Bernd Kromer
Biographic Data
| ID | 330747 |
|---|---|
| NAME | Bernd Kromer |
| GIVEN NAMES | Bernd |
| FAMILY NAME | Kromer |
| SIGNATURE | KROMER B |
| AFFILIATIONS | Heidelberg University |
| ORCID | 0000-0003-1058-4436 |
| VERIFIED | Yes |
| TOTAL WORKS | 92 |
| TOTAL CITATIONS | 7330 |
| AUTHOR COUNT | 92 |
| EDITOR COUNT | 0 |
| FIRST PUBLICATION YEAR | 1983 |
| LATEST PUBLICATION YEAR | 2025 |
| H-INDEX | 20 |
Multi-Proxy Tree-Ring Dating during the Younger Dryas
The world's longest tree-ring chronology comprises thousands of oak and pine series from Germany and continuously covers the Holocene back to 12,325 cal BP. A lack of relict wood from the Younger Dryas cold reversal ca. 12,900–11,700 cal BP, however, challenges the extension of this absolutely dated ring width record further back in time. Here, we combine 646 high-resolution stable oxygen isotope and 795 radiocarbon measurements from subfossil pi…
Safe Preparation and Delivery of Graphite Targets for 14 C Analysis
Nowadays, most radiocarbon ( 14 C) laboratories can reliably avoid and remove any possible sample contamination during the pretreatment of organic samples (e.g., bones, charcoal, or trees) thanks to a series of methods commonly used by the radiocarbon community. However, what about the final step, the storage of graphite? Rarely do the laboratories produce their graphite and ship it as pressed targets to accelerator mass spectrometry (AMS) facili…
Contrasting paired benthic and planktonic foraminifera radiocarbon ages from Bermuda Rise ODP Site 1063 during Heinrich Stadials 1 and 2
We report 27 planktonic and 21 benthic radiocarbon ages from the subtropical marine sediment core ODP Site 1063 (Bermuda Rise) for the time range between 30 and 14 ka before present. Despite low abundances of benthic specimens, it was possible to measure radiocarbon ages down to ∼10 μg carbon using a MICADAS and the gas ion source developed at ETH Zurich. Based on a tentative radiocarbon–independent age-model we found that the radiocarbon reservo…
Origin and Age of Carbon in the Cellulose of Mid-Latitude Tree Rings
Cellulose of tree rings is often assumed to be predominantly formed by direct assimilation of CO 2 by photosynthesis and consequently can be used to reconstruct past atmospheric 14 C concentrations at annual resolution. Yet little is known about the extent and the age of stored carbon from previous years used in addition to the direct assimilation in tree rings. Here, we studied 14 C in earlywood and latewood cellulose of four different species (…
Development of the Intcal Database
The IntCal family of radiocarbon ( 14 C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14 C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified c…
Radiocarbon in Global Tropospheric Carbon Dioxide
Since the 1950s, observations of radiocarbon ( 14 C) in tropospheric carbon dioxide (CO 2 ) have been conducted in both hemispheres, documenting the so-called nuclear “bomb spike” and its transfer into the oceans and the terrestrial biosphere, the two compartments permanently exchanging carbon with the atmosphere. Results from the Heidelberg global network of Δ 14 C-CO 2 observations are revisited here with respect to the insights and quantitativ…
Dendrochronology and Radiocarbon Dating
Both dendrochronology and radiocarbon ( 14 C) dating have their roots back in the early to mid-1900s. Although they were independently developed, they began to intertwine in the 1950s when the founder of dendrochronology, A. E. Douglass, provided dated wood samples for Willard Libby to test his emerging 14 C methods. Since this early connection, absolutely dated tree-rings have been key to calibration of the Holocene portion of the 14 C timescale…
Karl Otto Münnich (1925–2003)
Karl Otto Mnnich (KO) came to the field of radiocarbon by accident. Born in Heidelberg, Germany, in 1925, he had studied nuclear physics at the local university. KO planned to continue a career as a nuclear physicist when, after finishing his studies in 1952, Prof. Otto Haxel (inspired after meeting Willard Libby) offered him a position to set up a radiocarbon laboratory. Haxel had recognized KO's experimental skills in an advanced lab course. Si…
Initial Upper Palaeolithic Homo sapiens from Bacho Kiro Cave, Bulgaria
Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP)
The concentration of radiocarbon ( 14 C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14 C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-aver…
A New Annual 14 C Dataset for Calibrating the Thera Eruption
Annually resolved tree-ring samples of the time period 1625–1510 BCE were analyzed from the German oak tree-ring chronology. Blocks of the same tree rings were previously used to generate IntCal calibration data. The new dataset shows an offset to the calibration data IntCal13 of 24 years and resembles annual data for the same time period derived from tree-ring records in other growth locations. A subset of samples of the period 1625–1585 BCE was…
Onset of the Younger Dryas Recorded with 14 C at Annual Resolution in French Subfossil Trees
Subfossil trees with their annual rings constitute the most accurate and precise archive to calibrate the radiocarbon ( 14 C) method. The Holocene part of the IntCal curve is based on tree-ring chronologies, absolutely dated by dendrochronological matching. For the Northern Hemisphere, the absolute curve starts at 12,325 cal BP. For the early part of the Younger Dryas (YD) climatic event (≈ 12,850–11,650 cal BP), there are only a few floating den…
Quality Dating
Advances in accelerator mass spectrometry have resulted in an unprecedented amount of new high-precision radiocarbon ( 14 C) -dates, some of which will redefine the international 14 C calibration curves (IntCal and SHCal). Often these datasets are unaccompanied by detailed quality insurances in place at the laboratory, questioning whether the 14 C structure is real, a result of a laboratory variation or measurement-scatter. A handful of intercomp…
Illuminating Intcal During the Younger Dryas
As the worldwide standard for radiocarbon ( 14 C) dating over the past ca. 50,000 years, the International Calibration Curve (IntCal) is continuously improving towards higher resolution and replication. Tree-ring-based 14 C measurements provide absolute dating throughout most of the Holocene, although high-precision data are limited for the Younger Dryas interval and farther back in time. Here, we describe the dendrochronological characteristics …
The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)
Radiocarbon ( 14 C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14 C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth syste…
Direct radiocarbon dates of mid Upper Palaeolithic human remains from Dolní Věstonice II and Pavlov I, Czech Republic
Annual 14 C Tree-Ring Data Around 400 AD
Two tree-ring series, one from a high-latitude pine tree (located in northern Scandinavia) and one from a mid-latitude oak tree (located in eastern Germany) were analyzed for radiocarbon ( 14 C) at annual resolution. The new records cover the calendar date ranges 290–460 AD and 382–486 AD, respectively, overlapping by 79 yr. The series show similar trends as IntCal13. However, some significant deviations around 400 AD are present with lower Δ 14 …
Wood 14 C Dating with AixMicadas
The AixMICADAS facility is in part dedicated to research on radiocarbon ( 14 C) calibration by means of various archives. For this purpose, we are improving upon the capacity to accurately date subfossil wood. In the current study, nine chemical pretreatment protocols are tested on six wood samples of known ages. The optimization based on 14 C ages, 13 C/ 12 C ratios, carbon % and overall mass yield % leads us to favor the acid-base-acid-bleachin…
Size Matters
For many of archaeology’s rarest and most enigmatic bone artifacts (e.g. human remains, bone ornaments, worked bone), the destruction of the 500 mg material necessary for direct accelerator mass spectrometry (AMS) dating on graphite targets would cause irreparable damage; therefore many have not been directly dated. The recently improved gas ion source of the MICADAS (MIni CArbon DAting System) offers a solution to this problem by measuring gaseo…
Speed Dating
Radiocarbon measurements in tree rings can be used to estimate atmospheric 14 C concentration and thereby used to create a 14 C calibration curve. When wood is discovered in construction sites, rivers, buildings, and lake sediments, it is unclear if the wood could fill gaps in the 14 C calibration curve or if the wood is of historical interest until the age is determined by dendrochronology or 14 C dating. However, dendrochronological dating is s…
Compatibility of Atmospheric 14 CO 2 Measurements
Combining atmospheric Δ 14 CO 2 data sets from different networks or laboratories requires secure knowledge on their compatibility. In the present study, we compare Δ 14 CO 2 results from the Heidelberg low-level counting (LLC) laboratory to 12 international accelerator mass spectrometry (AMS) laboratories using distributed aliquots of five pure CO 2 samples. The averaged result of the LLC laboratory has a measurement bias of –0.3±0.5‰ with respe…
Investigating the Local Reservoir Age and Stable Isotopes of Shells from Southeast Arabia
We recently started a systematic approach to determine the reservoir age in southeast Arabia and its dependence on mollusk species and their environment. This part of the study concentrates on local reservoir age and stable isotopes of the lagoonal species Terebralia palustris and Anadara uropigimelana at Khor Kalba, Oman Sea. Environmental and nutritive influences on mollusks are reflected in the radiocarbon and stable isotope signal. We found a…
Titelseiten
Die Zeit der großen Gräben
Vorgestellt wird der Versuch einer präziseren Datierung des Erdwerks von Heilbronn-Klingenberg “Schlossberg” am mittleren Neckar. Die angewendete Methode empfiehlt sich als Ausgangspunkt für weitere Untersuchungen zur Datierung und Belegungsdauer anderer Michelsberger Erdwerke des späten 5. bis frühen 4. Jahrtausends calBC. Vom Erdwerk von Klingenberg wurden in den Jahren 1986–1987 zwei Abschnittsgräben ausgegraben, die einen Lößsporn abriegeln, …
Decadally Resolved Lateglacial Radiocarbon Evidence from New Zealand Kauri
The Last Glacial–Interglacial Transition (LGIT; 15,000–11,000 cal BP) was characterized by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global paleoclimatic, paleoenvironmental, and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 14 C calibration curv…
IntCal09 and Marine09 Radiocarbon Age Calibration Curves, 0-50,000 Years cal BP
The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14 C and calendar timescales as established in 2002. No change was made to the curves…
IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP
The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14 C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were r…
INTCAL98 Radiocarbon Age Calibration, 24,000-0 cal BP
The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000-0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14 C age-cal age information, produced by many laboratories, is converted to Δ 14 C profiles and calibration curves, for the atmosphere as well as the ocean…
Intcal04 Terrestrial Radiocarbon Age Calibration, 0–26 Cal Kyr BP
A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period f…
The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)
Radiocarbon ( 14 C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14 C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth syste…
Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP)
The concentration of radiocarbon ( 14 C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14 C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-aver…
Marine04 Marine Radiocarbon Age Calibration, 0–26 Cal Kyr Bp
New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision, and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically-dated tree-ring…
The IAEA 14 C Intercomparison Exercise 1990
As a follow-up to the meeting of experts convened at the International Atomic Energy Agency (IAEA) in February 1989, and the International 14 C Workshop held in Glasgow in September 1989, the 14 C Quality Assurance Program was formulated. In a joint effort of several radiocarbon teams and IAEA staff, we have prepared a set of five new intercomparison materials. These are natural materials frequently used by radiocarbon laboratories. The materials…
The Tropospheric 14 CO 2 Level in Mid-Latitudes of the Northern Hemisphere (1959–2003)
A comprehensive tropospheric 14 CO 2 data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented. Samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsland), 1800 m (Vermunt), and 3450 m asl (Jungfraujoch), and analyzed in the Heidelberg Radiocarbon Laboratory. The data set from Jungfraujoch (1986–2003) is considered to represent the free tropospheric background level at mid-l…
Years of Tropospheric 14 C Observations in Central Europe
A long-term mountain station series of tropospheric 14 C data for the period 1959 to 1984 is presented. This series is considered representative of the higher altitude 14 C level over central Europe. Even tree-ring 14 C levels from a rural ground level site in southern Germany are consistently lower (by Δ 14 C depression = −15‰ if compared with the mountain station summer average in atmospheric CO 2 ). The rural tree-ring series is considered to …
Twenty Years of Atmospheric 14 Co 2 Observations At Schauinsland Station, Germany
We present and discuss quasi-continuous long-term 14 CO 2 observations from the continental background station Schauinsland (48°N, 8°E, 1205 m asl, Black Forest, southern Germany). The observed steady decline of atmospheric 14 CO 2 from 1977 to 1996 can be described by a single exponential function with an e-folding time of (16.3 ± 0.2) yr. Summer means (May to August) in atmospheric 14 CO 2 at Schauinsland compare within Δ 14 C = ±4‰ with measur…
German Oak and Pine 14 C Calibration, 7200–9439 BC
Radiocarbon calibration data derived from German oak chronologies, ranging back to 7200 BC, have been published in the previous Calibration Issue (Stuiver & Kra 1986). In recent years, the German oak chronology has been extended to 7938 BC (Becker, this issue). For earlier intervals, tree-ring chronologies must be based on pine, because oak re-emigrated to central Europe at the Preboreal/Boreal transition, at about 8000 BC. We have established a …
The 12,460-Year Hohenheim Oak and Pine Tree-Ring Chronology from Central Europe—A Unique Annual Record for Radiocarbon Calibration and Paleoenvironment Reconstructions
The combined oak and pine tree-ring chronologies of Hohenheim University are the backbone of the Holocene radiocarbon calibration for central Europe. Here, we present the revised Holocene oak chronology (HOC) and the Preboreal pine chronology (PPC) with respect to revisions, critical links, and extensions. Since 1998, the HOC has been strengthened by new trees starting at 10,429 BP (8480 BC). Oaks affected by cockchafer have been identified and d…
Between the Vinča and Linearbandkeramik Worlds
A comprehensive numerical chronology for the pre-Columbian cultures of the Palpa valleys, south coast of Peru
Selection and Treatment of Data for Radiocarbon Calibration
High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14 C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14 C/ 12 C in these archives, i…
Radiocarbon Age Calibration Back to 13,300 Years BP and the 14 C Age Matching of the German Oak and US Bristlecone Pine Chronologies
With the recent establishment of an unbroken West European tree-ring sequence spanning the past 7272 years (Pilcher et al , 1984) the calibration of the 14 C time scale was advanced considerably. It is now possible to use this chronology as an independent cross-check on the 8681-year US Bristlecone Pine series (Ferguson & Graybill, 1983). There also are opportunities for 14 C matching (wiggle matching) between the older portion of the Bristlecone…
Late Glacial 14 C Ages from a Floating, 1382-Ring Pine Chronology
We built a floating, 1382-ring pine chronology covering the radiocarbon age interval of 12,000 to 10,650 BP. Based on the strong rise of Δ 14 C at the onset of the Younger Dryas (YD) and wiggle-matching of the decadal-scale Δ 14 C fluctuations, we can anchor the floating chronology to the Cariaco varve chronology. We observe a marine reservoir correction higher than hitherto assumed for the Cariaco site, of up to 650 yr instead of 400 yr, for the…
Revisions and Extension of the Hohenheim Oak and Pine Chronologies
Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the …
The Continental European Suess Effect
Observations of 14 C in atmospheric CO 2 at four different sites in central Europe, Heidelberg, Westerland, Schauinsland and Jungfraujoch have enabled us to determine individual fossil-fuel contributions to atmospheric CO 2 concentration. The data clearly show a decrease of fossil-fuel CO 2 with distance from anthropogenic source regions. At Heidelberg during winter we observe 14 C/ 12 C ratios up to 10% lower than at the clean air mountain stati…
Radiocarbon Calibration Data for the 6th to the 8th Millennia BC
14 C calibration curves derived from South German oak tree-ring series are presented. They cover the interval between 4400 and 7200 BC complementing existing data sets and extending them to older periods. The atmospheric 14 C level before 6200 BC no longer follows the long-term sinusoidal trend fitted to the bristlecone data. This observation is supported by a tentative match of the Main 9 series
A 7400-year tree-ring chronology in northern Swedish Lapland
Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus syl vestris L.) have been assembled into a continuous and precisely dated chronology (the Torneträsk chronology) covering the period 5407 BC to ad 1997. Biological trends in the data were removed with autoregressive standardization (ARS) to emphasize year-to-year variability, and with regional curve stan dardization (RCS) to emphasize variability on timescales…
Revision and Tentative Extension of the Tree-Ring Based 14 C Calibration, 9200–11,855 cal BP
We report radiocarbon calibration data based on the revised German oak and pine series. The age range of the absolutely dated German oak series has been extended to 10,430 cal bp. The German pine series is tentatively linked to the oak series by 14 C, and now reaches back to 11,871 cal bp (±20 yr). The revisions of the tree-ring time scale of the German oak chronology solved long-standing apparent discrepancies in the mid-Holocene 14 C calibratio…
The New Zealand Kauri ( Agathis Australis ) Research Project
Wc describe here the New Zealand kauri ( Agathis australis ) Younger Dryas (YD) research project, which aims to undertake Δ 14 C analysis of ∼140 decadal floating wood samples spanning the time interval ∼13.1–11.7 kyr cal BP. We report 14 C intercomparison measurements being undertaken by the carbon dating laboratories at University of Waikato (Wk), University of California at Irvine (UCI), and University of Oxford (OxA). The Wk, UCI, and OxA lab…
Geoarchaeological Evidence From Desert Loess in the Nazca–palpa Region, Southern Peru
The paper presents proxies from an interdisciplinary geoarchaeological working group. Sediment analyses and geomorphological studies, radiocarbon ages of snail shells and luminescence dating of loess allow a preliminary chronology of the environmental evolution of the eastern Atacama desert, Nazca–Palpa region (southern Peru). Until now, typical desert loess was unknown from the arid western flank of the Andes (southern Peru). The loess points to…
Anthropogenic 14 C Variations
Continuous 14 C data of 1 or 2 weekly samples of atmospheric CO 2 are presented, collected near two nuclear power plants (NPP-Biblis and NPP-Philippsburg) located in the rather densely populated upper Rhine valley. Tree-leaf and tree-ring samples from the area of a boiling water reactor in northern Germany (NPP-Würgassen) are also presented and discussed. Additional atmospheric 14 CO 2 samples from two continental ‘clean-air’ stations in Germany …
Years of Tropospheric 14 C Observations in Central Europe
A long-term mountain station series of tropospheric 14 C data for the period 1959 to 1984 is presented. This series is considered representative of the higher altitude 14 C level over central Europe. Even tree-ring 14 C levels from a rural ground level site in southern Germany are consistently lower (by Δ 14 C depression = −15‰ if compared with the mountain station summer average in atmospheric CO 2 ). The rural tree-ring series is considered to …
Radiocarbon Age Calibration Back to 13,300 Years BP and the 14 C Age Matching of the German Oak and US Bristlecone Pine Chronologies
With the recent establishment of an unbroken West European tree-ring sequence spanning the past 7272 years (Pilcher et al , 1984) the calibration of the 14 C time scale was advanced considerably. It is now possible to use this chronology as an independent cross-check on the 8681-year US Bristlecone Pine series (Ferguson & Graybill, 1983). There also are opportunities for 14 C matching (wiggle matching) between the older portion of the Bristlecone…
Extension of the Holocene Dendrochronology by the Preboreal Pine Series, 8800 to 10,100 BP
Holocene tree-ring chronologies have been established for south-central Europe covering the past 11,000 years. The Hohenheim absolute oak chronology extends to 4089 bc. The C-calibrated mid-Holocene floating oak master covers a 3181-year period from ca 4045 to 7225 bc. The earliest well-replicated floating oak master (estimated calendar age 7215 to 7825 bc) extends the European oak dendrochronology back to Boreal times. Further extension of the H…
Radiocarbon Calibration Data for the 6th to the 8th Millennia BC
14 C calibration curves derived from South German oak tree-ring series are presented. They cover the interval between 4400 and 7200 BC complementing existing data sets and extending them to older periods. The atmospheric 14 C level before 6200 BC no longer follows the long-term sinusoidal trend fitted to the bristlecone data. This observation is supported by a tentative match of the Main 9 series
Measurement of Small Volume Oceanic 14 C Samples by Accelerator Mass Spectrometry
A technique for 14 C measurement of small volume (0.5L) oceanic water samples by Accelerator Mass Spectrometry (AMS) is described. Samples were taken from a CTD/rosette system used for standard hydrographic work. After CO 2 extraction and target preparation, the samples were measured at the Zürich tandem accelerator facility. On the basis of 14 C data from samples collected on a station in the northern Weddell Sea, the precision of the measuremen…
The Continental European Suess Effect
Observations of 14 C in atmospheric CO 2 at four different sites in central Europe, Heidelberg, Westerland, Schauinsland and Jungfraujoch have enabled us to determine individual fossil-fuel contributions to atmospheric CO 2 concentration. The data clearly show a decrease of fossil-fuel CO 2 with distance from anthropogenic source regions. At Heidelberg during winter we observe 14 C/ 12 C ratios up to 10% lower than at the clean air mountain stati…
C Profiles in the Central Weddell Sea
14 C data from stations in the central Weddell Sea are presented and discussed using additional parameters (potential temperature, salinity and 3 He). The low 14 C concentrations of the surface water (≈-90‰) are explained by suppressed gas exchange due to ice cover during the winter and rapid turnover of the surface layer caused by entrainment of Warm Deep Water (WDW) with low 14 C concentrations. A simple time-dependent balance calculated for th…
Fast 14C Sample Preparation of Organic Material
A fast 14 C sample preparation technique for organic material in conventional 14 C counting is described. The basic difference from conventional preparation is oxidation of the organic substances in a closed system under an oxygen pressure of ca 10 bars. After the explosion-like combustion, the reaction products SO 2 and NO 2 are oxidized immediately to SO 4 2- and NO 3 − and precipitated on the wall of the reaction vessel. The residual gas mixtu…
Radiocarbon Dating of the Neolithic Early Bronze Age Site of Mandalo, W Macedonia
The following list of dates was obtained in a joint German-Greek project to establish a radiocarbon dating laboratory in the National Research Centre for Physical Sciences “Demokritos,” Athens, Greece. 1 Although our initial aim in selecting these samples was to study laboratory procedures, we found that when the dates were arranged in stratigraphic order they provided a chronological framework for Thessalian and northern Macedonian site of the L…
Climatic, Solar, Oceanic, and Geomagnetic Influences on Late-Glacial and Holocene Atmospheric 14 C/ 12 C Change
Late-glacial and Holocene 14 C/ 12 C ratios of atmospheric CO 2 vary in magnitude from a few per mil for annual/decadal pertubations to more than 10% for events lasting millennia. A data set illuminating 10- to 10 4 -yr variability refines our understanding of oceanic (climatic) versus geomagnetic or solar forcing of atmospheric 14 C/ 12 C ratios. Most of the variance in the Holocene atmospheric 14 C/ 12 C record can be attributed to the geomagne…
The IAEA 14 C Intercomparison Exercise 1990
As a follow-up to the meeting of experts convened at the International Atomic Energy Agency (IAEA) in February 1989, and the International 14 C Workshop held in Glasgow in September 1989, the 14 C Quality Assurance Program was formulated. In a joint effort of several radiocarbon teams and IAEA staff, we have prepared a set of five new intercomparison materials. These are natural materials frequently used by radiocarbon laboratories. The materials…
German Oak and Pine 14 C Calibration, 7200–9439 BC
Radiocarbon calibration data derived from German oak chronologies, ranging back to 7200 BC, have been published in the previous Calibration Issue (Stuiver & Kra 1986). In recent years, the German oak chronology has been extended to 7938 BC (Becker, this issue). For earlier intervals, tree-ring chronologies must be based on pine, because oak re-emigrated to central Europe at the Preboreal/Boreal transition, at about 8000 BC. We have established a …
On the 14 C and 39 Ar Distribution in the Central Arctic Ocean
We present ΔA 14 C and 39 Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ 14 C values, to describe the distribution of Δ 14 C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39 Ar distribution in the Nansen Basin and the deep …
Bernd Becker, 1940–1994
at the age of 53 after a yearlong battle with cancer
Tree-rings, absolute chronology and climatic change
In the Hohenheim tree-ring laboratory, two long tree-ring chronologies have been built, spanning the past 11 600 years. This is the world's longest continuous tree-ring calendar. It has become the backbone of the calibration of the radiocarbon time scale, offering absolute and accurate dates for archaeology, vegetation history and paleoclimate studies. 14 C analyses of the tree-ring chronologies provide insight into the process controlling the pr…
Locating Archaeological Horizons with 14 C Sediment Dating
In 373 bc a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a su…
Synchronized Terrestrial Atmospheric Deglacial Records Around the North Atlantic
On the basis of synchronization of three carbon-14 ( 14 C)-dated lacustrine sequences from Sweden with tree ring and ice core records, the absolute age of the Younger Dryas-Preboreal climatic shift was determined to be 11,450 to 11,390 ± 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising Δ 14 C values, is evident in all records and indicates an ocean ventilation change. This cooling is similar to e…
Report
Recently, in an intercomparison of the Hohenheim German oak chronology (Becker 1993) and the Göttingen chronology (Leuschner and Delorme 1988), an error was discovered in the former (Leuschner, in preparation). Due to an error in adding sections at 5241 bc, 41 yr are missing in the published Hohenheim chronology. After correction of the error, the two chronologies synchronize over their entire common length, back to 7200 bc
Conference Participants
From the 16th International Radiocarbon Conference held in Gronigen, Netherlands, June 16-20, 1997
Study of the Parameters Affecting the Correlation of Background Versus Cosmic Radiation in Co 2 Counters
Systematic treatment of the data recorded by our guard counters and corrections introduced for meteorological factors has allowed observations on solar events clearly manifested in the readings. Examples are the solar flares of March 1989 and especially of June 1991, which caused a ca. 10% decrease in the cosmic radiation flux reaching the counters. A sinusoidal variation in the cosmic-ray flux with a period of one year is also clearly manifested…
Twenty Years of Atmospheric 14 Co 2 Observations At Schauinsland Station, Germany
We present and discuss quasi-continuous long-term 14 CO 2 observations from the continental background station Schauinsland (48°N, 8°E, 1205 m asl, Black Forest, southern Germany). The observed steady decline of atmospheric 14 CO 2 from 1977 to 1996 can be described by a single exponential function with an e-folding time of (16.3 ± 0.2) yr. Summer means (May to August) in atmospheric 14 CO 2 at Schauinsland compare within Δ 14 C = ±4‰ with measur…
Segments of Atmospheric 14 C Change as Derived from Late Glacial and Early Holocene Floating Tree-Ring Series
We present results of 14 C dating of several tree-ring series from the Late Glacial and Early Holocene, analyzed at the Heidelberg University radiocarbon laboratory. Although these are floating series, they contribute high-resolution information about the variability of atmospheric 14 C during those periods
Apparent 14 C Ages of Marine Mollusk Shells from a Greek Island
The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Sporades (39°22'N, 24°10'E), revealed material of marine and terrestrial origin in undisturbed layers, suitable for radiocarbon dating. In some cases, material from different reservoirs was found together in the same archaeological layer. This research had two aims. The first was the dating of charcoal-seashell pairs in order to determine the marine reser…
Revision and Tentative Extension of the Tree-Ring Based 14 C Calibration, 9200–11,855 cal BP
We report radiocarbon calibration data based on the revised German oak and pine series. The age range of the absolutely dated German oak series has been extended to 10,430 cal bp. The German pine series is tentatively linked to the oak series by 14 C, and now reaches back to 11,871 cal bp (±20 yr). The revisions of the tree-ring time scale of the German oak chronology solved long-standing apparent discrepancies in the mid-Holocene 14 C calibratio…
Geography (68 works) · Radiocarbon dating (67 works) · Geology (61 works) · Archaeology and ancient environmental studies (59 works) · Geology and Paleoclimatology Research (57 works) · Archaeology (52 works) · Paleontology (46 works) · Physical geography (40 works) · Dendrochronology (27 works) · Chronology (26 works)