Age Uncertainties Research Articles

An integrated proximal-distal radiocarbon dating approach provides improved age constraints for a key Holocene tephra isochron

Volcanic ash (tephra) horizons are an essential tool for the spatial and temporal correlation of many natural archives. However, tephrochronology is accompanied by age uncertainties that often limit its capacity to effectively constrain age models. This is particularly problematic for paleoseismology in complex tectonic settings such as New Zealand, where the accuracy and precision of earthquake ages is important for interpreting past fault interactions and earthquake sequences. We use the widespread Waimihia tephra, erupted at ∼3.4 ka from Taupō volcano, as a case study for generating improved age constraints for Holocene tephra isochrons. Our dating strategy minimizes uncertainties by (i) conducting detailed assessments to identify the most reliable dateable material, (ii) using precise AMS dating techniques, and (iii) constructing Bayesian age models. By applying consistent procedures to date tephra deposits at proximal, onshore distal and offshore distal locations, we also facilitate the detection of any geographic radiocarbon bias. Based on high agreement between the independently derived tephra ages from each location, we demonstrate no offsets in radiocarbon results between proximal and distal deposits, precluding bias from near-vent magmatic degassing. Our integrated age model exploits the benefits of each individual dating approach and uses the full suite of 42 new radiocarbon dates to yield an age of 3574–3478 cal yr BP (highest 95% range) for the Waimihia eruption. Compared to previous estimates, this older and more precise age has implications for refining existing paleoearthquake correlations and other chronologies that rely on the Waimihia isochron to provide age control. We recommend applying this multi-location approach to existing tephrochronologies where possible, to achieve more accurate and precise eruption age estimates that allow for the detection of radiocarbon bias.

The Empirical Limits of Gyrochronology

The promise of gyrochronology is that, given a star’s rotation period and mass, its age can be inferred. The reality of gyrochronology is complicated by effects other than ordinary magnetized braking that alter stellar rotation periods. In this work, we present an interpolation-based gyrochronology framework that reproduces the time- and mass-dependent spin-down rates implied by the latest open cluster data, while also matching the rate at which the dispersion in initial stellar rotation periods decreases as stars age. We validate our technique for stars with temperatures of 3800–6200 K and ages of 0.08–2.6 gigayears (Gyr), and use it to reexamine the empirical limits of gyrochronology. In line with previous work, we find that the uncertainty floor varies strongly with both stellar mass and age. For Sun-like stars (≈5800 K), the statistical age uncertainties improve monotonically from ±38% at 0.2 Gyr to ±12% at 2 Gyr, and are caused by the empirical scatter of the cluster rotation sequences combined with the rate of stellar spin-down. For low-mass K dwarfs (≈4200 K), the posteriors are highly asymmetric due to stalled spin-down, and ±1σ age uncertainties vary non-monotonically between 10% and 50% over the first few gigayears. High-mass K dwarfs (5000 K) older than ≈1.5 Gyr yield the most precise ages, with limiting uncertainties currently set by possible changes in the spin-down rate (12% systematic), the calibration of the absolute age scale (8% systematic), and the width of the slow sequence (4% statistical). An open-source implementation, gyro-interp, is available online at github.com/lgbouma/gyro-interp.

Neoproterozoic ophiolite exotic blocks in the Outer Western Carpathians, southern Poland: a record of the fast ocean-floor cooling and alterations

Ophiolitic blocks, represented by metagabbro and serpentinite containing relict pyroxene, olivine, baddeleyite, zirconolite, Ni-pyrite and pyrrhotite, were found as exotic blocks in an olistostrome in the Magura Nappe, Outer Western Carpathians. The geochemical and isotopic features of the blocks suggest they represent mantle-derived rocks, with within-plate geochemistry signatures, modified by subduction, with lithospheric mantle input. A U-Pb apatite cooling age (614 ±3 Ma) is within age uncertainty of a published U-Pb zircon magmatic crystallization age (~614 Ma) implying rapid post-crystallization cooling. Pervasive alteration with replacement of primary minerals by low-temperature assemblages is observed in all rock fragments and is interpreted as contemporaneous with shearing. The secondary mineral assemblages and temperature modelling allow the interpretation that the pervasive ocean-floor metamorphism is the alteration in these meta-mafic rocks. These ophiolitic fragments can be linked to the Neoproterozoic break up of Rodinia/Pannotia.

Trace element geochemistry, oxygen isotope and U–Pb geochronology of multistage scheelite: Implications for W-mineralization and fluid evolution of Shizhuyuan W–Sn deposit, South China

The Shizhuyuan oxidized skarn-greisen W–Sn deposit (South China) has widely developed scheelite in the prograde skarn stage, retrograde skarn stage, oxide stage, sulfide-quartz vein stage, greisen stage, and quartz-calcite-fluorite vein stage that are related to the reduced A-Type Qianlishan granite. In this contribution, we used trace elements, oxygen isotopic compositions, and U–Pb isotopes for tracing the W metallogenic processes in skarn and greisen, and the genesis of the Shizhuyuan W–Sn deposit. The total rare-earth element (∑REE) contents of scheelite grains from prograde and retrograde skarn stages to oxide stage show a decreasing fractionation trend (means from 1647 to 181 ppm) and the increasing trend in sulfide-quartz vein stage and greisen (mean = 428 ppm and 2074 ppm) indicate multi-stage fluid activities. Scheelites formed in skarn show HREE depletion REE patterns (LaN/YbN values means from 159 to 1.40) which results from paragenetic mineral precipitation (e.g., garnet and diopside), and negative or small positive Eu anomaly. In contrast, scheelite grains from the greisen stage have a flat REE pattern and a pronounced negative Eu anomaly identical to those of the Qianlishan granite that mirror the magmatic-hydrothermal fluid. The MoO3 contents in scheelite decrease from the prograde and retrograde skarn stages through the oxide stage to the sulfide-quartz vein stage (mean = 27.4 wt%, 1.97 wt%, 0.51 wt%, and 0.12 wt%). However a slight rise in MoO3 contents was observed in scheelite grains from the greisen to the latest-stage quartz-calcite-fluorite vein stage (mean = 0.28 wt% and 0.52 wt%, respectively). It is suggested to be the result of a change in fluid fO2 conditions and periodic transition from oxidizing to reducing metallogenic environment.The mean δ18OH2O values of the ore-forming fluid in the different mineralization stages as calculated by δ18Oscheelite are 7.98 ‰ (prograde skarn), 6.20 ‰ (retrograde skarn), 4.96 ‰ (proximal greisen), 2.83 ‰ (distal greisen), and 3.29 ‰ (quartz-calcite-fluorite vein). Scheelite grains formed in the retrograde skarn stage yielded a U–Pb isochron age of 164.4 ± 7.6 Ma, which is within the uncertainty of the emplacement age of the Qianlishan granite. Although scheelite grains formed in different stages have different trace elements and oxygen isotope compositions, they are all associated with the Qianlishan granite. We assume that the giant skarn-greisen W–Sn deposit has mainly resulted from multistage fluid activities derived from reduced intrusions and long-term fluid-rock interactions with thick marbleized limestone in an oxidizing setting.

Specific patterns of adaptive human kinematics

A study of healthy individuals (n = 90) was carried out under standardized environmental conditions using tests of adaptive kinematics in the form of a battery of postural tests. A model of adaptive kinematics of healthy individuals, resistant to personal (age and anthropometric) uncertainties, has been developed. 34 criteria selected from a total pool of 170 indicators were used as relevant parameters underlying the developed biomechanical model.

The Ages of Galactic Bulge Stars with Realistic Uncertainties

Using modern isochrones with customized physics and carefully considered statistical techniques, we recompute the age distribution for a sample of 91 microlensed dwarfs in the Galactic bulge presented by Bensby et al. and do not produce an age distribution consistent with their results. In particular, our analysis finds that only 15 of 91 stars have ages younger than 7 Gyr, compared to their finding of 42 young stars in the same sample. While we do not find a constituency of very young stars, our results do suggest the presence of an ∼8 Gyr population at the highest metallicities, thus contributing to the long-standing debate about the age–metallicity distribution of the Galactic bulge. We supplement this with attempts at independent age determinations from two sources of photometry, BDBS and Gaia, but find that the imprecision of photometric measurements prevents reliable age and age uncertainty determinations. Lastly, we present age uncertainties derived using a first-order consideration of global modeling uncertainties in addition to standard observational uncertainties. The theoretical uncertainties are based on the known variance of free parameters in the 1D stellar evolution models used to generate isochrones, and when included, result in age uncertainties of 2–5 Gyr for this spectroscopically well-constrained sample. These error bars, which are roughly twice as large as typical literature values, constitute realistic lower limits on the true age uncertainties.

Effects of Aging Uncertainty on the Estimation of Growth Functions of Major Tuna Species

Fishery stock assessment requires accurate specification of the growth function of target species, and aging uncertainty is an important factor that affects the estimation of growth parameters. In this study, we used simulations to study the effects of two types of aging uncertainty, aging error and sampled age range, on the parameter estimation of the Von Bertalanffy growth function, including asymptotic length (L∞), growth coefficient (k), and theoretical age in the year at zero length (t0) of five important tuna species. We found that the uncertainty of the estimated growth curves increased with increasing aging errors. When aging errors were fixed among ages, the effects of age range on estimation error of growth parameters were different among species and growth parameters. When the aging error increased with age, the estimation uncertainty of L∞ and k was the greatest when only young age groups were sampled, while the estimation uncertainty of t0 was the greatest when only old age groups were sampled. Therefore, reducing the aging error and sampling individuals with a wider age range are important for increasing the accuracy and decreasing the uncertainty of the estimated growth function, which will further reduce the uncertainty in fishery stock assessment.

Evolution of the preserved European continental crust, constrained by U-Pb, O and Hf isotopic analyses of river detrital zircons

Integrated U-Pb, O and Lu-Hf isotopic analyses of detrital zircons, collected from fourteen European river sands and one beach sand from northern Germany, were carried out to study the evolution of the preserved European continental crust. The drainage area of these sand samples covers large areas in eastern and western Europe, which evolved independently until their amalgamation during the Paleozoic. U-Pb ages of detrital zircons from eastern and western Europe generally match the ages of the major magmatic events in the two tectonic regions. The combined histogram of 2403 zircon U-Pb ages, obtained for this study, shows five major periods of zircon crystallisation: 2.80–2.65, 1.95–1.35, 1.25–0.85, 0.65–0.40, and 0.40–0.25 Ga, which correspond broadly with the timing of supercontinent assembly. The correlation could be due to enhanced granitoid magmatism and zircon growth during the supercontinent amalgamation, or the high preservation potential of igneous rocks generated during continental collisions. The O and Hf isotopic data of the analysed European river zircons show wide spreads in δ18O and εHf(t) values at ca. 1.9 Ga and 650–250 Ma, contrasting with the limited range for the Mesoproterozoic zircons. This indicates that extensive reworking of pre-existing crustal rocks occurred during the late Paleoproterozoic and Paleozoic in the evolution of the European continental crust, whereas the formation of new crust played an important role during the Mesoproterozoic.Arc mantle Hf model ages for the detrital zircons were calculated to estimate when European juvenile crust was extracted from the mantle. Model age uncertainties were estimated using the bootstrap method, considering three sources of uncertainty: (i) uncertainty in the Hf isotopic composition of the mantle reservoir, (ii) uncertainty in the 176Lu/177Hf for the crustal source region, and (iii) analytical uncertainties. Two types of model ages are calculated based on constant crustal 176Lu/177Hf (TAMC), and on variable176Lu/177Hf (TAMV), the latter being constrained by zircon δ18O values. Histograms of the calculated TAMC and TAMV model ages both show major juvenile extraction events between the late Paleo- and Mesoproterozoic. Although the principal periods in the European crustal growth contrast with those identified in the African, Russian and Mississippi river basins, the overall growth curves for the four continents show comparable results: (i) the formation of little or no continental crust before 4.0 Ga, and (ii) the formation of 50 % of the present crustal volume by ca. 2.0–1.6 Ga.

A statistical model for quantifying age-reading errors and its application to the Antarctic minke whales

A statistical method for quantifying age-reading error, i.e. the extent of bias and inter-reader variability among readers, is introduced. The method assumes the availability of an independent ‘control reader’ who produces reference ages for age-reading structures which are also read by additional readers. This control reader is assumed to provide unbiased or consistently biased age estimates so that the additional readers’ age-reading outcomes can be standardised. Linear structures in bias and variance are incorporated in a conditional probability matrix representing the stochastic nature of age-determination for each reader. A joint likelihood function for the parameters related to age-reading bias, variance and nuisance parameters is defined based on observed age-reading outcomes from both the control and additional readers. The method is applied to data for Antarctic minke whales taken during Japanese commercial (1971/72–1986/87) and scientific (JARPA: 1987/88–2004/05, JARPA II: 2005/06–2010/11) whaling. A total of 250 earplugs selected according to a predetermined protocol were used in the analyses to estimate the inter-reader variation for four Japanese readers. One of the authors acted as the control reader. The Japanese readers and the control reader differed in terms of both the expected age given the true age, and variance in age-estimates. The expected age and random uncertainty in age-estimates differed among the Japanese readers, although the two readers in charge of age-reading for samples taken during Japanese scientific whaling (JARPA and JARPA II) provided quite similar agereading outcomes. These results contribute to analyses using catch-at-age data for this species. It should also be noted that the model and approach in this paper can be applied to populations other than the Antarctic minke whales, if a control reader is available, even retrospectively.

A new rodent chronology for the late Neogene of Spain

The number of late Neogene Spanish micromammal-containing continental sections with a correlation to the Geomagnetic Time Scale is steadily growing. Nonetheless, well-calibrated sections with dense micromammal records are still rare, biostratigraphic correlations between basins are not straightforward, and ages of uncalibrated sites are poorly constrained. Here, we aim at improving the chronology of Iberian micromammal sections and sites for the interval 8.5–2 Ma by: (i) analyzing qualitative and quantitative similarities between rodent assemblages and turnover in the different basins, (ii) formulating a system of fifteen Iberian assemblage biozones, and (iii) constraining the ages of zone boundaries, assuming isochroneity across basins. Age uncertainty ranges for most known Iberian micromammal sites are obtained by combining regional biozone boundary ages with local magnetostratigraphic records, sedimentation rates and/or evolutionary rates. In addition, our results include new, integrated stratigraphic records from the Jumilla-La Celia and Teruel Basins, which are used to constrain the thus far poorly dated interval covering the latest Tortonian and earliest Messinian (8–7 Ma).

Inconsistent patterns of Holocene rainfall changes at the East Asian monsoon margin compared to the core monsoon region

Documenting spatiotemporal patterns of the Holocene Optimum (HO) at the climatically sensitive East Asian monsoon (EAM) margin are essential for understanding monsoon climate dynamics. However, the timing of the onset of the HO at the EAM margin is still debated and progress has been partly hindered by age uncertainties in different proxy records. To avoid the bias of these chronological uncertainties, we compared moisture variations from the marginal EAM region reconstructed from dust and aluminum (Al) flux records with tree pollen percentages in a dated lake sediment core that tracked moisture changes in the region around the lake. We show a delay (∼1500 years) of HO initiation in the core EAM region in northeastern China compared to the monsoon margin. Synthesizing pollen records with reliable chronologies show a synchronous HO occurrence at ∼8000-7000 cal yr BP at the monsoon margin, which is likely attributed to the shrinkage of the Northern Hemisphere ice sheet. Therefore, although the monsoon margin has always been considered a climate-sensitive area, it might be sensitive to different forcing factors from the core monsoon region.

Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters ofGaiaDR3

Context.Gaia’s third data release provides radial velocities for 33 million stars and spectroscopically derived atmospheric parameters for more than 5 million targets. When combined with the astrometric data, these allow us to derive orbital and stellar parameters that are key to understanding the stellar populations of the Milky Way and to perform Galactic archaeology.Aims.We used the calibrated atmospheric parameters, 2MASS andGaia-EDR3 photometry, and parallax-based distances to compute the ages, initial stellar masses, and reddenings for the stars with spectroscopic parameters. We also derived the orbits for all of the stars with measured radial velocities and astrometry, adopting two sets of line-of-sight distances from the literature.Methods.Four different sets of ages, masses, and absolute magnitudes in different photometric bands are obtained through an isochrone fitting method, considering different combinations of input parameters. The reddenings are obtained by comparing the observed colours with those obtained from the isochrone projection. Finally, the orbits are computed adopting an axisymmetric potential of the Galaxy.Results.Comparisons with reference catalogues of field and cluster stars suggest that reliable ages are obtained for stars younger than 9–10 Gyr when the estimated relative age uncertainty is < 50 per cent. For older stars, ages tend to be underestimated. The most reliable stellar type for age determination are turn-off stars, even when the input atmospheric parameters have large uncertainties. Ages for giants and main-sequence stars are retrieved with uncertainties of the order of 2 Gyr when extinction towards the star’s line of sight is less thanAV ≲ 2.5 mag.Conclusions.The catalogue of ages, initial stellar masses, reddenings, galactocentric positions and velocities, as well as the stellar orbital actions, eccentricities, apocentre, pericentre and maximum distance from the Galactic plane reached during their orbits, is made publicly available to be downloaded. With this catalogue, the full chemo-dynamical properties of the extended solar neighbourhood unfold and allow us to better identify the properties of the spiral arms, to parametrise the dynamical heating of the disc, and to thoroughly study the chemical enrichment of the Milky Way.

Estimating reproductive and juvenile survival rates when offspring ages are uncertain: A novel multievent mark‐resight model with beluga whale case study

Abstract Understanding the survival and reproductive rates of a population is critical to determining its long‐term dynamics and viability. Mark‐resight models are often used to estimate these demographic rates, but estimation of survival and reproductive rates is challenging, especially for wide‐ranging, patchily distributed, or cryptic species. In particular, existing mark‐resight models cannot accommodate data from populations in which offspring remain with parents for multiple years, are not always detected, and cannot be aged with certainty. Here we describe a Bayesian multievent mark‐resight modelling framework that uses all available adult and adult‐offspring sightings (including sightings with older offspring of uncertain age) to estimate reproductive rates and survival rates of adults and juveniles. We extend existing multievent mark‐resight models that typically only incorporate adult breeding state uncertainty by additionally accounting for age uncertainty in unmarked offspring and uncertainty in the duration of the mother‐offspring association. We describe our model in general terms and with a simple illustrative example, then apply it in a more complex empirical setting using 13 years of photo‐ID data from a critically endangered population of beluga whales Delphinapterus leucas. We evaluated model performance using simulated data under a range of sample sizes, and adult and offspring detection rates. Applying our model to the beluga data yielded precise estimates for all demographic rates of interest (despite substantial uncertainty in calf ages), including nonbreeder survival and reproductive rates lower than in other beluga populations. Simulations suggested our model yields asymptotically unbiased parameter estimates with good precision and low bias even with moderate sample sizes and detection rates. This work represents an important new development in multievent mark‐resight modelling, allowing estimation of reproductive and juvenile survival rates for populations with extended adult—offspring associations and uncertain offspring ages (e.g. some marine mammals, elephants, bears, great apes, bats and birds). Our model facilitated estimation of robust demographic rates for an endangered beluga population that were previously inestimable (e.g. nonbreeder and juvenile survival, reproductive rate) and that will yield new insights into this population's continued decline.

Paleomagnetic secular variation and revised chronostratigraphy of Bering sea (IODP Ex. 323) deep-sea sediments (MIS 1–4)

This study develops composite full-vector paleomagnetic secular variation (PSV) records from IODP Ex. 323 Sites U1339, U1343, U1344, and U1345 in the Bering Sea (51°N-60°N). These PSV records cover the last 71 ka (Marine Isotope Stages (MIS) 1–4). This is the first time that long PSV records have been recovered from such high latitudes. The records have been dated by oxygen isotope records and paleointensity correlations. The records have an age uncertainty of ∼1000 years. The paleomagnetic data come from shipboard paleomagnetic studies of deep-sea sediments with sediment accumulation rates of 20–40 cm/ky. The sample interval is 5 cm, with a time resolution of ±120–200 years. We have identified 66 correlatable inclination features and 59 declination features in all four sites. The relative paleointensity has been estimated by normalizing the natural remanence (after 20 mT af demagnetization) by magnetic susceptibility. This normalization process is strongly biased by environmental variability and so our relative paleointensity records are limited to correlating variability among the four sites. We can identify 8 key, dated paleointensity highs/lows in our composite records. There are two magnetic field excursions recorded reproducibly at these four sites – the Laschamp Excursion (∼41 ka) and the Norwegian-Greenland Sea Excursion (∼61 ka). Both occur quickly, in 1000 years or less, are associated with the lowest paleointensities, and show no significant evidence for pre- or post-excursion anomalous PSV. Both of these are Class I excursions. There are no excursional directions associated with the time interval of the Mono Lake Excursion (∼34 ka). We have carried out a statistical study using our PSV records to assess 3ky and 9ky average variability over the last 71 ky after removing all excursional directions. The averaged inclinations and declinations have correlatable variability, mostly on ∼104 yr time scales. We see significant variation in averaged angular dispersion that appears to be bimodal. Most time is spent with low angular dispersion (∼10°–12°) with shorter time intervals with significantly higher angular dispersion (∼24–30°). This study suggests that excursions, high angular dispersion, and low paleointensities occur together. This may define a distinctive low-intensity (or low-energy) state to the geomagnetic field.

Tropical Indian Ocean basin hydroclimate at the Mid- to Late-Holocene transition and the double drying hypothesis

The spatial pattern of Holocene climate anomalies is crucial to determining the mechanisms of change, distinguishing between unforced and forced climate variability, and understanding potential impacts on past and future human societies. The 4.2 ka event is often regarded as one of the largest and best documented abrupt climate disturbances of the Holocene. Yet outside the data-rich Northern Hemisphere mid-latitudes, the global pattern of climate anomalies is uncertain. In this study we investigate the spatial and temporal variability of the tropical Indian Ocean hydroclimate at the Mid- to Late-Holocene transition. We conducted Monte-Carlo principal component analysis, considering full age uncertainty, on ten high-resolution, precisely dated paleohydroclimate records from around the tropical Indian Ocean basin, all growing continuously or almost continuously between 5 and 3 kyr BP. The results indicate the dominant mode of variability in the region was a drying between 3.97 kyr BP (±0.08 kyr standard error) and 3.76 kyr BP (±0.07 kyr standard error) with dry conditions lasting for an additional 300 years in some records, and a permanent change in others. This drying in PC1, which we interpret as a proxy of summer monsoon variability, fits with a previously recognised tropic wide change in hydroclimate around 4.0 kyr BP. An abrupt event from 4.2 to 3.9 kyr BP is seen locally in individual records but lacks regional coherence.A lack of apparent 4.2 ka event in tropical Indian Ocean hydroclimate has ramifications for climate variability in the Indus valley, and for the Harappan civilization. Through a comparison of existing Indian subcontinent paleoclimate records, upstream climatic variability in the Indian Summer Monsoon and winter Westerly Disturbances source regions, and modern climatology, we present the “Double Drying hypothesis”. A winter rainfall drying between 4.2 and 3.9 kyr BP was followed by a summer rainfall drying between 3.97 kyr BP and at least 3.4 kyr BP. The Double Drying hypothesis provides more detailed climatic context for the Harappan civilization, resolves the cropping paradox, and fits the spatial-temporal pattern of urban abandonment. The consequences for the new Mid- to Late-Holocene Global Boundary Stratotype Section and Point in a stalagmite from Meghalaya are explored.

Estimating the Age of Poorly Dated Fossil Specimens and Deposits Using a Total-Evidence Approach and the Fossilized Birth-Death Process.

Bayesian total-evidence approaches under the fossilized birth-death model enable biologists to combine fossil and extant data while accounting for uncertainty in the ages of fossil specimens, in an integrative phylogenetic analysis. Fossil age uncertainty is a key feature of the fossil record as many empirical data sets may contain a mix of precisely dated and poorly dated fossil specimens or deposits. In this study, we explore whether reliable age estimates for fossil specimens can be obtained from Bayesian total-evidence phylogenetic analyses under the fossilized birth-death model. Through simulations based on the example of the Baltic amber deposit, we show that estimates of fossil ages obtained through such an analysis are accurate, particularly when the proportion of poorly dated specimens remains low and the majority of fossil specimens have precise dates. We confirm our results using an empirical data set of living and fossil penguins by artificially increasing the age uncertainty around some fossil specimens and showing that the resulting age estimates overlap with the recorded age ranges. Our results are applicable to many empirical data sets where classical methods of establishing fossil ages have failed, such as the Baltic amber and the Gobi Desert deposits. [Bayesian phylogenetic inference; fossil age estimates; fossilized birth-death; Lagerstätte; total-evidence.].

Evidence for wind patterns and associated landscape response in Western Europe between 46 and 16 ka cal. BP

During the last glacial period, the North Atlantic region experienced pronounced, millennial-scale alternations in climate characterized by cold stadial and milder interstadial conditions. These rapid climatic changes are recorded in Greenland ice cores and various terrestrial proxy records of Europe. Nonetheless, the scarcity and age uncertainties associated with records north of the Alps have long hindered our understanding of continental-scale climate impacts and associated environmental responses. Here we present high-resolution geochemical records from Bergsee Lake (SW Germany) to probe centennial changes in aeolian and organic matter fluxes between 46 and 16 ka cal. BP. We compare and combine these data with a pollen-based vegetation reconstruction. Abrupt decreases in dust influx were followed by tree expansions during Greenland interstadials 11 to 2. A further five interstadial-like warming phases are recorded between 31 and 16 ka cal. BP. These warming phases are not recorded in Greenland but rather relate to European-scale shifts in atmospheric circulation patterns. We find that the wind activity varies on a persistent period of 2400–3100 years that probably reflects a dominant solar forcing on the glacial climate of Europe.

Uniformitarian Prediction of Early‐Pleistocene Atmospheric CO2

AbstractDespite recent empirical and modeling advances, atmospheric CO2 concentrations during the early Pleistocene remain uncertain. Using a recently‐developed Bayesian paleoclimate model, an ensemble of seven different CO2 records is inferred conditional on reconstructions of past sea level. Five ensemble members give a consensus prediction that CO2 concentrations averaged 241 ppm (238–245 ppm 95% CI) between 2 and 0.8 Ma. Uncertainty estimates account for contributions from orbital forcing, age uncertainties, and other factors. Our consensus prediction aligns well with a compilation of previously published δ11B‐based CO2 reconstructions after calibration to late‐Pleistocene ice‐core CO2 values, as well as with 60 early‐Pleistocene CO2 measurements from the Allan Hills in East Antarctica. Our consensus prediction can be definitively tested by obtaining continuous ice‐core atmospheric CO2 records that extend into the early Pleistocene.

DEVELOPMENT OF FUZZY INFERENCE SYSTEM FOR COVID-19 DATA ANALYSIS

As COVID-19 Pandemic and related data is very recent. COVID-19 infected most of the population from entire globe with different impact. It disclosed the limitation of access of health and care resources. Various parameters like different symptoms, different existing health conditions, different age, diagnosis level and great uncertainties made the condition vaguer. Fuzzy can handle such vagueness and uncertainty of such voluminous data of patients and can support to medical stakeholders, experts, hospitals, pharmaceuticals etc. Fuzzy Logic is widely used to address so many uncertainties, incompleteness or imprecision. The current experiment implements Fuzzy Inference System for pattern identification and classification by applying fuzzy approach with Fuzzy Logic in R for performance improvement. This focuses on designing Fuzzy Rule base, Model and inference for COVID 19 data analysis.

A Hydro-based MCMC Analysis of SNR 0509−67.5: Revealing the Explosion Properties from Fluid Discontinuities Alone

Using Hubble Space Telescope/ACS Hα images of SNR 0509−67.5 taken ∼10 yr apart, we measure the forward shock (FS) proper motions (PMs) at 231 rim locations. The average shock radius and velocity are 3.66 ± 0.036 pc and 6315 ± 310 km s−1. Hydrodynamic simulations, recast as similarity solutions, provide models for the supernova remnant’s expansion into a uniform ambient medium. These are coupled to a Markov chain Monte Carlo (MCMC) analysis to determine explosion parameters, constrained by the FS measurements. For our baseline model, the MCMC posteriors yield an age of 315.5 ± 1.8 yr, a dynamical explosion center at 5h09m31.ˢ16, and ambient medium densities at each azimuth ranging over 3.7–8.0 × 10−25 g cm−3. The age uncertainty can be an order of magnitude larger when considering other models, or subsets of the data. We detect stellar PMs corresponding to speeds in the Large Magellanic Cloud ≥ 770 km s−1. Five stars in the remnant show measurable PMs but none are moving radially from the dynamical center. There are four stars 1.″4 from the center, including three faint, previously unidentified ones. Using coronal [Fe xiv] λ5303 emission as a proxy for the reverse shock location, we constrain the explosion energy (for a compression factor of 4) to a value of E = (1.30 ± 0.41) × 1051 erg for the first time from shock kinematics alone. Higher compression factors (7 or more) are strongly disfavored based on multiple criteria, arguing for inefficient particle acceleration in the Balmer shocks of SNR 0509−67.5.