carbonate ion concentration in glacial age deep waters of the caribbean sea 1 on the basis of the whole foraminifera shell weights for g sacculifer and n dutertrei from caribbean cores it appears that the carbonate ion concentration of water at 1800 m depth in the open atlantic i e the depth of the caribbean sill was 14 mol kg greater during glacial time than during the holocene the sense of this difference is consistent with the observation that the 13c 12c ratio for benthic foraminifera from glacial age atlantic upper deep water was higher than that for their holocene equivalents it is also consistent with fragment to whole foraminifera results however as several questions regarding the assumptions involved in converting shell weights to paleocarbonate ion concentrations remain unanswered this reconstruction must be considered tentative critical in this regard are the assumptions that shell wall thicknesses were the same as today s at any given site during glacial time and that the 0 3 g per mol kg relationship between shell weight and carbonate ion concentration is applicable over the entire deep water column the records reported here reveal no evidence for an early holocene preservation event however that for core v28 122 documents a dissolution event close to the mis 5 4 boundary

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

july temperature during the second millennium reconstructed from idaho tree rings an 858 year proxy record of july temperature for east central idaho shows multi decadal periods of extreme cooling centered around ad 1300 1340 1460 and after ad 1600 these cold intervals are interrupted by prolonged warm spells in the early 1400s late 1500s and in the 1930s the spatial signature of the paleoclimate record is centered on the north central rockies and central great plains and expands over north america following a wave like pattern neither instrumental nor proxy data in idaho northeast valleys show unusual warming during the twentieth century climate episodes over the last three centuries are in broad agreement with the greenland borehole temperature history low frequency patterns are consistent with other northern hemisphere tree ring records for the late holocene and provide a chronology of warm and cold intervals during the little ice age

an evaluation of lohmann s foraminifera weight dissolution index down water column traverses of core top weights for three planktonic species confirm lohmann s 1995 relationship between foraminifera shell weight loss and bottom water carbonate ion content however they also suggest that the initial shell thickness varies with growth habitat and that the offset between bottom water and pore water carbonate ion concentration varies even on small space scales

sea surface temperatures of the western arabian sea during the last deglaciation 1 in this study we present a sea surface temperature sst record from the western arabian sea for the last 20 000 years we produced centennial scale d 18 o and mg ca sst time series of core niop929 with focus on the glacial interglacial transition the western arabian sea is influenced by the seasonal ne and sw monsoon wind systems lowest ssts occur during the sw monsoon season because of upwelling of cold water and highest ssts can be found in the low productivity intermonsoon season the mg ca based temperature record reflects the integrated sst of the sw and ne monsoon seasons the results show a glacial interglacial sst difference of 2c which is corroborated by findings from other arabian sea cores at 19 ka b p a yet undescribed warm event of several hundred years duration is found which is also reflected in the d 18 o record a second centennial scale high sst low d 18 o event is observed at 17 ka b p this event forms the onset of the stepwise yet persistent trend toward holocene temperatures highest mg ca derived ssts in the niop929 record occurred between 13 and 10 ka b p interglacial sst is 24c indicating influence of upwelling the onset of arabian sea warming occurs when the north atlantic is experiencing minimum temperatures the rapid temperature variations at 19 17 and 13 ka b p are difficult to explain with monsoon changes alone and are most likely also linked to regional hydrographic changes such as trade wind induced variations in warm water advection

methodological advances in the use of faunal gradient analysis for regional high resolution correlation in the type cincinnatian series upper ordovician abstract historically strata of the type cincinnatian series have not been correlated with precision because of an assumption that individual beds are not regionally persistent in an effort to establish a regional chronostratigraphic framework for the cincinnatian a technique has been developed recently that uses gradient analysis of fossil abundance data to compare vertical trends in biotic composition among five localities that span a distance of 65 km using faunal data to establish correlations below the meter scale has been problematic because variability in the lateral expression of many beds has made it difficult to sample equivalent fossiliferous strata at all localities here this correlation technique is modified in an attempt to draw meter scale correlations of the kope and lower fairview formations this modification involves grouping fossil census samples into stratigraphic intervals such that the stratigraphic spacing of samples is identical at all localities samples are binned using two protocols one that groups samples into 0 5 m thick intervals and another that groups samples by lithologically delineated meter scale cycles gradient analysis of binned samples using both protocols produces curves in which patterns in faunal composition below the meter scale can be correlated with success only for limited intervals at select localities the inability to consistently correlate at high resolution might indicate that correcting for regional variations in the expression of strata is not enough alternatively the ability to correlate some intervals below the meter scale suggests that other problems such as fine scale lateral variations in biotic composition might be impeding correlation in addition gradient analysis techniques are employed at a new locality to extend the lateral breadth of the existing broader scale chronostratigraphic framework by approximately 40 km although interpreted to be in an up ramp direction from previously measured localities this new locality does not have an overall shallower water faunal assemblage until just below the kope fairview contact

holocene fire occurrence and alluvial responses at the leading edge of pinyon juniper migration in the northern great basin usa abstract fire and vegetation records at the city of rocks national reserve ciro south central idaho display the interaction of changing climate fire and vegetation along the migrating front of single leaf pinyon pinus monophylla and utah juniper juniperus osteosperma radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response and fossil woodrat neotoma middens revealed pinyon and juniper arrivals fire peaks occurred 10 700 9500 7200 6700 2400 2000 850 700 and 550 400 cal yr bp whereas 9500 7200 6700 4700 and 1500 1000 cal yr bp are fire free wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late holocene whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid holocene increased fires during the wetter and more variable late holocene suggest variable climate and adequate fuels augment fires at ciro utah juniper and single leaf pinyon colonized ciro by 3800 and 2800 cal yr bp respectively though pinyon did not expand broadly until 700 cal yr bp increased fire related deposition coincided with regional droughts and pinyon infilling 850 700 and 550 400 cal yr bp early and late holocene vegetation change probably played a major role in accelerated fire activity which may be sustained into the future due to pinyon juniper densification and cheatgrass invasion

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

western equatorial pacific deep water carbonate chemistry during the last glacial maximum and deglaciation using planktic foraminiferal mg ca to reconstruct sea surface temperature and seafloor dissolution 1 we present a reconstruction of deep water carbonate saturation state co32 in the western equatorial pacific for the last glacial maximum lgm and deglaciation based on changes in the mg ca ratio of planktic foraminifers with increased water depth our data suggest there have been changes in bottom water co32 over the past 25 000 years at water depths as shallow as 1 6 km the co32 reconstruction for the lgm suggests co32 was similar or slightly higher than modern values between 1 6 and 2 0 km shifting sharply to lower values an average 30 mol kg lower below 2 5 km the shift in chemistry between 2 0 and 2 5 km supports a hypothesis that pacific overturning circulation occurred deeper during the lgm with a slightly more ventilated water mass above 2 0 km the data are not consistent with enhanced preservation in this region of the deep pacific at depths greater than 2 5 km suggesting that the long held view of better preservation throughout the glacial deep pacific must be reevaluated for the deglaciation we have evidence of a co32 maximum that suggests enhanced deglacial preservation between 1 6 and 4 0 km in comparison to the holocene and the lgm the deglacial co32 was as much as 28 mol kg higher than modern between 1 6 and 4 0 km results suggest carbonate burial rates were 1 5 times greater during the deglacial than the over the past 5 kyr

el nino controls holocene rabbit and hare populations in baja california abstract the el nino southern oscillation enso is a major source of climatic variation worldwide with significant impacts on modern human and animal populations however few detailed records exist on the long term effects of enso on prehistoric vertebrate populations here we examine how lagomorph rabbit and hare deposition rate population age structure and taxonomic composition from abrigo de los escorpiones a well dated trans holocene vertebrate fauna from northern baja california mexico vary as a function of the frequency of wet el nino events and eastern pacific sea surface temperatures ssts derived from eastern pacific geological records faunal indices vary significantly in response to el nino based precipitation and sst with substantial moisture driven variability in the middle and late holocene the late holocene moisture pulse is coincident with previously documented changes in the population dynamics of other vertebrates including humans as the frequency and intensity of enso is anticipated to vary in the future these results have important implications for change in future vertebrate populations

assessing ocean alkalinity for carbon sequestration over the coming century humanity may need to find reservoirs to store several trillions of tons of carbon dioxide co2 emitted from fossil fuel combustion which would otherwise cause dangerous climate change if it were left in the atmosphere carbon storage in the ocean as bicarbonate ions by increasing ocean alkalinity has received very little attention yet recent work suggests sufficient capacity to sequester copious quantities of co2 it may be possible to sequester hundreds of billions to trillions of tonnes of c without surpassing post industrial average carbonate saturation states in the surface ocean when globally distributed the impact of elevated alkalinity is potentially small and may help ameliorate the effects of ocean acidification however the local impact around addition sites may be more acute but is specific to the mineral and technology the alkalinity of the ocean increases naturally because of rock weathering in which 1 5 moles of carbon are removed from the atmosphere for every mole of magnesium or calcium dissolved from silicate minerals e g wollastonite olivine anorthite and 0 5 moles for carbonate minerals e g calcite dolomite these processes are responsible for naturally sequestering 0 5 billion of co2 tons per year alkalinity is reduced in the ocean through carbonate mineral precipitation which is almost exclusively formed from biological activity most of the previous work on the biological response to changes in carbonate chemistry have focused on acidifying conditions more research is required to understand carbonate precipitation at elevated alkalinity to constrain the longevity of carbon storage a range of technologies have been proposed to increase ocean alkalinity accelerated weathering of limestone enhanced weathering electrochemical promoted weathering ocean liming the cost of which may be comparable to alternative carbon sequestration proposals e g 20 100 tco2 1 there are still many unanswered technical environmental social and ethical questions but the scale of the carbon sequestration challenge warrants research to address these

late pleistocene and holocene seasonal temperatures reconstructed from fossil beetle assemblages in the rocky mountains abstract mutual climatic range mcr analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14 500 to 400 yr b p the fossil sites represent a transect of the rocky mountain region from northern montana to central colorado the analyses yielded estimates of mean july and mean january temperatures the oldest assemblage 14 500 yr b p yielded mean july values of 10 11 c colder than present and mean january values 26 30 c colder than present postglacial summer warming was rapid as indicated by an assemblage dating 13 200 yr b p with mean july values only 3 4 c cooler than modern by 10 000 yr b p several assemblages indicate warmer than modern mean summer and winter values by 9000 yr b p mcr reconstructions indicate that both summer and winter temperatures were already declining from an early holocene peak mean july values remained above modern levels and mean january values remained below modern levels until 3000 yr b p a series of small scale oscillations followed

decadal changes in the aragonite and calcite saturation state of the pacific ocean 1 based on measurements from the woce jgofs global co2 survey the clivar co2 repeat hydrography program and the canadian line p survey we have observed an average decrease of 0 34 yr 1 in the saturation state of surface seawater in the pacific ocean with respect to aragonite and calcite the upward migrations of the aragonite and calcite saturation horizons averaging about 1 to 2 m yr 1 are the direct result of the uptake of anthropogenic co2 by the oceans and regional changes in circulation and biogeochemical processes the shoaling of the saturation horizon is regionally variable with more rapid shoaling in the south pacific where there is a larger uptake of anthropogenic co2 in some locations particularly in the north pacific subtropical gyre and in the california current the decadal changes in circulation can be the dominant factor in controlling the migration of the saturation horizon if co2 emissions continue as projected over the rest of this century the resulting changes in the marine carbonate system would mean that many coral reef systems in the pacific would no longer be able to sustain a sufficiently high rate of calcification to maintain the viability of these ecosystems as a whole and these changes perhaps could seriously impact the thousands of marine species that depend on them for survival

the use of faunal gradient analysis for intraregional correlation and assessment of changes in sea floor topography in the type cincinnatian abstract in paleobiology and stratigraphy there is a growing need to develop high resolution chronostratigraphic frameworks at regional scales which would permit unprecedented assessments of spatiotemporal variation in preserved biotas here we present an intraregional correlation for the kope and lower fairview formations of the type cincinnatian on the basis of detrended correspondence analysis dca of faunal census data we believe that the method also holds promise as a tool of correlation in other fossiliferous venues the data were collected directly in the field at closely spaced stratigraphic intervals but with relatively coarse taxonomic and quantitative data resolution this approach is independent of lithologic assessments and does not require the delineation of sequence stratigraphic architecture in the study area faunal curves were constructed for each locality on the basis of stratigraphic changes in sample scores for dca axis 1 the curves were smoothed to reveal a long term signal of

late glacial to early holocene climate changes from a central appalachian pollen and macrofossil record abstract a late glacial to early holocene record of pollen plant macrofossils and charcoal has been obtained from two cores from browns pond in the central appalachians of virginia an ams radiocarbon chronology defines the timing of moist and cold excursions superimposed on the overall warming trend from 14 200 to 7500 14 c yr b p this site had cold moist conditions from ca 14 200 to 12 700 14 c yr b p with warming at 12 730 11 280 and 10 050 14 c yr b p a decrease in deciduous broad leaved tree taxa and pinus strobus haploxylon pollen simultaneous with a reexpansion of abies denotes a brief cold reversal from 12 260 to 12 200 14 c yr b p a second cold reversal inferred from increases in montane conifers is centered at 7500 14 c yr b p the cold reversals at browns pond may be synchronous with climate change in greenland and northwestern europe warming at 11 280 14 c yr b p shows the complexity of regional climate responses during the younger dryas chronozone

pattern and forcing of northern hemisphere glacier variations during the last millennium time series depicting mountain glacier fluctuations in the alps display generally similar patterns over the last two centuries as do chronologies of glacier variations for the same interval from elsewhere in the northern hemisphere episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production as inferred from acidity variations in a greenland ice core advances occur whenever acidity levels rise sharply from background values to reach concentrations 1 2 equiv h kg above background a phase lag of about 10 15 yr equivalent to reported response lags of alpine glacier termini separates the beginning of acidity increases from the beginning of subsequent ice advances a similar relationship but based on limited and less reliable historical data and on lichenometric ages is found for the preceding 2 centuries calibrated radiocarbon dates related to advances of non calving and non surging glaciers during the earlier part of the little ice age display a comparable consistent pattern an interval of reduced acidity values between about 1090 and 1230 a d correlates with a time of inferred glacier contraction during the medieval optimum the observed close relation between noothern hemisphere glacier fluctuations and variations in greenland ice core acidity suggests that sulfur rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations and therefore of climate on a decadal scale the amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of little ice age alacier advances ca 0 5 1 2 c as inferred from depression of equilibrium line altitudes

calcite dissolution in sediments of the ontong java plateau in situ measurements of pore water o2 and ph we present in situ electrode measurements of sediment resistivity pore water oxygen and pore water ph from three stations between 2300 and 3000 m depth on the ontong java plateau in the western equatorial pacific one of these stations is also the site of a concurrent benthic chamber incubation experiment jahnke et al 1994 the pore water oxygen data and a steady state diffusion and reaction model constrain the depth dependent rate of oxic respiration in the sediments and imply a diffusive flux of oxygen to the sediments of 10 21 mol cm 2 yr 1 given these respiration rates the pore water ph data cannot be explained without calcite dissolution driven by metabolically produced co2 the dissolution necessary to explain the observations quantified by a statistical approach is 3 5 6 mol cm 2 yr 1 which corresponds to at least 20 40 of the calcite rain to these sediments over 65 of the total dissolution is driven by metabolic co2 oxygen fluxes and net calcite dissolution constrained by the electrode data are compatible with the benthic chamber measurements of jahnke et al 1994 the dissolution flux while a significant part of the early diagenesis of calcite in these sediments is less than would be predicted by earlier models of dissolution and jahnke et al 1994 probably could not distinguish it from zero with the benthic chamber technique the dissolution rates found in this study are lower than previous estimates because the respiration reaction is concentrated near the sediment water interface and the calcite dissolution rate constants are very small the statistical evaluation of the pore water ph data and model constrain the calcite dissolution rate constant to 0 005 0 16 d 1 following the general trend of lower values determined by in situ techniques rather than by laboratory methods

bryozoan bathymetric gradients within a late ordovician epeiric sea the large scale spatial zonation of the late ordovician epeiric sea in north america is reflected in the distributions of bryozoans and other invertebrates their major life zones biomes reflect changing patterns of sedimentation across the platform from major siliciclastic to carbonate lithotopes deeper water within the epeiric sea most likely existed in an area centered on the michigan basin and between the clastic wedges of the taconic orogen and the extensive cratonic carbonate platform stratigraphic gradients in the cincinnati arch area indicate a first order cycle of transgression regression throughout the late ordovician on which second order fluctuations in sea level have been superimposed the second order fluctuations indicate three transgressive regressive subcycles closely corresponding to the eden maysville and richmond stages

the effect of holocene temperature fluctuations on the evolution and ecology of neotoma woodrats in idaho and northwestern utah abstract animals respond to climatic change by adapting or by altering distributional patterns how an animal responds is influenced by where it is positioned within its geographic range the probability of extirpation is increased near range boundaries here we examine the impact of holocene climatic fluctuations on a small mammalian herbivore the bushy tailed woodrat neotoma cinerea at five locations within south central idaho and northwestern utah previous work demonstrated that woodrats adapt to temperature shifts by altering body size we focus here on the relationship between body mass temperature and location within the geographic range body mass is estimated by measuring fossil fecal pellets a technique validated in earlier work overall we find the predicted phenotypic response to climate change animals were larger during cold periods and smaller during warmer episodes however we also identify several time periods when changes in environmental temperature exceeded the adaptive flexibility of n cinerea a smaller bodied species the desert woodrat n lepida apparently invaded lower elevation sites during the mid holocene despite being behaviorally and physically subordinate to n cinerea analysis of contemporary patterns of body size and thermal tolerances for both woodrat species suggests this was because of the greater heat tolerance of n lepida the robust spatial relationship between contemporary body size and ambient temperature is used as a proxy to reconstruct local climate during the holocene

investigating a symmetry in a small mammal s response to warming and cooling events across western north america over the late quaternary many mammalian populations conform spatially and temporally to bergmann s rule this ecogeographic pattern is driven by selection for larger body masses by cooler temperatures and smaller ones by warming temperatures however it is unclear whether the response to warming or cooling temperatures is a symmetrical studies of the evolutionary record suggest that mammals evolve smaller body sizes more rapidly than larger ones suggesting that it may be easier to adapt to warming climates than cooling ones here we examine the potential asymmetrical response of mammals to past temperature fluctuations we use the fossil midden record of the bushy tailed woodrat neotoma cinerea a well studied animal that generally conforms to bergmann s rule to test the ability of populations to respond to warming versus cooling climate throughout its modern range in western north america over the late quaternary we quantified the response to temperature change as characterized by the greenland ice sheet project 2 temperature record using n cinerea presence absence and darwins our results show that populations within the modern range of n cinerea show little difference between warming and cooling events however northern peripheral populations are absent during older cooler periods possibly due to climate or taphonomy our study suggests adaptation in situ may be an underestimated response to future climate change

within taxon morphological diversity in late quaternary neotoma as a paleoenvironmental indicator bonneville basin northwestern utah usa ecological data indicate that as the amount of precipitation in an arid areas increases so too does mammalian taxonomic richness this correspondence has been found in two late quaternary mammalian faunas from utah one from homestead cave in the bonneville basin we use the remains of two species of woodrat neotoma cinerea and neotoma lepida from homestead cave to test the hypothesis that as the amount of precipitation in an arid area increases so too does morphological diversity within individual mammalian taxa morphological diversity is measured as corrected coefficients of variation and as richness of size classes of mandibular alveolar lengths coefficients of variation for n cinerea are few and coincide with moisture history if temporally successive small samples are lumped together more abundant coefficients of variation for n lepida coincide only loosely with moisture history likely because such coefficients measure dispersion but not necessarily other aspects of variation richness of size classes of n lepida is high during the early and late holocene when moisture was high and lowest during the middle holocene when climate was most arid d 2005 university of washington all rights reserved

pliocene arctic temperature constraints from the growth rings and isotopic composition of fossil larch instrumental records reveal that the current rate of arctic warming greatly exceeds mean global warming however arctic temperatures during the pliocene were considerably warmer than present making it an excellent time period for investigating potential consequences of current warming trends here we focus on an early pliocene 4 to 5 ma peat deposit from ellesmere island characterized by a remarkable fossil assemblage representative of a modern boreal forest among the fossils are wellpreserved samples of an extinct larch larix groenlandii which were exploited as an archive of paleoclimatic information we reconstruct pliocene terrestrial temperatures in the high arctic using a novel approach that combines measurements of ring width and oxygen isotopes this technique was calibrated by analyzing modern analog larch growing at the northern extent of their range and accounting for biotic fractionation of oxygen isotopes using a global database of modern trees based on this approach we estimated mean annual temperature in the arctic during the pliocene to be 5 5 1 9 c indicating that arctic temperatures were 14 2 c warmer than today this more precise multi proxy estimate is slightly warmer than previous estimates derived from empirical evidence and general circulation models our results also demonstrate that the biotic fractionation of oxygen isotopes in cellulose is non linear and dependent upon regional factors affecting aridity such as latitude and elevation therefore the simultaneous measurement of oxygen isotopes and morphological characteristics in paleovegetation can be useful in constraining climatic variables of earth s past

response of bushy tailed woodrats neotoma cinerea to late quaternary climatic change in the colorado plateau abstract temperature profoundly influences the physiology and life history characteristics of organisms particularly in terms of body size because so many critical parameters scale with body mass long term temperature fluctuations can have dramatic impacts we examined the response of a small mammalian herbivore the bushy tailed woodrat neotoma cinerea to temperature change from 20 000 yr b p to present at five sites within the colorado plateau our investigations focused on the relationship between temperature plant composition and abundance and woodrat size body size was estimated by measuring fossil fecal pellets a technique validated in earlier work we found significant and highly covariable patterns in body mass over the five locations suggesting that responses to temperature fluctuations during the late quaternary have been very similar although woodrat mass and the occurrence of several plant species in the fossil record were significantly correlated in virtually all instances changes in woodrat size preceded changes in vegetational composition these results may be due to the greater sensitivity of woodrats to temperature or to the shorter generation times of woodrats as compared to most plants an alternative hypothesis is that winter temperatures increased before summer ones woodrats are highly sensitive to warmer winters whereas little response would be expected from forest woodland plants growing at their lower limits our work suggests that woodrat size is a precise paleothermometer yielding information about temperature variation over relatively short term temporal and regional scales

biogeography of ordovician bryozoans abstract the following biogeographic patterns have been determined from a quantitative analysis of the global distribution of the ordovician genera arenig faunas are of low diversity with provinces appearing in north america and baltica three provinces appear in the llanvirn a baltic province a north american province and a siberian province bryozoan provinciality is most pronounced in the llandeilo and caradoc with four provinces appearing north american baltic siberian and a mediterranean province consisting of faunas from southern europe and northern africa a dramatic decrease in provinciality occurred in the ashgill as only two provinces are recognizable a north american siberian province and a baltic mediterranean province subprovincial units or biomes existed on the north american baltic and siberian plates as geosynclinal and platform faunas can be distinguished biomes are also recognized in north american caradoc and ashgill platform faunas and correspond to major lithotopes the baltic fauna was an open ocean fauna which also inhabited oceanic islands and localities around the north american continental margin the presence of a baltic bryozoan fauna in mid to late ashgill formations of the missouri southern illinois region may indicate the invasion of an oceanic fauna into the north american midcontinent through the subsiding reelfoot basin a precursor to the mississippi embayment baltic migrants from the missouri region settled in adjacent midwestern localities forming the maquoketa biome

holocene multidecadal and multicentennial droughts affecting northern california and nevada abstract continuous high resolution 18 o records from cored sediments of pyramid lake nevada indicate that oscillations in the hydrologic balance occurred on average about every 150 years yr during the past 7630 calendar years cal yr the records are not stationary during the past 2740 yr drought durations ranged from 20 to 100 yr and intervals between droughts ranged from 80 to 230 yr comparison of tree ring based reconstructions of climate change for the past 1200 yr from the sierra nevada and the el malpais region of northwest new mexico indicates that severe droughts associated with anasazi withdrawal from chaco canyon at 820 cal yr bp calendar years before present and final abandonment of chaco canyon mesa verde and the kayenta area at 650 cal yr bp may have impacted much of the western united states during the middle holocene informally defined in this paper as extending from 8000 to 3000 cal yr bp magnetic susceptibility values of sediments deposited in pyramid lake s deep basin were much larger than late holocene 3000 0 cal yr bp values indicating the presence of a shallow lake in addition the mean 18 o value of caco 3 precipitated between 6500 and 3430 cal yr bp was 1 6 less than the mean value of caco 3 precipitated after 2740 cal yr bp numerical calculations indicate that the shift in the 18 o baseline probably resulted from a transition to a wetter 30 and cooler 3 5 c climate the existence of a relatively dry and warm middle holocene climate in the truckee river pyramid lake system is generally consistent with archeological sedimentological chemical physical and biological records from various sites within the great basin of the western united states two high resolution holocene climate records are now available from the pyramid and owens lake basins which suggest that the holocene was characterized by five climatic intervals tic and 18 o records from owens lake indicate that the first interval in the early holocene 11 600 10 000 cal yr bp was characterized by a drying trend that was interrupted by a brief 200 yr wet oscillation centered at 10 300 cal yr bp this was followed by a second early holocene interval 10 000 8000 cal yr bp during which relatively wet conditions prevailed during the early part of the middle holocene 8000 6500 cal yr bp high amplitude oscillations in tic in owens lake and 18 o in pyramid lake indicate the presence of shallow lakes in both basins during the latter part of the middle holocene 6500 3800 cal yr bp drought conditions dominated owens lake desiccated and lake tahoe ceased spilling to the truckee river causing pyramid lake to decline at the beginning of the late holocene 3000 cal yr bp lake tahoe rose to its sill level and pyramid lake increased in volume

surface water conditions and calcium carbonate preservation in the fram strait during marine isotope stage 2 28 8 15 4 kyr 1 we present a high resolution record of calcium carbonate preservation alongside the distribution pattern of planktic foraminifera from the fram strait the record covers the marine isotope stage mis 2 28 8 to 15 4 kyr including the last glacial maximum lgm and the early deglaciation in multidecadal temporal resolution the investigation is based on the distribution patterns of planktic foraminifera stable isotopes mean shell weight of neogloboquadrina pachyderma the degree of fragmentation of planktic shells caco3 content and geochemical and sedimentological data the dissolution proxies indicate long lasting periods of markedly reduced preservation of calcium carbonate at 28 8 27 2 24 1 23 2 and 16 6 15 4 kyr in addition to a number of short lasting periods 300 year during the lgm these periods are accompanied by a simultaneous and significant reduction in specimens of subpolar planktic foraminifera indicating a southward expansion of arctic surface water masses prolonged periods with high abundances of subpolar foraminiferal species and good preservation of calcium carbonate are attributed to increased influence of atlantic water masses which appears to persist throughout most of the mis 2 comparison to holocene mis 1 shell weight records shows that the preservation during mis 2 was overall better even during the events of dissolution this was probably a reflection of the low concentration of atmospheric co2 at the time

modeling the dissolution of settling caco3 in the ocean 1 the production transport and dissolution of carbonate shells plays an important role in the global carbon cycle for instance these processes affect the ocean s co32 concentration which on glacial interglacial timescales is involved in the regulation of atmospheric pco2 the saturation state of the ocean with respect to calcium carbonate suggests that any dissolution of calcium carbonate takes place not in the water column but at the seafloor on the other hand several authors suggest that a significant part of the dissolution takes place in the upper part of the water column in the present paper a simple model is presented to investigate under which circumstances dissolution of calcium carbonate in the water column may be plausible our analysis also includes dissolution facilitated by co2 release from organic carbon remineralization which may generate a microenvironment that is undersaturated with respect to caco3 in marine snow aggregates however respiration driven dissolution is shown to be insignificant due to the size and settling velocities of the aggregates with respect to aragonite dissolution in the water column attributable to the bulk saturation state alone is significant and may well contribute to the alkalinity maximum in the undersaturated intermediate waters of the north pacific ocean the suggested large loss of calcium carbonate dissolved in the water column 60 80 of caco3 production however cannot be explained by the mechanisms investigated here

deepwater carbonate ion concentrations in the western tropical pacific since 250 ka evidence for oceanic carbon storage and global climate influence we present new size normalized weight snw co32 core top calibrations for three planktonic foraminiferal species and assess their reliability as a paleo alkalinity proxy snws of globigerina sacculifer and neogloboquadrina dutertrei can be used to reconstruct past deep pacific co32 whereas snws of pulleniatina obliquiloculata are controlled by additional environmental factors based on this methodological advance we reconstruct snw based deepwater co32 for core wp7 from the western tropical pacific since 250 ka secular variation in the snw proxy documents little change in deep pacific co32 between the last glacial maximum and the holocene further back in time deepwater co32 shows long term increases from marine isotope stage mis 5e to mis 3 and from early mis 7 to late mis 6 consistent with the coral reef hypothesis that the deep pacific ocean carbonate system responded to declining shelf carbonate production during these two intervals during deglaciations we have evidence of co32 peaks coincident with terminations 2 and 3 which suggests that a breakdown of oceanic vertical stratification drove a net transfer of co2 from the ocean to the atmosphere causing spikes in carbonate preservation i e the deglacial ventilation hypothesis during mis 4 a transient decline in snw based co32 along with other reported co32 and or dissolution records implies that increased deep ocean carbon storage resulted in a global carbonate dissolution event these findings provide new insights into the role of the deep pacific in the global carbon cycle during the late quaternary

impact of the ocean carbonate chemistry on living foraminiferal shell weight comment on carbonate ion concentration in glacial age deep waters of the caribbean sea by w s broecker and e clark broecker and clark 2002 use the size normalized weight of planktic foraminifera to estimate the carbonate ion concentration co3 of atlantic glacial upper deep water this method was introduced by lohmann 1995 and is based on the fact that within a defined size fraction dissolution decreases shell weight in proportion to the degree of undersaturation with respect to caco3 based on the following assumptions 1 the thickness of the foraminiferal shell wall does not depend on growth conditions 2 the saturation co3 for calcite co3 sat increases by 20 mol kg 1 km 1 broecker and clark 2001 3 the weight loss slope is universal and ca 0 3 g mol kg 1 1 broecker and clark 2001 4 the offset between the bottom water and pore water co3 was the same during glacial time as during the holocene broecker and clark 2002 calculate that the co3 of atlantic glacial upper deep water was 14 mol kg 1 higher than during the holocene although they recognize that some of their assumptions are not strictly valid they do not assess the impact of those assumptions on their co3 estimate here we comment on several of those assumptions and attempt to quantify their impact on broecker and clark s 2002 calculations

exploring foraminiferal sr ca as a new carbonate system proxy in present day paleoclimate research one of the most pressing challenges is the reconstruction of atmospheric co2 concentrations a variety of proxies for several components of the marine inorganic carbon system have been developed in this context e g b isotopes b ca u ca to allow reconstruction of past seawater ph hco3 and co32 and thereby facilitate estimates of past atmospheric pco2 based on culture experiments using the benthic foraminifera ammonia sp we describe a positive correlation between sr ca and the carbonate system namely dic bicarbonate ion concentration foraminiferal sr ca ratios provide potentially additional constraints on the carbonate system proxy because the analysis of foraminiferal carbonate sr ca is straightforward and not easily contaminated applying our calibration to a published dataset of paleo sr ca suggests the validity of sr ca as a carbonate system proxy furthermore we explore how our data can be used to advance conceptual understanding of the foraminiferal biomineralization mechanism

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

multivariate data analysis in palaeoecology and palaeobiogeography a review abstract palaeoecologists and palaeobiogeographers are often confronted with large multivariate data sets from which fossil communities assemblages or associations or faunal provinces are to be recognized the complex multidimensional nature of these data sets the recognition of the enormous variation of communities and environments both in space and time and the difficulties of dealing with these problems by the human mind justify the use of multivariate statistical methods in palaeoecology and palaeobiogeography concepts and basic procedures of several commonly used multivariated statistical methods of palaeoecology and palaeobiogeography are reviewed in the wider context of quantitative community ecology and biogeography basic assumptions about data structure and theoretical and practical limitations are discussed the emphasis is on evaluation of binary similarity coefficients and two multivariate approaches cluster analysis and ordination thirty nine binary similarity coefficients are evaluated against nine criteria jaccard s coefficient of community is found most suitable as a similarity measure between samples under the conditions tested algorithmic procedures of cluster analysis especially the agglomerative hierarchical cluster analysis techniques and indirect ordinations particularly polar ordination principal component analysis principal coordinate analysis correspondence analysis detrended correspondence analysis and nonmetric multidimensional scaling are outlined and their applicability to palaeoecological and palaeobiogeographical data is discussed where the data are appropriate an integration of cluster analysis and ordination is suggested to be applied to the same data

planktic foraminiferal dissolution in the twilight zone abstract calcite dissolution of planktic foraminifers that settle from the surface ocean to depths has been assessed using the weight size relationship of tests and correlated to carbonate ion concentration co 3 2 of ambient sea water globigerina bulloides and globigerinita glutinata were sampled from the north atlantic and the arabian sea during different seasons spring and fall and the monsoons respectively test weight has been determined for single tests from narrow size classes 250 8 m and 300 7 m minimum test diameter initial test weight of both species in surface waters differs between regions and seasons weight loss of settling tests in the twilight zone between 100 and 1000 m water depths averaged 19 below the twilight zone 1000 2500 m no weight loss occurs on average and tests may even gain weight remineralization of settling planktic foraminiferal tests is most pronounced at maximum co 3 2 accordingly strong dissolution occurs in the twilight zone at the depth of maximum decrease in co 3 2 it is assumed that dissolution of planktic foraminiferal calcite is caused by co 3 2 under saturation inside the test buffered by diffusive exchange of co 3 2 ions with the ambient sea water through the pores and aperture consequently reconstruction of small scale differences in seawater co 3 2 from test weight alone is not feasible and systematic correlation between test weight and co 3 2 of the ambient sea water is statistically not significant at constant co 3 2 remineralization cannot be deduced from test weight neither at high nor low co 3 2 saturation in total our data suggest that the global vertical planktic foraminiferal caco 3 flux is about 19 lower than calculated by schiebel 2002 planktic foraminiferal sedimentation and the marine calcite budget global biogeochemical cycles 16 4 1065 doi 10 1029 2001gb001459

lapse rates and other variables applied to estimating paleoaltitudes from fossil floras abstract a previous method for determining paleoaltitude from fossil floras has used the difference between sea level and upland paleotemperatures which is then multiplied by the reciprocal of a normal lapse rate the present study examines other variables that can significantly influence such results terrestrial lapse rates have been calculated for 39 areas of the world based upon mean annual temperature mat mean warm month temperature mat and mean cold month ttemperature cmt these show regional and seasonal variability that is explained by factors including continentality elevation of large massifs or high base levels cold air drainage fog mountain barrier effects and the location of the subtropical high pressure zone lapse rates and projected sea level temperatures based on data from the western united states show distinct regional patterns these indicate that within this region the highest lapse rate and temperature values are correlated with 1 continental climates in the subtropical high pressure zone and 2 areas having relief where the lowest elevation land surfaces base levels occur at high altitude the data are applied to evaluate and revise the methodology for estimating paleoaltitudes variables of climatic change sea level fluctuation and paleogeography are also considered limitations in application of the method are emphasized the method is exemplified by application to the latest eocene florissant flora of colorado u s a although the results are conjectural they strongly suggest that the late eocene erosion surface in the southern rocky mountains occurred at a much higher paleoaltitude than previously thought this high elevation may have resulted from earlier laramide crustal thickening