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1. Atmospheric ¹⁴ C/ ¹² C changes during the last glacial period from Hulu Cave

   https://doi.org/10.1126/science.aau0747  

   Cheng, Hai; Edwards, R. Lawrence; Southon, John; Matsumoto, Katsumi; Feinberg, Joshua M.; Sinha, Ashish; Zhou, Weijian; Li, Hanying; Li, Xianglei; Xu, Yao; et al (December 2018, Science)

   Paired measurements of¹⁴C/¹²C and²³⁰Th ages from two Hulu Cave stalagmites complete a precise record of atmospheric¹⁴C covering the full range of the¹⁴C dating method (~54,000 years). Over the last glacial period, atmospheric¹⁴C/¹²C ranges from values similar to modern values to values 1.70 times higher (42,000 to 39,000 years ago). The latter correspond to¹⁴C ages 5200 years less than calibrated ages and correlate with the Laschamp geomagnetic excursion followed by Heinrich Stadial 4. Millennial-scale variations are largely attributable to Earth’s magnetic field changes and in part to climate-related changes in the oceanic carbon cycle. A progressive shift to lower¹⁴C/¹²C values between 25,000 and 11,000 years ago is likely related, in part, to progressively increasing ocean ventilation rates. 

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2. A NEW RAMPED PYROXIDATION/COMBUSTION FACILITY AT ¹⁴ CHRONO, BELFAST: SETUP DESCRIPTION AND INITIAL RESULTS

   https://doi.org/10.1017/RDC.2021.46  

   Keaveney, Evelyn M; Barrett, Gerard T; Allen, Kerry; Reimer, Paula J (August 2021, Radiocarbon)

   ABSTRACT The Belfast Ramped Pyroxidation/Combustion (RPO/RC) facility was established at the 14 CHRONO Centre (Queen’s University Belfast). The facility was created to provide targeted analysis of bulk material for refined chronological analysis and carbon source attribution for a range of sample types. Here we report initial RPO results, principally on background material, but also including secondary standards that are routinely analyzed at 14 CHRONO. A description of our setup, methodology, and background (blank) correction method for the system are provided. The backgrounds (anthracite, spar calcite, Pargas marble) reported by the system are in excess of 35,000 14 C years BP with a mean age of 39,345 14 C years BP (1σ = 36,497–43,800 years BP, N=44) with F 14 C = 0.0075 ± 0.0032. Initial results for standards are also in good agreement with consensus values: TIRI-B pine radiocarbon age = 4482 ± 47 years BP (N=13, consensus = 4508 years BP); IAEA-C6 ANU Sucrose F 14 C= 1.5036 ± 0.0034 (N=10, consensus F 14 C = 1.503). These initial tests have allowed problematic issues to be identified and improvements made for future analyses. 

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3. Comparing MICADAS Gas Source, Direct Carbonate, and Standard Graphite ¹⁴C Determinations of Biogenic Carbonate

   https://doi.org/10.1017/RDC.2024.45  

   Bright, Jordon; Ebert, Chris; Flores, Carola; Harnik, Paul G; Huntley, John Warren; Kowalewski, Michał; Portell, Roger W; Retelle, Michael; Schuur, Edward A; Kaufman, Darrell S (April 2024, Radiocarbon)

   Abstract Northern Arizona University, Flagstaff, Arizona, USA, recently installed a MIni CArbon DAting System (MICADAS) with a gas interface system (GIS) for determining the¹⁴C content of CO₂gas released by the acid dissolution of biogenic carbonates. We compare 48 paired graphite, GIS, and direct carbonate¹⁴C determinations of individual mollusk shells and echinoid tests. GIS sample sizes ranged between 0.5 and 1.5 mg and span 0.1 to 45.1 ka BP (n = 42). A reduced major axis regression shows a strong relationship between GIS and graphite percent Modern Carbon (pMC) values (m = 1.011; 95% CI [0.997–1.023], R²= 0.999) that is superior to the relationship between the direct carbonate and graphite values (m = 0.978; 95% CI [0.959-0.999], R²= 0.997). Sixty percent of GIS pMC values are within ±0.5 pMC of their graphite counterparts, compared to 26% of direct carbonate pMC values. The precision of GIS analyses is approximately ±70¹⁴C yrs to 6.5 ka BP and decreases to approximately ±130¹⁴C yrs at 12.5 ka BP. This precision is on par with direct carbonate and is approximately five times larger than for graphite. Six Plio-Pleistocene mollusk and echinoid samples yield finite ages when analyzed as direct carbonate but yield non-finite ages when analyzed as graphite or as GIS. Our results show that GIS¹⁴C dating of biogenic carbonates is preferable to direct carbonate¹⁴C dating and is an efficient alternative to standard graphite¹⁴C dating when the precision of graphite¹⁴C dating is not required. 

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4. Dental Wear and Molar Pulp Volume Reduction in Macaca fascicularis

   https://doi.org/10.1002/ajpa.70035  

   Selig, Keegan_R; Morse, Paul_E; Pampush, James_D; Kay, Richard_F (March 2025, American Journal of Biological Anthropology)

   ABSTRACT ObjectivesOdontoblasts lining the pulp cavity deposit dentine throughout life, meaning the volume of the pulp cavity decreases with age. Primates with more abrasive diets have relatively higher molar pulp volume in their unworn molars than those with less abrasive diets. We propose that species with more abrasive diets deposit additional dentine across their lifespans to help resist wear and extend the effective lifespan of their molars. Whereas both age and wear affect dentine deposition, it is unknown which of these two variables has the greater impact. Materials and MethodsWe measured pulp volume and calculated wear from micro‐CT scans of lower first molars of captive‐bredMacaca fascicularis(n = 13) of known age. We used reduced major axis regressions (alpha = 0.05) to test if age or wear was a better predictor of pulp volume. ResultsBoth variables have a significant negative relationship with pulp volume (age:p = 0.004,R² = 0.546; wear:p < 0.001,R² = 0.890). A mixed linear model of pulp volume against wear as main effect and age as covariant had a non‐significant interaction effect (p = 0.078) and confirmed that both age (p = 0.030) and wear (p = 0.004) are significantly negatively correlated with pulp volume. DiscussionResults suggest that whereas pulp volume decreases with age, wear is more strongly correlated with decreasing pulp volume. These findings have implications for interpreting odontoblast activity in response to sensory feedback and the relationship between pulp volume and diet. These results also have implications for using molar pulp volume to estimate age at death in humans. 

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5. Decomposition of Deglacial Pacific Radiocarbon Age Controls Using an Isotope‐Enabled Ocean Model

   https://doi.org/10.1029/2021PA004363  

   Zanowski, Hannah; Jahn, Alexandra; Gu, Sifan; Liu, Zhengyu; Marchitto, Thomas M. (August 2022, Paleoceanography and Paleoclimatology)

   Abstract During the last deglaciation Earth’s climate experienced strong and abrupt variations, resulting in major changes in global temperature, sea level, and ocean circulation. Although proxy records have significantly improved our understanding of climate during this period, questions remain regarding the connection between ocean circulation evolution and resulting geotracer distributions, including those of deep waters in the Pacific. Here we use the C‐iTRACE simulation, a transient ocean‐only, isotope‐enabled version of the Community Earth System Model, to better understand deglacial deep Pacific radiocarbon evolution in the context of circulation and reservoir age changes. Throughout the deglaciation, the Pacific Ocean circulation in C‐iTRACE responds strongly to glacial meltwater forcing, leading to large changes in deep Pacific Δ¹⁴C age. A multi‐millennial weakening of the overturning circulation from 20 to 15 ka BP leads to increases in deep Pacific Δ¹⁴C ages, but from 20 to 18 ka BP, nearly half (40%–60%) of this aging is controlled by changing surface reservoir age, corroborating previous studies showing that Δ¹⁴C is not solely a circulation age tracer. As the deglaciation proceeds, circulation change controls progressively more of the Δ¹⁴C age, accounting for more than 75% of it across the deep Pacific from 15 to 8 ka BP. 

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