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

We have conducted a series of radiocarbon measurements on decadal samples of dendrochronologically dated wood from both hemispheres, spanning 1000 years (McCormac et al. 1998; Hogg et al. this issue). Using the data presented in Hogg et al., we show that during the period AD 950-1850 the 14C offset between the hemispheres is not constant, but varies periodically (~130 yr periodicity) with amplitudes varying between 1 and 10‰ (i.e. 8-80 yr), with a consequent effect on the 14C calibration of material from the Southern Hemisphere. A large increase in the offset occurs between AD 1245 and 1355. In this paper, we present a Southern Hemisphere high-precision calibration data set (SHCal02) that comprises measurements from New Zealand, Chile, and South Africa. This data, and a new value of 41 ± 14 yr for correction of the IntCal98 data for the period outside the range given here, is proposed for use in calibrating Southern Hemisphere 14C dates.

/pdf/calibration-of-the-radiocarbon-time-scale-for-the-southern-dqwi02l60k.pdf

Calibration of the Radiocarbon Time Scale for the Southern Hemisphere: AD 1850-950

A variable solar (helio-magnetic) modulation of the cosmic ray flux causes atmospheric 14C to change on a decadal to century timescale. Ocean-atmosphere exchange rates and atmospheric circulation patterns play a role in Northern-Southern Hemispheric 14C offsets and regional 14C differences that are significant for radiocarbon dating. Time dependent radiocarbon age differences, relative to Washington, were determined for Alaska (A.D. 1884–1932), South Chile (A.D. 1850–1952 and A.D. 1670–1722), Tasmania (A.D. 1895–1950) and Siberia (A.D. 1545–1715). Twentieth century fossil fuel CO2, lacking 14C and mostly released in the Northern Hemisphere (N), has entered the Southern Hemisphere (S) by atmospheric N-S exchange. Regional 14C time series show that initial (19th century) positive N-S 14C offsets switch to negative values by AD 1940. First order carbon reservoir modeling predicts such crossovers.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/97GL03694

Anthropogenic and solar components of hemispheric 14C

This paper is the third of a series detailing the general features of 14C distribution in the world oceans. In the preceding papers, we discussed the 14C activities of Atlantic and Pacific Ocean waters (Stuiver and Ostlund, 1980; Ostlund and Stuiver, 1980). We now give an outline of the 14C distribution of the Indian Ocean and profiles for one Mediterranean and three Red Sea stations.

/pdf/geosecs-indian-ocean-and-mediterranean-radiocarbon-2jmq0kpmit.pdf

GEOSECS Indian Ocean and Mediterranean radiocarbon.

Radiocarbon calibration curves are essential for converting radiocarbon dated chronologies to the calendar timescale. Prior to the 1980's numerous differently derived calibration curves based on radiocarbon ages of known age material were in use, resulting in ''apples and oranges'' comparisons between various records (Klein et al., 1982), further complicated by until then unappreciated inter-laboratory variations (International Study Group, 1982). The solution was to produce an internationally-agreed calibration curve based on carefully screened data with updates at 4-6 year intervals (Klein et al., 1982; Stuiver and Reimer, 1986; Stuiver and Reimer, 1993; Stuiver et al., 1998). The IntCal working group has continued this tradition with the active participation of researchers who produced the records that were considered for incorporation into the current, internationally-ratified calibration curves, IntCal04, SHCal04, and Marine04, for Northern Hemisphere terrestrial, Southern Hemisphere terrestrial, and marine samples, respectively (Reimer et al., 2004; Hughen et al., 2004; McCormac et al., 2004). Fairbanks et al. (2005), accompanied by a more technical paper, Chiu et al. (2005), and an introductory comment, Adkins (2005), recently published a ''calibration curve spanning 0-50,000 years''. Fairbanks et al. (2005) and Chiu et al. (2005) have made a significant contribution to the database on which the IntCal04 and Marine04 calibration curves are based. These authors have now taken the further step to derive their own radiocarbon calibration extending to 50,000 cal BP, which they claim is superior to that generated by the IntCal working group. In their papers, these authors are strongly critical of the IntCal calibration efforts for what they claim to be inadequate screening and sample pretreatment methods. While these criticisms may ultimately be helpful in identifying a better set of protocols, we feel that there are also several erroneous and misleading statements made by these authors which require a response by the IntCal working group. Furthermore, we would like to comment on the sample selection criteria, pretreatment methods, and statistical methods utilized by Fairbanks et al. in derivation of their own radiocarbon calibration.

/pdf/comment-on-radiocarbon-calibration-curve-spanning-0-to-50-1nefl2iisp.pdf

Comment on "Radiocarbon Calibration Curve Spanning 0 to 50,000 Years B.P. Based on Paired 230Th/234U/238U and 14C Dates on Pristine Corals" by R.G. Fairbanks, R. A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T. P. Guilderson, T. W. Fairbanks, A. L. Bloom, P

Minze Stuiver

Papers

Calibration of the Radiocarbon Time Scale for the Southern Hemisphere: AD 1850-950

Anthropogenic and solar components of hemispheric 14C

GEOSECS Indian Ocean and Mediterranean radiocarbon.

Comment on "Radiocarbon Calibration Curve Spanning 0 to 50,000 Years B.P. Based on Paired 230Th/234U/238U and 14C Dates on Pristine Corals" by R.G. Fairbanks, R. A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T. P. Guilderson, T. W. Fairbanks, A. L. Bloom, P

The Taylor Dome Antarctic 18O Record and Globally Synchronous Changes in Climate