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Context: The potential lifespan of alligator gar (Atractosteus spatula) is currently unknown. A previous study applied bomb radiocarbon (14C) dating to establish ages >60 years, but maximum age was limited by the rise of bomb-produced 14C in the 1950s. Aims: An exceptionally large specimen (2.6 m, 148 kg) was captured in Mississippi and otolith growth zones revealed an age estimate of 95 years. This specimen provided an opportunity to apply new technology to validate the lifespan of alligator gar. Methods: Developments in accelerator mass spectrometry (AMS) led to technology that measures 14C continuously from carbonates (laser ablation-AMS), as opposed to single sample 14C analysis. Key results: Use of laser ablation AMS on the 2.6-m alligator gar otolith, and two smaller fish aged >60 years, supported ages that were older than original estimates by 5–20 years. Conclusions: Our study indicates that alligator gar age can be underestimated for the largest fish, maximum recorded length is 2.6 m based on a historical photograph, and lifespan is at least 75–95 years with support for an age of 100 years for the 2.6-m fish. Implications: An increase in lifespan of this magnitude would affect our understanding of population dynamics and recovery efforts. The otoliths (ear stones) of an exceptionally large alligator gar revealed an estimated age of 95 years. A previous study validated the lifespan of this species to 60 years using bomb-produced radiocarbon from nuclear testing. Our study revised the maximum recorded length to 2.6 m based on a historical photograph and used new radiocarbon technology to establish a 100-year lifespan for alligator gar. [ABSTRACT FROM AUTHOR]

We successfully measured four radiocarbon dates on two specimens of a black geometric rock painting with a fragment in jeopardy of naturally spalling off in the wall of a rock shelter in the Ẓufār region, in the south of the Sultanate of Oman. Extraction of carbon dioxide (CO2) for radiocarbon dating of the binder in the black pigment of the rock painting specimen was conducted in the plasma oxidation laboratory at the Office of Archeological Studies in Santa Fe, NM. The radiocarbon content was measured on the Swiss ETH-Zürich accelerator mass spectrometer MICADAS. The dates obtained agreed with one another within the statistical uncertainty and the average date of the four samples was 1500 ± 35 radiocarbon years BP. The calendric equivalents of the average date results in calendric calibration date ranges that span the mid-fifth through mid-seventh centuries (440–453 CE, 478–496 CE, and 534–646 CE). This research demonstrates that it is possible to date the black paintings of the Jebel al-Qara' area of Oman; this is the first pictogram that was dated using radiocarbon dating in the region. [ABSTRACT FROM AUTHOR]

Beachrock formations represent a powerful paleo-environmental proxy in tectonically active coasts because they are ideal marker horizons for reconstructing past sea-level positions and revealing vertical uplift rates. In this study, beachrocks from the Tekirdağ-Altınova coastal area were used to model the evolution of the late Holocene coastline in the northern Sea of Marmara. As the Tekirdağ-Altınova coastal area is located in the tectonically active western Marmara region, this study aimed to investigate the role of tectonic processes in the late Holocene evolution of the coastal landscape in the study area by assessing long-term vertical deformation rates. To document and estimate coastal uplift, lesser known submerged beachrocks within the nearshore coastal area of the northern Sea of Marmara were analyzed with novel laser ablation (LA)–accelerator mass spectrometry (AMS) and standard 14C-AMS techniques and correlated with late Holocene sea level variations. The preservation state of these beachrocks allowed for their identification and mapping through the use of an unmanned aerial vehicle (UAV) equipped with a high-resolution (5 cm) camera, followed by sampling via the coring method. The determined ages of marine shells and calcite cements from selected samples of submerged beachrock span between 2.6 and 13.6 ky BP. These ages could be correlated with the late Holocene sea-level highstand and were used to estimate the long-term uplift rate. Based on these findings, an uplift rate of approximately 0.56–0.79 mm/yr over the last 6500 years has been suggested for the area studied. [ABSTRACT FROM AUTHOR]

A novel technique making use of laser ablation coupled online to accelerator mass spectrometry (LA-AMS) allows analyzing the radiocarbon (14C) concentration in carbonate samples continuously at high spatial resolution within very short analysis times. This new technique can provide radiocarbon data similar to the spatial resolution of stable carbon (C) isotope measurements by isotope-ratio mass spectrometry (IRMS) and, thus, can help to interpret d13C signatures, which otherwise are difficult to understand due to numerous processes contributing to changes in C-isotope changes ratios. In this work we analyzed d13C and 14C on the Holocene stalagmite SPA 127 from the high-alpine Spannagel Cave (Austria). Combined stable carbon and radiocarbon profiles allow to identify three growth periods characterized by different d13C signatures: (i) the period > 8 ka BP is characterized by relatively low d13C values with small variability combined with a comparably high radiocarbon reservoir effect (expressed as dead carbon fraction, dcf) of around 60%. This points towards C contributions of host rock dissolution and/or from an old organic matter (OM) reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 3.8 – 8 ka BP a strong variability in d13C reaching values from -8 to +1‰ with a generally lower dcf was observed. The d13C variability is most likely caused by changes in gas exchange processes in the cave, which are induced by reduced drip rates as derived from reduced stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir is contributing less to stalagmite growth in this period possibly as a result of reduced precipitation or because it is exhausted. (iii) In the youngest section between 2.4 – 3.8 ka BP, comparably stable and low d13C values combined with an increasing dcf reaching up to 50% are again hinting towards a contribution of an aged OM reservoir in the karst. [ABSTRACT FROM AUTHOR]

Bomb-produced 14C has been used to make valid estimates of age for various marine organisms for 25 years, but fish ages that lead to birth years earlier than the period of increase in 14C lose their time specificity. As a result, bomb 14C dating is limited to a minimum age from the last year of prebomb levels because the temporal variation in 14C in the marine surface layer is negligible for decades before c. 1958. The longevity of red snapper (Lutjanus campechanus) in the Gulf of Mexico remains unresolved despite various forms of support for ages near 50–60 years. Although the age and growth of red snapper have been verified or validated to a limited extent, some scepticism remains about longevity estimates that exceed 30 years. In this study, red snapper otoliths were analysed for 14C using a novel laser ablation–accelerator mass spectrometry technique to provide a continuous record of 14C uptake. This approach provided a basis for age validation that extends beyond the normal limits of bomb 14C dating with confirmation of a 60-year longevity for red snapper in the Gulf of Mexico. A radiocarbon signal produced by testing nuclear bombs in the atmosphere has been used to age fishes for 25 years, but the method was limited to birth years later than 1958. Although validated to a minimum age near 40 years, the longevity of red snapper (Lutjanus campechanus) was unresolved until its otoliths were analysed for radiocarbon using laser ablation–accelerator mass spectrometry, with confirmation of a 60-year lifespan. [ABSTRACT FROM AUTHOR]

Leaf wax n-alkanes are increasingly used for quantitative reconstructions of past environmental changes. However, this is complicated in sediment archives with associated hydrological catchments since the stored n-alkanes can have different ages and origins. Direct 14C-dating of the n-alkanes has a great potential to derive independent age information for these proxies, allowing their correct paleoenvironmental interpretation. This holds also true for fluvial sediment-paleosols sequences (FSPS), where the n-alkane signal is divided into (i) a catchment signal that is deposited with fluvial sediments, and (ii) an in-situ signal from local biomass that increasingly dominates (paleo)soils with time. Therefore, age and origin of n-alkanes in FSPS are complex: In fluvial sediment layers they can be pre-aged and reworked when originating from eroded catchment soils, or originate from organic-rich sediment rocks in the catchment. In (paleo)soils, besides an inherited contribution from the catchment they were formed in-situ during pedogenesis and originate from local biomass. Depending on the different relative contributions from these sources, the n-alkane signal from an FSPS can show variable age offsets between its formation and final deposition. During this study, we applied compound-class 14C-dating to n-alkanes from a fluvial sediment-paleosol sequence (FSPS) along the upper Alazani River in eastern Georgia with Jurassic black clay shales in its upper catchment. Our results show that pre-heating the n-alkanes with 120 °C for 8 h before 14C-dating effectively removed the shorter chains (< C25), including a part of the catchment-derived n-alkanes from Jurassic black clay shales. The remaining petrogenic contributions on the longer chains (≥ C25) were estimated and corrected for using a constant correction factor. This was based on n-alkane concentrations in a Jurassic black clay shale sample from the upper catchment. Due to different degrees of pre-aging and reworking, the corrected leaf wax n-alkane ages still indicate relatively large age offsets between n-alkane formation and deposition: While due to a dominance of in-situ produced leaf wax n-alkanes no age offsets existed in intensively developed (paleo)soils, much larger age offsets in less intensively developed paleosols indicate larger proportions of inherited leaf wax n-alkanes from the fluvial parent material. Accordingly, age offsets in non-pedogenic fluvial sediments were largest, and strongly increase after ~ 4 ka cal. BP due to a greater proportion of pre-aged and reworked leaf wax n-alkanes. The leaf wax n-alkanes from intensively developed (paleo)soils indicate a local dominance of grasses/herbs throughout the Holocene, which was most likely caused by anthropogenic activity. The leaf wax n-alkanes from fluvial sediments show a dominance of both deciduous trees/shrubs and grasses/herbs in different parts of the FSPS between ~ 8 and ~ 5.6 cal. ka BP. Since no older deciduous trees/shrub-derived n-alkanes from the catchment were dated, this seems to confirm the formerly proposed delayed regional post-glacial reforestation compared with western and central Europe. [ABSTRACT FROM AUTHOR]

Recently a novel approach enabling spatially resolved analyses of radiocarbon (14C) in carbonates has been introduced, combining laser ablation with accelerator mass spectrometry (LA-AMS). Here, we present a comprehensive study to find optimum working conditions for LA-AMS. The stepwise optimization and characterization process comprises (i) finding a suitable laser source for the ablation of carbonates with highest CaCO3 to Cgas (i.e. CO2 or CO) conversion rate, (ii) studying different capillaries with different gas flow resistance that interface the LA-cell with the ion source of the AMS system, and (iii) determining the exchange rate of the LA cell and the width of a stalagmite's growth stop under real measurement conditions. Three laser sources (Nd:YAG@266 nm; Nd:YAG@213 nm; ArF excimer@193 nm) were tested at different fluences (3 and 23 J cm−2) for their Cgas-conversion efficiencies. Highest Cgas-conversion efficiencies of (70 ± 4)% were found with an ArF excimer laser, independently of laser fluence. The characterization of the system using different capillaries showed that gas flow rates applied in LA-AMS are more than a factor of five higher than for regular 14C AMS gas measurements, which probably results in reduced ionization efficiencies of the LA-AMS setup. An exchange rate of 10 min−1 is determined for the LA-cell design applied in this study by matching a 14C dataset derived by LA-AMS with modeled data (χ2-fit). Additionally, the model allowed to estimate the width of a growth stop in a stalagmite sample to be on the order of 0.25 mm. [ABSTRACT FROM AUTHOR]

Macrofossils of terrestrial plants, such as seeds, twigs, wood or leaf fragments are idealcandidates for establishing radiocarbon (14C) -based chronologies of lake sediments (1, 2).They are quickly transported from land to sediment and unlike the bulk organic carbon reflectatmospheric 14C concentrations. For accurate and precise 14C analysis samples are typicallyconverted into graphite and measured by accelerator mass spectrometry (AMS). In manycases, the terrestrial plant debris preserved in the lake sediments contain far less than 1 mgcarbon (C) and are consequently unsuited for robust 14C dating by conventional means.At the MICADAS AMS system at ETH Zurich, Switzerland, the 14C analyses ofcombustible samples ranging from 100 μg C down to 10 μg C, are performed on aroutine basis using an elemental analyzer (EA) for sample introduction. Such smallsamples are extremely sensitive to extraneous C, which is inevitably introduced duringsample preparation (acid-base-acid cleaning). Furthermore, the vessels carrying thesample material during EA-combustion are an additional source for extraneouscarbon. These different contamination sources will bias the results; hence, a minimumnumber of pretreatment steps and a suitable data correction strategy are necessary inorder to obtain accurate 14C dates (3). Processing standards that closely match thematrix of the sample material are required to precisely determine the contaminationparameters, namely the mass and its 14C contribution. Optimized 14C gas measurementprocedures and the subsequent data correction will be presented for EA-AMS analyses ofmacrofossils. [1] Hajdas, I. et al. (1995), QSR 14, 137. [2] Haas, M. et al. (2019) EPSL 505, 110. [3]Welte, C. et al. (2018) NIM B 437, 66. [ABSTRACT FROM AUTHOR]