charcoal analysis for paleoenvironmental interpretation a chemical assay a nitric acid digestion and ignition technique developed to measure relative frequencies of charcoal in lake and bog sediments measures the weight of charcoal relative to the dry weight of the sample percentage charcoal and gives results comparable to counting of microscopic charcoal differences in the two techniques caused by changes in sediment type were found especially in postsettlement and late glacial parts of cores charcoal values from sediments less than 100 yr old cannot be compared to older charcoal values unless wood charcoal and charcoal from fossil fuel burning are separated microscopically tests of this chemical assay on mixtures of known weights of charcoal leaves and sand give correlations between observed and expected values of 0 99 to 1 00

climate instability during the penultimate glaciation evidence from two high resolution loess records china the xinzhuangyuan and lijiayuan loess sections in the northwestern part of the chinese loess plateau were studied down to paleosol unit s2 which probably formed during marine oxygen isotopic stage 7 200 000 years b p the thickness of the loess soil sequence above s2 is 63 m at xinzhuangyuan and 43 m at lijiayuan a 2 cm sample spacing yields a mean depositional resolution of 50 80 years for the last and penultimate glacial loess units l1 and l2 and 200 years for the last interglacial soil unit sl thus enabling us to reconstruct high resolution climatic changes during the last two glacial interglacial cycles the grain size records of the two sections are regarded as a proxy for changes in the monsoon desert system over northern china results show that frequent large amplitude climatic oscillations on millennial timescales occurred during the penultimate glaciation in a manner similar to that during the last glaciation suggesting that suborbital scale climatic variations may be a common feature of the climate system during glacial periods of the pleistocene the last interglacial soil s1 is composed of three individual soils and two thin intervening loess horizons in both of the sections short term variations in grain size are not prominent within the soil complex implying the absence of strong millennial scale climatic oscillations during the last interglaciation in northern china

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

magnetic susceptibility evidence of monsoon variation on the loess plateau of central china during the last 130 000 years the magnetic susceptibility of loess and paleosols in central china represents a proxy climate index closely related to past changes of precipitation and vegetation and thus to summer monsoon intensity time series of magnetic susceptibility constructed for three loess paleosol sequences in the southern part of the chinese loess plateau document the history of summer monsoon variation during the last 130 000 yr they correlate closely with the oxygen isotope record of stages 1 to 5 in deep sea sediments soils were forming during intervals of strong summer monsoon whereas loess units were deposited at times of reduced monsoon intensity the chinese loess paleosol sequence can thus be viewed as a proxy record of asian monsoon variability extending over the last 2 5 myr

sphericity as a characteristic of solids from fossil fuel burning in a lake michigan sediment abstract the property of sphericity is used to identify some anthropogenic particles in a lake michigan sediment three classes of products from high temperature processes primarily fossil fuel burning have been isolated charcoals iron oxides and aluminosilicates the morphologies structures and surface characteristics are indicative of the combustion process

phosphate lu hf geochronology abstract igneous metamorphic and biogenic apatite contains lu and hf in proportions that make this mineral suitable for dating by the 176lu 176hf method we present a new method for separation of lu and hf from apatite that involves a single extraction column step for hf and a second exchange column step for lu this procedure allows rapid sample processing prior to analysis by mc icp ms results from the igneous gardiner skaergaard and khibina intrusions indicate that the closure temperature for the lu hf isotopic system in apatite is relatively high the lu hf isochron age of 60 ma for the skaergaard intrusion east greenland is older than the generally accepted emplacement age but does not appear to be a product of mixing a centimeter sized apatite from the otter lake area grenvillian province yields high and variable 176lu 177hf ratios showing that metamorphic apatite may in some cases allow for mono mineral dating the most important application of the method is undoubtedly its potential use for dating sedimentary formations although we find biogenic apatite in porous matrix highly susceptible to post depositional resetting of the lu hf isotopic system the preservation of a near depositional age for a shark tooth from the impermeable london clay and recent work on crystalline authigenic phosphorites earth planet sci lett 201 2002 203 show the lu hf system to be a promising tool for direct dating of sedimentary formations

stable carbon isotope records of black carbon on chinese loess plateau since last glacial maximum an evaluation on their usefulness for paleorainfall and paleovegetation reconstruction abstract stable carbon isotope composition of soil organic matter 13 c som has been widely used to infer past environmental or vegetation c 3 c 4 changes however as a carbonaceous product of incomplete burning of biomass the carbon isotope signature of black carbon bc has received little study and a limited usage on this purpose moreover the environmental or vegetation indication of bc carbon isotope composition 13 c bc in sedimentary records remains ambiguous although the 13 c bc is supposed to reflect carbon isotope composition of vegetation being burnt this deserves site specific studies here we analyzed 13 c bc and 13 c som on loess paleosol samples from lijiayuan and yangling sections on chinese loess plateau clp spanning the last glacial maximum to decipher the environmental or vegetation meaning of 13 c bc at each study site opposite changing patterns were observed on the 13 c bc values for the two sections the 13 c bc at yangling in southern part of the clp varied from 19 18 to 21 93 mean 20 62 with more positive values occurred during the middle holocene than those during the lgm demonstrating more c 4 plants occupied in the region during the warm humid middle holocene this is consistent with the changing pattern widely documented in 13 c som records over the clp during the same period by contrast the 13 c bc at lijiayuan in northwestern part of the clp changed within the range of 21 83 24 64 mean 23 34 and displayed more negative values during the early middle holocene with respect to the lgm period the 13 c bc at lijiayuan were about 2 5 lower than those at yangling indicating a northward decrease of c 4 plants on the clp the anti phased changes of 13 c bc at lijiayuan were considered to reflect variations in paleorainfall because the vegetation is dominated by c 3 plants at the study site and carbon isotope compositions of c 3 plants decrease as rainfall increases compared with 13 c som record at the same profile 13 c bc seem biased against capturing c 4 signal during mid holocene possibly due to dominance of c 3 plants at the study site during fire seasons and a potentially extra source of bc from forest fires occurred on surrounding mountains by contrast 13 c bc tend to exaggerate c 4 signal during the lgm attributed to a possible shift of fire season from spring to summer these findings suggest that we probably underestimate the abundance of c 4 plants during mid holocene and overestimate c 4 biomass during the lgm using bc carbon isotope composition

radiometric time scale for the upper eocene and oligocene based on k ar and rb sr dating of volcanic biotites from the pelagic sequence of gubbio italy several samples of unaltered volcanic biotite were recovered from five biostratigraphically and magnetostratigaphically controlled bentonite horizons in the continuous upper eocene oligocene pelagic carbonate sequence of gubbio northern italy k ar and rb sr dates on these samples offer a unique opportunity to calibrate with closely spaced points the late paleogene biostratigraphic and magnetostratigraphic time scales until now time scales have been constructed by interpolating between less certain and more widely spaced data points our combined k ar and rb sr dates are here used to calibrate the following five stratigraphic levels from top to bottom level 5 upper part of globorotalia opima opima planktonic foraminiferal zone upper part of indistinct np23 np24 nannoplankton zone and cp18 nannoplankton zone bottom of magnetic anomaly 9n 28 0 0 3 ma level 4 globigerina ampliapertura and cassigerinella chipolensis zone lower part of np23 zone and bottom of cp18 zone upper part of anomaly 12r 32 0 0 8 ma level 3 pseudohastigerina micra zone upper part of np21 and cp16b zones top of anomaly 13n 35 4 0 4 ma level 2 upper part of globigerinatheka semiinvoluta zone upper part of np18 and cp15a zones top of magnetic anomaly 16n 36 0 0 4 ma level 1 lower part of g semiinvoluta zone between zones np18 and np19 middle part of zone cp15a upper part of anomaly 17n 36 4 0 3 ma from these data the interpolated age for the much debated eocene oligocene boundary is 35 7 ma with a 2 standard deviation uncertainty of 0 4 ma

correlation of grassy lake and cedar lake ambers using infrared spectroscopy stable isotopes and palaeoentomology the late cretaceous grassy lake and cedar lake amber deposits of western canada are among north america s most famous amber producing localities although it has been suggested for over a century t

marine transgressions and the evolution of cretaceous dinosaurs fluctuations transgressions and regressions of intercon tinental sea ways during the mesozoic era affected the habitat area of coastal plains by alternately restricting the space during transgressive phases and expanding the space during regressive phases in western north america a coastal plain stretched along the eastern front of the young rocky mountains during most of the late cretaceous here we report results of a six year field study of the sediments and dinosaur remains from this coastal plain in montana that provide evidence that anagenesis characterized dinosaur evolution at this time and that the evolutionary pulse coincided with a marine transgression

40ar 39ar age and correlation of the nonmarine two medicine formation upper cretaceous northwestern montana u s a the age of the nonmarine two medicine formation of northwestern montana is currently based upon correlations with k ar dated western interior ammonite zones 40ar 39ar dating of biotite and plagioclase separated from four bentonites and one crystal rich tuff permits for the first time direct determination of the age of two medicine strata biotite and plagioclase from a bentonite 10 m below the top of the two medicine formation yield concordant 40ar 39ar ages of 74 ma while biotite and plagioclase from two bentonites and a crystal rich tuff from approximately 100 m above the base of the formation cluster in age around 80 ma the total duration of two medicine deposition is estimated using these new radio isotopic ages via extrapolation of an average rock accumulation rate the new 40ar 39ar ages facilitate regional correlation of the dinosaur dominated paleofauna recovered from the two medicine formation and help constrain the timing of the claggett and bearpaw transgressions the ages support correlatio

new insights into magnetic enhancement mechanism in chinese paleosols article i nfo magneticsusceptibilityof chineseloess paleosolsequenceshasbeenextensivelyusedasareliablepaleoclimatic proxy for reconstruction of the asian summer monsoon system and its enhancement is usually attributed to neoformation of fine grained ferrimagnetic particles via pedogenesis but there is little understanding of either the formation process of such magnetic particles or their actual form and grain sizes to investigate these problems scanning electron microscope observations were conducted on magnetic extracts from pristine loess and strongly pedogenicpaleosol samples from xifeng onthe chineseloess plateau both magneticextracts commonly contained coarse grained detrital magnetite with grain size ranging from a few mt o several tens of m however the magnetic extract from the mature paleosol sample additionally included coarse silicate parti cles with ultrafine ferrimagnetic inclusions while that from the pristine loess sample did not the size of the ferrimagnetic inclusions mainly ranged from tens to hundreds of nanometers the temperature dependent susceptibility and hysteresis loops of the paleosol sample combined with the stratigraphic variations of rock magnetic parameters showed that the pedogenic maghemite inclusions should be a potential contributor to magnetic enhancements in chinese paleosols the fine grained ferrimagnetic inclusions have been pedogenically formed by weathering of coarse grained fe bearing silicate minerals our proposed magnetic enhancement mechanism is consistent with the accepted rock magnetic result that magnetic enhancement in chinese paleosols is caused by pedogenic maghemite grains in superparamagnetic and single domain size regions the presence of ultrafine ferrimagnetic grains as inclusions within coarse silicate particles is also consis tent with han and jiang s 1999 significant experimental result that magnetic enhancement in chinese paleosols is mainly contributed by the 0 5 m sediment fractions

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

a new centrosaurine ceratopsid from the oldman formation of alberta and its implications for centrosaurine taxonomy and systematics centrosaurus brinkmani sp nov is distinguished from centrosaurus apertus by key features of its cranial ornamentation including the shape and orientation of the postorbital horn and parietal ornamentation at parietal locus 3 the shape of the parietal ornamentation at locus 2 and the possession of accessory parietal ossifications developed as short spines on the caudal parietal ramus this species is restricted to the oldman formation of southern alberta and is the oldest ceratopsid represented by diagnostic material in canada phylogenetic analysis of the centrosaurinae suggests that the development of spike like ornamentation at the parietal locus 3 parietal locus is inversely related to the development of the p1 parietal ornamentation

bentonite chemical features as proxy of late cretaceous provenance changes a case study from the western interior basin of canada abstract bentonite beds are fairly common in both marine and terrestrial upper cretaceous campanian maastrichtian deposits of the western interior basin of western canada and northwestern united states a detailed stratigraphic sedimentologic geochemical x ray fluorescence and mineralogical x ray diffraction study of twenty one bentonites from the puskwaskau and wapiti formations in the grande prairie area west central alberta canada is here presented major and trace element concentrations from altered volcanic ashes document the presence in the study area of predominantly trachyandesitic and rhyolitic volcanogenic products resulted from intense volcanic arc to within plate pyroclastic activity concentration values of high field strength elements hfse and selected large ion lithophile elements lile e g nb zr th and y obtained by x ray fluorescence spectroscopy strongly support the presence of multiple volcanic sources integrated paleoenvironmental and geochemical criteria for provenance determination indicate a bimodal occurrence of basic and acid volcanic products interpreted as reflection of source areas characterized by different tectonic setting and magmatic composition a comparative analysis of geochemical compositions between grande prairie bentonites and 30 known volcanic beds from central and southern alberta manitoba and montana 1 documents a trend toward more acidic and alkali depleted volcanic products during the late campanian early maastrichtian interval and 2 suggests a well constrained stratigraphic and geographic subdivision of the non marine successions of the foreland basin on the basis of geochemical characteristic of volcanic ash beds furthermore geochemical fingerprints of several decimeter to meter thick bentonite beds have been coupled with volcanic ash subsurface signature in order to investigate their role as marker beds this multiple approach provides a reliable tool for basin scale identification and correlation of non marine sedimentary successions

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

the long term paleomonsoon variation recorded by the loess paleosol sequence in central china abstract the loess paleosol sequence in central china during the last 2 5 ma is a good record of the asian monsoon variation which could be considered as the concrete realization of global paleoclimatic cycles the geological and biological evidence of the loess paleosol sequence indicates that the loess was mainly the dust deposits transported by the northerly wind of winter monsoons and also suffered to some extent from pedogenesis caused by weakened summer monsoons and that the paleosol accreted by the rather slow dust accumulation was closely related to strengthened summer monsoons an alternating occurrence of loess and paleosol in the luochuan section implies the variation history of warm humid climate with a summer monsoon dominance and cold dry climate with a winter monsoon dominance the magnetic susceptibility of loess and paleosol can be regarded as a proxy index of asian monsoon variation an analysis of the susceptibility curve and structure characters of luochuan section shows that the asian monsoon circulation was strengthened from early pleistocene to late pleistocene and the 500 ka bp point and 1200 ka bp point seem to be a threshold and a turning point respectively in terms of the long term paleomonsoon variation in asia

chinese loess and the paleomonsoon abstract this paper presents a general review of the recent research advances of the east asian paleomonsoon based mainly on studies of the loess soil sequences in the chinese loess plateau in the last 2 6 million years the paleomonsoonal history may be divided into about 166 events on a time scale of the earth s orbital variations during the last glacial period millenial scale oscillations of the monsoon system were prominent which can be fairly well correlated with the dansgaard oeschger cycles recognized in the greenland ice cores the monsoonal rainfall belt has experienced a wide repeated advance retreat change during the glacial interglacial cycles of the pleistocene both temporal and spatial changes of the monsoon system in the quaternary could have been linked closely to global ice volume variations

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

new chronology for the early miocene mammalian faunas of kisingiri western kenya new total fusion k ar ages indicate that all of the fossiliferous formations that make up the lower part of the early miocene kisingiri sequence in western kenya at rusinga island mfwangano island and karungu were deposited during an interval of less than 0 5 million years at c 17 8 ma ago this contrasts markedly with k ar ages previously published from these detrital tuffaceous formations which suggested that they were deposited over an interval of as much as 7 million years between 23 and 16 ma overlapping the age ranges of all other east african early miocene sites including koru songhor napak bukwa loperot muruarot and buluk in addition the analytical problems revealed by the new kisingiri results cast doubt on biotite ages which provide dating for the most important sites thus the strong differences between the kisingiri fauna and those of koru sonhor and napak long held to be due to ecology because of the apparent overlap in ages may actually be due to a difference in time if this view of the geochronology is correct it may now be possible to identify adaptive trends and evolutionary succession in the east african early miocene faunas

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

climate fire and vegetation between about 13 000 and 9200 14c yr b p in the chilean lake district abstract a pollen record from lago condorito 41 45 s 73 07 w shows that north patagonian rain forest taxa predominated between about 13 000 and 12 200 14c yr b p in the lowlands of southern chile near the city of puerto montt this was followed by the expansion and persistence of the conifer podocarpus nubigena between 12 200 and 9900 14c yr b p trees favored by disturbance expanded between 11 200 and 9900 14c yr b p concurrent with sharp and sustained increases of microscopic charcoal particles taxa of low elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14c yr b p following the disappearance of p nubigena these data suggest conditions approaching modern climate between about 13 000 and 12 200 14c yr b p the climate cooled between 12 200 and 9900 14c yr b p then quickly warmed to interglacial conditions stand replacing fires occurred near lago condorito between 11 200 and 9900 14c yr b p under cool temperate humid conditions the proximity and reported antiquity of the monte verde archeological site raise the possibility that these fires were set by human activities

coeval changes in grain size and sedimentation rate of eolian loess the chinese loess plateau to determine the temporal spatial relationship between strength of the winds transporting the chinese loess and aridity conditions of the loess source area six loess sections located respectively in the northern middle and southern loess plateau were studied grain size distributions were analyzed on loess paleosol samples that are closely spaced in the sections time scales were established by tuning each of the grain size records to theoretical changes in the earth s orbital parameters results obtained show that during the last two glacial cycles particle size of the loess co varies with apparent sedimentation rates suggesting that variations in winter monsoon intensity and the aridity of the loess source area are tightly coupled this proximal relationship is in striking contrast with the observation of distal eolian clays in north pacific sediments we propose that this phenomenon may result from the proximity of the loess plateau to the source area and from the significant control of the winter monsoon on the expansion retreat changes of the deserts in the northern and northwestern china

cave aerosols distribution and contribution to speleothem geochemistry there is developing interest in cave aerosols due to the increasing awareness of their impacts on the cave environment and speleothem this paper provides the first attempt to synthesize the issues processes of cave aerosol introduction transport deposition distribution and incorporation are explored and reviewed from existing literature key issues of specific aerosol processes of distribution and production as well as cave location and morphology effects are highlighted through the presentation of preliminary monitoring data this study identifies the strong relationship between cave ventilation cave aerosols and their consequent spatial distribution the contribution of cave aerosol deposition to speleothem geochemistry is modelled and evaluated using a mass balance framework as an example speleothem trace element data from obir cave austria are compared with aerosol inputs to evaluate their significance the mass balance study demonstrates that generally under normal continuous growth and environmental conditions aerosol deposition will be of only minor importance however it highlights specific scenarios in which aerosol contributions will be significant speleothem hiatuses or slow growth high aerosol deposition and secondary microbiological feedback

the first radiometric ages from the judith river formation upper cretaceous hill county montana a new isotopic age of ca 78 ma was obtained by the conventional k ar method and by laser fusion 40ar 39ar analysis of biotite and sanidine crystals from two bentonites in the judith river formation of kennedy coulee hill county montana the 40ar 39ar analyses yielded weighted mean ages of 78 2 0 2 ma biotite and 78 2 0 2 ma sanidine for sample 84mg8 3 4 and 79 5 0 2 ma biotite and 78 5 0 2 ma sanidine for sample 85mg7 16 1 these are the first isotopic age determinations from the judith river formation the dated bentonites in kennedy coulee bracket two significant judithian age mammal localities ucmp v77083 and v81234 the radioisotopic age of ca 78 ma for the hill county local faunas and correlations of other judithian local faunas with marine units suggest that the duration of the judithian was at least 5 ma judithian local faunas are probably correlative with the late campanian of the western interior similarities in the principal judithian mammalian faunas from alberta monta

a coupled environmental system formed at about 2 5 ma in east asia abstract the somewhat abrupt commencement of loess deposition on a large scale in north central china is palaeomagnetically measured at about 2 5 ma the formation of the dynamical conditions responsible for windblown loess processes implies a reorganization of the atmospheric circulation over eastern asia it is speculated that at that time the accelerated uplift of the tibetan plateau had reached a threshold height giving rise to the intensification and northward shift of the siberian high and deepening of the cyclone in the lee of the tibetan plateau the uplift of tibet and the resulting reorganization of atmospheric circulation at about 2 5 ma would initiate a coupled environmental system tibetan plateau inland desert loess plateau in eastern asia that could be a key system in understanding the onset of glaciation in northern hemisphere and climatic change in the quaternary the climatic shift from near continuous warm condition before 2 5 ma to frequent and chaotic fluctuations after is speculated to be triggered to a significant extent by the uplift of the tibetan plateau an orography cold surge albedo temperature feedback mechanism is developed in explaining the harsher climate over east asia during glacial time and is thought to be one of the major contributors in promoting glacial development on the globe

fire history and human activity revealed through poly cyclic aromatic hydrocarbon pah records at archaeological sites in the middle reaches of the yellow river drainage basin china abstract disentangling the role of natural and anthropogenic factors is a major challenge in paleofire studies here we introduce the molecular biomarkers of polycyclic aromatic hydrocarbon pahs combined with charcoal and black carbon in sediments of archaeological sites to identify anthropogenic signals of environmental change during the middle holocene in the prehistoric period an intensified fire regime period inferred on the basis of pahs char and macro charcoal levels has been attributed to intensified anthropogenic biomass burning from dry crop cultivation between 6500 and 5000 and 3900 3600 yr bp corresponding to the earliest chinese settlements during the miaodigou banpo iv culture and the development of the erlitou culture under drier climate conditions subsequently the fire frequency decreased notably between 4500 and 4000 yr bp as the climate became wetter and there were shifts in the frequency of high magnitude floods corresponding to the abandonment of late neolithic settlements in the floodplain changes in the pah fluxes in sediments are positively correlated with intensified fire regime periods consistent with the charcoal and black carbon fluxes during those periods principal component analysis of pah fluxes suggests that these intensified fire events have a pyrogenic signature implying that the pahs were derived from biomass burning of fuelwood and other woody plants in this study pahs in loess sediments have been used as the indicators of anthropogenic biomass burning through time meanwhile pahs also record the shift of modes of production and the evolution of human settlements as well as the choices made in response to limited natural resources to comprehensively analyze the paleofire records of pahs charcoal and black carbon combined with multiproxy evidence are needed to understand wildfire history as well as human land use and social and cultural development across the study regions in depth

determination of black carbon by chemical oxidation and thermal treatment in recent marine and lake sediments and cretaceous tertiary clays abstract several sample treatments and analytical methods for the measurement of black carbon in a wide variety of sediments were considered in which the removal of organic carbon is a critical step in the procedure a comparison between chemical oxidation and thermal treatment was conducted and the latter was shown to be inappropriate due to the polymerisation of organic matter using acid dichromate oxidation reactive kerogen was separated from black carbon in a variety of lake and marine and recent and ancient sediments with relatively small and quantifiable losses 1 6 of black carbon under carefully controlled reaction conditions

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

charred micro particles characterization in archaeological contexts identifying mixing between sediments with implications for stratigraphy abstract charred micro remains in archaeological sediments vary from large destruction layers to localized lenses and they are invaluable stratigraphic anchors when found in situ visual observations of black sediments are a good marker for primary depositions of burning events however an independent criteria is necessary to verify these sediments were not mixed with other contexts in this study a microarchaeological approach was used to quantify charred micro components in sediments from a pyrotechnological pit at qubur el walaydah allowing the assessment of their diffusion between sediments organic micro particles were purified from black lenses in situ and their surrounding sediments based on their density showing the organic fraction is composed of particles that are lighter than a density of 1 7 g ml and smaller than 1 mm3 thermal and structural characterizations show that the micro particles from black lenses are charred between 30 and 40 compared with 5 in the surrounding sediments a new method to quantify the charred micro particles was developed based on microscopy showing black lenses and hearths have between 40 000 110 000 charred micro particles per gram of sediments while their surrounding archaeological sediments have less than 20 000 these results show micro particles could be purified and characterized providing a quantifiable approach for assessing mixing between sediments based on particles concentrations one application is micro stratigraphic interpretations of primary depositions allowing portable microscopes on site to assess the mixing between sediments another application is to include the charred micro particles in the radiocarbon dating assemblage as evidence for in situ burning dating charred micro remains should be used only to solve chronological questions that do not require high resolution accuracy when cultural material and macro charred remains are not found

correlations among charcoal records of fires from the past 16 000 years in indonesia papua new guinea and central and south america microscopic charcoal preserved in lake and swamp sediments from 10 sites in indonesia and papua new guinea and from 5 sites in central and south america have been used to reconstruct long term fire histories for these two regions comparison of these records demonstrates that fire is promoted during periods of rapid climate change and high climate variability regardless of the presence or absence of humans broad synchrony of changes in corrected charcoal values in each region supports an atmospheric transmission of the climate signal via the dominant large scale atmospheric circulation systems walker circulation that appears to have persisted since 16 000 cal yr b p altered climate boundary conditions under the influence of changing el nino related variability insolation sea level and sea surface temperature all influenced the strength of this connection correlation of biomass burning records between the regions tends to increase in the holocene the main period of inverse correlation occurs during the younger dryas stade when extratropical climate most affected the tropics the strongest correlation between the two regions postdates 5000 cal yr b p when el nino related variability intensified fluctuations in tropical biomass burning are at least partly controlled by orbital forcing precession although extratropical climate influences and human activity are also important

black carbon records in chinese loess plateau over the last two glacial cycles and implications for paleofires abstract to study the temporal and spatial changes in paleofires over the chinese loess plateau black carbon concentrations were analyzed on the loess paleosol samples from three sections along a north south transect using the orbitally tuned time scales of the sections the black carbon mass sedimentation rates bcmsr were calculated results show that in the last two glacial cycles the bcmsr values in glacial periods are 2 3 times higher than in interglacial periods and the bcmsr variability has a relatively strong precession associated 23 ky period suggesting that the glacial cold dry climate conditions were apt to induce natural fires over the loess plateau comparison of the bcmsr records among the three loess sections demonstrates that natural fire occurrence was much more intensive and frequent in the northern loess plateau than in the southern part coinciding with the previous conclusion that the northern plateau has experienced a drier climate regime in both glacial and interglacial periods the substantial increase in bcmsr of the upper s0 relative to the lower s0 at lingtai and weinan indicates that human activities have exerted a significant influence on fire regimes in the middle and southern loess plateau during late holocene due to the relatively intensive agricultural usage of land

late cretaceous to early tertiary magnetostratigraphy of a continental sequence red deer valley alberta canada the red deer valley exposes a conformable 350 m thick late campanian to early paleocene fluvial deltaic coal bearing sequence named the edmonton group systematic sampling and paleomagnetic analysis of the dominant lithologies mudstones sandstones and shales were carried out over five sections correlated by coal seams to provide some 500 sites stratigraphic levels primary detrital remanent magnetization directions after alternating field cleaning produce a polarity reversal pattern correlatable to sea floor magnetic anomalies 29 33 the campanian maastrichtian boundary based upon the first appearance of wodehouseia and the maastrichtian paleocene cretaceous tertiary boundary based upon an ir anomaly associated with dinosaur and cretaceous palynofloral extinctions correlate closely magnetostratigraphically with the marine foraminiferal section at gubbio italy radiometric dating of bentonites has indicated the ages of these boundaries to be approximately 71 and 64 ma respectively