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Joerg M Schaefer - One of the best experts on this subject based on the ideXlab platform.
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West Greenland and global in situ 14C Production-Rate calibrations
Journal of Quaternary Science, 2014Co-Authors: Nicolas E Young, Joerg M Schaefer, Brent M Goehring, Nathaniel A. Lifton, Irene Schimmelpfennig, Jason P BrinerAbstract:The in situ cosmogenic nuclide 14 C is unique compared with other nuclides because of its short half- life, and when combined with longer-lived isotopes (e.g. 10 Be), in situ 14 C can be a powerful tool for deciphering recent and complex surface exposure histories. Like all in situ cosmogenic nuclides, quantifying earth surface processes with in situ 14 C requires a well-constrained in situ 14 C Production Rate. We present a Production-Rate calibration from an independently dated moraine in West Greenland, previously used as an in situ 10 Be Production-Rate calibration site. The local in situ 14 C Production Rate is 22.8 � 1.4 atoms g � 1 a � 1 (69.28uN, 50.76u W; 350m asl) and when scaled to sea level/high latitude using time-dependent Lal/Stone scaling (Lm), we calculate a spallation-only in situ 14 C Production Rate of 12.0 � 0.9 atoms g � 1 a � 1 and a 14 C/ 10 Be Production Rate ratio of 3.1 � 0.2. The West Greenland in situ 14 C Production Rate is indistinguishable from the New Zealand, Promontory Point and Scottish Highlands in situ 14 C Production Rates. When combined, we calculate a global Production Rate of 12.1 � 0.5 atoms g � 1 a � 1 (Lm). Copyright # 2014 John Wiley & Sons, Ltd.
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a 10be Production Rate calibration for the arctic
Journal of Quaternary Science, 2013Co-Authors: Nicolas E Young, Joerg M Schaefer, Jason P Briner, Brent M GoehringAbstract:We present a Baffin Bay 10 Be Production-Rate calibration derived from glacial deposits in western Greenland and Baffin Island, and test our results against published 10 Be calibration datasets to develop an Arctic 10 Be Production Rate. Our calibration comprises: (i) 10 Be measurements from moraine boulders linked to a 14 C- dated moraine at Jakobshavn Isfjord in western Greenland, (ii) an independent and previously published 10 Be Production Rate at Jakobshavn Isfjord and (iii) re-measured 10 Be concentrations from a Baffin Island calibration site that is included in the north-eastern North America dataset. Combined, we calculate a sea-level/high-latitude 10 Be Production Rate for the Baffin Bay region of 3.96 � 0.07 atoms g � 1 a � 1 (Lal/Stone scaling model). After testing the Baffin Bay Rate against calibration sites in Norway and north-eastern North America, we calculate a more conservative Arctic Production Rate of 3.96 � 0.15 atoms g � 1 a � 1 . The Baffin Bay and Arctic 10 Be Production Rates are indistinguishable from the north-eastern North America 10 Be Production Rate (3.91 � 0.19 atoms g � 1 a � 1 ) and yield overall uncertainties of <2-3.7% (1s). These Production Rates reduce systematic uncertainties in 10 Be-based chronologies of ice-margin change and allow 10 Be-based chronologies to be more confidently compared with high-resolution climate records, such as those from Greenland ice cores. Copyright # 2013 John Wiley & Sons, Ltd.
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Calibration of the in situ cosmogenic 14 C Production Rate in New Zealand's Southern Alps
Journal of Quaternary Science, 2012Co-Authors: Irene Schimmelpfennig, Joerg M Schaefer, Brent M Goehring, Nathaniel Lifton, Aaron E. Putnam, David J. A. BarrellAbstract:In situ cosmogenic 14C (in situ 14C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ∼25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibRate the Production Rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C Production Rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibRate 10Be Production Rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic Production Rate of 11.4 ± 0.9 atoms 14C (g quartz)−1 a−1 and a 14C/10Be spallogenic Production Rate ratio of 3.0 ± 0.2. The results are comparable with Production Rates from previous calibrations in the northern hemisphere.
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in situ cosmogenic 10be Production Rate at lago argentino patagonia implications for late glacial climate chronology
Earth and Planetary Science Letters, 2011Co-Authors: Michael R Kaplan, Joerg M Schaefer, Aaron E. Putnam, Jorge A Strelin, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J VandergoesAbstract:Abstract When calculated with the commonly accepted average Northern Hemisphere Production Rate, 10 Be dates of surface boulders on moraines in the Lago Argentino area of Patagonia are younger than minimum-limiting 14 C ages for the same landforms. This disagreement could result from the lack of a regional 10 Be Production-Rate calibration site. To assess this possibility, we here present high-precision measurements of 10 Be in samples collected from surface boulders on the Herminita and Puerto Bandera moraine complexes deposited alongside Lago Argentino on the eastern flank of the Andes at 50°S in Patagonia. Together with maximum- and minimum-limiting 14 C ages for the two moraine systems, these measurements confine the local 10 Be Production Rate to between 3.60 and 3.82 atoms/g/yr (midpoint = 3.71 ± 0.11 atoms/g/yr) when using a time-dependent scaling method that incorpoRates a high-resolution geomagnetic model. This range includes upper and lower error bounds of acceptable Production Rates derived from both the Herminita and the Puerto Bandera sites. The upper limit of this range is more than 12% below the average Northern Hemisphere Production Rate, as calculated using the same scaling method, given in Balco et al. [Quat. Geochron 3 (2008) 174–195]. Other scaling models yield Production Rates with similarly large offsets from the Balco et al. (2008) Rate. On the other hand, the range of acceptable Production Rate values determined from Patagonia overlaps at 1σ with, and encompasses, the Production Rate recently derived in Macaulay valley in the Southern Alps of New Zealand [A. Putnam et al., Quat. Geochron. 5 (2010a) 392–409]. Within uncertainties (i.e., overlap at 1 sigma) this Patagonian Production Rate range also agrees with a recently determined Production Rate from low-elevation sites in northeastern North America and northern Norway. When the Macaulay Production Rate is used to calculate Patagonian exposure dates, 14 C and 10 Be chronologies are mutually compatible for late-glacial moraine systems. Both chronologies then indicate that outlet glaciers of the Southern Patagonian Icefield achieved a late-glacial maximum in the western reaches of Lago Argentino at 13,000 cal. yr BP at the end of the Antarctic Cold Reversal (14,500–12,900 cal. yr BP). Outlet glaciers subsequently receded to near present-day ice margins during the Younger Dryas stadial (12,900–11,700 cal. yr BP). This general retreat was interrupted about 12,200 cal. yr BP when Upsala Glacier constructed an interlobate complex of moraine ridges on Herminita Peninsula. Mountain glaciers in Patagonia and New Zealand, on both sides of the South Pacific Ocean, exhibited a coherent pattern of late-glacial ice-margin fluctuations.
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in situ cosmogenic 10be Production Rate calibration from the southern alps new zealand
Quaternary Geochronology, 2010Co-Authors: Aaron E. Putnam, Joerg M Schaefer, David J. A. Barrell, Michael R Kaplan, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J Vandergoes, Brent M GoehringAbstract:Abstract We present a 10 Be Production-Rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 ± 50 calendar years before AD2008. Surface 10 Be concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of ∼2%. Conversion of the 10 Be measurements to sea level/high-latitude values using each of five standard scaling methods indicates 10 Be Production Rates of 3.84 ± 0.08, 3.87 ± 0.08, 3.83 ± 0.08, 4.15 ± 0.09, and 3.74 ± 0.08 atoms g −1 a −1 , relative to the ‘07KNSTD’ 10 Be AMS standard, and including only the local time-integRated Production-Rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is ∼2.5% (1 σ ) for each Rate. To test the regional applicability of this Production-Rate calibration, we measured 10 Be concentrations in a set of nearby moraines deposited before 18 060 ± 200 years before AD2008. The 10 Be ages are only consistent with minimum-limiting 14 C age data when calculated using the new Production Rates. This also suggests that terrestrial in situ cosmogenic-nuclide Production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our Production Rates agree well with those of a recent calibration study from northeastern North America, but are 12–14% lower than other commonly adopted values. The Production-Rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period.
Brent M Goehring - One of the best experts on this subject based on the ideXlab platform.
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West Greenland and global in situ 14C Production-Rate calibrations
Journal of Quaternary Science, 2014Co-Authors: Nicolas E Young, Joerg M Schaefer, Brent M Goehring, Nathaniel A. Lifton, Irene Schimmelpfennig, Jason P BrinerAbstract:The in situ cosmogenic nuclide 14 C is unique compared with other nuclides because of its short half- life, and when combined with longer-lived isotopes (e.g. 10 Be), in situ 14 C can be a powerful tool for deciphering recent and complex surface exposure histories. Like all in situ cosmogenic nuclides, quantifying earth surface processes with in situ 14 C requires a well-constrained in situ 14 C Production Rate. We present a Production-Rate calibration from an independently dated moraine in West Greenland, previously used as an in situ 10 Be Production-Rate calibration site. The local in situ 14 C Production Rate is 22.8 � 1.4 atoms g � 1 a � 1 (69.28uN, 50.76u W; 350m asl) and when scaled to sea level/high latitude using time-dependent Lal/Stone scaling (Lm), we calculate a spallation-only in situ 14 C Production Rate of 12.0 � 0.9 atoms g � 1 a � 1 and a 14 C/ 10 Be Production Rate ratio of 3.1 � 0.2. The West Greenland in situ 14 C Production Rate is indistinguishable from the New Zealand, Promontory Point and Scottish Highlands in situ 14 C Production Rates. When combined, we calculate a global Production Rate of 12.1 � 0.5 atoms g � 1 a � 1 (Lm). Copyright # 2014 John Wiley & Sons, Ltd.
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a 10be Production Rate calibration for the arctic
Journal of Quaternary Science, 2013Co-Authors: Nicolas E Young, Joerg M Schaefer, Jason P Briner, Brent M GoehringAbstract:We present a Baffin Bay 10 Be Production-Rate calibration derived from glacial deposits in western Greenland and Baffin Island, and test our results against published 10 Be calibration datasets to develop an Arctic 10 Be Production Rate. Our calibration comprises: (i) 10 Be measurements from moraine boulders linked to a 14 C- dated moraine at Jakobshavn Isfjord in western Greenland, (ii) an independent and previously published 10 Be Production Rate at Jakobshavn Isfjord and (iii) re-measured 10 Be concentrations from a Baffin Island calibration site that is included in the north-eastern North America dataset. Combined, we calculate a sea-level/high-latitude 10 Be Production Rate for the Baffin Bay region of 3.96 � 0.07 atoms g � 1 a � 1 (Lal/Stone scaling model). After testing the Baffin Bay Rate against calibration sites in Norway and north-eastern North America, we calculate a more conservative Arctic Production Rate of 3.96 � 0.15 atoms g � 1 a � 1 . The Baffin Bay and Arctic 10 Be Production Rates are indistinguishable from the north-eastern North America 10 Be Production Rate (3.91 � 0.19 atoms g � 1 a � 1 ) and yield overall uncertainties of <2-3.7% (1s). These Production Rates reduce systematic uncertainties in 10 Be-based chronologies of ice-margin change and allow 10 Be-based chronologies to be more confidently compared with high-resolution climate records, such as those from Greenland ice cores. Copyright # 2013 John Wiley & Sons, Ltd.
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Calibration of the in situ cosmogenic 14 C Production Rate in New Zealand's Southern Alps
Journal of Quaternary Science, 2012Co-Authors: Irene Schimmelpfennig, Joerg M Schaefer, Brent M Goehring, Nathaniel Lifton, Aaron E. Putnam, David J. A. BarrellAbstract:In situ cosmogenic 14C (in situ 14C) analysis from quartz‐bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ∼25 ka). It is particularly powerful when combined with longer‐lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibRate the Production Rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C Production Rate estimate derived from a well‐dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibRate 10Be Production Rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic Production Rate of 11.4 ± 0.9 atoms 14C (g quartz)−1 a−1 and a 14C/10Be spallogenic Production Rate ratio of 3.0 ± 0.2. The results are comparable with Production Rates from previous calibrations in the northern hemisphere.
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in situ cosmogenic 10be Production Rate calibration from the southern alps new zealand
Quaternary Geochronology, 2010Co-Authors: Aaron E. Putnam, Joerg M Schaefer, David J. A. Barrell, Michael R Kaplan, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J Vandergoes, Brent M GoehringAbstract:Abstract We present a 10 Be Production-Rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 ± 50 calendar years before AD2008. Surface 10 Be concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of ∼2%. Conversion of the 10 Be measurements to sea level/high-latitude values using each of five standard scaling methods indicates 10 Be Production Rates of 3.84 ± 0.08, 3.87 ± 0.08, 3.83 ± 0.08, 4.15 ± 0.09, and 3.74 ± 0.08 atoms g −1 a −1 , relative to the ‘07KNSTD’ 10 Be AMS standard, and including only the local time-integRated Production-Rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is ∼2.5% (1 σ ) for each Rate. To test the regional applicability of this Production-Rate calibration, we measured 10 Be concentrations in a set of nearby moraines deposited before 18 060 ± 200 years before AD2008. The 10 Be ages are only consistent with minimum-limiting 14 C age data when calculated using the new Production Rates. This also suggests that terrestrial in situ cosmogenic-nuclide Production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our Production Rates agree well with those of a recent calibration study from northeastern North America, but are 12–14% lower than other commonly adopted values. The Production-Rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period.
Dita B Vizoso - One of the best experts on this subject based on the ideXlab platform.
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Phenotypic plasticity in sperm Production Rate: there’s more to it than testis size
Evolutionary Ecology, 2007Co-Authors: Lukas Schärer, Dita B VizosoAbstract:Evolutionary theory predicts that males should produce more sperm when sperm competition is high. Because sperm Production Rate is difficult to measure in most organisms, comparative and experimental studies have typically used testis size instead, while assuming a good correspondence between testis size and sperm Production Rate. Here we evaluate this common assumption using the marine flatworm Macrostomum lignano , in which we can estimate sperm Production Rate because the accumulation of produced sperm can be observed in vivo. In earlier studies we have shown that testis size is phenotypically plastic in M. lignano : worms can be induced to make larger testes by raising them in groups instead of pairs, and these larger testes have a higher cell proliferation activity (i.e. they are more energetically costly). Here we demonstRate that worms with such experimentally enlarged testes have a higher sperm Production Rate. Moreover, although testis size and sperm Production Rate were related linearly, worms with experimentally enlarged testes had a higher sperm Production Rate per unit testis size (i.e. a higher spermatogenic efficiency). We thus show that phenotypically plastic adjustment of sperm Production Rate includes a component that is independent of testis size. We discuss possible reasons for this novel finding, and suggest that the relationship between testis size and sperm Production needs to be evaluated in other species as well.
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Phenotypic plasticity in sperm Production Rate: there's more to it than testis size
Evolutionary Ecology, 2006Co-Authors: Lukas Schärer, Dita B VizosoAbstract:Evolutionary theory predicts that males should produce more sperm when sperm competition is high. Because sperm Production Rate is difficult to measure in most organisms, comparative and experimental studies have typically used testis size instead, while assuming a good correspondence between testis size and sperm Production Rate. Here we evaluate this common assumption using the marine flatworm Macrostomum lignano, in which we can estimate sperm Production Rate because the accumulation of produced sperm can be observed in vivo. In earlier studies we have shown that testis size is phenotypically plastic in M. lignano: worms can be induced to make larger testes by raising them in groups instead of pairs, and these larger testes have a higher cell proliferation activity (i.e. they are more energetically costly). Here we demonstRate that worms with such experimentally enlarged testes have a higher sperm Production Rate. Moreover, although testis size and sperm Production Rate were related linearly, worms with experimentally enlarged testes had a higher sperm Production Rate per unit testis size (i.e. a higher spermatogenic efficiency). We thus show that phenotypically plastic adjustment of sperm Production Rate includes a component that is independent of testis size. We discuss possible reasons for this novel finding, and suggest that the relationship between testis size and sperm Production needs to be evaluated in other species as well.
Marcus J Vandergoes - One of the best experts on this subject based on the ideXlab platform.
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in situ cosmogenic 10be Production Rate at lago argentino patagonia implications for late glacial climate chronology
Earth and Planetary Science Letters, 2011Co-Authors: Michael R Kaplan, Joerg M Schaefer, Aaron E. Putnam, Jorge A Strelin, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J VandergoesAbstract:Abstract When calculated with the commonly accepted average Northern Hemisphere Production Rate, 10 Be dates of surface boulders on moraines in the Lago Argentino area of Patagonia are younger than minimum-limiting 14 C ages for the same landforms. This disagreement could result from the lack of a regional 10 Be Production-Rate calibration site. To assess this possibility, we here present high-precision measurements of 10 Be in samples collected from surface boulders on the Herminita and Puerto Bandera moraine complexes deposited alongside Lago Argentino on the eastern flank of the Andes at 50°S in Patagonia. Together with maximum- and minimum-limiting 14 C ages for the two moraine systems, these measurements confine the local 10 Be Production Rate to between 3.60 and 3.82 atoms/g/yr (midpoint = 3.71 ± 0.11 atoms/g/yr) when using a time-dependent scaling method that incorpoRates a high-resolution geomagnetic model. This range includes upper and lower error bounds of acceptable Production Rates derived from both the Herminita and the Puerto Bandera sites. The upper limit of this range is more than 12% below the average Northern Hemisphere Production Rate, as calculated using the same scaling method, given in Balco et al. [Quat. Geochron 3 (2008) 174–195]. Other scaling models yield Production Rates with similarly large offsets from the Balco et al. (2008) Rate. On the other hand, the range of acceptable Production Rate values determined from Patagonia overlaps at 1σ with, and encompasses, the Production Rate recently derived in Macaulay valley in the Southern Alps of New Zealand [A. Putnam et al., Quat. Geochron. 5 (2010a) 392–409]. Within uncertainties (i.e., overlap at 1 sigma) this Patagonian Production Rate range also agrees with a recently determined Production Rate from low-elevation sites in northeastern North America and northern Norway. When the Macaulay Production Rate is used to calculate Patagonian exposure dates, 14 C and 10 Be chronologies are mutually compatible for late-glacial moraine systems. Both chronologies then indicate that outlet glaciers of the Southern Patagonian Icefield achieved a late-glacial maximum in the western reaches of Lago Argentino at 13,000 cal. yr BP at the end of the Antarctic Cold Reversal (14,500–12,900 cal. yr BP). Outlet glaciers subsequently receded to near present-day ice margins during the Younger Dryas stadial (12,900–11,700 cal. yr BP). This general retreat was interrupted about 12,200 cal. yr BP when Upsala Glacier constructed an interlobate complex of moraine ridges on Herminita Peninsula. Mountain glaciers in Patagonia and New Zealand, on both sides of the South Pacific Ocean, exhibited a coherent pattern of late-glacial ice-margin fluctuations.
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in situ cosmogenic 10be Production Rate calibration from the southern alps new zealand
Quaternary Geochronology, 2010Co-Authors: Aaron E. Putnam, Joerg M Schaefer, David J. A. Barrell, Michael R Kaplan, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J Vandergoes, Brent M GoehringAbstract:Abstract We present a 10 Be Production-Rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 ± 50 calendar years before AD2008. Surface 10 Be concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of ∼2%. Conversion of the 10 Be measurements to sea level/high-latitude values using each of five standard scaling methods indicates 10 Be Production Rates of 3.84 ± 0.08, 3.87 ± 0.08, 3.83 ± 0.08, 4.15 ± 0.09, and 3.74 ± 0.08 atoms g −1 a −1 , relative to the ‘07KNSTD’ 10 Be AMS standard, and including only the local time-integRated Production-Rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is ∼2.5% (1 σ ) for each Rate. To test the regional applicability of this Production-Rate calibration, we measured 10 Be concentrations in a set of nearby moraines deposited before 18 060 ± 200 years before AD2008. The 10 Be ages are only consistent with minimum-limiting 14 C age data when calculated using the new Production Rates. This also suggests that terrestrial in situ cosmogenic-nuclide Production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our Production Rates agree well with those of a recent calibration study from northeastern North America, but are 12–14% lower than other commonly adopted values. The Production-Rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period.
Robert C Finkel - One of the best experts on this subject based on the ideXlab platform.
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in situ cosmogenic 10be Production Rate at lago argentino patagonia implications for late glacial climate chronology
Earth and Planetary Science Letters, 2011Co-Authors: Michael R Kaplan, Joerg M Schaefer, Aaron E. Putnam, Jorge A Strelin, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J VandergoesAbstract:Abstract When calculated with the commonly accepted average Northern Hemisphere Production Rate, 10 Be dates of surface boulders on moraines in the Lago Argentino area of Patagonia are younger than minimum-limiting 14 C ages for the same landforms. This disagreement could result from the lack of a regional 10 Be Production-Rate calibration site. To assess this possibility, we here present high-precision measurements of 10 Be in samples collected from surface boulders on the Herminita and Puerto Bandera moraine complexes deposited alongside Lago Argentino on the eastern flank of the Andes at 50°S in Patagonia. Together with maximum- and minimum-limiting 14 C ages for the two moraine systems, these measurements confine the local 10 Be Production Rate to between 3.60 and 3.82 atoms/g/yr (midpoint = 3.71 ± 0.11 atoms/g/yr) when using a time-dependent scaling method that incorpoRates a high-resolution geomagnetic model. This range includes upper and lower error bounds of acceptable Production Rates derived from both the Herminita and the Puerto Bandera sites. The upper limit of this range is more than 12% below the average Northern Hemisphere Production Rate, as calculated using the same scaling method, given in Balco et al. [Quat. Geochron 3 (2008) 174–195]. Other scaling models yield Production Rates with similarly large offsets from the Balco et al. (2008) Rate. On the other hand, the range of acceptable Production Rate values determined from Patagonia overlaps at 1σ with, and encompasses, the Production Rate recently derived in Macaulay valley in the Southern Alps of New Zealand [A. Putnam et al., Quat. Geochron. 5 (2010a) 392–409]. Within uncertainties (i.e., overlap at 1 sigma) this Patagonian Production Rate range also agrees with a recently determined Production Rate from low-elevation sites in northeastern North America and northern Norway. When the Macaulay Production Rate is used to calculate Patagonian exposure dates, 14 C and 10 Be chronologies are mutually compatible for late-glacial moraine systems. Both chronologies then indicate that outlet glaciers of the Southern Patagonian Icefield achieved a late-glacial maximum in the western reaches of Lago Argentino at 13,000 cal. yr BP at the end of the Antarctic Cold Reversal (14,500–12,900 cal. yr BP). Outlet glaciers subsequently receded to near present-day ice margins during the Younger Dryas stadial (12,900–11,700 cal. yr BP). This general retreat was interrupted about 12,200 cal. yr BP when Upsala Glacier constructed an interlobate complex of moraine ridges on Herminita Peninsula. Mountain glaciers in Patagonia and New Zealand, on both sides of the South Pacific Ocean, exhibited a coherent pattern of late-glacial ice-margin fluctuations.
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in situ cosmogenic 10be Production Rate calibration from the southern alps new zealand
Quaternary Geochronology, 2010Co-Authors: Aaron E. Putnam, Joerg M Schaefer, David J. A. Barrell, Michael R Kaplan, George H Denton, Robert C Finkel, Roseanne Schwartz, Marcus J Vandergoes, Brent M GoehringAbstract:Abstract We present a 10 Be Production-Rate calibration derived from an early Holocene debris-flow deposit at about 1000 m above sea level in the central Southern Alps, New Zealand, in the mid-latitude Southern Hemisphere. Ten radiocarbon ages on macrofossils from a soil horizon buried by the deposit date the deposit to 9690 ± 50 calendar years before AD2008. Surface 10 Be concentrations of seven large boulders partially embedded in the stable surface of the deposit are tightly distributed, yielding a standard deviation of ∼2%. Conversion of the 10 Be measurements to sea level/high-latitude values using each of five standard scaling methods indicates 10 Be Production Rates of 3.84 ± 0.08, 3.87 ± 0.08, 3.83 ± 0.08, 4.15 ± 0.09, and 3.74 ± 0.08 atoms g −1 a −1 , relative to the ‘07KNSTD’ 10 Be AMS standard, and including only the local time-integRated Production-Rate uncertainties. When including a sea level high-latitude scaling uncertainty the overall error is ∼2.5% (1 σ ) for each Rate. To test the regional applicability of this Production-Rate calibration, we measured 10 Be concentrations in a set of nearby moraines deposited before 18 060 ± 200 years before AD2008. The 10 Be ages are only consistent with minimum-limiting 14 C age data when calculated using the new Production Rates. This also suggests that terrestrial in situ cosmogenic-nuclide Production did not change significantly from Last Glacial Maximum to Holocene time in New Zealand. Our Production Rates agree well with those of a recent calibration study from northeastern North America, but are 12–14% lower than other commonly adopted values. The Production-Rate values presented here can be used elsewhere in New Zealand for rock surfaces exposed during or since the last glacial period.
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regional beryllium 10 Production Rate calibration for late glacial northeastern north america
Quaternary Geochronology, 2009Co-Authors: Greg Balco, Jason P Briner, Robert C Finkel, John A Rayburn, John C Ridge, Joerg M SchaeferAbstract:Abstract The major uncertainty in relating cosmogenic-nuclide exposure ages to ages measured by other dating methods comes from extrapolating nuclide Production Rates measured at globally scattered calibration sites to the sites of unknown age that are to be dated. This uncertainty can be reduced by locating Production Rate calibration sites that are similar in location and age to the sites to be dated. We use this stRategy to reconcile exposure age and radiocarbon deglaciation chronologies for northeastern North America by compiling 10Be Production Rate calibration measurements from independently dated late-glacial and early Holocene ice-marginal landforms in this region. 10Be Production Rates measured at these sites are 6–12% lower than predicted by the commonly accepted global 10Be calibration data set used with any published Production Rate scaling scheme. In addition, the regional calibration data set shows significantly less internal scatter than the global calibration data set. Thus, this calibration data set can be used to improve both the precision and accuracy of exposure dating of regional late-glacial events. For example, if the global calibration data set is used to calculate exposure ages, the exposure-age deglaciation chronology for central New England is inconsistent with the deglaciation chronology inferred from radiocarbon dating and varve stratigraphy. We show that using the regional data set instead makes the exposure age and radiocarbon chronologies consistent. This increases confidence in correlating exposure ages of ice-marginal landforms in northeastern North America with glacial and climate events dated by other means.
