O01_01

Holocene glacier chronologies from various cosmogenic nuclides combined with radiocarbon dating

Schimmelpfennig I¹, Charton J¹, Jomelli V¹, Schaefer J², Lamp J², Godard V¹, Bard E¹

¹Aix Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix En Provence, France, ²LDEO, Columbia University, Palisades, USA

This presentation deals with the reconstruction of Holocene glacier advances and retreats using cosmogenic nuclide dating of glacial landforms in combination with radiocarbon-dates in various glacier forefields. One site is Steingletscher (Central European Alps, Northern mid-latitudes), where we applied the emerging approach of paired ¹⁰Be-¹⁴C dating of recently deglaciated bedrock to constrain the duration of Holocene glacier recession. Combining the results with the ¹⁰Be moraine chronology and existing radiocarbon dates of organic material from the same site allowed reconstructing the glacier’s Holocene retreat and advance history (Schimmelpfennig et al., Clim. Past 18, 23-44, 2022). Large glacier extents prevailed in the Earliest and the Late Holocene, while in between significant retreat occurred during several millennia, which is in agreement with existing glacier chronologies in the Alps and other parts of the North-Atlantic region as well as in the Tropics (Jomelli et al., Nat. Comm. 13, 1419, 2022).

Another site is Ampere glacier on the basaltic Kerguelen archipelago in the Southern mid-latitudes. We reconstructed the Holocene behavior of this glacier, using ³⁶Cl dating of moraines and paired bedrock and erratic boulder surfaces (Charton et al., QSR 283, 107461, 2022). The results, combined with earlier published radiocarbon-dates of peat, imply that glaciers had significantly retracted extents throughout the Holocene, while Holocene maximum extents occurred only in the last millennium. This pattern is quasi-unique and highlights the non-uniformity of Holocene glacier behavior throughout southern mid-latitudes.

O01_02

Ion-Laser InterAction Mass Spectrometry for long-lived cosmogenic radionuclides in stony meteorites

Martschini M¹, Merchel S¹, Marchhart O¹, Wieser A¹, Golser R¹

¹University of Vienna - Faculty of Physics, Isotope Physics - VERA, Vienna, Austria

Accelerator mass spectrometry (AMS) is usually the method-of-choice for the detection of long-lived cosmogenic nuclides such as ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁵³Mn and 60Fe with half-lifes between 6 ka and 4 Ma. Until recently however, tedious radiochemical separation to deplete matrices and isobars was a prerequisite for AMS hindering fast analysis.

Now, the world-wide unique Ion-Laser InterAction Mass Spectrometry (ILIAMS) system developed at the Vienna Environmental Research Accelerator (VERA) [1] can eliminate the need for chemistry in selected cases, i.e. presently for samples with stable isotope abundance of ≥1‰ and isotopic ratios above 10^−11.

Laser photodetachment and ion-molecule-reactions of anions provide unprecedented isobar suppression for many AMS-isotopes by up to eleven orders of magnitude. Hence, ILIAMS-assisted AMS enables the direct detection of e.g., ²⁶Al/²⁷Al (~10⁻¹⁰, extraction of AlO⁻) and ⁴¹Ca/⁴⁰Ca (~10⁻¹¹, extraction of CaF3⁻) in simply-crushed stony meteorites containing intrinsic ~1% Al and Ca. The presence of isobars originating from the natively-abundant elements (15% Mg, 1‰ K) does not cause any analysis problem making radiochemical separation redundant.

This newly-established instrumental AMS (IAMS) is opening routes to high-sample throughput analysis, reasonable and fast provenance checks for (extra-)terrestrial origin and identification of frauds. Additionally, first ²⁶Al/²⁷Al (~10⁻¹¹) tests on terrestrial quartz samples from high altitudes used for exposure dating look promising to instantly set-up IAMS as a pre-screening and sample selection method for in-situ dating applications before starting tedious chemistry for more accurate results.

[1] M. Martschini et al. Radiocarbon 2021, first view, doi.org/10.1017/RDC.2021.73.

O01_03

Soil dynamics revealed by cosmogenic nuclides

HATTÉ C^1,2, CORNU S³

¹Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France, ²Silesian University of Technology, Gliwice, Poland, ³CEREGE, Aix-en-Provence, France

Over the last few years, considerable attention has been devoted in the scientific literature and in the media to the concept of “ecosystem” services of soils. The monetary valuation of these services is often depicted as a necessary condition for the preservation of the natural capital that soils represent. Amongst the eleven recognized services of soil, at least eight are associated to soil carbon dynamics and to particles displacement: carbon sequestration, climate regulation, provision of food, nutrient cycling, habitat for organisms, flood regulation and foundation for human infrastructure.

Assessing the capacity of soils to provide these services is an immediate societal priority. Conventional solutions such as measuring carbon content, bulk density, particle size distribution... don’t always allow to reach the dynamics notion and/or to answer questions quickly enough for a process reversal to take place. As an alternative method, measuring cosmogenic nuclides can be used to determine the timing of events and the dynamics of major pedological processes. They can provide clues to soil carbon dynamics and particle movement within the profiles themselves. Their use is thus beyond determining rates of erosion, denudation and uplift by analyzing the upper layers of soil profiles as typically done with such isotopes.

In this presentation, we will outline key elements delivered by cosmogenic nuclides to the soil sciences. They have been used alone or in combination with others isotopes. ¹⁴C, ¹⁰Be, ¹³⁷Cs, ²¹⁰Pb will be discussed for the modeling of carbon dynamics in soils and for the transfer of fine particles in profiles.

O01_04

What we still need to learn: lessons from five years operation of the ANSTO in-situ ¹⁴C laboratory

Fulop R¹, SMITH A¹, Yang B¹, White D², Stutz J³, Codilean A⁴, Fink D¹

¹Australia's Nuclear Science and Technology Organisation, Sydney, Australia, ²University of Canberra, Canberra, Australia, ³Victoria University of Wellington, Wellington, New Zealand, ⁴University of Wollongong, Wollongong, Australia

In-situ ¹⁴C is slowly but steadily gaining its place in the cosmogenic nuclide toolkit. The isotope’s relatively short half-life of 5730 years, when compared to the longer-lived and more routinely analysed cosmogenic nuclides, means that it is substantially more sensitive to short term variations in process rates or more suitable at investigating recent exposure events. The above property has proven very valuable in studying deglaciation histories in Antarctica, where the low erosion rates and cold-based glaciation produce widespread inheritance in erratics or bedrock surfaces making it difficult to quantify ice sheet retreat solely with ¹⁰Be. Furthermore, in-situ ¹⁴C used in combination with ²⁶Al and ¹⁰Be is also particularly well suited to studying the relatively short timescales that characterize fluvial sediment transfer and storage, once more illustrated well by recent work.

Despite the above, the extraction of in-situ ¹⁴C from geological samples is still problematic, with recent laboratory intercomparison studies showing considerable overdispersion in both intra and inter laboratory comparisons of standard materials. The discrepancies between laboratories have been attributed to several factors, including the quality of some intercomparison materials, however, clear consensus on the matter is yet to be reached.

We will discuss issues of in-situ ¹⁴C systematics related to phase transformation and micro graphitisation. We will also showcase examples where sample type and quartz impurity have large bearing on success of sample extraction and obtained ¹⁴C results. Lastly, we revisit aspects of in-situ ¹⁴C systematics that still carry considerable uncertainty.

O01_05

Reconstructing the timing of Pleistocene glacier advances in the Swiss northern Alpine Foreland

Dieleman C¹, Christl M², Vockenhuber C², Gautschi P², Akçar N¹

¹University of Bern, Bern, Switzerland, ²ETH Zurich, Zurich, Switzerland

During the last decade, isochron-burial dating was successfully used in constraining the timing of fluvial sediment deposition. Though, its application to glacial and glaciofluvial deposits is challenging because these deposits are generally characterized by low cosmogenic nuclide concentrations due to repeated glacial erosion. The Swiss northern Alpine Foreland witnessed repeated glacier advances during the Quaternary; thirteen advances were identified yet. The records of these advances are found in, from the oldest to the youngest, Höhere Deckenschotter (HDS; Higher Cover Gravels), Tiefere Deckenschotter (TDS; Lower Cover Gravels), Hochterrasse (HT; Higher Terrace) and Niederterrasse (NT; Lower Terrace). The Deckenschotter are characterized by a succession of glaciofluvial gravel beds intercalated with glacial and/or overbank deposits and considered to be the oldest Quaternary deposits, however their chronology is still under debate, because the first cosmogenic nuclide chronology, recently established at few sites, contradicts the existing morphostratigraphy. In this study, we present a solid cosmogenic nuclide chronology for the Swiss Deckenschotter reconstructed at eighteen sites during the last decade. Based on this chronology, we revealed the timing of five Pleistocene glaciations between ca. 2.5 Ma and ca. 250 ka, whereof three occurred during the Early Pleistocene prior to the Mid-Pleistocene Revolution (MPR) and two during the Middle Pleistocene. Based on this new chronostratigraphy, we conclude that the Swiss Deckenschotter are cut-and-fill sequences. Furthermore, these ages indicate a rather constant local base level between 2.5 Ma and 1 Ma, which has likely been lowered afterwards probably induced by the MPR.

O01_06

Developing an in-situ ¹⁴C chronology for North Greenland

Søndergaard A¹, Steineman O¹, Haghipour N¹, Wacker L¹, Ivy-Ochs S¹, Larsen N²

¹Laboratory for Ion Beam Physics, Eth Zürich, Zürich, Switzerland, ²Centre for GeoGenetics, GLOBE Institute, Univeristy of Copenhagen, Copenhagen, Denmark

Determining the sensitivity of the Greenland Ice Sheet during the Holocene is a key prerequisite for understanding the future response of the ice sheet to global warming. It has proven difficult to constrain the glacial history of particularly North Greenland using ¹⁰Be exposure dating, an area predicted to be a key component in future mass loss from the ice sheet. This project  will use cosmogenic in-situ ¹⁴C exposure dating to constrain Holocene ice sheet fluctuations in North Greenland.

Cosmogenic nuclides are produced in rocks when cosmic rays hit the surface of the Earth. The cosmogenic nuclide inventory of a rock surfaces is therefore a key tool for chronicling the waxing and waning of ice. The most commonly analyzed nuclide is ¹⁰Be, which has a half-life of 1.4 Myr. However, a particular challenge arises in regions where the ice sheet base is cold and slow-moving. In these regions, erosion rates are low and ¹⁰Be inventories produced during earlier exposure periods accumulate instead of being removed, which result in exposure ages older than the last period of exposure. To circumvent this problem, we use in-situ produced cosmogenic ¹⁴C. Due to the shorter half-life (5730 yr), in-situ ¹⁴C inventories will, contrary ¹⁰Be, decrease not only because of rock surface erosion but also due to shielding from ice cover. Measurements of in-situ ¹⁴C , carried out at the in-situ ¹⁴C  line at Laboratory of Ion Beam Physics, ETH Zürich, can therefore help to obtain more reliable ice reconstructions for North Greenland.

O01_07

Studying LiBO₂ fluxes and low-temperature combustion systematics with a fully automated in situ cosmogenic ¹⁴C processing system at PRIME Lab

Lifton N¹, Koester A¹

¹Purdue University, West Lafayette, United States

Extraction procedures for in situ cosmogenic ¹⁴C (in situ ¹⁴C) from quartz require quantitative isotopic yields while maintaining scrupulous isolation from ubiquitous atmospheric/organic ¹⁴C. These time- and labor-intensive procedures are ripe for automation; unfortunately, our original automated in situ ¹⁴C extraction and purification systems, reconfigured and retrofitted from our original systems at the University of Arizona, proved less reliable than hoped. We therefore installed a fully automated stainless-steel system (except for specific glass or fused-quartz components) incorporating more reliable valves and improved actuator designs, along with a more robust liquid nitrogen distribution system. As with earlier versions, the new system uses a degassed LiBO₂ flux to dissolve the quartz sample in an ultra-high-purity oxygen atmosphere, after a lower-temperature combustion step to remove atmospheric/organic ¹⁴C.

We first compared single-use high-purity Al₂O₃ vs. reusable Pt/10%Rh sample combustion boats. The Pt/10%Rh boats heat more evenly than the Al₂O₃, reducing procedural blank levels and variability for a given LiBO₂ flux. This lower blank variability also allowed us to trace progressively increasing blanks to the fluxes from our original manufacturer. Switching to a new manufacturer returned our blanks to consistently low levels.

We also analyzed the CRONUS-A intercomparison material to investigate sensitivity of extracted ¹⁴C concentrations to the temperature and duration of the combustion step. Results indicate that 1-hr combustion steps at either 500 or 600°C yield results consistent with the original intercomparison value of Jull et al. (2015), while 2 hr at 600°C results in loss of ca. 10% of the high-temperature ¹⁴C inventory.

O01_08

Calculating catchmentwide erosion rates using an existing online calculator

Stübner K¹, Balco G²

¹Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ²Berkeley Geochronology Center, Berkeley, USA

The calculation of exposure ages and erosion rates from ¹⁰Be and ²⁶Al concentrations in quartz is widely used in geomorphological and Quaternary geological applications. Existing calculators provide a simple means to compute age or erosion rate in a consistent and reproducible way and without the need to delve deeply into production scaling schemes and palaeomagnetic field models. Catchmentwide erosion rates reflect the production rates of the entire basin, and their calculation requires knowledge of the complete production rate model. A "basin production rate" may be approximated from the basin mean geographic coordinates and mean elevation, but because production varies (approximately) exponentially with elevation this approach generally underestimates the true production. Dedicated programs calculate production rates on the scale of a river catchment and explore, for example, the impact of different scaling schemes, muogenic production models, palaeomagnetic models, or the spatial resolution of topographic data. While these programs compute catchmentwide erosion rates the calculation is independent from the commonly used exposure age and erosion rate calculators, and the results are not directly comparable. Here we introduce a new python-based tool that uses the popular online calculator by G. Balco [http://hess.ess.washington.edu/] to compute the complete production rate model of a river catchment and to determine catchmentwide erosion rates from cosmogenic nuclide data. Our goal is to provide an easy-to-use catchmentwide erosion rate calculator, which is fully integrated with existing exposure age and (in situ) erosion rate calculators for consistent and reproducible evaluation of cosmogenic nuclide data in Quaternary geology.

O01_09

A software framework for calculating compositionally dependent in situ ¹⁴C production rates

Koester A¹, Lifton N¹

¹Purdue University, West Lafayette, United States

In situ cosmogenic nuclides have revolutionized surficial process and Quaternary geologic studies, yet in situ cosmogenic ¹⁴C (in situ ¹⁴C) is unique among commonly measured nuclides in that its 5.7 ky half-life enables constraints on complex exposure/burial histories during the last ~25 ka. However, measurements are currently limited to common, but not ubiquitous, coarse-grained quartz-bearing rocks. The ability to extract in situ ¹⁴C from quartz-poor and fine-grained rocks would expand applications to a broader array of landscapes. As a first step toward this goal, a robust means of interpreting in situ ¹⁴C concentrations derived from rocks and minerals spanning wider compositional ranges is crucial. We have developed a MATLAB®-based software framework to quantify spallogenic production of in situ ¹⁴C from a wide range of silicate rock and mineral compositions, based on measured and modelled excitation functions. As expected from prior work, production from oxygen dominates the overall in situ ¹⁴C signal, accounting for >90% of production at sea-level and high latitudes. This work confirms that Si, Al, and Mg are important targets, but predicts greater production from Na than previously recognized. The compositionally dependent production rates predicted for rock and mineral compositions considered are typically lower than that for quartz, dropping as compositions become more mafic (particularly Fe-rich). Production rates predicted for quartz and albite are comparable, however, reflecting the significance of production from Na. This framework should thus be a useful tool in efforts to broaden the utility of in situ ¹⁴C, but would benefit from improved excitation functions.

O01_P01

Isochron-burial dating of the oldest glaciofluvial sediments in the northern Alpine Foreland

Broś E¹, Ivy-Ochs S¹, Grischott R², Kober F³, Vockenhuber C¹, Christl M¹, Maden C⁴, Synal H¹

¹Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland, ²BTG Büro für Technische Geologie AG, Sargans, Switzerland, ³NAGRA, Wettingen, Switzerland, ⁴Geochemistry and Petrology, ETH Zurich, Zurich, Switzerland

During the Middle and Early Pleistocene, the northern Alpine Foreland was glaciated several times and witnessed numerous phases of alternating incision and deposition, shaping the landscape that can be seen today. High elevated plateaus separated by deeply incised valleys, create a topography with relief of several hundreds of meters. On top of these plateaus can be found the oldest Quaternary glaciofluvial sediments in the northern Alpine Foreland. They have traditionally been divided into two gravel units: older Höhere (Higher, HDS) and younger Tiefere (Lower, TDS) Deckenschotter. The HDS is located topographically higher by ~100-150 m than the TDS. The Deckenschotter consist mainly of glaciofluvial sediments intercalated with glacial and/or overbank deposits and form gravel terraces located up to about 250 m above the modern valley bottom. Their exact time of deposition is an important source of information for establishing erosion and incision scenarios and quantification of landscape evolution in the northern Alpine Foreland during the Middle and Early Pleistocene. Our focus is placed on similar and complementary Deckenschotter deposits outcropping in several sites across the northern Alpine Foreland. In selected six sites, we implement isochron-burial dating technique with a pair of cosmogenic nuclides ²⁶Al and ¹⁰Be, to further examine and refine the question of the age of the Deckenschotter. The first preliminary age estimates point to deposition in the latter part of the Early Pleistocene. With the aim to determine the age of these sediments, the results will also complement our understanding of landscape change during and after Deckenschotter times.

O01_P02

New evidence for the persistence of the Ilanzersee (Flims rockslide)

Grischott R^1,2, Wacker L², von Poschinger A³, Gilli A⁴

¹Büro Für Technische Geologie, Sargans, Switzerland, ²Laboratory for Ion Beam Physics, Zurich, Switzerland, ³Private adress, Kempfenhausen, Germany, ⁴Department of Earth Sciences, Zurich, Switzerland

The Flims rockslide is one of the largest known rockslide in the Alps and had a strong influence on the landscape evolution in the Vorderrhein-Valley. The Flims rockslide (volume 9–12 km³) has been dated to 9400 cal yr BP with the radiocarbon method [2]. The Vorderrhein was completely blocked by a more than 600 m-thick landslide dam and a lake, Ilanzersee, formed upstream [1]. Its maximum level obviously did not reach higher up than 930 m a.s.l. After the breach of the dam, an important sediment transport down the Rhine valley had occurred. Nevertheless, a relict lake existed for a longer time, probably for centuries. A level of about 820 m a.s.l that was held for fairly long time. The duration of this second lake level, until the lake was finally emptied, has not been clear so far. Drill cores retrieved along a transect of 4 km on top of the former delta plain of Ilanzersee revealed the continuous presence of typical fine-grained delta sediments overlain by recent fluvial sediments. A wood fragment embedded in delta sediment was dated to 8900-9000 cal yr BP and supports geological evidence found elsewhere, that the lake persisted during quite a long time. More samples from other drillings will be analysed to underline this first evidence.

[1]: Von Poschinger 2005

[2]: Deplazes et al., 2007

O01_P03

Comparison of two ¹⁰Be purification methods for AMS measurement

Loftfield J¹, Lachner J², Malter M¹, Stübner K², Adolphi F¹

¹Alfred Wegener Institute, Bremerhaven, Germany, ²Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

The cosmogenic radionuclide ¹⁰Be is a powerful tool in paleosciences. Its applications include the dating of rocks and sediments, reconstruction of past changes in solar activity and the geomagnetic field strength, and the synchronization of climate archives.

However, sample preparation and especially purification of Beryllium from environmental samples can be time consuming and expensive. Typically, purification of sediment samples is achieved by a combination of hydroxide precipitations and ion exchange chromatography. Here, we test a method of successive hydroxide precipitations at different pH-values in combination with precipitation in NaHCO₃, to purify samples of marine sediments from the Norwegian Sea and the Lomonosov Ridge for ¹⁰Be-analysis. We compare the performance of this method to an ion chromatography-based method (Simon et al., 2016) with respect to the Beryllium yield, purity of the resulting Be(OH)₂, blank, and performance in the AMS for both protocols. We discuss the advantages and challenges of the protocols, their applicability, and their capacity in terms of sample throughput.

Simon, Q., Thouveny, N., Bourlès, D. L., Nuttin, L., Hillaire-Marcel, C., & St-Onge, G. (2016). Authigenic ¹⁰Be/⁹Be ratios and ¹⁰Be-fluxes (230Thxs-normalized) in central Baffin Bay sediments during the last glacial cycle: Paleoenvironmental implications. Quaternary Science Reviews, 140, 142–162. https://doi.org/10.1016/j.quascirev.2016.03.027

O01_P04

Status report of the in-situ ¹⁴C extraction line at HEKAL AMS laboratory

Buró B¹, Fülöp R², Jull A^1,3, Molnar M¹

¹INTERACT AMS Laboratory, Debrecen, Hungary, ²Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia, ³Department of Geosciences, University of Arizona, Tucson, USA

In this study we presented a new cosmogenic in-situ ¹⁴C extraction line at the ICER laboratory, which is similar as the one published by Fülöp et al.(2019). These extraction system used the phase transformation of quartz to cristobalite on high temperature in order to quantitatively extract the carbon as CO₂. The system consists of three independent components. 1: used for remove the atmospheric and meteoric ¹⁴C, 2: offline high-temperature (1650 °C) oven  for extract and trapped the cosmogenic in-situ ¹⁴C from quartz, 3: CO₂ gas purification and mass measurement line. After the extraction and cleaning, the purified CO₂ sapmles are measured with compact ¹⁴C AMS system (Environ MICADAS) and the gas ion source interface. The extraction line allows for rapid sample throughput of about 6 samples per week. The  sample masses ranging between 4 and 7 g of clean quartz.

Purified quartz samples were sieved and used for analyse the fraction of  250 – 500 µm. The carbon yield from quartz samples are good and we have the expected values.

Our first tests were on the borehole CO₂ blank gas and Cronus-R standards. The blank level of the whole line is quite low. We get similar experiences and results as Fülöp et al. (2019).

O01_P05

³²Si – An alternative radionuclide for dating the recent past?

Schlomberg M¹, Vockenhuber C¹, Synal H¹

¹Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland

Dating the last few hundred years is challenging with currently used radionuclides: To date with ¹⁴C (half-life of 5700 a) is difficult due to ambiguities in the calibration curve in the last ~400 years, although the last 80 years can be again well dated due to the bomb peak of the ¹⁴C concentration and its subsequent dilution. Dating methods based on shorter-lived nuclides like ³H (12.3 a) and ²¹⁰Pb (22.3 a) can only be used in the last ~100 a. A promising candidate for filling this dating gap is cosmogenic ³²Si with a half-life of ~150 a.

However, the application of ³²Si has so far been limited by the imprecisely known half-life. As part of the SINCHRON collaboration which aims at a redetermination of the half-life of ³²Si, the Laboratory of Ion Beam Physics (LIP) at ETH Zurich will perform the AMS measurements for the determination of the absolute number of ³²Si atoms in samples used for activity measurements.

In this poster, the potential of ³²Si as dating tool is discussed and an overview of the previous half life measurements is given. First results concerning the AMS measurement technique are presented and an outlook for potential ³²Si measurements in environmental samples is given.

O01_P06

Studying ¹⁴C production in meteorites using the Bernese ¹⁴C extraction line and the MICADAS system at LARA, University of Bern

Tauseef M¹, Leya I¹, Szidat S², Gattacceca J³

¹Space Research and Planetary Sciences, University of Bern, , Switzerland, ²Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, , Switzerland, ³CNRS, Aix Marseille University, CEREGE,  Aix-en-Provence, France

Carbon-14 dating is the most robust technique for determining the terrestrial ages of meteorites. With our updated ¹⁴C extraction system, we can measure up to 15 samples without breaking the vacuum, thereby achieving low blanks and a high sample throughput (Sliz et al. 2018, 2020). Briefly, we are able to quantitatively and reproducibly extract CO₂ gas from pre-cleaned meteorite samples (typical masses 50 mg). Preheating the samples at 500 °C in a continuous flow of pure oxygen reduces the remaining atmospheric contamination. Gas extraction is at ~1600 °C under an O₂ partial pressure of 30±5 mbar for 10 min. Evolved gases are first purified at 500°C –1000°C using CuO, quartz spherules, and silver wool. Next, gases are cleaned and separated using a water trap at –78 °C and cold fingers (~100 °C). The purified CO₂ gas is then collected in a glass capillary and is subsequently introduced into the gas ion source of the MICADAS AMS system (University of Bern). We finally give our results as specific activity concentrations (dpm/kg), which are then used to determine the terrestrial ages of meteorites. Here we will present new data for ¹⁴C and ¹⁰Be activity concentrations in freshly fallen meteorites to better constrain the ¹⁴C and ¹⁰Be production rates and consequently determine more accurate and more precise terrestrial ages of meteorites.

References

Sliz M.U. et al. 2018. 81st Annual Meeting of The Meteoritical Society 2018 (LPI Contrib. No. 2067)

Sliz M.U. et al. 2020. Radiocarbon Vol 62, Nr 5, p 1371–1388