Silke Merchel's research while affiliated with Australian National University and other places
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Publications (179)
Oceanic archives are contemporary witnesses of Earth’s recent astrophysical history by incorporating extraterrestrial radionuclides. VA13/2 - 237KD is one of the most studied ferromanganese crusts and it has been shown that the crust contains live interstellar ⁶⁰Fe. Here, we have characterized a large piece of this crust with a 3D optical scan, a m...
The Centre of Excellence for Dark Matter Particle Physics aims to measure ²¹⁰Pb (half-life of 22.2 years) in 1 kg of NaI via accelerator mass spectrometry (AMS) for the SABRE (Sodium iodide with Active Background REjection) South dark matter experiment. The first step is to find the optimal target material (chemical compound and binder) to produce...
Summary Scientific analysis, especially the chemical composition, of artistic and cultural heritage objects reveals information, which cannot be gained from art historical investigations alone. The improvement of X-ray analytical method, like X-ray fluorescence (XRF) analysis and Particle-Induced X-ray Emission (PIXE) analysis, makes it possible to...
In the last 7 years, three meteorites (Blaubeuren, Cloppenburg, and Machtenstein) found in Germany were identified as chondrites. Two of these rocks had been recovered from the impact sites decades ago but not considered to be meteorites. The aim of this study is to fully characterize these three meteorites. Based on the compositional data on the s...
The discovery of live ⁶⁰ Fe in a deep-sea crust with proposed interstellar origin followed by evidence for elevated interplanetary ³ He in the same crust raised the question on how to unambiguously identify the true production site of the identified ⁶⁰ Fe. Here, we show the implementation of the dyadic radionuclide system ⁶⁰ Fe / ⁵³ Mn to serve as...
A pilot study to quantify 55Fe in steel from a reactor vessel of a nuclear power plant by accelerator mass spectrometry (AMS) without any chemical sample preparation was validated by liquid scintillation counting (LSC) and AMS after radiochemical separation. AMS reaches an uncertainty < 10% at the 1 kBq gFe−1 level within less than 10 min measuring...
Commercial ⁹Be solutions used for chemical preparation of samples for accelerator mass spectrometry contain the cosmogenic long-lived radionuclide ¹⁰Be at elevated but different ¹⁰Be/⁹Be levels. Within a systematic study of recently produced solutions, comparison to published data and new data on customised solutions from minerals, we recommend - i...
Dating of ancient permafrost is essential for understanding long-term permafrost stability and interpreting palaeoenvironmental conditions but presents substantial challenges to geochronology. Here, we apply four methods to permafrost from the megaslump at Batagay, east Siberia: (1) optically stimulated luminescence (OSL) dating of quartz, (2) post...
1st March 21, 1 ... 3 ... 21, on a date that sounds like the beginning of a sad song, terrible news darkened our day; Didier left us. His contagious laugh won’t echo through the corridors of CEREGE anymore (Fig. 1). It is a trying time for many of us. In addition to being an extraordinarily warm and accessible human being, a devoted husband and fat...
Several hundred thousand year old moraines preserved in the semi-arid environment of High Mountain Asia attest to Middle Pleistocene glaciations, but the regional correlation of glacial stages and the spatial extent of the glacial advances remain poorly constrained. We examined glacial landforms and Quaternary sediments in the Bartang valley, north...
Located between the Northern Province of Zambia and the southeastern Katanga Province of the Democratic Republic of Congo, Lakes Mweru and Mweru Wantipa are part of the southwest extension of the East African Rift System (EARS). Fault analysis reveals that, since the Miocene, movements along the active Mweru-Mweru Wantipa Fault System (MMFS) have b...
High-mountain environments in an active tectonic setting are prone to landsliding. The triggering mechanisms can vary, as these areas are influenced by several pre-conditioning factors coupled with active seismicity and climatic forcings. Understanding the intrinsic and external mechanisms by which these events are influenced would help to establis...
Multiple periods of advance and retreat of piedmont glaciers in the German Alpine Foreland due to changing climatic conditions were classically defined by Penck and Brückner in 1909. However, a robust absolute chronology has not yet been established. Age assignments in previous studies have mostly been based on the interpretation of terrace deposit...
We present here a record of atmospheric 10Be locked in the millennial old ice deposits from Scărișoara Ice Cave, Romania. To our knowledge, our project is the very first in measuring atmospherically-produced 10Be in cave ice deposits.
On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Ger- many, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The pres- ence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the...
Significance
Nearby supernova explosions shape the interstellar medium. Ejecta, containing fresh nucleosynthetic products, may traverse the solar system as a transient passage, or alternatively the solar system may traverse local clouds that may represent isolated remnants of supernova explosions. Such scenarios may modulate the galactic cosmic-ray...
The concentrations of long-lived in-situ produced cosmogenic nuclides (10Be, 21Ne, 26Al) in quartz obtained from a very recent (~200 a; based on 14C data on organic material) terrace of the Swakop River in Namibia are nearly constant throughout a 322 cm-long depth profile. These findings corroborate earlier hypotheses postulating a homogeneous dist...
Activations with neutrons in the keV energy range were routinely performed at the Karlsruhe Institute of Technology (KIT) in Germany in order to simulate stellar conditions for neutron-capture cross sections. A quasi-Maxwell-Boltzmann neutron spectrum of kT = 25 keV, being of interest for the astrophysical s-process, was produced by the ⁷ Li(p,n) r...
We measured specific activities of the long‐lived cosmogenic radionuclides ⁶⁰Fe in 28 iron meteorites and ⁵³Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron me...
We report on an attempt to reproduce the observation of \(\beta ^-\)-delayed proton emission from \(^{11}\)Be through detection of the final state nucleus \(^{10}\)Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination...
Here we present an integrated earth surface process and paleoenvironmental study from the Tingri graben and the archaeological site of Su-re, located on the southern rim of the Tibetan plateau, spanning the past ca. 30 ka. The study area is characterized by cold climate earth surface processes and aridity due to its altitude and location in the rai...
Despite being the main drinking water resource for over 5 million people, the water balance of the Eastern Mountain Aquifer system on the western side of the Dead Sea is poorly understood. The regional aquifer consists of fractured and karstified limestone – aquifers of Cretaceous age, and it can be separated into a Cenomanian aquifer (upper aquife...
![Mass values (in u) of selected isotopes and molecules, from [13], their...](profile/Oliver-Forstner/publication/338476311/figure/tbl1/AS:845271797878784@1578539909550/Mass-values-in-u-of-selected-isotopes-and-molecules-from-13-their-mass-difference_Q320.jpg)
We report on an attempt to reproduce the observation of $\beta^-$-delayed proton emission from $^{11}$Be through detection of the final state nucleus $^{10}$Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be c...
The long-lived radioisotope ¹⁸² Hf (T 1/2 = 8.9 Ma) is of high astrophysical interest as its potential abundance in environmental archives would provide insight into recent r-process nucleosynthesis in the vicinity of our solar system. Despite substantial efforts, it could not be measured at natural abundances with conventional AMS so far due to st...
We measured the He, Ne, and Ar isotopic concentrations and the 10Be, 26Al, 36Cl, and 41Ca concentrations in 56 iron meteorites of groups IIIAB, IIAB, IVA, IC, IIA, IIB, and one ungrouped. From 41Ca and 36Cl data, we calculated terrestrial ages indistinguishable from zero for six samples, indicating recent falls, up to 562 ± 86 ka. Three of the stud...
Despite being the main drinking water resource for over five million people, the water balance of the Eastern Mountain Aquifer system on the western side of the Dead Sea is poorly understood. The regional aquifer consists of fractured and karstified limestone – aquifers of Cretaceous age and can be separated in Cenomanian aquifer (upper aquifer) an...
Earth is constantly bombarded with extraterrestrial dust containing invaluable information about extraterrestrial processes, such as structure formation by stellar explosions or nucleosynthesis, which could be traced back by long-lived radionuclides. Here, we report the very first detection of a recent Fe60 influx onto Earth by analyzing 500 kg of...
Natural ¹⁰Be (t1/2 = 1.387 ± 0.012 Ma) is produced by cosmic rays and is present on Earth's surface only at ultratrace concentrations (typically 10⁴ to 10¹⁰ atoms/g). Its cosmogenic origin makes it an important tracer for many applications in Earth and environmental sciences. An improved accelerator mass spectrometry (AMS) method has been developed...
A major research focus of the DREsden Accelerator Mass Spectrometry (DREAMS) facility is sample preparation: in-house and at cooperating laboratories. Besides routine applications, developments are mainly driven by the users’ demands such as “new” radionuclides (e.g. short-lived ⁷Be), radionuclides from new matrices or in larger sample amounts and...
The Ploučnice River system, located in the central Bohemian Massif, is draining an area almost not covered by continental ice sheets but instead archiving the fluvial deposits. The fluvial style changes from a high-energy braided to a long-bend meandering river in the upper terrace levels (36 to 29 m above present floodplain). The middle terrace le...
The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (D...
Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparisonmaterial (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N isderived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystalof alkali-feldspar...
Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic ³⁶Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-felds...
The neutron capture cross section of Be9 for stellar energies was measured via the activation technique using the Karlsruhe Van de Graaff accelerator in combination with accelerator mass spectrometry at the Vienna Environmental Research Accelerator. To characterize the energy region of interest for astrophysical applications, activations were perfo...
The nuclide Cl35 can act as a minor “neutron poison” in the stellar slow neutron capture process. Neutron activation combined with accelerator mass spectrometry (AMS) was applied to measure the (n,γ) cross section of Cl35 for neutron spectra simulating Maxwell-Boltzmann distributions of kT≈30 and 40 keV. The neutron activations were performed at th...
Beryllium-7, mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science. For activities < 0.1 Bq and samples containing also longer-lived ¹⁰Be, accelerator mass spectrometry (AMS) is the method-of-choice. We demonstrate that ⁷Be and ¹⁰Be can be quantified at the Dresden AMS facility on the same prepared BeO. De...
We searched for the presence of Al26 in deep-sea sediments as a signature of supernova influx. Our data show an exponential dependence of Al26 with the sample age that is fully compatible with radioactive decay of terrigenic Al26. The same set of samples demonstrated a clear supernova Fe60 signal between 1.7 and 3.2 Myr ago. Combining our Al26 data...
Glacial deposits on the high-altitude, arid southern Central Andean Plateau (CAP), the Puna in northwestern Argentina, document past changes in climate, but the associated geomorphic features have rarely been directly dated. This study provides direct age control of glacial moraine deposits from the central Puna (24°S) at elevations of 3900–5000 m...
Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co‐seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after eart...
Cosmogenic nuclide (CN) dating relies on specific target minerals such as quartz as markers to identify geologic events, including the timing of landscape evolution. The presence of feldspar in sediment samples poses a challenge to the separation of quartz and affects the chemical procedures for extracting the radioactive CNs 10Be and 26Al. Additio...
During the Last Glacial Maximum (~19-30 ka) extensive ice caps and large outlet glaciers covered the alpine valleys and forelands in the Swiss Alps (e.g. Ivy-Ochs, 2015). The former Rhône Glacier expanded onto the Swiss Plateau, was deflected and bounded by the Jura Mountain Range, and reached ’Wangen an der Aare’ (Niederbipp Stade). Various studie...
The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for...
This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, backg...
Multiple year-round (2006–2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (100 ± 28 ng m⁻³ versus 4.4 ± 2.3 ng m⁻³ in July) is consistent with observations made at the coast (280 ± 78 ng...
Be with its relatively short half-life (53.22 days) is a possibly suitable radionuclide for radiotracer experiments. Low-level activities of natural ⁷Be can be found in rainwater and might be available as a tracer after radiochemical isolation. Herein, beryllium was first concentrated by evaporation of rainwater and/or iron(III) hydroxide co-precip...
Elevated shorelines and lake sediments surrounding Issyk Kul, the world's second largest mountain lake, record fluctuating lake levels during Quaternary times. Together with bathymetric and geochemical data, these markers document alternating phases of lake closure and external drainage. The uppermost level of lake sediments requires a former dammi...
The Twannberg iron meteorite is one out of only six members of the group IIG. The combined noble gas and radionuclide data obtained in this new systematic study indicate that Twannberg with its ~570 recently recovered specimens was a large object with a preatmospheric radius in the range of ~2 m, which corresponds to ~250 × 10E3 kg. The cosmic-ray...
Multiple year-round (2006–2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (84 ± 25 ng m−3 against 4.4 ± 2.3 ng m−3 in July) is consistent with observations made at the coast (280 ± 78 ng...
Temporal variations of the radionuclide 10Be are broadly synchronous across the globe and thus provide a powerful tool to synchronize ice core chronologies from different locations. We compared the 10Be record of the Akademii Nauk (AN) ice core (Russian Arctic) for the time period CE 1590–1950 to the 10Be records of two well-dated Greenland ice cor...
Cliff erosion may be a major problem in settled areas affecting populations and producing economic and ecological losses. In this paper we present a procedure to calculate the long-term retreat rate of a cliff affected by rockfalls in the Montsec Range, Eastern Pyrenees (Spain). It is composed of low, densely fractured limestones; and the rockwall...
Our multi-method MS study (AMS, noble gas MS, LA-(MC)-ICP-MS) aims to constrain the evolution of the western Namibian drainages since the last ca. 40 Ma. Therefore, fluvial sediments of several rivers and their precursors were sampled. In order to obtain precise surface exposure ages of the various terrace levels, the routinely used cosmogenic nucl...
![Fig. 1. Decay-corrected 60 Fe/Fe versus time [5]. The sediment data is...](profile/Ulf-Linnemann/publication/314106545/figure/fig1/AS:467034334076928@1488361070063/Decay-corrected-60-Fe-Fe-versus-time-5-The-sediment-data-is-shown-as-200-kyr-averages_Q320.jpg)
Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activit...
Der vorliegende Band versammelt die Beiträge eines internationalen Workshops, der unter gleichem Titel im Jahr 2011 in Berlin stattfand. Er stellte die erste Initiative des kurz zuvor gegründeten „Netzwerks Archäologisch-Historisches Metallhandwerk (NAHM)“ dar und wurde im Verbund mit dem Exzellenzcluster Topoi durch geführt. Die Aufsätze widmen si...
Die naturwissenschaftliche Analyse historischer Materialen ermöglicht die Beantwortung kulturhistorischer Fragestellungen, die mit kunsthistorischen oder archäologischen Ansätzen allein nicht zu leisten sind. In dieser Studie wurden sechs römische Münzen mit unterschiedlich stark ausgeprägten Korrosionsschichten an unbehandelten und polierten Stell...
![Figure 1: Decay-corrected 60 Fe/Fe versus time [5]. The sediment data...](profile/Breitschwerdt-Dieter/publication/309729808/figure/fig1/AS:425624968929280@1478488308134/Decay-corrected-60-Fe-Fe-versus-time-5-The-sediment-data-is-shown-as-200-kyr-averages_Q320.jpg)
Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activit...
The recent stream network of western Namibia is characterised by numerous non-perennial rivers with relatively small catchment areas, framed by the perennial Kunene and Orange Rivers. Most of them originate in the hinterland of the Great Escarpment. Studies based on terrestrial cosmogenic nuclides (TCN) revealed very low erosion rates of 3-16 m/Ma...
Significance
Massive stars, which terminate their evolution in a cataclysmic explosion called a type-II supernova, are the nuclear engines of galactic nucleosynthesis. Among the elemental species known to be produced in these stars, the radioisotope ⁶⁰ Fe stands out: This radioisotope has no natural, terrestrial production mechanisms; thus, a detec...
Introduction: The main mass of the Twannberg meteorite (15.9 kg) has been found 1984 in the Canton of Bern, Switzerland. The Twannberg meteorite belongs to the IIG group, which comprises so far only six members and which is characterized by large amounts of schreibersite (Fe,Ni)3P and a low nickel content of 5% only [1]. Twannberg is so far the lar...
Multiple age tracers were measured to estimate groundwater residence times in the regional aquifer system underlying southwestern Oman. This area, known as the Najd, is one of the most arid areas in the world and is planned to be the main agricultural center of the Sultanate of Oman in the near future. The three isotopic age tracers ⁴He, ¹⁴C and ³⁶...
The recently installed and unique PIXE (particle-induced X-ray emission) set-up at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is mainly dedicated to applications for a detailed overview of elemental composition over large sample areas within a short time even at trace level. The so-called High-Speed-PIXE (HS-PIXE), a combination of a pnCCD-bas...
The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries. To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismologi...
The rate of supernovae in our local Galactic neighbourhood within a distance of about 100 parsecs from Earth is estimated to be one every 2-4 million years, based on the total rate in the Milky Way (2.0 ± 0.7 per century). Recent massive-star and supernova activity in Earth's vicinity may be traced by radionuclides with half-lives of up to 100 mill...
The Himalayas and their foreland belong to the world's most earthquake-prone regions. With millions of people at risk from severe ground shaking and associated damages, reliable data on the spatial and temporal occurrence of past major earthquakes is urgently needed to inform seismic risk analysis. Beyond the instrumental record such information ha...
DREAMS, the DREsden AMS-facility, is performing routine accelerator mass spectrometry of 10Be, 26Al, 36Cl, 41Ca, and 129I for a wide range of applications. All DREAMS-data is normalised directly to primary standards or traceable to those via cross-calibration of secondary standards. Recent technical developments such as a low-memory ion source for...
River response to strong earthquake shaking in mountainous terrain often entails the flushing of sediments delivered by widespread co-seismic landsliding. Detailed mass-balance studies following major earthquakes in China, Tai-wan, and New Zealand suggest fluvial recovery times ranging from several years to decades. We report a detailed chronology...
Ice cores offer unique multi-proxy paleoclimate records, but provide only very limited sample material, which has to be carefully distributed for various proxy analyses. Beryllium-10, for example, is analysed in polar ice cores to investigate past changes of the geomagnetic field, solar activity, and the aerosol cycle, as well as to more accurately...
Nepal's quake-driven landslide hazards
Large earthquakes can trigger dangerous landslides across a wide geographic region. The 2015 M w 7.8 Gorhka earthquake near Kathmandu, Nepal, was no exception. Kargal et al. used remote observations to compile a massive catalog of triggered debris flows. The satellite-based observations came from a rapid respo...
79th Annual Meeting of the Meteoritical-Society, Berlin, GERMANY, AUG 07-12, 2016
A clear understanding of erosion processes is fundamental in order to comprehend the evolution of
actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and
their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide denudation
rates from cosmogenic Be-10 conc...
The understanding of erosion processes is fundamental to study the evolution of actively deforming mountain ranges, whereas the relative contributions tectonic and climatic factors and their feedbacks are debated. The Pamir is peculiar in both, high deformation rates induced by the India–Eurasia collision and its position at the transition between...