to predict future climates

latitudinal temperature gradient during the cretaceous upper campanian middle maastrichtian y18o record of continental vertebrates latitudinal variations in model biogenic apatite d18o values were calculated using fractionation equations of vertebrates and weighted rainfall y18o values along with mean annual air temperatures provided by iaea wmo meteorological stations the reference equation obtained was used to compute a continental temperature gradient for the late campanian middle maastrichtian interval by using published and new d18o values of phosphate from vertebrates samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83 4 n alaska to 32 3 s madagascar the temperature gradient was less steep 0 4 0 1 c latitude than the present day one 0 6 c latitude with temperatures that decreased from about 30 c near the equator to about 5 c at the poles above 30 of paleolatitude air temperatures were higher than at present the validity of these results is discussed by comparison with climatic criteria inferred from paleontological paleobotanical and sedimentological data the latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying mesozoic terrestrial climates

putting the younger dryas cold event into context abstract the younger dryas event is by far the best studied of the millennial scale cold snaps of glacial time yet its origin remains a subject of debate the long held scenario that the younger dryas was a one time outlier triggered by a flood of water stored in proglacial lake agassiz has fallen from favor due to lack of a clear geomorphic signature at the correct time and place on the landscape the recent suggestion that the younger dryas was triggered by the impact of a comet has not gained traction instead evidence from chinese stalagmites suggests that rather than being a freak occurrence the younger dryas is an integral part of the deglacial sequence of events that produced the last termination on a global scale

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

assessment of archaeological bone and dentine preservation from lazaret cave middle pleistocene in france chemical and structural changes in bones and dentine from cervus elaphus jaws during fossilization were studied by chemical analysis infrared spectroscopy ir and x ray diffraction xrd data were used to discuss the modifications of bones and dentine from the lazaret prehistoric cave nice france which is an important archeologic site of middle pleistocene age fossil bones and dentine mainly consisted of hydroxy carbonate apatite as the primary phase and of calcite as a secondary phase carbonation fluorination and recrystallization processes are shown as more important in bone and dentine than in tooth enamel a good correlation was found between the a cell parameter of apatite and its co3 and fluorine contents in the bones studied fluorine enrichment seems to be related to the permeability of the upper sedimentary levels lazaret fossil bones and dentine are less stable than enamels and their use for dating has to be taken with caution

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

geochemistry and geochronology of native copper mineralization related to the emeishan flood basalts yunnan province china abstract native copper mineralization in northeastern yunnan is related to the emeishan flood basalts which have high cu background concentrations the deposits are located in the ludian maoling and yiche synclines between the flood basalts and the overlying xuanwei formation evidence from ree and hsfe concentrations oxygen isotope compositions bitumen reflectance and mineral paragenesis indicates that the high grade copper orebodies were deposited from moderate to low temperature hydrothermal solutions 420 to 100 c in a reducing environment 40 ar 39 ar spectra for the laumontites that coexist with native copper in the high grade ores yield consistent plateau and isochron ages 226 to 228 ma these are interpreted to represent the age of the first stage of hydrothermal mineralization which took place at temperatures of 200 to350 c concordant with that of zn pb ag ge mineralization also occurring in the area the heulandites yield a stable 40 ar 39 ar plateau age of 134 0 1 7 ma consistent with isochron ages indicated by u th pb isotopic systematics indicating a second stage of native copper mineralization at lower temperatures 100 to 200 c that took place during the early cretaceous

stable isotope analyses of tooth enamel carbonate of large herbivores from the tugen hills deposits palaeoenvironmental context of the earliest kenyan hominids abstract understanding shifts in past climatic and environmental conditions are crucial for throwing light on human evolution available reconstructions of the palaeoecology of faunal and floral assemblages indicate that the earliest kenyan hominids including orrorin tugenensis are associated with forest landscapes in this study we present stable isotope data of tooth enamel carbonate of large herbivores associated with these hominids in order further to evaluate their environmental context fossil teeth were sampled in the lukeino formation 6 1 5 7 ma late miocene and the mabaget formation 5 3 4 5 ma early pliocene at the foot of the tugen hills great rift valley despite chemical changes in fossil enamel preservation of the palaeoenvironmental signals is supported by the difference in 18 o between hippos and terrestrial fauna moreover the giraffid specimen from the mabaget formation exhibits one of the highest 18 o values as expected for a drought tolerant animal the 13 c of large herbivores indicates that the earliest kenyan hominids inhabited a mixed c 3 c 4 environment as did ardipithecus ethiopia and sahelanthropus chad two early putative hominids the tugen hills might have been a wooded grassland with patches of woodland there is no record of closed canopy forest at the time of deposition we emphasize differences in food habits among herbivore groups deinotheres nearly all elephantids and the giraffid individual had a c 3 diet which reflected browsing behaviour the intake of c 4 plants prevailed for equids and gomphotheres and was consistent with grazing habits most hippos and suids were mixed c 3 c 4 feeders and consequently were generalist herbivores bovids and rhinos had a diet ranging from c 3 to c 4 plants variations in 13 c and 18 o among faunal assemblages suggest changes in local climate and vegetation moister conditions likely occurred in the early pliocene and the latest miocene ca 5 7 ma than before the c 3 plant biomass would have increased in the latest miocene there were probably denser stands of trees within the depositional environment during the early pliocene than in the late miocene which is consistent with palaeontological studies

anti phase oscillation of asian monsoons during the younger dryas period evidence from peat cellulose δ13c of hani northeast china abstract significant changes in the global atmospheric and oceanic circulation system occurred during the younger dryas cold period several researchers have demonstrated a weakening of intensity of the indian ocean summer monsoon during that period however the exact characteristics of the east asian summer monsoon still remain vague here we present a late glacial precipitation proxy record of the east asian summer monsoon based on the peat cellulose 13 c found in hani northeast china both the peat cellulose record and a pollen record from lake sihailongwan sediment indicate an abrupt increase in precipitation in the region during the younger dryas period these results support the occurrence of wet conditions in the north and of dry conditions in the south of the chinese mainland during that period by examining the activity of the east asian summer monsoon on an interannual timescale we propose a theory for the anomalous precipitation distribution that we attribute to the occurrence of an el nino like phenomenon in the equatorial pacific ocean during the younger dryas in this case the intensity of the western pacific subtropical high may strengthen and its position over the western pacific ocean may move northward this could cause an enhancement of the east asian summer monsoon and migration of a monsoonal rainbelt towards the northern region of the chinese mainland resulting in a precipitation distribution of wet conditions in the north and dry conditions in the south therefore this anomalous rainfall distribution should be considered to indicate the strengthening of the east asian summer monsoon in anti phase with the indian ocean summer monsoon that weakened during the same period this agrees with the previously revealed anti phase variations of the two monsoons during the ice rafted debris cold events of the north atlantic ocean it appears that in relation to the abrupt temperature drop in the northern hemisphere on centennial to millennial time scales anti phase variations of the two asian summer monsoons occurred

precise radiocarbon dating of late glacial cooling in mid latitude south america abstract variability of atmospheric 14c content often complicates radiocarbon based chronologies however specific features such as periods of constant 14c age or steep changes in radiocarbon ages can be useful stratigraphic markers the younger dryas event in the northern hemisphere is one of those periods showing conspicuous 14c wiggles although the origin of those variations is not fully understood we can make practical use of them and determine i whether the younger dryas was global in extent if so ii were the initial cooling and the final warming synchronous worldwide and iii what are the implications of these similarities differences here we report high resolution ams 14c chronologies from the mid latitudes of south america that pinpoint a cool episode between 11 400 and 10 20014c yr b p the onset of the final cool episode of the late glacial in the southern mid latitudes i e the huelmo mascardi cold reversal preceded the onset of the younger dryas cold event by 550 calendar years both events ended during a radiocarbon age plateau at 10 20014c yr b p thus the huelmo mascardi cold reversal encompasses the younger dryas as well as a couple of short term cool warm oscillations that immediately preceded its onset in the north atlantic region

atomic scale transformation of bone in controlled aqueous alteration experiments abstract the chemical and isotopic compositions of biogenic apatite are important geochemical markers which can suffer modifications during fossilisation compared with modern ones fossil apatites generally exhibit variations in carbonate content enrichment in fluorine incorporation of trace elements and an increase in crystallinity parameters detailed understanding of these transformations induced by fossilisation should help assess the preservation of geochemical records in apatites in this contribution we investigate the transformation of modern bone altered under controlled conditions modern bone samples were soaked in aqueous solutions of neutral to alkaline ph 9 10 for one and three weeks at various temperatures 20 and 70 c and experiments were duplicated in fluorine free and in 10 2 m naf solutions bone transformation was monitored through the modifications of chemical f ca p and isotopic 13c 18oc 18op composition as well as using vibrational atr ftir raman and solid state 1h 13c 19f nmr spectroscopies the observed modifications sustain a transformation mechanism through partial dissolution of biogenic apatite and precipitation of secondary apatite this transformation occurs irrespective of the presence or absence of fluorine and leads to the formation of carbonate bearing fluorapatite or carbonate bearing hydroxylapatite respectively the fraction of secondary apatite seems to be limited to 60 suggesting that its formation has a protecting role against further dissolution of the primary apatite the observation of clumped co32 f defects in the structural b site of some samples as well as perturbation of the isotopic compositions attest to carbonate incorporation in the secondary apatite although the incorporation of fluoride ions can serve as a probe revealing dissolution recrystallization of bone the present study also underlines the difficulty to systematically relate mineralogical transformations to an open system behaviour in bioapatite

crystallinity and diagenesis of sedimentary apatites the crystallinity of sedimentary apatites was determined by fourier transform infrared spectroscopy ft ir using the splitting of a triply degenerate antisymmetric bending vibration of orthophosphate the crystallinity indices of recent marine apatites are low 3 0 3 6 while those of onland ancient apatites are high 4 5 7 8 indicating post depositional recrystallization the infrared spectra reveal that recrystallization is associated with a decrease in carbonate content substituting for po43 and an increase in fluoride order within the apatite structure the relationship between the crystallinity index and po43 18o suggests alteration of the primary isotopic composition by exchange reactions between po43 oxygens and surrounding waters the monterey samples have a large range of crystallinity index that reflects a set of complex and highly variable diagenetic conditions this demonstrates the use of ft ir criteria for differentiating between pristine and altered apatites and as a consequence for relating geochemical markers to formation or diagenetic environments it is suggested that only those samples that have low crystallinity indices c i 3 8 should be considered as pristine apatite spectra of fish remains indicate that differences in rare earth element ree patterns correspond to variations in crystallinity carbonate content and f order in the apatite lattice the fact that crystallinity is not correlated with geologic age suggests that environmental factors such as accumulation rate and pore water chemistry govern the recrystallization process in general sr content decreases and 18op exhibits high variability with increasing crystallinity

water washing of proterozoic oil in the midcontinent rift system whole oil gas chromatography shows that petroleum inclusions trapped in 1 05 ga veins in the midcontinent rift experienced variable water washing but no significant biodegradation or phase separation by comparing our results with published experimental data we estimate that water petroleum ratios varied from 200 1 to much greater than 9000 1 extreme water washing with water petroleum ratios very much greater than 9000 1 likely produced pyrobitumen solid hydrocarbon that was locally trapped as primary inclusions in vein calcite hydrothermal ore deposits with their extremely high water rock ratios are one of the best places to search for end member water washed petroleum sedimentary basins however with their variable water rock ratios also have a wide range of water petroleum ratios which significantly affect the composition of crude oils along the flow path between source rock and trap water petroleum ratios may be a useful concept to help evaluate crude oil compositions in a variety of settings

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

alteration of enamel carbonate environments during fossilization an understanding of enamel diagenesis is necessary to ensure sound isotopic palaeodietary and palaeoenvironmental reconstructions although carbon isotope signals of browsing and grazing herbivores remain distinct in enamel even after millions of years subtle alteration of isotopic signatures does occur to better understand this change we analysed modern and fossil enamel from a number of south african sites using fourier transform infra red spectroscopy our results indicate that while there is little evidence of increased crystallinity in fossil enamel there is a small but significant change in the proportion of carbonate ions occupying hydroxyl and phosphate sites this seems to occur early in the process of fossilization after which there is no noticeable change it is also important to note that the degree of alteration varies significantly within and between sites we suggest that this change results from one or some combination of three mechanisms exogenous carbonate incorporation endogenous carbonate loss and endogenous carbonate reorganization determining which mechanism s contribute to this alteration is important because all three are likely to affect biogenic carbon isotope ratios differently ftir spectroscopy promises to increase our knowledge of diagenesis and in so doing should improve our palaeodietary and palaeoenvironmental reconstructions

the origin distribution and hydrocarbon generation potential of organic rich facies in the nonesuch formation central north american rift system a regional study abstract precambrian unmetamorphosed organic rich clastic rocks whilst uncommon in the geologic record are of interest with respect to their potential for hydrocarbon generation the 1 1 billion year old nonesuch formation is primarily a lacustrine deposit which is part of a thick sequence of volcanic and clastic sedimentary rocks that filled an aborted rift in central north america previous organic geochemical investigations of the nonesuch formation have been limited to isolated samples from the basal portion of the nonesuch formation at a copper mine white pine in northern michigan in the present study 183 outcrop and core samples of the nonesuch formation from northern wisconsin and michigan upper peninsula were collected for sedimentologic and organic geochemical analyses total organic carbon toc values for the samples ranged from 0 0 to 2 5 and showed a strong correlation between organic richness and depositional environment detailed petrographic analysis using incident white light and reflected blue light fluorescence revealed two major organic petrographies 1 and 2 which could be further distinguished using combined pyrolysis gas chromatography mass spectrometry py gc ms whereas the composition of organic petrography 1 kerogens is primarily aliphatic the composition of organic petrography 2 kerogens is dominated by aromatic and or phenolic constituents the geographic and stratigraphic distribution of rocks bearing the two organic petrographies indicate that variable source input or preservation superimposed over maturity differences is responsible for both organic petrographic and kerogen pyrolysate compositions

organic matter and copper mineralization at white pine michigan u s a mauk j l and hieshima g b 1992 organic matter and copper mineralization at white pine michigan u s a in p a meyers l m pratt and b nagy guest editors geochemistry of metalliferous black shales chem geol 99 189211 indigenous and exogenous organic matter in sediments of the north american midcontinent rift were involved in precipitation of cu bearing minerals during main and second stage mineralization events at white pine michigan samples of the proterozoic nonesuch formation from the white pine mine and adjacent areas were investigated petrographically and geochemically in order to determine the influence of organic matter on the precipitation of cu and to determine whether mineralization influenced thermal maturity of organic matter during main stage mineralization introduction of cupriferous fluids into the lower nonesuch fro formed cu bearing sulfides by replacement of pyrite sulfur may have been added to the system via abiogenic sulfate reduction with organic matter providing a direct source of reducing potential in basal ore horizons where all sulfide had been incorporated into chalcocite during main stage mineralization native cu also precipitated locally with organic matter presumably acting as a direct reductant later compressional faulting at white pine provided conduits for additional cupriferous fluids these fluids deposited second stage cu mineralization inclusions of liquid petroleum and solid pyrobitumen in veins filling fractures associated with compressional faults record migration of petroleum into the white pine district from the deeper hotter axis of the rift penecontemporaneous with second stage fluids some of this petroleum may have acted as a reductant during precipitation of native cu in basal ore horizons biomarker compositions of bitumens and isotopic compositions of individual n alkanes from petroleums and bitumens suggest that these materials were all derived from organic matter deposited during sedimentation of the nonesuch fro biomarker data demonstrate that bitumens from the white pine area have significantly higher levels of thermal maturity than bitumens from unmineralized strata outside the mine area therefore cu mineralization at white pine coincides with a thermal anomaly seep petroleums from the northeast and southwest domains of the mine contain different n alkane distributions we propose that this difference reflects elevated thermal maturity of seep petroleums spatially associated with second stage mineralization in the southwestern domain of the mine

precambrian oil inclusions in late veins and the role of hydrocarbons in copper mineralization at white pine michigan liquid oil was trapped as primary fluid inclusions in calcite crystals in late cu fe sulfide bearing veins that crosscut and offset the cupriferous shale deposit at white pine the age of the calcite 1047 35 ma is an entrapment age and thus a minimum age for the oil close temporal and spatial associations of oil and metallic sulfides in the late veins suggest that liquid and solid hydrocarbons may have been dominant controls of the main stage white pine copper mineralization

nanodiamonds in the younger dryas boundary sediment layer we report abundant nanodiamonds in sediments dating to 12 9 0 1 thousand calendar years before the present at multiple locations across north america selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval cubic diamonds form under high temperature pressure regimes and n diamonds also require extraordinary conditions well outside the range of earth9s typical surficial processes but common to cosmic impacts n diamond concentrations range from 10 to 3700 parts per billion by weight comparable to amounts found in known impact layers these diamonds provide strong evidence for earth9s collision with a rare swarm of carbonaceous chondrites or comets at the onset of the younger dryas cool interval producing multiple airbursts and possible surface impacts with severe repercussions for plants animals and humans in north america

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

relationship between organic matter and copper mineralization in the proterozoic nonesuch formation northern michigan abstract comparison of organic and inorganic geochemical data of stratigraphically equivalent mineralized and unmineralized samples from strata hosting the white pine stratiform copper deposit in northern michigan provides insight into the ore forming process whole rock and organic extract analyses were performed on mine and core samples from five gray beds stripey shale uzv siltstone thinly shale dgm siltstone domino shale of the proterozoic nonesuch formation and from the lower sandstone of the underlying copper harbor conglomerate bitumen is degraded in both mineralized and unmineralized samples of the lower nonesuch formation presumably this degradation is not a direct result of the mineralizing process but represents either regional scale water washing or biodegradation in contrast the pristane n c 17 and phytane n c 18 ratios are lower in mineralized samples than in unmineralized samples suggesting thermal maturation of the lower nonesuch formation during mineralization copper mineralization most likely proceeded via three mechanisms 1 deposition of native copper 2 conversion of precursor pyrite to chalcocite and 3 deposition of chalcocite with copper and sulfur derived entirely from mineralizing fluids a positive correlation between organic carbon and copper contents in mineralized strata implies that organic matter served as a reducing agent during copper mineralization however redox reactions must have conserved total organic carbon since the total organic carbon contents of mineralized and unmineralized samples are similar

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

possible effects of thermal degradation of organic matter on carbonate paragenesis and fluorite precipitation in mississippi valley type deposits heating of organic matter to progressively higher temperatures causes a sequence of chemical changes in which carbonate minerals are first dissolved then precipitated and then again dissolved the initial carbonate dissolution is related to the production of organic acids as heating continues organic acids begin to decompose to carbon dioxide and methane this addition of carbon dioxide to a solution with an organic acid ph buffer causes carbonates to precipitate eventually a temperature is reached at which any remaining organic acids quickly decompose addition of carbon dioxide to a solution in which carbonate species rather than organic acids now control the ph lowers the ph and causes renewed carbonate dissolution the similarity of this sequence to the carbonate paragenesis of mississippi valley type deposits suggests that the carbonate paragenesis in these deposits may be related to the thermal alteration of organic matter by competing with fluoride for magnesium bicarbonate ions from decarboxylation off organic matter and dissolution of carbonates may break the mgf complex form the mghco3 complex and thereby liberate fluoride to trigger the precipitation of fluorite

cathodoluminescence tools provide clues to depositional history in miocene and pliocene mammalian teeth abstract this paper presents the results of a study which used cathodoluminescence cl observations optical images and sem spectra as a tool for assessing diagenetic processes during fossilisation of continental mammalian teeth the study was performed on fossil teeth of large mammals gomphotheriidae rhinocerotidae and hippopotamidae from namibia and from kenya with ages from the lower and middle miocene to pliocene the fossil sites are distinguished by their environmental conditions they include floodplain deposits fluvial deposits of the proto orange river and aeolianite deposits in namibia and fluvio lacustrine deposits of different ages in kenya optical cl provides information about the sites environments and diagenetic processes related to those environments a blue intrinsic luminescence for the aeolianite deposits and purple to yellowish for floodplain or fluvial deposits the cl spectra of these samples show sharp emission bands which are classically related to late recent incorporation of rare earth elements ree substituting in the ca 2 sites high resolution mapping of the distribution of these ree shows a gradient from the enamel interior low concentrations to the outer enamel margin high concentrations

apparent synchroneity of submillennial scale climate events between greenland and santa barbara basin california from 30 10 ka abstract evidence is presented from odp hole 893a santa barbara basin for possible synchroneity between greenland and california margin submillennial climate change records during termination 1 and the last glacial maximum lgm planktonic foraminiferal isotope and faunal records are compared to the gisp2 18o records greenland for the interval between 30 and 10 ka using a new chronology based on 38 planktonic 14c dates apparent synchronous climatic events include interstadial is events 2 3 and 4 a broad warming trend between 21 and 19 ka and a broad cooling trend between 19 and 17 ka bolling and allerod warm episodes separated by the cooler older dryas event younger dryas cool episode and the preboreal the resulting tight correlation supports an intimate teleconnection between santa barbara basin surface waters and greenland air temperatures differences between greenland and santa barbara basin suggest that some regional variations were superimposed on the global pattern of climate change e g the pre bolling warming

routing of meltwater from the laurentide ice sheet during the younger dryas cold episode rooth1 proposed that the younger dryas cold episode which chilled the north atlantic region from 11 000 to 10 000 yr bp was initiated by a diversion of meltwater from the mississippi drainage to the st lawrence drainage system the link between these events is postulated to be a turnoff during the younger dryas cold episode of the north atlantic s conveyor belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the north atlantic region2 this turnoff is attributed to a reduction in surface water salinity and hence also in density of the waters in the region where north atlantic deep water nadw now forms here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from orca basin core en32 pc4 which reveal a significant reduction in meltwater flow through the mississippi river to the gulf of mexico from about 11 200 to 10 000 radiocarbon years ago this finding is consistent with the record for lake agassiz which indicates that the meltwater from the southwestern margin of the laurentide ice sheet was diverted to the northern atlantic ocean through the st lawrence valley during the interval from 11 000 to 10 000 years before present yr bp

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

atmospheric 14c variations derived from tree rings during the early younger dryas abstract atmospheric radiocarbon variations over the younger dryas interval from 13 000 to 11 600 cal yr bp are of immense scientific interest because they reveal crucial information about the linkages between climate ocean circulation and the carbon cycle however no direct and reliable atmospheric 14c records based on tree rings for the entire younger dryas have been available in this paper we present 1 high precision 14c measurements on the extension of absolute tree ring chronology from 12 400 to 12 560 cal yr bp and 2 high precision high resolution atmospheric 14c record derived from a 617 yr long tree ring chronology of huon pine from tasmania australia spanning the early younger dryas the new tree ring 14c records bridge the current gap in european tree ring radiocarbon chronologies during the early younger dryas linking the floating lateglacial pine record to the absolute tree ring timescale a continuous and reliable atmospheric 14c record for the past 14 000 cal yr bp including the younger dryas is now available the new records indicate that the abrupt rise in atmospheric 14c associated with the younger dryas onset occurs at 12 760 cal yr bp 240 yrs later than that recorded in cariaco varves with a smaller magnitude of 40 followed by several centennial 14c variations of 20 25 comparing the tree ring 14c to marine derived 14c and modelled 14c based on ice core 10be fluxes we conclude that changes in ocean circulation were mainly responsible for the younger dryas onset while a combination of changes in ocean circulation and 14c production rate were responsible for atmospheric 14c variations for the remainder of the younger dryas

variations of younger dryas atmospheric radiocarbon explicable without ocean circulation changes the concentration of radiocarbon 14c in the atmosphere depends on its production rate by cosmic rays and on the intensity of carbon exchange between the atmosphere and other reservoirs for example the deep oceans for the holocene the past 11 500 years it has been shown that fluctuations in atmospheric radiocarbon concentrations have been caused mostly by variations in the solar magnetic field1 2 3 recent progress in extending the radiocarbon record backwards in time4 5 6 7 8 9 10 has indicated especially high atmospheric radiocarbon concentrations in the younger dryas cold period between 12 700 and 11 500 years before the present these high concentrations have been interpreted as a result of a reduced exchange with the deep ocean reservoir caused by a drastic weakening of the deep ocean ventilation7 8 9 11 12 here we present a high resolution reconstruction of atmospheric radiocarbon concentrations derived from annually laminated sediments of two polish lakes lake go ciaz and lake perespilno these records indicate that the maximum in atmospheric radiocarbon concentrations in the early younger dryas was smaller than previously believed and might have been caused by variations in solar activity if so there is no indication that the deep ocean ventilation in the younger dryas was significantly different from today s

crystal chemical controls on rare earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions abstract fossil biogenic apatites display rare earth element ree patterns which have been proposed to reflect environmental and biological controls on past seawater composition these patterns can be separated in two groups 1 patterns that are similar to those of open ocean and epicontinental waters and 2 patterns that exhibit a strong enrichment in intermediate ree bell shaped patterns because ree trapping in biogenic apatites occurs mostly post mortem it is essential to understand the crystal chemical inorganic factors that can influence the fractionation of ree between apatite and water a model is proposed by which partition coefficients of ree between apatite and water for a substitution mechanism can be extrapolated from mineral melt partition data to seawater or sedimentary basin conditions these are compared with available experimental partition coefficients for ree adsorption mechanism and used to discuss ree patterns in fossil biogenic apatites calculations of ree patterns for apatites at equilibrium with water show that the bell shaped patterns in fossil apatites can be explained by fractionation with seawater or continental fluids at low temperature under crystal chemical control involving a substitution mechanism and in the context of extensive or late diagenesis in that case the equilibrium composition of the fluid cannot be unequivocally determined from observed ree concentrations in fossil apatites this type of sample is inappropriate to discuss the past environmental or biological controls on ree concentrations in the ocean other sample compositions suggest little to moderate alteration of the original oceanic to freshwater pattern through the adsorption mechanism in the context of weak or early diagenesis and may be used with caution for that purpose

wildfire and abrupt ecosystem disruption on california s northern channel islands at the allerod younger dryas boundary 13 0 12 9 ka abstract sedimentary records from california s northern channel islands and the adjacent santa barbara basin sbb indicate intense regional biomass burning wildfire at the allerod younger dryas boundary 13 0 12 9 ka all age ranges in this paper are expressed in thousands of calendar years before present ka radiocarbon ages will be identified and clearly marked 14c years multiproxy records in sbb ocean drilling project odp site 893 indicate that these wildfires coincided with the onset of regional cooling and an abrupt vegetational shift from closed montane forest to more open habitats abrupt ecosystem disruption is evident on the northern channel islands at the allerod younger dryas boundary with the onset of biomass burning and resulting mass sediment wasting of the landscape these wildfires coincide with the extinction of mammuthus exilis pygmy mammoth the earliest evidence for human presence on these islands at 13 1 12 9 ka 11 000 10 900 14c years is followed by an apparent 600 800 year gap in the archaeological record which is followed by indications of a larger scale colonization after 12 2 ka although a number of processes could have contributed to a post 18 ka decline in m exilis populations e g reduction of habitat due to sea level rise and human exploitation of limited insular populations we argue that the ultimate demise of m exilis was more likely a result of continental scale ecosystem disruption that registered across north america at the onset of the younger dryas cooling episode contemporaneous with the extinction of other megafaunal taxa evidence for ecosystem disruption at 13 12 9 ka on these offshore islands is consistent with the younger dryas boundary cosmic impact hypothesis firestone r b west a kennett j p becker l bunch t e revay z s schultz p h belgya t kennett d j erlandson j m dickenson o j goodyear a a harris r s howard g a kloosterman j b lechler p mayewski p a montgomery j poreda r darrah t que hee s s smith a r stich a topping w wittke j h wolbach w s 2007 evidence for an extraterrestrial impact 12 900 years ago that contributed to the megafaunal extinctions and younger dryas cooling proceedings of the national academy of sciences 104 16016 16021

strong evidence for dietary mineral imbalance as the cause of osteodystrophy in late glacial woolly mammoths at the berelyokh site northern yakutia russia abstract paleoecological analysis of over 1500 mammoth remains from the famous non archaeological berelyokh site 13 12 ka bp has demonstrated that 42 show destructive changes osteoporosis osteolysis osteofibrosis osteomalacia articular diseases and others for the first time non closure of cervical vertebral foramina transversaria and loose intra articular bodies have been recorded in mammoths the overall pathological picture resembles that of kashin beck or urovskaya disease the etiology of which is associated with mineral starvation the alimentary dietary nutritional character of the observed osteodystrophy can be explained by the strong acidification of geochemical landscapes which is manifested in the territory of northern eurasia after 30 ka bp and especially clearly during the late glacial 15 10 ka bp thus the berelyokh site reflects the terminal stage of the last mass extinction of large mammals

proboscideans and paleoenvironments of the pleistocene great lakes landscape vegetation and stable isotopes abstract in this study we review the history of proboscideans in the great lakes region ontario and western new york in the context of local glacial and vegetational histories further we investigate mammoth mammuthus and mastodon mammut environmental niche partitioning using stable isotope analysis of bone and dentin collagen 13 c col 15 n col and structural carbonate in tooth enamel bioapatite 13 c sc 18 o sc and demonstrate that stable isotopes can be used to identify non locals among museum specimens with no contextual records new radiocarbon dates suggest that ontario mastodons lived in tundra like environments as well as their more common spruce forest habitat local ontario new york mammoths and mastodons consumed 100 c 3 plant diets and drank low 18 o waters consistent with colder than modern climates and proximity to glacial meltwater sources mammoths and mastodons occupied distinct environmental niches characterized by different oxygen and nitrogen isotope compositions and geographical locations this suggests that direct competition for resources was not a major factor in their local extinction we suggest that both mammoths and mastodons obtained water from sources formed primarily from precipitation rather than glacial meltwater we describe how high 15 n values in mammoths could have been caused by a combination of preferences for dry environments consumption of low nutrient forage particularly stems and stalks coprophagy geophagy and dung fertilization we argue that low 15 n values in mastodons could have been caused by consumption of trees and shrubs including nitrogen fixing taxa and a preference for recently deglaciated landscapes and or spruce environments finally we raise the possibility that mastodons contributed to the spruce pine transition by browsing directly on spruce trees

enhanced organic carbon burial in large proterozoic lakes implications for atmospheric oxygenation abstract the burial of organic carbon in sedimentary systems has been a fundamental part of the carbon cycle throughout the geological record and was instrumental in major oxygenations of the atmosphere in the early palaeoproterozoic and neoproterozoic while much focus has been placed on the burial of carbon in precambrian marine carbonate and organic carbon rich rocks deposited around the time of these major oxygenations such deposits yield little information on the evolution of the atmosphere in the significant time between there is however growing evidence from terrestrially deposited sediments to suggest the surface environment may have been at least intermittently well oxygenated from the late mesoproterozoic hence proterozoic sediments deposited in terrestrial near surface environments are useful targets for the study of atmospheric evolution during a time which is hitherto poorly understood thus far little attention has been paid to the contribution of large lakes and intercontinental basins to the global burial of organic carbon and thus the progressive oxygenation of the atmosphere especially given that the highest rates of organic carbon burial in modern aquatic environments occur in lacustrine settings in stark contrast to the low rates observed in the contemporary marine realm here we report high burial rates of organic carbon in large lacustrine systems of late mesoproterozoic to early neoproterozoic age which are comparable with modern lacustrine systems and significantly higher than modern and ancient marine deposits these data emphasise the significance of lakes as a global repository for organic carbon and imply proterozoic lakes were at least as efficient and perhaps as important as modern lakes in the global burial of organic carbon such findings suggest large proterozoic lakes and epicontinental basins played a crucial role in the progressive oxygenation of the atmosphere before the major neoproterozoic oxygenation

reconstruction of a lateglacial younger dryas mountain ice field in sutherland northwestern scotland and its palaeoclimatic implications quaternary geomorphological and geological mapping of a large area 1800 km2 in the northwestern scottish highlands has led to the reconstruction of a coherent mountain ice field approximately 45 km long and 30 km wide at its maximum extent this west sutherland ice field covered an area of 350 km2 and had a mean equilibrium line altitude of 334 m assuming that the outlet glaciers all reached their maxima simultaneously numerical dating strongly suggests a younger dryas 12 9 11 7 ka age of the mapped limits of this mountain ice field this study also shows that the area of northwestern scotland covered by younger dryas glaciers was five times larger than previously thought palaeo temperature estimates obtained from chironomid and beetle assemblages elsewhere have been used to reconstruct palaeo precipitation during the younger dryas for west sutherland using a previously published global empirical dataset annual precipitation of 2344 248 mm a 1 at sea level is inferred from our new palaeo glacier reconstruction suggesting slightly wetter conditions compared to the present day these figures are in good agreement with those reconstructed for other parts of the scottish highlands and islands and this may indicate a marked w e palaeo precipitation gradient during the younger dryas this paper goes on to discuss the wider validity of palaeo climatic reconstructions from inferred palaeo glacier geometries and presents a number of possible scottish lateglacial climate scenarios which warrant further testing copyright 2010 john wiley sons ltd

variability of monsoon climate in east asia at the end of the last glaciation abstract high resolution paleomonsoon proxy records from peat and eolian sand paleosol sequences at the desert loess transition zone in china denote a rapid oscillation from cold dry conditions 11 200 10 60014c yr b p to cool humid conditions 10 600 10 20014c yr b p followed by a return to cold dry climate 10 200 10 00014c yr b p variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern asia during the younger dryas interval late glacial climate in the chinese desert loess belt that lies downwind from europe was strongly influenced by cold air from high latitudes and from the north atlantic via the westerlies the inferred precipitation variations were likely caused by variations in the strength of the siberian high which influenced the pressure gradient between land and ocean and therefore influenced the position of the east asian monsoon front

reduced meltwater outflow from the laurentide ice margin during the younger dryas the cause of the younger dryas cold event which interrupted the last deglaciation is still a matter of debate1 a prevalent hypothesis proposed by broecker et al 2 is that the abrupt climate change was driven by a decrease in the rate of north atlantic deep water production triggered by a sudden dilution of north atlantic surface water in response to the diversion of laurentide icesheet melt water from the mississippi drainage system to that of the st lawrence river here we investigate the feasibility of this triggering mechanism by reconstructing sea surface temperature salinity and sea ice cover records for the outlet of the gulf of st lawrence into the north atlantic ocean these reconstructions based on dinoflagellate cyst assemblages3 4 in sediment cores from the region show reduced meltwater runoff low temperatures and extensive sea ice cover during the younger dryas dated here between 10 800 and 10 300 bp meltwater pulses did occur before and after the younger dryas event as early as 11 700 bp during the development of the champlain sea in the st lawrence lowland and afterwards until 10 100 bp at the resolution of our salinity proxy 0 7 the meltwater pulses preceding the younger dryas did not affect sea surface salinity off the shelf break these constraint on the meltwater outflow through the st lawrence drainage system do not support the triggering mechanism of the broecker et al hypothesis2 unless the north atlantic thermohaline circulation is more sensitive to small salinity changes than most models suggest23

isotopic records of climate seasonality in equid teeth abstract we investigate how oxygen isotopes in equid teeth can be used as a record of seasonality first we use in situ laser ablation and conventional microsampling techniques to understand time averaging of environmental signals in intra tooth isotope profiles in modern feral horse teeth n 5 from mongolia where there is a large seasonal gradient in the oxygen isotopic composition of precipitation we demonstrate that laser ablation can be used to sample inner middle and outer enamel layers in large mammalian herbivore teeth the inner enamel layer records less attenuated isotopic signals than other layers as predicted by the mineralization patterns but intra tooth signal amplitude is similar for laser and conventional sampling methods second we use modern zebra teeth n 21 collected in eastern africa to evaluate how intra tooth oxygen isotope variation relates to rainfall patterns in the tropics we show that the intra tooth isotopic range increases with intra annual precipitation isotopic range which in turn relates to aridity in the equatorial bimodal rainfall region but is influenced by other hydroclimate processes in the region as a whole finally we address isotopic seasonality during the early pleistocene in eastern africa using oxygen isotopes in fossil equid teeth from southwestern kenya n 11 and northern tanzania n 5 we find variable isotopic seasonality in the past similar to present day eastern africa consistent with the notion that hominins and other mammals were able to accommodate environmental variability on intra annual scales in addition to well documented orbital cycles

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

mammoth tooth enamel growth rates inferred from stable isotope analysis and histology abstract mammoth mammuthus sp teeth are relatively abundant in quaternary deposits from eurasia and north america and their isotopic compositions can be used to reconstruct past seasonal patterns in precipitation diet and migration strategies for collecting and interpreting such data however are strongly dependent on growth rates which can vary among species individuals and within teeth in this study we use histological and isotopic measurements to determine enamel growth rates for a columbian mammoth mammuthus columbi tooth in two directions using histology the growth rate through the enamel thickness et perpendicular to the height of the tooth is estimated at 0 8 to 1 5 mm yr isotopic sampling through the innermost 0 36 mm of the et recovered less than half a period of variation i e half an inferred year of growth which is consistent with the histological estimate for et growth rate a combination of histological and isotopic measurements suggests that the enamel extension rate growth in the height of the tooth is 13 14 mm yr knowledge of enamel growth rates should improve the design and interpretation of future isotopic studies of mammoth teeth the combination of histological and isotopic measurements may also prove useful in determining growth rates for other extinct taxa

high resolution greenland ice core data show abrupt climate change happens in few years the last two abrupt warmings at the onset of our present warm interglacial period interrupted by the younger dryas cooling event were investigated at high temporal resolution from the north greenland ice core project ice core the deuterium excess a proxy of greenland precipitation moisture source switched mode within 1 to 3 years over these transitions and initiated a more gradual change over 50 years of the greenland air temperature as recorded by stable water isotopes the onsets of both abrupt greenland warmings were slightly preceded by decreasing greenland dust deposition reflecting the wetting of asian deserts a northern shift of the intertropical convergence zone could be the trigger of these abrupt shifts of northern hemisphere atmospheric circulation resulting in changes of 2 to 4 kelvin in greenland moisture source temperature from one year to the next

exploring the variation of the δ18op and δ18oc relationship in enamel increments abstract comparisons between the oxygen isotope ratios in the carbonate and phosphate fractions of bioapatite have been proposed and applied as an internal check for diagenesis because oxygen in the two compartments is believed to be incorporated simultaneously from the same body water it has become clear however that the relationship is quite variable and for some time this variability was thought to be induced by a species effect although it has never been clear why that should be the case we studied sequential samples in enamel crowns of eight equid and cervid teeth from five different upper palaeolithic sites in peninsular italy encompassing an area with different geological units results suggest that 18 o c values are slightly attenuated compared to the 18 o p values in their seasonal profiles the observation is unexpected if both bioapatite mineral fractions precipitate simultaneously from body water one explanation could be diagenetic effects on the carbonate fraction the same pattern however has been observed in data comparing incremental 18 o c and 18 o p in modern mammal enamel crowns if confirmed attenuation of intra tooth 18 o c sequences compared to 18 o p variability would imply that seasonal climate inferences from the two proxies are not completely equivalent our results may also go some way in explaining the extent of variability amongst different sets of data in the 18 o p 18 o c relationship and suggest that the classical approach in the bioapatite community of using a constant offset between 18 op and 18 oc values needs to be approached with caution

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

preservation assessment of miocene pliocene tooth enamel from tugen hills kenyan rift valley through ftir chemical and stable isotope analyses abstract we investigated fossil tooth enamel of mammals and crocodiles from two mio pliocene east african formations lukeino and mabaget fms using infrared spectroscopy and chemical and stable isotope analyses infrared spectra indicate that the fossil enamel contains biological apatite bioapatite without significant secondary carbonate contaminations several empirical infrared indexes were used to analyze the crystal chemical characteristics of enamel fossil enamel has less organic matter water and structural carbonate of apatite than modern enamel with which it was compared fossil apatite has a better crystallinity than bioapatite the calcium phosphorus mass ratio and the fluorine content of fossil apatite show intermediate values between bioapatite and geological fluorapatite the samples also display significant crystal chemical variations depending on the vertebrate group mammals vs reptiles and the taphonomic context lukeino fm vs mabaget fm in spite of these changes no relationship was observed between the chemical contents carbonate and fluorine and the stable isotope ratios of carbonate 13 c and 18 o in fossil enamel preservation of the palaeoenvironmental signals is strongly supported by the fact that the stable isotope composition of the three investigated fossil mammalian taxa deinotheres equids and hippos is consistent with their ecological features for instance typical c 3 and c 4 plant isotope compositions are reflected in the deinotheres and equids respectively and amphibious hippos display lower 18 o values than terrestrial herbivores as expected

timing is everything in a game of two hemispheres what causes ice ages and other episodes of violent climate change one clue comes from a new study of ice cores which unexpectedly seems to show rapid warming events happening first in the southern hemisphere

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

bone diagenesis variability among multiple burial phases at al khiday sudan investigated by atr ftir spectroscopy abstract in this study the diagenetic pathways of archaeological human bones are investigated through fourier transform infrared spectroscopy in attenuated total reflection mode atr ftir archaeological excavations at al khiday 16 d 4 site khartoum sudan revealed a multi stratified cemetery with distinct burial phases chronologically attributed to different periods spanning from the early holocene to the beginning of the 1st millennium ce atr ftir measurements are carried out on a set of 56 bone samples representative of each burial phase parameters related to collagen content and to bioapatite crystallinity and structural carbonate are calculated from infrared spectra in order to monitor the types and extent of diagenetic alteration to assess the preservation state of bones and to define the alteration processes occurring during burial a new method is here developed to quantify the amount of secondary calcite and to remove its contribution to the infrared spectrum when interfering with the signal of structural carbonate from bioapatite considering the wide span of time covered by the archaeological record the variability of bones alteration among burial phases is related to the climatic changes occurring in central sudan during the holocene the more humid environment occurring in the early holocene characterised by higher precipitation rates seasonal swamps and palaeo lakes progressively changed towards drier conditions until the current arid climate of the sub saharan belt the change of palaeoenvironmental and local burial conditions over time differently influenced the types and extent of diagenetic processes affecting bones during burial in this research are also discussed advantages and disadvantages of atr ftir spectroscopy with respect to the more established ftir spectroscopy in transmission mode

relative timing of deglacial climate events in antarctica and greenland the last deglaciation was marked by large hemispheric millennial scale climate variations the bolling allerod and younger dryas periods in the north and the antarctic cold reversal in the south a chronology from the high accumulation law dome east antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the antarctic cold reversal did not follow the abrupt warming during the northern bolling transition around 14 500 years ago this result suggests that southern changes are not a direct response to abrupt changes in north atlantic thermohaline circulation as is assumed in the conventional picture of a hemispheric temperature seesaw

why are the δ13corg values in phanerozoic black shales more negative than in modern marine organic matter the 13corg values of phanerozoic black shales average 27 whereas those of modern marine organic matter average 20 the black shale isotopic values mimic those of continental organic matter yet their organic geochemical properties mandate that they contain predominantly marine organic matter hypotheses that proposed to explain the low 13c values of black shales include diagenetic losses of isotopically heavier organic matter components releases of isotopically light carbon from methane clathrates or extensive magmatic events greater photosynthetic discrimination against 13c during times of higher atmospheric pco2 and greenhouse climate stratification of the surface ocean that magnified photic zone recycling of isotopically light organic matter although the last possibility seems contrary to the vertical mixing that leads to the high productivity of modern oceanic upwelling systems it is consistent with the strongly stratified conditions that accompanied deposition of the organic carbon rich pliocene pleistocene sapropels of the mediterranean sea because most phanerozoic black shales contain evidence of photic zone anoxia similar to the sapropels well developed surface stratification of the oceans was likely involved in their formation existence of isotopically light land plant organic matter during several episodes of extensive magmatism that accompanied black shale deposition implies massive release of mantle co2 that added to the greenhouse conditions that favored oceanic stratification the 13c depletion common to most phanerozoic black shales apparently resulted from a greenhouse climate associated with elevated atmospheric pco2 that led to a strongly stratified ocean and photic zone recycling of organic matter in augmented by magmatic co2 releases

why do crystallinity values fail to predict the extent of diagenetic alteration of bone mineral spectroscopic indicators of bone crystallinity such as the infrared splitting factor irsf are commonly used to determine the general state of preservation of ancient bone in principle such indices might be expected to act as a proxy for alteration of bone mineral and thus could be used to screen bones or portions of bones for likely preservation of in vivo biogenic trace element and stable isotope signals we tested the relationship between irsf and bone mineral composition in two suites of well characterised recent and pleistocene bones initially crystallinity change and trace element uptake are correlated apparently both controlled by decomposition of the organic phase and exposure of bone crystal surfaces this relationship breaks down in older bones where authigenic phosphate growth and mineral pore water interactions are no longer rate limited by the breakdown of collagen and exposure of crystal surfaces in these conditions the extent of chemical alteration of bone will be controlled by site specific conditions and thus while ftir spectra of bone provide a broad indication of organic content and apatite recrystallisation they are not reliable proxies for the degree of diagenetic alteration in terms of biogenic geochemical signals

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

thermodynamics of organic transformations in hydrothermal fluids hydrothermal fluids obtain organic compounds through diverse pathways in submarine systems organic compounds are already dissolved in seawater that is heated and transformed into hydrothermal fluids through water rock reactions microbes inhabiting hydrothermal systems produce metabolites that enter the fluids and cells can be carried into the reaction zones by circulating fluids and pyrolyzed analogous sources of organic compounds can be anticipated in continental systems with the possible addition of novel plant and soil derived organic compounds from the surface in addition hydrothermal systems possess large potentials for abiotic organic synthesis that may add a novel suite of compounds when sedimentary rocks are present ancient biogenic organic matter can be mobilized or transformed by hot fluids these transformations accompany the generation of petroleum coal and other fossil fuels suggesting that expectations for hydrothermal transformations can be built on those that occur in sedimentary basins likewise some types of ore deposition are accompanied by transformations of organic compounds and metal organic complexes may be involved in enhancing the transport of metals in ore forming and other crustal fluids with these thoughts in mind this review starts with an inventory of the types of organic compounds found in hydrothermal systems and some ways that hydrothermal organic compounds are transformed methane can be generated biotically and abiotically from organic or inorganic reactants and since it lacks a carbon carbon bond some researchers would not consider it to be an organic compound nevertheless more data exist for methane in hydrothermal fluids than for any organic compound that fits the definition methane has been quantified in continental and submarine hydrothermal fluids fumarolic gases associated with hydrothermal systems oil field brines deep fluids in sedimentary basins and igneous basement rocks fluids associated with active serpentinization and fluid inclusions in minerals from ore deposits sedimentary basins and deep crustal settings recent examples include

bone diagenesis in arid environments an intra skeletal approach bone trace element content and isotopic composition are closely related to human nutrition the investigation of archaeological bone geochemistry can help us to better understand the relationship between past populations and their environment alongside cultural practices as inferred from dietary reconstruction however dietary in formation may be altered post mortem by diagenetic processes in soil in this study bone mineralogy ca p sec ondary minerals organic matter content and bone apatite crystallinity histology element content mg na f sr ba mn fe la ce and u and stable isotope composition 13cand 18o carbonate were investigated at the intra individual scale in order to understand the effects of diagenesis on skeletons buried in different saharo sahelian environments between 10 to 18 bone samples were taken from 4 neolithic skeletons excavated in the mauritanian dhar oualata and nema and in the daounas mali additionally the enamel of two third molar teeth was also analysed from each skeleton for comparison with bone the results show that the four skeletons buried in the same desert climate area all exhibited different degrees of diageneticmodification relatedto localtaphonomic conditions highly drainedand periodically flooded environments generated substantial bone bacterial damage low to moderate apatite crystallinity and secondary minerals in bone pores bone trace element content and isotopic composition were more diagenetically affected than in bones from skeletons buried in a drier environment which display little bioerosion high apatite crystallinity and the absence or late precipitation of secondary minerals in their bone pores intra skeletal variability of the geochemical composition and the comparison of geochemical data from bones and teeth enables the approximation of ante mortem bone trace element and stable isotope compositions using the best preserved bones from each skeleton

a model of fossil tooth and bone diagenesis implications for paleodiet reconstruction from stable isotopes abstract diagenesis of structural carbonate in biogenic apatite in the postmortem environment is modeled as a process of water mineral interaction both closed and open system model calculations suggest that 13 c of structural carbonate in biogenic apatite is much more resistant to diagenetic modification than 18 o apatite structural carbonate retains an original 13 c signal in closed system diagenesis for open systems 13 c of biogenic apatite with very low porosity such as tooth enamel can survive most diagenesis and retain a primary isotopic signature on the hand 18 o of structural carbonate in biogenic apatite may not be a reliable indicator of the original isotopic ratios except in a diagenetic system with low temperature and very low water biomineral ratio application of the model to teeth and carbonate cement in sediments from the badlands south dakota illustrates that 13 c values of enamel samples preserve the original signal whereas 13 c values of dentine represent varying extents of diagenesis 18 o values of fossil teeth may record an early or late part of their water biomineral interaction history during diagenesis

review and update of the applications of organic petrology part 2 geological and multidisciplinary applications abstract the present paper is focused on organic petrology applied to unconventional and multidisciplinary investigations and is the second part of a two part review that describes the geological applications and uses of this branch of earth sciences therefore this paper reviews the use of organic petrology in investigations of i ore genesis when organic matter occurs associated with mineralization ii the behavior of organic matter in coal fires self heating and self combustion iii environmental and anthropogenic impacts associated with the management and industrial utilization of coal iv archeology and the nature and geographical provenance of objects of organic nature such as jet amber other artifacts and coal from archeological sites and v forensic science connected with criminal behavior or disasters this second part of the review outlines the most recent research and applications of organic petrology in those fields

determination of organic degradation rates in 100 my old sediments application to cretaceous black shale intervals from demerara rise odp leg 207 abstract thick organic rich albian to santonian black shale sequences were recovered from ocean drilling program sites 1261 and 1257 on the demerara rise offshore surinam at depths of 564 and 174 m below seafloor bsf respectively total organic carbon toc concentration varies between 3 9 and 17 3 wt rock eval pyrolysis parameters and elemental analysis indicate that the kerogen samples are of type ii thermally immature and with well preserved organic matter the hydrogen index hi values fluctuate between 608 and 765 mg hydrocarbon hc g toc and correlate well with c n and the sorg c atomic ratios indicating varying early diagenesis conditions between samples higher c n and sorg c values for kerogen from site 1261 suggest more reducing depositional conditions than at site 1257 long term organic diagenesis is marked by a linear decrease in the oxygen index oi at site 1261 from 34 to 22 mg co2 g toc ester and carboxyl functional groups are the main target of the degradation as inferred from the decrease in c o and o c c fourier transform infrared spectroscopy ftir bands as well as in the ch oh and the o ch3 chx n bands in 13c nuclear magnetic resonance nmr spectra degradation rate at site 1261 determined combining quantitative nmr spectra and bulk elemental characterization is between 1 7 and 12 1 mol m3 yr per 1 toc at the lower end of reported rates in a similar context kerogen samples from site 1257 do not show any decrease in oxygen content with depth indicating significantly lower degradation rate we propose that the long term exposure to moderate temperature 30 c at site 1261 activated the organic matter thereby sustaining microbial diagenesis

states of preservation of bones from prehistoric sites in the near east a survey abstract a survey of the states of preservation of organic material in 30 fossil bones from 16 different prehistoric sites in the near east shows that whereas almost all the bones have little or no collagen preserved they do with few exceptions contain non collagenous proteins these macromolecules therefore represent an important reservoir of indigenous fossil bone constituents

rock varnish evidence for latest pleistocene millennial scale wet events in the drylands of western united states rock varnish from late to latest pleistocene geomorphic features in the drylands of the western u s provides evidence of nine millennial scale wet events from 11 500 18 000 calendar yr b p represented by regionally replicable and approximately evenly spaced manganese and barium rich dark bands in varnish microstratigraphy preliminary radiometric age calibration indicates that these events appear to be broadly coeval with millennial scale cooling events identified in the greenland ice sheet project 2 gisp2 ice core record six of these wet events are associated with the cold intervals of the younger dryas and heinrich event h1 and the other three with the short lived cooling phases of the intra allerod cold period the older dryas and the oldest dryas these results combined with our previous documentation of millennial scale wet events in the holocene varnish record for the same region indicate that such wet oscillations in the western u s may be parts of regionally widespread manifestation of well documented pervasive millennial scale cycles of the north atlantic climate

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

tree rings and ice cores reveal c 14 calibration uncertainties during the younger dryas the younger dryas interval during the last glacial termination was an abrupt return to glacial like conditions punctuating the transition to a warmer interglacial climate despite recent advances in the layer counting of ice core records of the termination the timing and length of the younger dryas remain controversial also a steep rise in the concentration of atmospheric radiocarbon at the onset of the interval recorded primarily in the cariaco basin has been difficult to reconcile with simulations of the younger dryas carbon cycle here we discuss a radiocarbon chronology from a tree ring record covering the late glacial period that has not been absolutely dated we correlate the chronology to ice core timescales using the common cosmic production signal in tree ring 14c and ice core 10be concentrations the results of this correlation suggest that the cariaco record may be biased by changes in the concentration of radiocarbon in the upper ocean during the early phase of the younger dryas climate reversal in the cariaco basin this bias in the marine record may also affect the accuracy of a widely used radiocarbon calibration curve over this interval our tree ring based radiocarbon record is easily reconciled with simulated production rates and carbon cycle changes associated with reduced ocean ventilation during the younger dryas attaching a floating tree ring chronology to ice core records that cover the abrupt younger dryas cold interval during the last glacial termination provides a better estimate of the onset and duration of the radiocarbon anomaly the chronology suggests that marine records may be biased by changes in the concentration of radiocarbon in the ocean which may affect the accuracy of a popular radiocarbon calibration program during this interval

evaluating the impact of acetic acid chemical pre treatment on old and cremated bone with the perio spot technique and perios endos profiles abstract the impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in vivo chemical and isotopic characteristics such bone is often pre treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses although very few standardized approaches exist for evaluating pre treatment effectiveness in this pilot study we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre treatment on the trace element and structural characteristics of four bones from belgium including an early medieval cremated bone from broechem and three representative old bones of different ages ca 40 130 ka from the late pleistocene sedimentary sequence of scladina cave each bone was analyzed before and after acetic acid pre treatment using the perio spot technique and perios endos profiles we measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry la icp ms and micro x ray fluorescence spectroscopy xrf structural characteristics were investigated with raman spectroscopy and fourier transform infrared spectroscopy ftir our results indicate that chemical pre treatment had little to no significant impact on the trace element content of the early medieval cremated bone had the most impact on the youngest bone from scladina cave and had less impact on the trace element content of two older bones from scladina cave this suggests that the effectiveness of acetic acid chemical pre treatment is greater for bones undergoing early diagenetic processes has minimal impact on highly crystalline cremated bone and may preferentially leach in vivo signatures from bones undergoing later diagenesis the weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre treatment therefore our new approach may provide a valuable step toward effectively and consistently differentiating among in and ex vivo trace element signatures and by proxy those of their isotopes in archaeological and palaeontological bone

the palaeoecology of the non mammalian cynodonts diademodon and cynognathus from the karoo basin of south africa using stable light isotope analysis abstract the palaeoecology of the coeval middle triassic non mammalian cynodonts diademodon and cynognathus therapsida remains poorly understood although their gross morphology has been studied intensively significant differences in their growth patterns suggest inherent biological differences despite having inhabited similar environments in this study the palaeoecology of cynognathus and diademodon specimens were examined using intra tooth stable carbon and oxygen isotope analyses of enamel carbonate the resulting stable isotope patterns of cynognathus and diademodon were compared with that of crocodylus niloticus and published mammalian tooth enamel data predictably the non mammalian cynodont 13 c values fall within the expected range for c 3 plant diets both 18 o and 13 c values of diademodon are markedly more depleted than those of cynognathus suggesting that the former fed in shadier damper areas was nocturnal and or depended more directly on environmental water the seasonal amplitude reflected in the cynognathus teeth is relatively low however high amplitude directional 18 o intra tooth variations in the diademodon teeth are comparable to or higher than those observed for extant mammalian and c niloticus teeth from semi arid seasonal regions this suggests that marked seasonality prevailed in the karoo basin during the middle triassic and that diademodon was sensitive to these variations these isotopic differences between diademodon and cynognathus indicate differing responses to climatic fluctuations and reveal new insights into the palaeoecology of non mammalian cynodonts

glacier retreat in new zealand during the younger dryas stadial the younger dryas a period of sudden cooling in the northern hemisphere about 12 900 years ago is perhaps the best known example of abrupt climate change but the global extent of the younger dryas is a topic of intense debate particularly in the record of glacial behaviour in new zealand a new reconstruction of the growth and retreat patterns of glaciers in the southern alps in new zealand at the time of the younger dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the southern hemisphere through a series of climate feedbacks the younger dryas during which northern hemisphere temperatures cooled drastically in just a few years is perhaps the best known example of abrupt climate change but its global extent is under debate particularly in the record of glacial behaviour in new zealand these authors present evidence for glacial retreat in new zealand during the younger dryas supporting the hypothesis that northern hemisphere climate changes caused southern hemisphere warming through a series of climate feedbacks millennial scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions the presence of the younger dryas stadial 12 9 to 11 7 kyr ago is established throughout much of the northern hemisphere but the global timing nature and extent of the event are not well established evidence in mid to low latitudes of the southern hemisphere in particular has remained perplexing1 2 3 4 5 6 the debate has in part focused on the behaviour of mountain glaciers in new zealand where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1 2 3 the interhemispheric behaviour of the climate system during the younger dryas thus remains an open question fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period here we show that new zealand s glaciers retreated after 13 kyr bp at the onset of the younger dryas and in general over the subsequent 1 5 kyr period our evidence is based on detailed landform mapping a high precision 10be chronology7 and reconstruction of former ice extents and snow lines from well preserved cirque moraines our late glacial glacier chronology matches climatic trends in antarctica southern ocean behaviour and variations in atmospheric co2 the evidence points to a distinct warming of the southern mid latitude atmosphere during the younger dryas and a close coupling between new zealand s cryosphere and southern high latitude climate these findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the north atlantic led to a strong interhemispheric thermal gradient8 during late glacial times in turn leading to increased upwelling and co2 release from the southern ocean9 thereby triggering southern hemisphere warming during the northern younger dryas

organic geochemical study of mineralization in the keweenawan nonesuch formation at white pine michigan the role of organic matter in the formation of metal ores has been investigated in the nonesuch formation at white pine michigan organic matter in mineralized strata was characterized by isotopic molecular and spectrophotometric procedures and compared to organic matter in non mineralized rocks samples from the white pine copper mine contain little organic carbon in comparison to samples from non mineralized sections of the nonesuch formation residual organic matter in mine samples is depleted in solvent extractable matter is relatively aromatic in character and appears to be thermally overmature yet no difference in carbon isotopic contents exists between kerogcn isolated from mineralized and non mineralized rocks comparisons suggest that oxidation of organic matter was involved in the reduction of oxidized metalliferous brines to precipitate copper sulfides and native copper and silver in this setting

evidence for warm wet heinrich events in florida analyses of pollen and plant macrofossils from a new core spanning the past 60 000 years from lake tulane florida show a strong antiphase relationship in temperature between florida and the north atlantic region during the pleistocene oak scrub and prairie phases were coeval with long intense dansgaard oeschger interstadials warm periods that initiated bond cycles pine phases were coeval with the north atlantic long stadials cold periods that ended bond cycles and were terminated by heinrich events lake levels were higher during pine phases and climate was wetter however climate in florida was also warmer during these phases which were cold periods in the north atlantic perhaps diminution of thermohaline circulation before and during heinrich events reduced northward heat transport and retained warmth in the subtropical atlantic and gulf of mexico

synchronous radiocarbon and climate shifts during the last deglaciation radiocarbon data from the cariaco basin provide calibration of the carbon 14 time scale across the period of deglaciation 15 000 to 10 000 years ago with resolution available previously only from holocene tree rings reconstructed changes in atmospheric carbon 14 are larger than previously thought with the largest change occurring simultaneously with the sudden climatic cooling of the younger dryas event carbon 14 and published beryllium 10 data together suggest that concurrent climate and carbon 14 changes were predominantly the result of abrupt shifts in deep ocean ventilation

prelude to the extinction revision of the achchagyi allaikha and berelyokh mass accumulations of mammoth abstract the little known achchagyi allaikha mass assemblage of mammoths and the well known berelyokh site lower indigirka river arctic siberia were studied detailed study of the achchagyi allaikha site provided ample data concerning its geology stratigraphy taphonomy and the gender age structure of the taphocoenosis the achchagyi allaikha assemblage included redeposited bones from numerous young not less than 21 and some adult female mammoths with limited quantities of bison equus and rangifer bones collagen from mammoth bones preserved at the achchagyi allaikha site n 6 was radiocarbon dated at 12 490 80 to 12 400 60 bp at the berelyokh site eight mammoth bones were radiocarbon dated at 12 720 100 to 11 900 50 bp one bison bone was dated at 12 380 150 bp and one mammoth bone dated at 36 500 1000 redeposited bone included in younger sediments the mass accumulations are synchronous and are similar in their mode of formation the assemblage of mammoths in the achchagyi allaikha and berelyokh sites resulted from simultaneous deaths of a large number of animals probably herd family groups in one or several seasons it is very probable that the deposits in both cases were not of cultural origin the formation of the burials is a direct consequence of short but strong climatic warming bolling oscillation that resulted in many unfavorable environmental conditions among these the increase of snow cover and stronger spring floods were very notable bolling warming is a model of the large scale holocene event mass death of mammoths during the bolling phase was a prelude to their final extinction

the mysterious onset of the younger dryas abstract the 1300 year long younger dryas cold reversal 12 900 11 600 cal bp is seen most clearly in greenland ice cores contemporaneous changes of climate and environment in more southerly regions were variably expressed the precise timing of the abrupt younger dryas onset is still uncertain it was linked to a sudden increase in 14c manifest as a cliff where 14c dates drop from 11 000 to 10 600 radiocarbon years bp within a century of real time followed by a long plateau changes in ocean and or atmospheric circulation or solar radiation and even a comet impact have been proposed as triggers but the abruptness and severity of yd onset still elude explanation

synchroneity of tropical and high latitude atlantic temperatures over the last glacial termination a high resolution western tropical atlantic sea surface temperature sst record from the cariaco basin on the northern venezuelan shelf based on mg ca values in surface dwelling planktonic foraminifera reveals that changes in sst over the last glacial termination are synchronous within 30 to 90 years with the greenland ice sheet project 2 air temperature proxy record and atmospheric methane record the most prominent deglacial event in the cariaco record occurred during the younger dryas time interval when ssts dropped by 3 to 4 c a rapid southward shift in the atmospheric intertropical convergence zone could account for the synchroneity of tropical temperature atmospheric methane and high latitude changes during the younger dryas