19 results for Palmer, Jonathan G.

  • The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000–11,700 years ago)

    Turney, Chris S.M.; Fifield, L. Keith; Hogg, Alan G.; Palmer, Jonathan G.; Hughen, Konrad A.; Baillie, Mike G.L.; Galbraith, Rex; Ogden, John; Lorrey, Andrew; Tims, Stephen G.; Jones, Richard T. (2010)

    Journal article
    University of Waikato

    The latter part of the Last Glacial Interval (LGI; 60,000 to 11,700 years ago) experienced a range of climatic and environment extremes. To elucidate the mechanisms of these changes requires records of past variability that are precisely dated and correlated on the same absolute timescale. However, despite decades of research, it is still not possible to align most marine and terrestrial records of past change with ice-core records, largely because of ongoing uncertainties over the conversion of pre-Holocene ¹⁴C ages on to a calendar timescale and uncertainties with in ice-core chronologies. As a result, it is equivocal whether climate changes in both hemispheres during the LGI led, lagged or were synchronous with one another. A decadally-resolved radiocarbon calibration is urgently required to test these models of the Earth system. Here we report radiocarbon measurements obtained from subfossil New Zealand kauri (Agathis australis) spanning a collective 3500 years dated between 25,000 and 45,000 years ago. The results are compared to the recently published international calibration curve IntCal09 and to the marine Cariaco Basin datasets. We show that kauri have considerable potential for development of a Southern Hemisphere component of a unified global calibration curve suite, and that tree-ring sequences can be superposed on other radiocarbon records to constrain atmospheric–marine offsets and precisely test the synchronicity of abrupt climate change.

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  • The New Zealand Kauri (Agathis Australis) Research Project: A Radiocarbon Dating Intercomparison of Younger Dryas Wood and Implications for IntCal13

    Hogg, Alan G.; Turney, Chris S.M.; Palmer, Jonathan G.; Southon, John R.; Kromer, Bernd; Ramsey, Christopher Bronk; Boswijk, Gretel; Fenwick, Pavala; Noronha, Alexandra; Staff, Richard; Friedrich, Michael; Reynard, Linda; Guetter, Dominik; Wacker, Lukas; Jones, Richard T. (2013)

    Journal article
    University of Waikato

    We describe here the New Zealand kauri (Agathis australis) Younger Dryas (YD) research project, which aims to undertake Δ14C analysis of ~140 decadal floating wood samples spanning the time interval ~13.1–11.7 kyr cal BP. We report 14C intercomparison measurements being undertaken by the carbon dating laboratories at University of Waikato (Wk), University of California at Irvine (UCI), and University of Oxford (OxA). The Wk, UCI, and OxA laboratories show very good agreement with an interlaboratory comparison of 12 successive decadal kauri samples (average offsets from consensus values of –7 to +4 14C yr). A University of Waikato/University of Heidelberg (HD) intercomparison involving measurement of the YD-age Swiss larch tree Ollon505, shows a HD/Wk offset of ~10–20 14C yr (HD younger), and strong evidence that the positioning of the Ollon505 series is incorrect, with a recommendation that the 14C analyses be removed from the IntCal calibration database.

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  • Bayesian evaluation of the southern hemisphere radiocarbon offset during the holocene

    Hogg, Alan G.; Ramsey, Christopher Bronk; Turney, Chris S.M.; Palmer, Jonathan G. (2009)

    Journal article
    University of Waikato

    While an interhemispheric offset in atmospheric radiocarbon levels from AD 1950–950 is now well established, its existence earlier in the Holocene is less clear, with some studies reporting globally uniform 14C levels while others finding Southern Hemisphere samples older by a few decades. In this paper, we present a method for wiggle-matching Southern Hemisphere data sets against Northern Hemisphere curves, using the Bayesian calibration program OxCal 4.1 with the Reservoir Offset function accommodating a potential interhemispheric offset. The accuracy and robustness of this approach is confirmed by wiggle-matching known-calendar age sequences of the Southern Hemisphere calibration curve SHCal04 against the Northern Hemisphere curve IntCal04. We also show that 5 of 9 Holocene Southern Hemisphere data sets are capable of yielding reliable offset information. Those data sets that are accurate and precise show that interhemispheric offset levels in the Early Holocene are similar to modern levels, confirming SHCal04 as the curve of choice for calibrating Southern Hemisphere samples.

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  • Investigating the interhemispheric ¹⁴C offset in the 1st millennium AD and assessment of laboratory bias and calibration errors

    Hogg, Alan G.; Palmer, Jonathan G.; Boswijk, Gretel; Reimer, Paula J.; Brown, David (2009)

    Conference item
    University of Waikato

    Past measurements of the radiocarbon interhemispheric offset have been restricted to relatively young samples because of a lack of older dendrochronologically secure Southern Hemisphere tree-ring chronologies. The Southern Hemisphere calibration data set SHCal04 earlier than AD 950 utilizes a variable interhemispheric offset derived from measured 2nd millennium AD Southern Hemisphere/Northern Hemisphere sample pairs with the assumption of stable Holocene ocean/atmosphere interactions. This study extends the range of measured interhemispheric offset values with 20 decadal New Zealand kauri and Irish oak sample pairs from 3 selected time intervals in the 1st millennium AD and is part of a larger program to obtain high-precision Southern Hemisphere 14C data continuously back to 200 BC. We found an average interhemispheric offset of 35 ± 6 yr, which although consistent with previously published 2nd millennium AD measurements, is lower than the offset of 55–58 yr utilized in SHCal04. We concur with McCormac et al. (2008) that the IntCal04 measurement for AD 775 may indeed be slightly too old but also suggest the McCormac results appear excessively young for the interval AD 755–785. In addition, we raise the issue of laboratory bias and calibration errors, and encourage all laboratories to check their consistency with appropriate calibration curves and invest more effort into improving the accuracy of those curves.

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  • Towards a radiocarbon calibration for oxygen isotope stage 3 using New Zealand kauri (Agathis australis)

    Turney, Chris S.M.; Fifield, L. Keith; Palmer, Jonathan G.; Hogg, Alan G.; Baillie, Mike G.L.; Galbraith, Rex; Ogden, John; Lorrey, Andrew; Tims, Stephen G. (2007)

    Journal article
    University of Waikato

    It is well known that radiocarbon years do not directly equate to calendar time. As a result, considerable effort has been devoted to generating a decadally resolved calibration curve for the Holocene and latter part of the last termination. A calibration curve that can be unambiguously attributed to changes in atmospheric ¹⁴C content has not, however, been generated beyond 26 kyr cal BP, despite the urgent need to rigorously test climatic, environmental, and archaeological models. Here, we discuss the potential of New Zealand kauri (Agathis australis) to define the structure of the ¹⁴C calibration curve using annually resolved tree rings and thereby provide an absolute measure of atmospheric ¹⁴C. We report bidecadally sampled ¹⁴C measurements obtained from a floating 1050-yr chronology, demonstrating repeatable ¹⁴C measurements near the present limits of the dating method. The results indicate that considerable scope exists for a high-resolution ¹⁴C calibration curve back through OIS-3 using subfossil wood from this source.

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  • Multi-decadal variations in Southern Hemisphere atmospheric ¹⁴C: Evidence against a Southern Ocean sink at the end of the Little Ice Age CO₂ anomaly.

    Turney, Chris S.M.; Palmer, Jonathan G.; Hogg, Alan G.; Fogwill, Christopher J.; Jones, Richard; Bronk Ramsey, Christopher; Fenwick, Pavla; Grierson, Pauline; Wilmshurst, Janet; O'Donnell, Alison; Thomas, Zoë; Lipson, Mathew (2016)

    Journal article
    University of Waikato

    Northern Hemisphere-wide cooling during the Little Ice Age (LIA; CE 1650-1775) is associated with a ~5 ppmv decrease in atmospheric carbon dioxide. Changes in terrestrial and ocean carbon reservoirs have been postulated as possible drivers of this relatively large shift in atmospheric CO₂, potentially providing insights into the mechanisms and sensitivity of the global carbon cycle. Here we report decadally-resolved radiocarbon (¹⁴C) levels in a network of tree rings series spanning CE 1700-1950 located along the northern boundary of, and within, the Southern Ocean. We observe regional dilutions in atmospheric radiocarbon (relative to the Northern Hemisphere) associated with upwelling of ¹⁴CO₂–depleted abyssal waters. We find the inter-hemispheric ¹⁴C offset approaches zero during increasing global atmospheric CO₂ at the end of the LIA, with reduced ventilation in the Southern Ocean and a Northern Hemisphere source of old carbon (most probably originating from deep Arctic peat layers). The coincidence of the atmospheric CO₂ increase and reduction in the inter-hemispheric ¹⁴C offset imply a common climate control. Possible mechanisms of synchronous change in the high latitudes of both hemispheres are discussed.

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  • A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

    Turney, Chiris S.M.; Jones, Richard T.; Fogwill, Christopher J.; Hatton J.; Williams, A.N.; Hogg, Alan G.; Thomas, Zoë; Palmer, Jonathan G.; Mooney, S; Reimer, Ron W (2016)

    Journal article
    University of Waikato

    Middle Holocene cultures have been widely studied around the Eastern-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and Eastern-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate–culture relation at fine timescales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from the Western-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in Northern Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yr BP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400–3800 yr BP blankets the onset of cave abandonment shortly after ca. 4403 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption.

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  • Dusty horizons

    Lowe, David J.; Tonkin, Philip J.; Palmer, Jonathan G.; Lanigan, Kerri Miriam; Palmer, Alan S. (2015)

    Book item
    University of Waikato

    Dust whipped up and deposited by wind forms sheets of loess, which drape over the land. These loess deposits and the soils formed within them yield insights into past climatic and environmental change.

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  • Dusty horizons

    Lowe, David J.; Tonkin, Philip J.; Palmer, Alan S.; Palmer, Jonathan G. (2008)

    Book item
    University of Waikato

    Dust whipped up and deposited by wind forms sheets of loess, which drape over the land. These loess deposits and the soils formed within them yield insights into past climatic and environmental change.

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  • Robust radiocarbon dating of wood samples by high-sensitivity liquid scintillation spectroscopy in the 50–70 kyr age range

    Hogg, Alan G.; Fifield, L. Keith; Palmer, Jonathan G.; Turney, Chris S.M.; Galbraith, Rex (2007)

    Journal article
    University of Waikato

    Although high-sensitivity liquid scintillation (LS) spectroscopy is theoretically capable of producing finite radiocarbon ages in the 50,000- to 70,000-yr range, there is little evidence in the literature that meaningful dates in this time period have been obtained. The pressing need to undertake calibration beyond 26 kyr has resulted in the regular publication of ¹⁴C results in excess of 50 kyr, yet very little effort has been made to demonstrate their accuracy or precision. There is a paucity of systematic studies of the techniques required to produce reliable dates close to background and the methods needed to assess contamination from either in situ sources or laboratory handling and processing. We have studied the requirements for producing accurate and reliable dates beyond 50 kyr. Laboratory procedures include optimization of LS spectrometers to obtain low and stable non-¹⁴C background count rates, use of low-background counting vials, large benzene volumes, long counting times, and preconditioning of vacuum lines. We also discuss the need for multiple analyses of a suitable material containing no original ¹⁴C (background blank) and the application of an appropriate statistical model to compensate for variability in background contamination beyond counting statistics. Accurate and reproducible finite ages >60 kyr are indeed possible by high-sensitivity LS spectroscopy, but require corroborating background blank data to be defensible.

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  • High-precision radiocarbon measurements of contemporaneous tree-ring dated wood from the British Isles and New Zealand: AD 1850–950

    Hogg, Alan G.; McCormac, F.G.; Higham, Thomas F.G.; Reimer, Paula J.; Baillie, Mike G.L.; Palmer, Jonathan G. (2002)

    Journal article
    University of Waikato

    The University of Waikato, Hamilton, New Zealand and The Queen’s University of Belfast, Northern Ireland radiocarbon dating laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus petraea) from Great Britain and cedar (Libocedrus bidwillii) and silver pine (Lagarostrobos colensoi) from New Zealand. The results show an average hemispheric offset over the 900 yr of measurement of 40 ± 13 yr. This value is not constant but varies with a periodicity of about 130 yr. The Northern Hemisphere measurements confirm the validity of the Pearson et al. (1986) calibration dataset.

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  • Calibration of the radiocarbon time scale for the southern hemisphere: AD 1850-950.

    McCormac, F.G.; Reimer, Paula J.; Hogg, Alan G.; Higham, Thomas F.G.; Baillie, Mike G.L.; Palmer, Jonathan G.; Stuiver, M. (2002)

    Journal article
    University of Waikato

    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.

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  • Variations of radiocarbon in tree rings: southern hemisphere offset preliminary results

    McCormac, F.G.; Hogg, Alan G.; Higham, Thomas F.G.; Baillie, Mike G.L.; Palmer, Jonathan G.; Xiong, Limin; Pilcher, J.R.; Brown, David; Hoper, S.T. (1998)

    Journal article
    University of Waikato

    The Queen's University of Belfast, Northern Ireland and University of Waikato, Hamilton, New Zealand radiocarbon laboratories have undertaken a series of high-precision measurements on decadal samples of dendrochronologically dated oak (Quercus patrea) and cedar (Libocedrus bidwillii) from Great Britain and New Zealand, respectively. The results show a real atmospheric offset of 3.4 ± 0.6% (27.2 ± 4.7 ¹⁴C yr) between the two locations for the interval AD 1725 to AD 1885, with the Southern Hemisphere being depleted in ¹⁴C. This result is less than the value currently used to correct Southern Hemisphere calibrations, possibly indicating a gradient in Δ¹⁴C within the Southern Hemisphere.

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  • Is there any Evidence for Regional Atmospheric 14C Offsets in the Southern Hemisphere?

    Hogg, Alan G.; Turney, Chris S.M.; Palmer, Jonathan G.; Cook, Ed; Buckley, Brendan (2013)

    Journal article
    University of Waikato

    Center for Accelerator Mass Spectrometry (CAMS) Tasmanian huon pine (Lagarostrobos franklinii) decadal measurements for the interval AD 745–855 suggest a mean interhemispheric radiocarbon offset (20 ± 5 yr), which is considerably lower than the previously reported mean interhemispheric offset for the last 2 millennia (44 ± 17 yr). However, comparable University of Waikato (Wk) New Zealand kauri (Agathis australis) measurements show significantly higher values (56 ± 6 yr), suggesting the possibility of a temporary geographic (intrahemispheric) offset between Tasmania, Australia, and Northland, New Zealand, during at least 1 common time interval. Here, we report 9 new Wk Tasmanian huon pine measurements from the decades showing the largest huon/kauri difference. We show statistically indistinguishable Wk huon and Wk kauri 14C ages, thus dispelling the suggestion of a 14C geographic offset between Tasmania and Northland.

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  • A wiggle-match date for Polynesian settlement of New Zealand

    Hogg, Alan G.; Higham, Thomas F.G.; Lowe, David J.; Palmer, Jonathan G.; Reimer, Paula J.; Newnham, Rewi M. (2002)

    Journal article
    University of Waikato

    Dating initial colonisation and environmental impacts by Polynesians in New Zealand is controversial. A key horizon is provided by the Kaharoa Tephra, deposited from an eruption of Mt Tarawera, because just underneath this layer are the first signs of forest clearance which imply human settlement. The authors used a log of celery pine from within Kaharoa deposits to derive a new precise date for the eruption via "wiggle-matching" – matching the radiocarbon dates of a sequence of samples from the log with the Southern Hemisphere calibration curve. The date obtained was 1314 ± 12 AD (2σ error), and the first environmental impacts and human occupation are argued to have occurred in the previous 50 years, i.e. in the late 13th – early 14th centuries AD. This date is contemporary with earliest settlement dates determined from archaeological sites in the New Zealand archipelago.

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  • Mapping and explaining the productivity of Pinus radiata in New Zealand

    Palmer, Jonathan G.; Watt, Michael S.; Kimberley, Mark O.; Hock, Barbara K.; Payn, Tim W.; Lowe, David J. (2010)

    Journal article
    University of Waikato

    Mapping Pinus radiata productivity for New Zealand not only provides useful information for forest owners, industry stakeholders and policy managers, but also enables current and future plantations to be visualised, quantified, and planned. Using an extensive set of permanent sample plots, split into fitting (n = 1,146) and validation (n = 618) datasets, models of P. radiata 300 Index (an index of volume mean annual increment) and Site Index (an index of height growth) were developed using a regression kriging technique. Spatial predictions were accurate and accounted for 61% and 70% of the variance for 300 Index and Site Index, respectively. Productivity predicted from these surfaces for the entire plantation estate averaged 27.4 m³ ha⁻¹ yr⁻¹ for the 300 Index and 30.4 m for Site Index. Surfaces showed wide regional variation in this productivity, which was attributable mainly to variation in air temperature and root-zone water storage from site to site.

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  • Evidence for suppressed mid-Holocene northeastern Australian monsoon variability from coral luminescence

    Lough, J.M.; Llewellyn, L.E.; Lewis, S.E.; Turney, Chris S.M.; Palmer, Jonathan G.; Cook, C.G.; Hogg, Alan G. (2014)

    Journal article
    University of Waikato

    Summer monsoon rainfall in northeastern (NE) Australia exhibits substantial interannual variability resulting in highly variable river flows. The occurrence and magnitude of these seasonal river flows are reliably recorded in modern inshore corals as luminescent lines. Here we present reconstructed annual river flows for two ~120 year mid-Holocene windows based on luminescence measurements from five cores obtained from three separate coral colonies. We were able to cross-date the luminescence signatures in four cores from two of the colonies, providing confidence in the derived reconstruction. Present-day NE Australian rainfall and river flow are sensitive to El Niño–Southern Oscillation (ENSO) variability, with La Niña (El Niño) events typically associated with wetter (drier) monsoon seasons. Thus, our replicated and annually resolved coral records provide valuable insights into the northern Australian summer monsoon and ENSO variability at a key period (6 ka) when greenhouse gas levels and ice sheet cover were comparable to the preindustrial period but orbital forcing was different. Average modern and mid-Holocene growth characteristics were very similar, suggesting that sea surface temperatures off NE Australia at 6 kyr were also close to present values. The reconstructed river flow record suggests, however, that the mid-Holocene Australian summer monsoon was weaker, less variable from year to year (possibly indicative of reduced ENSO variability), and characterized by more within-season flood pulses than present. In contrast to today, the delivery of moisture appears to have been dominated by eastward propagating convective coupled waves associated with the Madden-Julian Oscillation.

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  • SHCal13 Southern Hemisphere calibration, 0–50,000 years cal BP

    Hogg, Alan G.; Hua, Quan; Blackwell, Paul G.; Niu, Mu; Buck, Caitlin E.; Guilderson, Thomas P.; Heaton, Timothy J.; Palmer, Jonathan G.; Reimer, Paula J.; Reimer, Ron W.; Turney, Chris S.M.; Zimmerman, Susan R. H. (2013)

    Journal article
    University of Waikato

    The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the Northern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset.

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  • Revised calendar date for the Taupo eruption derived by ¹⁴C wiggle-matching using a New Zealand kauri ¹⁴C calibration data set

    Hogg, Alan G.; Lowe, David J.; Palmer, Jonathan G.; Boswijk, Gretel; Ramsey, Christopher Bronk (2011)

    Journal article
    University of Waikato

    Taupo volcano in central North Island, New Zealand, is the most frequently active and productive rhyolite volcano on Earth. Its latest explosive activity about 1800 years ago generated the spectacular Taupo eruption, the most violent eruption known in the world in the last 5000 years. We present here a new accurate and precise eruption date of AD 232 ± 5 (1718 ± 5 cal. BP) for the Taupo event. This date was derived by wiggle-matching 25 high-precision ¹⁴C dates from decadal samples of Phyllocladus trichomanoides from the Pureora buried forest near Lake Taupo against the high-precision, first-millennium AD subfossil Agathis australis (kauri) calibration data set constructed by the Waikato Radiocarbon Laboratory. It shows that postulated dates for the eruption estimated previously from Greenland ice-core records (AD 181 ± 2) and putative historical records of unusual atmospheric phenomena in ancient Rome and China (c. AD 186) are both untenable. However, although their conclusion of a zero north–south ¹⁴C offset is erroneous, and their data exhibit a laboratory bias of about 38 years (too young), Sparks et al. (Sparks RJ, Melhuish WH, McKee JWA, Ogden J, Palmer JG and Molloy BPJ (1995) ¹⁴C calibration in the Southern Hemisphere and the date of the last Taupo eruption: Evidence from tree-ring sequences. Radiocarbon 37: 155–163) correctly utilized the Northern Hemisphere calibration curve of Stuiver and Becker (Stuiver M and Becker B (1993) High-precision decadal calibration of the radiocarbon timescale, AD 1950–6000 BC. Radiocarbon 35: 35–65) to obtain an accurate wiggle-match date for the eruption identical to ours but less precise (AD 232 ± 15). Our results demonstrate that high-agreement levels, indicated by either agreement indices or χ² data, obtained from a ¹⁴C wiggle-match do not necessarily mean that age models are accurate. We also show that laboratory bias, if suspected, can be mitigated by applying the reservoir offset function with an appropriate error value (e.g. 0 ± 40 years). Ages for eruptives such as Taupo tephra that are based upon individual ¹⁴C dates should be considered as approximate only, and confined ideally to short-lived material (e.g. seeds, leaves, small branches or the outer rings of larger trees).

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