Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

/pdf/intcal13-and-marine13-radiocarbon-age-calibration-curves-0-4f3vsbzfqx.pdf

IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

The age calibration program, CALIB (Stuiver & Reimer 1986), first made available in 1986 and subsequently modified in 1987 (revision 2.0 and 2.1), has been amended anew. The 1993 program (revision 3.0) incorporates further refinements and a new calibration data set covering nearly 22,000 cal yr (≈18,400 14C yr). The new data, and corrections to the previously used data set, derive from a 6-yr (1986–1992) time-scale calibration effort of several laboratories.

/pdf/extended-14c-data-base-and-revised-calib-3-0-14c-age-4x1nxe8awy.pdf

Extended 14C Data Base and Revised Calib 3.0 14C Age Calibration Program

If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14C calibration curve. In most dating applications, however, we have larger numbers of 14C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used "uniform phase" models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.

/pdf/bayesian-analysis-of-radiocarbon-dates-26ui63c9ae.pdf

Bayesian analysis of radiocarbon dates

[1] We present a 53-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N Stacked sedimentation rates provide additional age model constraints to prevent overtuning Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 53 Myr and in the precession band for more than half of the record The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 27–16 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 16 Ma

/pdf/a-pliocene-pleistocene-stack-of-57-globally-distributed-n5iphe7mt2.pdf

A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records

The use of stable isotopes to solve biogeochemical problems in ecosystem analysis is increasing rapidly because stable isotope data can contribute both source-sink (tracer) and process information: The elements C, N, S, H, and all have more than one isotope, and isotopic compositions of natural materials can be measured with great precision with a mass spectrometer. Isotopic compositions change in predictable ways as elements cycle through the biosphere. These changes have been exploited by geochemists to understand the global elemental cycles. Ecologists have not until quite recently employed these techniques. The reasons for this are, first, that most ecologists do not have the background in chemistry and geochemistry to be fully aware of the possibilities for exploiting the natural variations in stable isotopic compositions, and second, that stable isotope ratio measurements require equipment not normally available to ecologists. This is unfortunate because some of the more intractable problems in ecology can be profitably addressed using stable isotope measurements. Stable isotopes are ideally suited to increase our understanding of element cycles in ecosystems. This review is written for ecologists who would like to learn more about how stable isotope analyses have been and can be used in ecosystem studies. We begin with an explanation of isotope terminology and fractionation, then summarize isotopic distributions in the C, N, and S biogeochemical cycles, and conclude with five case studies that show how stable isotope measurements can provide crucial information for ecosystem analysis. We restrict this review to studies of natural variations in C, N, and S isotopic abundances, cxcluding from consideration ~5N enrichment studies and hydrogen and oxygen isotope studies. Our focus on C, N, and S derives in part from our

Stable isotopes in ecosystem studies

Development and extension of the calibration of the radiocarbon time scale: Archaeological applications

Non-marine diatoms from late Wisconsin perched deltas in Taylor Valley, Antarctica

Southern Chile (41–56 °S), in the belt of westerly winds, receives mostly heavy precipitation, reaching 8,500 mm yr−1 near 50 °S and decreasing northwards and southwards from this latitude to ≤1,500 mm; mean January (summer) temperatures near sea level along the latitudinal gradient are 8–16 °C (refs 1, 2). Dense rain forest covers much of the region to 48 °S; south to Cape Horn, magellanic moorland prevails and rain forest becomes limited. Modern pollen measured in surface samples reflects the distribution of plant species in the vegetation. We have now applied regression equations relating present-day pollen to temperature and precipitation to fossil pollen data at Taiquemo to assess climatic conditions during the Quaternary. The results extend our previous record of the past 16,000 yr at Alerce3 beyond the lateglacial to ∼43,000 yr BP. For the 27,000-yr interval, they show mean January temperatures of 10–12 °C and mean annual precipitation centred around 1,000 mm except during the time span of ∼31,000–43,000 yr BP when amounts increased to 4,000 mm. In general fluctuations correspond to the isotopic climatic reconstruction in Antarctica4 and to changes inferred from pollen data at comparable latitudes in Tasmania5–8 and New Zealand9,10.

Temperature and precipitation record in southern Chile extended to ∼ 43,000 yr ago

Drift morphology, stratigraphy, and C-14 dates suggest chronology for Donjek and Kaskawulsh Glaciers. About 12,500 B.P. Kluane glaciers receded from near Kluane Lake and about 9780 B.P. withdrew behind present Kaskawulsh moraines. During Slims nonglacial interval, glaciers maintained retracted positions; Kaskawulsh terminus was located at least 13.7 miles up-glacier from its present position. Initial Neoglacial advance began before 2640 B.P.; continuous loess deposition suggests glaciers maintained positions more advanced than in Slims. The youngest advance occurring through the last few centuries is bracketed by seven C-14 dates; retreat beegan before A.D. 1865 and 1874. Comparison with events elsewhere supports initial widespread Neoglacial advance shortly before 2600-2800 B.P., and major events synchronous throughout the Northern Hemisphere.

Neoglacial chronology, northeastern Saint Elias Mountains, Canada

A three-dimensional global tracer transport model (derived from a general circulation model) simulates geographic variations in atmospheric Δ14C in response to oceanic boundary conditions. Regional atmosphere-ocean 14CO2 fluxes are controlled by regional wind-dependent gas exchange coefficients (E), air-sea pCO2 differences (ΔpCO2) and oceanic 14C/12C deficiencies. We find that various preindustrial oceanic scenarios reconstructed from reasonable sets of such air-sea variables all produce model latitudinal gradients in atmospheric Δ14CO2 (the “NS Δ14C”) significantly greater than the measured preindustrial NS Δ14C of +4.4 ± 0.5‰ (45°N to 45°S), as estimated from pre-twentieth century tree rings. The NS Δ14C is insensitive to regional ΔpCO2 but is strongly contingent on the chosen values for surface ocean Δ14C and E of southern high latitudes (>50°S). The simultaneous seasonality in sea ice extent and high-latitude wind speeds may in part explain the discrepancy between modeled and measured preindustrial NS Δ14C. Terrestrial 14C sinks with longer turnover times (such as peatlands) also potentially may help to reduce the NS Δ14C. With our best estimates for preindustrial surface ocean Δ14C, ΔpCO2, and E values for other regions, we find a “best fit” ocean scenario in which the preindustrial southern surface ocean Δ14C is −95 ± 10 ‰, its ΔpCO2 is 0 ± 20 ppmv, and its E is 0.088 ± 0.010 M m−2 yr−1 μatm−1 (about 20% reduced from the widely accepted value of 0.110). An independent estimate of +6.5 ± 0.5 kg yr−1 for the net preindustrial oceanic 14C uptake is an important constraint on global mean and Antarctic E.

Minze Stuiver

Papers

Development and extension of the calibration of the radiocarbon time scale: Archaeological applications

Non-marine diatoms from late Wisconsin perched deltas in Taylor Valley, Antarctica

Temperature and precipitation record in southern Chile extended to ∼ 43,000 yr ago

Neoglacial chronology, northeastern Saint Elias Mountains, Canada

The preindustrial atmospheric14CO2 latitudinal gradient as related to exchanges among atmospheric, oceanic, and terrestrial reservoirs