Marcus Christl

Last Name

Christl

First Name

Marcus

ORCID

0000-0002-3131-6652

Organisational unit

08619 - Labor für Ionenstrahlphysik (LIP) / Laboratory of Ion Beam Physics (LIP)

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Publications1 - 10 of 198

Initial tests of 26Al fluoride target matrix on MILEA AMS system
Fenclová, K.; Prášek, T.; Němec, Mojmír; et al. (2021)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
In this study, the possibility of using a superhalogenide ion AlF4- extracted from Na3AlF6 based target materials for 26Al/27Al measurements by Accelerator Mass Spectrometry (AMS) was investigated. Determination of 26Al by usual mass spectrometric methods is generally hampered by the presence of the isobar 26Mg. However, the AMS method enables significant suppression of this interference, particularly by negative ion formation. After initial current tests in a caesium sputtering ion source of the Tandetron system, performance of the fluoride materials was analysed on the MILEA AMS system at ETH Zürich. The AlF4- current was used to evaluate the performance of the respective samples. Additives as PbF2 were tested to increase the extracted ion currents and samples containing MgF2 were used to investigate the presence of isobaric ions. Subsequently, the ionization efficiency of AlF4- was determined by recording the 27Al2+ current on the high energy side and the signals of 26Al2+ were investigated with the gas ionization detector.
Constraining the aggradation mode of Pleistocene river deposits based on cosmogenic radionuclide depth profiling and numerical modelling
Vandermaelen, Nathan; Beerten, Koen; Clapuyt, François; et al. (2022)
Geochronology
Divide migration and escarpment retreat in Madagascar and the Western Ghats of India
Wang, Yanyan; Willett, Sean; Wu, Datian; et al. (2023)
Impact of nuclear fuel reprocessing on the temporal evolution of marine radiocarbon
Castrillejo, Maxi; Witbaard, Rob; Richardson, Christopher A.; et al. (2020)
Science of The Total Environment
Radiocarbon (14C) is broadly used in oceanography to determine water ages, trace water circulation, and develop sediment- and sclerochronologies. These applications require an accurate knowledge of marine 14C levels, which have been largely perturbed by human activities. Globally during the last century the above-ground nuclear weapon testings have been the primary cause of the increased atmospheric and marine 14C. However, other anthropogenic sources may have caused important regional deviations from the bomb pulse. For the last 70 years European nuclear fuel reprocessing plants have been major contributors of 14C to air and oceans, yet, their regional impact on surrounding marine 14C has been largely overlooked. Here we use a collection of bivalve shells of known capture date and age collected from various locations, including the North Sea, the Irish Sea, Norway, and the Bay of Biscay to reconstruct the sea surface 14C over the last five decades. The measured 14C values for the period 1969–2019, reported in fraction modern, ranged from 1.1 to 1.6 in coastal waters of the Netherlands and from 1.2 to 3.2 along the coast of the UK, indicating significantly higher levels of 14C than those expected for the marine bomb pulse (0.950–1.150). The 14C peaks revealed by the shells coincide with the increase of liquid 14C releases reported from the reprocessing plants of La Hague into the English Channel, and from Sellafield into the Irish Sea. Conversely, the shells from Norway and Spain showed 14C values close to the range of the global marine bomb pulse. The observed large spatial and temporal differences in sea surface 14C show that 14C dating and tracing studies could become problematic in the English Channel, Irish Sea and North Sea for the time period covering the discharge of liquid 14C from the reprocessing plants.
Rapid post-glacial bedrock weathering in coastal Norway
Andersen, Jane Lund; Margreth, Annina; Fredin, Ola; et al. (2022)
Geomorphology
Quantifying bedrock weathering rates under diverse climate conditions is essential to understanding timescales of landscape evolution. Yet, weathering rates are often difficult to constrain, and associating a weathered landform to a specific formative environment can be complicated by overprinting of successive processes and temporally varying climate. In this study, we investigate three sites between 59 degrees N and 69 degrees N along the Norwegian coast that display grussic saprolite, tafoni, and linear weathering grooves on diverse lithologies. These weathering phenomena have been invoked as examples of geomorphic archives predating Quaternary glaciations and consequently as indicators of minimal glacial erosion. Here we apply cosmogenic nuclide chronometry to assess the recent erosional history. Our results demonstrate that all three sites experienced sufficient erosion to remove most cosmogenic nuclides formed prior to the Last Glacial Maximum. This finding is inconsistent with preservation of surficial (<1-2 m) weathered landforms under non-erosive ice during the last glacial period, while simultaneously demonstrating that post-glacial weathering and erosion rates can be locally rapid (4-10 cm kyr(-1)) in cold temperate to subarctic coastal locations. (C) 2021 The Authors. Published by Elsevier B.V.
Spatio-temporal variability and controlling factors for postglacial denudation rates in the Dora Baltea catchment (western Italian Alps)
Serra, Elena; Valla, Pierre G.; Delunel, Romain; et al. (2022)
Earth Surface Dynamics
Disentangling the influence of lithology from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial and temporal scales involved. The Dora Baltea catchment (western Italian Alps) is an ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major lithotectonic units of the western Alps, whereas this region has experienced relatively homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new Be-10-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rates vary between 0.2 and 0.9 mm yr(-1), consistent with previously published values across the European Alps. Spatial variability in denudation rates was statistically compared with topographic, environmental and geological metrics. Be-10-derived denudation rates do not correlate with modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock structures and erodibility (lithotectonic origin) and glacial overprint, is the main driver of Be-10-derived denudation patterns. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support high elevations, steep slopes and high relief and thus favour intense glacial and periglacial processes and recurring rockfall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low Be-10 concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.
Performance of the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores for the analysis of 233U at environmental levels
Chamizo, Elena; López-Lora, Mercedes; Christl, Marcus (2022)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
233U (T1/2 = 0.159 My) has aroused much interest in the last few years because of the potential of 233U/236U to inform about anthropogenic U sources. The reported 233U/238U atom ratios in general environmental samples are in the 10−12–10−6 range. We demonstrate that 233U/238U abundance sensitivities at the 5 × 10−11 level can be achieved at the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores (CNA, Seville, Spain). Unresolved 234U, 235U and 232Th molecular fragments are identified as the main 233U background contributors and procedures to subtract them are proposed. 233U/238U and 236U/238U atom ratios were analysed in the IAEA reference materials coded Soil-6, 300, 385, 410, and 412 at the CNA and at the 600 kV ETH AMS system for intercomparison. 233U/238U atom ratios for samples 412 and 385 were only reported by the ETH.
231Pa/230Th: A proxy for upwelling off the coast of West Africa
Christl, Marcus; Lippold, Jörg; Hofmann, Alexander; et al. (2010)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
231Pa has widespread applications in the earth sciences including uranium series disequilibrium dating of carbonates and the reconstruction of ocean circulation or bio-productivity on glacial/interglacial timescales. Here we present the first 231Pa profile from a marine sediment core (GeoB3722) located in the large upwelling area off West Africa (Northern Cape Basin) measured with Accelerator Mass Spectrometry (AMS). Together with the Th and U-data (obtained with ICP-MS) 231Pa/230Th ratios were calculated covering the past 30,000 yr. Our results indicate that site GeoB3722 was located in the wind driven upwelling area during glacial times while it abruptly turned into an open ocean area at about 14,000 yr BP. A spatial shift of the large wind driven upwelling area off West Africa is consistent with the idea that atmospheric circulation patterns as well as ocean circulation dramatically changed at the last glacial interglacial transition.
Heliomagnetic and geomagnetic activity cycles on millennial timescales
Beer, Juerg; McCracken, Ken G.; Adolphi, Florian; et al. (2025)
Quaternary Science Reviews
We report 17 new solar activity cycles with periodicities ranging from 1,700 to 18,000 years. Using Bayesian spectral analysis we determined for each cycle period, amplitude and phase for the past 145,000 years. These results were obtained by analyzing 10Be in the 2775 m long EDML ice core from Dronning Maud Land, Antarctica. In addition, we have augmented the 10Be data with synchronous ice accumulation and δ18O data obtained from the same ice core; with paleomagnetic dipole moment data derived mainly from ocean sediments; and with calculated global insolation data. There is a close agreement between the 10Be periodicities in the first and the last 70 kyr intervals. We have developed a new analytical technique we call the “frequency domain differentiation technique” (FDDT) that distinguishes between the periodicities due to (a) variations in the cosmic ray intensity and (b) climate effects related to the accumulation rate. In a first step we have calculated the 10Be flux and then selected all periodicities which are common within 1 % in at least 2 of the investigated parameters (10Be concentration, 10Be flux, accumulation rate, δ18O, and insolation). Using these data we identified a total of 42 statistically significant periodicities. 20 of them are found in the 10Be concentration which we separated into 3 groups of origins: Four due to 10Be production only (group 1: 18012, 6508, 5782, 3833 yr), thirteen being a combination of production and accumulation related (system) effects with the production components being generally larger than the system components (group 2: 15503, 13837, 8441, 7722, 7136, 4695, 4556, 4110, 3961, 3292, 3104, 2025, 1680 y), and three being related to system effects only (group 3: 23971, 21101, 11637 y). In a second step we used independent paleomagnetic information to distinguish between heliomagnetic and geomagnetic periodicities in the 10Be production. We find an overall good agreement between the 10Be flux and the dipole moment in the time domain. In the frequency domain there is evidence for system effects in the geomagnetic data. Due to inconsistencies between the paleomagnetic records we do not draw conclusions regarding a potential geomagnetic origin of the 10Be cycles found in the EDML ice core.
Rapid, continuous radiocarbon analysis of carbonate archives using laser ablation
Wertnik, Melina; Welte, Caroline; Wacker, Lukas; et al. (2020)
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