Publications - Publications

Isotopic and historical evidence of regional stockfish trade in the Skagerrak during the 16th century

Maltin, E., Jonsson, L., Fuller, B. T., Olsen, J., Mannino, M. — Mon, 01 Jan 2024 05:06:23 +0100

Preserved fish was one of the main traded commodities in medieval and early modern times, and herring and cod were the socioeconomically most important species. This paper brings together stable isotope ratio analysis of archaeological cod bones and documentary data from customs records originating from the early modern Swedish town of Nya Lödöse (1473–1624 CE), shedding new light on the import of stockfish (dried cod). The combined results show that the stockfish imported to Nya Lödöse was mainly produced in the Danish town of Skagen, and the importance of Bergenfish was negligible. The Skagen fisheries targeted large gadids, skates, and flatfish and have hitherto been bypassed in archaeological research on the medieval and early modern fish trade. The findings of this research highlight the intense connectivity between communities across the Skagerrak and give an example of the comprehensive regional fish trade that existed alongside the long-distance trade. Another important conclusion is that the isotopic values for cod caught in the Skagerrak must be used with caution since this sea basin is populated by several different cod stocks. The North Sea cod population inhabits a large part of the Skagerrak, and cod bones with isotopic values consistent with the North Sea might thus have been fished in the Skagerrak.

The marine reservoir age of Greenland coastal waters

Pearce, C., Özdemir, K. S., Forchhammer Mathiasen, R., Detlef, H., Olsen, J. — Fri, 01 Dec 2023 05:06:23 +0100

Knowledge of the marine reservoir age is fundamental for creating reliable chronologies of marine sediment archives based on radiocarbon dating. This age difference between the 14C age of a marine sample and that of its contemporaneous atmosphere is dependent on several factors (among others, ocean circulation, water mass distribution, terrestrial runoff, upwelling, and sea-ice cover) and is therefore spatially heterogeneous. Anthropogenic influence on the global isotopic carbon system, mostly through atmospheric nuclear tests, has complicated the determination of the regional reservoir age correction Î"R, which therefore can only be measured in historic samples of known age. In this study we expand on the few existing measurements of Î"R for the coastal waters around Greenland, by adding 92 new radiocarbon dates on mollusks from museum collections. All studied mollusk samples were collected during historic expeditions of the late 19th and early 20th centuries, and besides coastal sites around Greenland, the new measurements also include localities from the western Labrador Sea, Baffin Bay, and the Iceland Sea. Together with existing measurements, the new results are used to calculate average Î"R values for different regions around Greenland, all in relation to Marine20, the most recent marine radiocarbon calibration curve. To support further discussions and comparison with previous datasets, we use the term Î"R13, where the suffix 13 refers to the previous calibration curve Marine13. Our study explores the links between the marine reservoir age and oceanography, sea-ice cover, water depth, mollusk feeding habits, and the presence of carbonate bedrock. Although we provide regional averages, we encourage people to consult the full catalogue of measurements and determine a suitable Î"R for each case individually, based on the exact location including water depth. Despite this significant expansion of the regional reservoir age database around Greenland, data from the northern coast, directly bordering the Arctic Ocean, remain missing.

Deglaciation of the highest mountains in Scandinavia at the Younger Dryas–Holocene transition

Matthews, J. A., Linge, H., Nesje, A., et al. — Mon, 01 Apr 2024 05:06:23 +0200

Surface exposure–age dating was applied to rock surfaces associated with ice-marginal moraines at elevations of ~1520–1780 m a.s.l. on the slopes of Galdhøpiggen and Glittertinden, the two highest mountains in Scandinavia located in the Jotunheimen mountains of central southern Norway. This is important for understanding the pattern and timing of wastage of the Scandinavian Ice Sheet at the Younger Dryas–Holocene transition. Cosmogenic exposure dating (here ¹⁰Be dating) of boulders from the moraine ridges yielded overall mean ages (corrected for glacio-isostatic uplift, surface erosion and snow shielding) of ~11.6 ka from Galdhøpiggen and ~11.2 ka from Glittertinden. Similar ¹⁰Be ages were also obtained from additionally collected proximal and distal erratic boulders and bedrock samples. These enabled age calibration of Schmidt-hammer R-values and independent Schmidt-hammer exposure-age dating (SHD) of the moraine ridges, which yielded comparable mean SHD ages of ~10.8 and ~10.6 ka from the Galdhøpiggen and Glittertinden sites, respectively. Taking account of the age resolution and other limitations of both dating techniques, the results suggest that the two sets of moraines have approximately the same age but that neither technique can distinguish unambiguously between moraine formation in the late Younger Dryas or Early Holocene. Together with features of moraine-ridge morphology and estimates of equilibrium-line altitude depression of ~360–575 m (corrected for land uplift), the results imply moraine formation during short-lived re-advances of active glaciers, at least the lower reaches of which were warm-based. It is concluded that the local glaciers remained active and advanced during deglaciation either very late in the Younger Dryas or very early in the Holocene, possibly in response to the Preboreal Oscillation at ~11.4 ka. The study supports the concept of a thin Younger Dryas ice sheet and places time constraints on the timing of final deglaciation in southern Norway.

Banatian DeathMetals

Daróczi, T. T., Balarie, A., Olsen, J., Birclin, M. — Fri, 01 Dec 2023 05:06:23 +0100

The lack of radiocarbon measurements of funerary contexts is a major shortcoming of the Late Bronze Age and Early Iron Age of the Eastern Carpathian Basin, especially in the Banat region. The present batch of samples tries to address these drawbacks, by detailing sampling strategies, employed pre-treatment and by providing a robust and coherent dataset of radiocarbon measurements. Implications of the new radiocarbon dates is discussed from a supra-regional perspective, while keeping aspects of typo-chronology, circulation of goods, and social nuances of employment of Bronze Age bronzes in the forefront. Ten burials were selected from four Banatian burial grounds according to the occurrence of metal finds in the funerary inventories. Beyond establishing a broad frame of absolute chronology for these sites of interment, the radiocarbon data provide reliable arguments for the precise attribution of metal discoveries. In addition, the data allow us to challenge some previously stated chronological assignments.

Achilles Tendon Tissue Turnover Before and Immediately After an Acute Rupture

Cramer, A., Højfeldt, G., Schjerling, P., et al. — Sat, 01 Jul 2023 05:06:23 +0200

Background: An Achilles tendon rupture (ATR) is a frequent injury and results in the activation of tendon cells and collagen expression, but it is unknown to what extent turnover of the tendon matrix is altered before or after a rupture. Purpose/Hypothesis: The purpose of this study was to characterize tendon tissue turnover before and immediately after an acute rupture in patients. It was hypothesized that a rupture would result in pronounced collagen synthesis in the early phase (first 2 weeks) after the injury. Study Design: Cross-sectional study; Level of evidence, 3. Methods: The study included patients (N = 18) eligible for surgery after an ATR. At the time of inclusion, the patients ingested deuterium oxide (²H₂O) orally, and on the day of surgery (within 14 days of the injury), they received a 3-hour flood-primed infusion of an ¹⁵N-proline tracer. During surgery, the patients had 1 biopsy specimen taken from the ruptured part of the Achilles tendon and 1 that was 3 to 5 cm proximal to the rupture as a control. The biopsy specimens were analyzed for carbon-14 (¹⁴C) levels in the tissue to calculate long-term turnover (years), incorporation of ²H-alanine (from ²H₂O) into the tissue to calculate the fractional synthesis rate (FSR) of proteins in the short term (days), and incorporation of ¹⁵N-proline into the tissue to calculate the acute FSR (hours). Results: Both the rupture and the control samples showed consistently lower levels of ¹⁴C compared with the predicted level of ¹⁴C in a healthy tendon, which indicated increased tendon turnover in a fraction (48% newly synthesized) of the Achilles tendon already for a prolonged period before the rupture. Over the first days after the rupture, the synthesis rate for collagen was relatively constant, and the average synthesis rate on the day of surgery (2-14 days after the rupture) was 0.025% per hour, irrespective of the length of time after a rupture and the site of sampling (rupture vs control). No differences were found in the FSR between the rupture and control samples in the days after the rupture. Conclusion: Higher than normal tissue turnover in the Achilles tendon before a rupture indicated that changes in the tendon tissue preceded the injury. In addition, we observed no increase in tendon collagen tissue turnover in the first 2 weeks after an ATR. This favors the view that an increase in the formation of new tendon collagen is not an immediate phenomenon during the regeneration of ruptured tendons in patients. Registration: NCT03931486 (ClinicalTrials.gov identifier).

Comparing methods for CO₂ purification of cremated bone samples

Olsen, J., Daróczi, T. T., Kanstrup, M. — Thu, 01 Jun 2023 05:06:23 +0200

During the last two decades the radiocarbon (14C) dating of hydroxyapatite archaeological cremated bones has become standard practice. Various pretreatment procedures exist among different laboratories of which some include fixation of SO2 using Sulfix prior to CO2 reduction. Recently it was reported that the use of Sulfix may cause the resulting 14C age to be too old. Here we report on the use Sulfix at the Aarhus AMS Centre. Further, we report on an experiment designed to test alternatives for the use of Sulfix as a purification agent.

Absence of Large-Scale Ice Masses in Central Northeast Siberia During the Late Pleistocene

Nørgaard, J., Margold, M., Jansen, J. D., et al. — Sun, 28 May 2023 05:06:23 +0200

Ongoing speculation regarding the existence of large Late Pleistocene ice masses in Northeast Eurasia reflects the dearth of age constraints on glaciations across this vast region. Here, we report the first dates from the central part of Northeast Siberia, consisting of 22 cosmogenic ¹⁰Be exposure ages from boulders deriving from a sequence of three moraines in the Chersky Range. The dated moraine sequence indicates progressive contraction of maximum glacier extent from Marine Isotope Stage 6 to the Last Glacial Maximum, while the remotely-sensed mapping indicates an older, more expansive glaciation in the region yet undated. Our results show that Late Pleistocene glaciations were limited to the highlands, and Northeast Siberia did not host a large, coalescent ice sheet during the Last Glacial Maximum or Marine Isotope Stage 6.

Ramped pyrolysis radiocarbon dating of lime lumps

Barrett, G. T., Allen, K., Reimer, P. J., Ringbom, Å., Olsen, J., Lindroos, A. — Mon, 01 May 2023 05:06:23 +0200

Ramped pyrolysis radiocarbon dating was carried out on lime lumps from what was believed to be the oldest remains of Turku Cathedral, Finland, the first sacristy. Lumps extracted from bulk mortar from five sampling locations were analysed. For each sample, 5–6 fractions of CO₂ from different temperature fractions were radiocarbon dated. One of the five samples exhibited significant contamination for its lowest temperature fractions. For the remaining samples, the age-temperature profiles were well-behaved, exhibiting a plateau of dates that were in statistical agreement and indicative of samples where only a single carbonate source (lime binder from the construction phase) is contributing to the radiocarbon dates. For each of the five samples, the combined radiocarbon age resulted in a calibrated age with a large probability distribution mode (typically > 85% probability) in the late 13th century AD. Combining the radiocarbon dates from all five samples (21 fractions in statistical agreement, χ²-test: df = 20, T = 7.1, 5% = 31.4) provided an age of 709 ± 11 yr BP and a calibrated age of 1276–1296 cal. AD (95.4%). This result finds excellent agreement with historical sources, previous mortar dating work, and a single radiocarbon date on organic material also embedded in some of the bulk mortar. The results demonstrate that ramped pyrolysis, applied to well-selected lime lumps, is (A) a useful diagnostic tool for establishing how reliable a sample is and (B) an accurate, precise, and repeatable technique for radiocarbon dating mortar. The results further confirm that Turku Cathedral's first sacristy was constructed from stone and mortar in the late 13th century AD. Additionally, using Turku Cathedral sacristy as a case study, two Bayesian models were presented to illustrate how, in general, mortar dating and Bayesian statistics might, in future, be applied to examine building construction dynamics for the case of (chronologically) ordered or unordered mortar derived radiocarbon dates.

Stone-paved cellars in the Danish Stone Age?

Brinch, M., Philippsen, B., Groß, D., Kanstrup, M. — Thu, 01 Sep 2022 05:06:23 +0200

We present the excavation results from a Middle Neolithic site associated with the Funnel Beaker
Culture. During a rescue excavation, a recessed area was recorded within two overlaying house features
which was constructed using different sized pebbles. The arrangement and form of the feature clearly
indicated anthropogenic origin and is understood as belonging to one of the house structures.
Consequently, it is interpreted as a paved cellar – a feature yet unknown from Danish Stone Age
archaeology. Additional features at the site were several pits and postholes that indicated the presence
of a palisade or fence structure with up to seven different parallel lines. Indirect dating of the features
through associated organic material has shown that the fence or palisade has existed
contemporaneously with the houses and can, hence, be interpreted as belonging to the same
settlement. We present the results from the excavation and integrate the site in its regional
archaeological landscape.
Finally, we discuss the radiocarbon dating strategies for rescue excavations both on the scale of
individual features as well as for entire development projects. We show how targeted sampling and
analysis can preserve the research potential of those sites for future research.

Contextualizing the presence of late bronze age millet at the arnbjerg site

Kanstrup, M., Olsen, J., Sørensen, C. — Thu, 01 Sep 2022 05:06:23 +0200

Situated near Viborg, just south of Lake Søndersø, large-scale archaeological excavations at Arnbjerg N revealed a great amount of Settlement evidence. A priority within the project was to Radiocarbon date a wide range of samples in order to investigate the duration of the different settlement features and the dynamics of the site compared with the Settlement History in the same region using Bayesian modelling. In total more than 220 samples were dated, giving ages mainly ranging from The Late Neolithic to the Early Iron Age with a relative large concentration of dates situated on the Hallstatt Plateau. The overall distribution of the dates demonstrates site continuity with a few interesting exceptions. Here we focus on the settlement recovery and consolidation phase following a clear hiatus from 1200-800 BCE. This Hallstatt settlement phase is particular since we here see clear evidence of Late Bronze Age Millet farming in the archaeobotanical assemblages. Millet is not a common crop found to be cultivated in Denmark. The spread of millet to Northern Europe tend to give rise to considerations about linkages to pan-continental communicative networks, and the exchange of both goods, social mobility and technology. Besides the obvious new and more exotic agrarian trait, the archaeology in the Hallstatt phase of Arnbjerg also reveal new features in the architectural lay out of the longhouses. Combined the different sources of evidence points out differences in the development in the Settlement structure compared to earlier phases.

Petrography and geochemical analysis of Arctic ikaite pseudomorphs from Utqiaġvik (Barrow), Alaska

Schultz, B. P., Huggett, J. M., Kennedy, G. L., et al. — Sun, 01 Jan 2023 05:06:23 +0100

Ikaite and pseudomorphs thereafter (“glendonites”) are a potentially powerful tool for palaeoclimatic studies, as a low-temperature proxy. However, much uncertainty still surrounds the drivers of ikaite formation, in particular prerequisite thermal and chemical conditions. Furthermore, the ikaite to
glendonite transformation is not fully understood, and it was unclear which calcite phases in glendonites were ikaite-derived and which were later diagenetic calcites. This leads to difficulties in choosing which phase to analyse in order to reconstruct the original ikaite growth environmental conditions. Petrographic
examination of air-transformed ikaite from the Isatkoak Lagoon in Utqiaġvik, Alaska, confirms that both ’Type I’ and ’Type II’ calcite phases seen in glendonites are directly derived from ikaite breakdown and not from secondary sources. Clumped isotope temperature reconstructions for transformed ikaites from Utqiaġvik, and comparison to Recent glendonites from the White Sea, Russia, confirm that clumped isotope thermometry may be used to reconstruct ikaite growth temperatures, whilst stable isotopes and minor elemental analysis reveal that a range of geochemical conditions characterise ikaite growth sites

Targeted radiocarbon dating of animal bones from ritual wetland depositions in early Iron Age (Denmark)

Kveiborg, J., Olsen, J. — Wed, 01 Feb 2023 05:06:23 +0100

The biography and chronology of ritual wetland deposits of animal bones has proven difficult to establish and has been based on the study and typology of associated groups of objects (ceramics and weapons) deposited at the same site. As a result, animal bone deposits are often generalised and perceived in plural, even though several sites exhibit evidence of multiple, clearly separate deposits of individual animals or animal parts. To surmount these shortcomings, this study presents and discusses the results of targeted radiocarbon dating of animal bone depositions from a number of well-established ritual wetland sites dated to the early Iron Age within the area of present-day Denmark. The study includes 154 radiocarbon dates from 10 different sites. The results confirm that the biography of ritual animal bone depositions in wetland sites is highly complex and indicate that the use of wetlands during the early Iron Age for ritualized deposition of animal bones lasted for up to 800 years from the 4th – 5th century BC. The study also shows that domestic animal species were preferred over wild animals, and it confirms that some species may have held a special significance. It is further suggested that some animal species were deposited in wetland ritual depositions for a longer period of time than others, and that some wetland sites were in use through multiple centuries, whereas others were not. All in all, the study suggests a complex and dynamic use of wetlands and animals as part of early Iron Age ritual life.

Radiocarbon and OSL dating of Caesar’s Forum in Rome

Olsen, J., Daugbjerg, T. S., C. Kinnaird, T., et al. — Thu, 01 Sep 2022 05:06:23 +0200

The Chronology of Neolithic-Eneolithic in the Steppe Zone of the Volga Basin

Vybornov, A. A., Giljazov, F. F., Doga, N. S., Kulkova, M. A., Philippsen, B. — Sat, 01 Jan 2022 05:06:23 +0100

Introduction. The steppe zone of the Volga basin is interesting in connection with the study of the Orlovskaya, Cis-Caspian, and Khvalinskaya cultures. These cultures have an important significance for the prehistorical archaeology of Eastern Europe. The Orlovskaya culture is characterized by the appearance of the most ancient ceramics in the region, early signs of domestication are connected with the Cis-Caspian culture but the earlier metal items were found in the Khvalinskaya culture. Together with the main features of these cultures, the important question is a determination of reliable boundaries of them. From 2007 more than 60 radiocarbon dates were obtained. The basis consisted of the materials of the Varfolomeevskaya site. The most of dates had been done on the organics from ceramics. That was under dispute. Methods and materials. During the last eight years, more than 30 radiocarbon dates were obtained on the different organic materials (charcoal, animal bones, and food charred crusts) from new open stratified sites – Algay and Oroshaemoe. This set of dates gave the possibility to develop a reliable chronological schema for the Neolithic-Eneolithic in the region under consideration. The comparison of dates on the different organic materials has been done. Results. The chronological framework of the Orlovskaya culture, the Cis-Caspian culture of transition period and the Eneolithic Khvalinskaya culture for the steppe zone of the Volga basin was determined. The place of the Orlovskaya cultural antiquities among of Neolithic cultures of neighboring regions was established. The age of transitional Neolithic-Eneolithic Cis-Caspian culture with the earliest pieces of evidence of domestication in Eastern Europe was definite. The chronological framework of the Khvalinskaya Eneolithic culture in the steppe zone was considered and made the comparison with the Cis-Caspian culture. Authors’contribution. A.A. Vybornov is prepared the archaeological part of the article and did analysis and their interpretation of the radiocarbon dates on the Neolithic of the steppe zone of the Volga basin. F.F. Giljazov collected all dates of the Orlovskaya culture of the Algay and Oroshaemoe sites. N.S. Doga did an analysis of dates of the Cis-Caspian and Khvalinskaya cultures on these sites. M.A. Kulkova obtained the radiocarbon dates for differentlayers of the Algay and Oroshaemoe sites and did the correlations on the different organic materials. B. Philippsen obtained the AMS dates on charcoal, bones, charred crusts and did their correlation.

Túrkeve-Terehalom in the Eastern Carpathian Basin. Bronze Age multi-stratified site provides high-precision chronology with continental implications

Daróczi, T. T., Csányi, M., Tárnoki, J., Nagy, F., Olsen, J. — Thu, 01 Jun 2023 05:06:23 +0200

The multi-stratified site of Túrkeve-Terehalom presents an exceptional opportunity to establish the start and the end of the Middle Bronze Age in the Eastern Carpathian Basin and to refine its inner chronology. The chronological potential of the site rests on the meticulous excavation campaigns over a decade. This potential has been harvested by linking stratified finds, particularly pottery, to narrow, calibrated age-ranges. The result has implications for local chronology while also prompting questions about how to synchronise long-range connectivity with central and northern Europe and the Aegean, as well. The resulting chronological model for Túrkeve-Terehalom firstly challenges prevailing chronological views regarding the life-spans of Bronze Age structures with beaten clay floors, secondly the direction of the wave of destruction and/or abandonment of multi-stratified sites in the Carpathian Basin, and thirdly the continental networking during the Middle Bronze Age.

Late glacial and Holocene glaciation history of North and Northeast Greenland

Larsen, N. K., Søndergaard, A. S., Levy, L. B., et al. — Thu, 01 Dec 2022 05:06:23 +0100

Northeast Greenland is the place where the Greenland Ice Sheet (GrIS) experienced the largest areal changes since the Last Glacial Maximum. However, the age constraints of the last deglaciation are in some areas sparse. In this study, we use forty-seven new ¹⁰Be cosmogenic exposure ages to constrain the deglaciation of the present-day ice-free areas in Northeast Greenland. Our results show that the outer coast region was deglaciated between 12.8 ± 0.6 and 11.5 ± 0.2 ka and the region close to the present ice margin was deglaciated 2 to 4 ka later between 9.2 ± 0.3 to 8.6 ± 0.3 ka. By combining our new results with previously published data from North and Northeast Greenland, we find that the ice sheet advanced to the shelf edge between 26 and 20 cal. ka BP. The outer coast was deglaciated between 12.8 and 9.7 ka and the present ice extent was reached between 10.8 to 5.8 ka. The ice margin continued to retreat farther inland during the Middle Holocene before it readvanced toward its Little Ice Age position. The deglaciation was probably forced by a combination of increased atmospheric and ocean temperatures, but local topography also played an important role. These results add to the growing knowledge about the glaciation history of the GrIS and add useful constraints for future ice sheet models.

Solar variability between 650 CE and 1900 - Novel insights from a global compilation of new and existing high-resolution ¹⁴C records

Thu, 01 Sep 2022 05:06:23 +0200

This study investigates solar variability between 650 CE and 1900 based on new and published ¹⁴C records with a time resolution of two years or higher. The new high-resolution ¹⁴C data presented here are derived from Danish oak and span the period 1058–1250 CE. We determine the durations of past solar minima and periods with moderate solar activity from the solar modulation potential calculated using a carbon-box model with the high-resolution ¹⁴C records as input. The observed intervals of solar minima and intermittent periods with moderate activity levels suggest that a Maunder-type minimum occurred in 656–707 CE. We tentatively propose to name this minimum the Horrebow Minimum after Christian Horrebow, an early Danish astronomer who studied the occurrence of sunspots and was the first to propose that they follow a cyclic behaviour. Changes in amplitude and cycle length of the 11-year solar cycle are investigated by bandpass filtering 23 individual ¹⁴C records. The filtered ¹⁴C data indicate that the length of the 11-year solar cycle may be prolonged before the onset of the Oort, Maunder, and Spörer minima. The amplitude of the 11-year solar cycle associated with solar minima and periods with moderate solar activity between 650 CE and 1900 is estimated to 1.1‰. A two-sample Kolmogorov-Smirnov goodness-of-fit test indicates that there is no significant difference between the amplitude distribution of 11-year solar cycles during solar minima and periods of moderate solar activity. A review of the high-resolution ¹⁴C records encompassing the near-Earth supernova events that occurred in 1006 CE, 1054, 1181, 1572, and 1604 suggests that these events were not accompanied by distinct changes in the ¹⁴C production rate. Nonetheless, an unusual increase of c. 10‰ in Δ¹⁴C between 1048 CE and 1055 is observed and discussed.

Radiocarbon chronology and Bayesian age model

Philippsen, B., Olsen, J. — Sat, 01 Jan 2022 05:06:23 +0100

Reply to “Marine abundance and its prehistoric past in the Baltic”

Lewis, J. P., Ryves, D. B., Rasmussen, P., et al. — Fri, 20 May 2022 05:06:23 +0200

The Chronology of Kilwa Kisiwani, AD 800–1500

Horton, M., Olsen, J., Fleisher, J., Wynne-Jones, S. — Wed, 01 Jun 2022 05:06:23 +0200

In this article, we present the results of a recent program of high-resolution radiocarbon dating on the urban sequence at Kilwa Kisiwani in southern Tanzania, including Bayesian modeling of 21 calibrated ¹⁴C dates. These data come from the 2016 excavation of a large trench directly adjacent to trench ZLL, one of the key 1960s excavations that served to establish the original chronology of the town. The new sequence reported here anchors the phases of Kilwa’s development for the first time in absolute terms. The dates, stratigraphy, and artifact assemblage offer a number of new insights into the timing and tempo of the occupation at Kilwa, notably placing the first coral buildings and coins at the end of the tenth century. Insights also include findings related to the earliest phases of settlement and periods of possible urban decline. We argue against a trend for understanding Swahili towns according to a common coastal trajectory and suggest that it is important to consider regional diversity by recognizing the particular, episodic sequence at Kilwa.

Radiocarbon dating of lime plaster from a Roman period cistern in ancient Gerasa, Jerash in Jordan

Fri, 01 Apr 2022 05:06:23 +0200

Ancient Gerasa (Jerash, since the Islamic period) is a city with a rich archaeological heritage from prehistory onwards, with the periods from Roman times into the Early Islamic period best attested. A Danish-German team has been working in the Northwest Quarter of the city since 2011. Among the findings was a Roman period monumental cistern that was intentionally filled in, at one point in time. The complexity of the archaeology raised chronological questions regarding the construction, destruction and subsequent backfilling of the cistern. This study contributed to answer these questions by radiocarbon dating lime plaster excavated from the cistern, and comparing the results with charcoal radiocarbon dates from other studies. Radiocarbon dating of plaster and mortar in Jerash is challenging because of contamination of geological carbonates from the local limestone geology. Quoting previous mortar dating studies, this study utilized sample characterization by alkalinity screening, petrography, SEM-EDS, and sample pre-treatment and preparation by wet sieving, sedimentation and stepwise injection. The plaster dates argued for the construction of the cistern being in the last half of the 1st century BCE to the middle of the 1st century CE. A few samples had later mortar dates, which argued for the filling event of the cistern taking place sometime in the late 3rd century CE or later.

To vikingeslægtninge med forskellige skæbner

Cordes, A., Philippsen, B., Varberg, J., Sørensen, L. — Tue, 01 Feb 2022 05:06:23 +0100

Borgring

Christensen, J., Daly, A. M., Henriksen, P. S., et al. — Thu, 01 Jul 2021 05:06:23 +0200

Single-year radiocarbon dating anchors Viking Age trade cycles in time

Philippsen, B., Feveile, C., Olsen, J., Sindbæk, S. M. — Sat, 01 Jan 2022 05:06:23 +0100

Recent discoveries of rapid changes in the atmospheric 14C concentration linked to solar particle events have spurred the construction of new radiocarbon annual calibration datasets [1–13]. With these datasets, radiocarbon dating becomes relevant for urban sites, which require dates at higher resolution than previous calibration datasets could offer. Here we use the single-year radiocarbon calibration curves to anchor the archaeological stratigraphy of the beginning of the Viking Age in time. We present absolutely dated evidence for artefact finds charting the expansion of long-distance trade from as far away as Arctic Norway and the Middle East, which we linked to the beginning of the Viking Age at ad 790 ± 10. The methods developed here enable human interactions and cultural, climatic and environmental changes to be compared in archaeological stratigraphies worldwide.

Revisiting radiocarbon dating of lime mortar and lime plaster from Jerash in Jordan

Daugbjerg, T. S., Lichtenberger, A., Lindroos, A., Raja, R., Olsen, J. — Tue, 01 Feb 2022 05:06:23 +0100

Ancient Gerasa (its Greco-Roman name)/Islamic Jerash (its later Arab name) is one of the most well-known pre-modern urban sites in northern Jordan, which flourished throughout antiquity and into the early Islamic period. Direct dating of mortar and plaster in Jerash is challenging due to the area's abundance of geological carbonates that hamper the use of radiocarbon mortar methodologies as shown by previous attempts. Therefore, this study revisited the important problem of Jerash mortar dating. The aim was to advance solutions to the challenges with geological carbonates through sample pre-treatment and preparation methods such as wet sieving, sedimentation, cryo2sonic and stepwise injection of diluted acid. To characterize the samples we used alkalinity screening and cathodoluminescence microscopy. Ten plaster samples from an Umayyad house, destroyed by the earthquake in 749 CE, in Jerash were radiocarbon dated. These produced 12 conclusive dates out of 20 attempted datings, and here some samples had multiple attempted datings. These dates confirmed the early Islamic date of the house structure, while some samples suggested reuse of older material. Five comparative mortar samples from medieval Finland and Sweden critically evaluated the methodology proposed in this article. These have known ages, and they produced five conclusive dates that compared accurately with the expected ages. Compared to previous attempts at Jerash mortar dating, this study made substantial contributions to Jerash mortar dating.

Late glacial and holocene shore-level changes in the aarhus bugt area, Denmark

Bennike, O., Andresen, K. J., Astrup, P. M., Olsen, J., Seidenkrantz, M. S. — Wed, 01 Sep 2021 05:06:23 +0200

We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas.

Holocene sea-ice dynamics in Petermann Fjord in relation to ice tongue stability and Nares Strait ice arch formation

Detlef, H., Reilly, B., Jennings, A., et al. — Wed, 01 Sep 2021 05:06:23 +0200

The Petermann 2015 expedition to Petermann Fjord and adjacent Hall Basin recovered a transect of cores, extending from Nares Strait to underneath the 48 km long ice tongue of Petermann glacier, offering a unique opportunity to study ice-ocean-sea ice interactions at the interface of these realms. First results suggest that no ice tongue existed in Petermann Fjord for large parts of the Holocene, raising the question of the role of the ocean and the marine cryosphere in the collapse and re-establishment of the ice tongue. Here we use a multi-proxy approach (sea-ice-related biomarkers, total organic carbon and its carbon isotopic composition, and benthic and planktonic foraminiferal abundances) to explore Holocene sea ice dynamics at OD1507-03TC-41GC-03PC in outer Petermann Fjord. Our results are in line with a tight coupling of the marine and terrestrial cryosphere in this region and, in connection with other regional sea ice reconstructions, give insights into the Holocene evolution of ice arches and associated landfast ice in Nares Strait. The late stages of the regional Holocene Thermal Maximum (6900-5500 cal yr BP) were marked by reduced seasonal sea ice concentrations in Nares Strait and the lack of ice arch formation. This was followed by a transitional period towards Neoglacial cooling from 5500-3500 cal yr BP, where a southern ice arch might have formed, but an early seasonal breakup and late formation likely caused a prolonged open water season and enhanced pelagic productivity in Nares Strait. Between 3500 and 1400 cal yr BP, regional records suggest the formation of a stable northern ice arch only, with a short period from 2500-2100 cal yr BP where a southern ice arch might have formed intermittently in response to atmospheric cooling spikes. A stable southern ice arch, or even double arching, is also inferred for the period after 1400 cal yr BP. Thus, both the inception of a small Petermann ice tongue at ĝ1/4 2200 cal yr BP and its rapid expansion at ĝ1/4 600 cal yr BP are preceded by a transition towards a southern ice arch regime with landfast ice formation in Nares Strait, suggesting a stabilizing effect of landfast sea ice on Petermann Glacier.

An intercomparison project on ¹⁴C from single-year tree rings

Kudsk, S. G.K., Olsen, J., Hodgins, G. W.L., et al. — Fri, 01 Jan 2021 05:06:23 +0100

A laboratory intercomparison project was carried out on 20 annually resolved late-wood samples from the Danish oak record. The project included the following three laboratories: (1) the University of Arizona AMS Laboratory, University of Arizona, USA (AA); (2) HEKAL AMS Laboratory, MTA Atomki, Hungary (DeA); and (3) Aarhus AMS Centre (AARAMS), Aarhus University, Denmark (AAR). The large majority of individual data points (96%) lie within ±2σ of the weighted mean. Further assessment of the accuracy associated with the individual laboratories showed good agreement, indicating that consistent and reliable 14C measurements well in agreement with each other are produced at the three laboratories. However, the quoted analytical uncertainties appear to be underestimated when compared to the observed variance of differences from the geometric mean of the samples. This study provides a general quality check of the single-year tree-ring 14C measurements that are included in the new calibration curve.

Lost and found

Rimstad, C., Mannering, U., Jorkov, M. L. S., Kanstrup, M. — Tue, 01 Jun 2021 05:06:23 +0200

The human remains recovered from the famous Bjerringhoj Viking Age burial in Denmark have been missing for more than 100 years. Recently, an assemblage of bones resembling those recorded at Bjerringhoj - some with adherent textiles - were discovered in a misplaced box in the National Museum of Denmark. Here, the authors use new skeletal and comparative textile analyses, along with radiocarbon dating, to confirm that the bones are indeed those from the Bjerringhoj burial. This rediscovery offers new data for interpreting Viking Age clothing, including the presence of long trousers, and emphasises the importance of reinvestigating old archaeological collections housed within museums and archives.

Vulnerability of the North Water ecosystem to climate change

Ribeiro, S., Limoges, A., Massé, G., et al. — Thu, 01 Jul 2021 05:06:23 +0200

High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world’s northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400–4200 cal yrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, leading to periods of polynya instability and marine productivity decline, is strikingly coeval with the human abandonment of Greenland from c. 2200–1200 cal yrs b2k. Our long-term perspective highlights the future decline of the North Water ecosystem, due to climate warming and changing sea-ice conditions, as an important climate change risk.

Early historical forest clearance caused major degradation of water quality at Lake Væng, Denmark

Bennike, O., Odgaard, B. V., Moorhouse, H., et al. — Wed, 01 Sep 2021 05:06:23 +0200

Although humans have impacted their environment over millennia, details of these impacts, especially on aquatic systems, is still surprisingly scarce despite potential disturbance by early land use. This study examined a high-resolution radiocarbon-dated Holocene record from the Danish Lake Væng, using geochemical and biological proxies, and related the observed impacts to other lake records with catchment disturbance. The results indicate a lengthy and varying history of aquatic eutrophication linked to human activity. Modest impacts on the lake coincided with the first signs of landscape disturbance during the Neolithic (c. 4500 cal. yrs BP). Observed impacts intensified in the Late Bronze and Pre-Roman Iron Age. Viking Age/Medieval deforestation and erosional inputs to the lake associated with new ploughing technology (1200 cal. yrs BP), however, led to a major reorganisation of the aquatic ecosystem. Filamentous bloom-forming cyanobacteria, common today in heavily culturally impacted lakes, reached a historical maxima. The lake ecosystem subsequently recovered somewhat but remains eutrophic to date. The erosion record from Lake Væng shows a striking similarity with other Danish lake records, especially the notable increase in Medieval Period catchment inputs, which are observed in other European lacustrine records. Numerous European lowland lakes may have shifted into a degraded ecological state millennia ago, but degradation intensified during the onset of the Medieval Period. Hence, assuming pre-industrial conditions as relatively pristine reference baselines for more recent cultural eutrophication could be flawed in landscapes intensively used by humans for millennia.

Leprosy in medieval Denmark

Brozou, A., Fuller, B. T., Grimes, V., et al. — Wed, 01 Sep 2021 05:06:23 +0200

Objectives: By focusing on two Danish leprosaria (Næstved and Odense; 13th–16th c. CE) and using diet and origin as proxies, we follow a multi-isotopic approach to reconstruct life histories of patients and investigate how leprosy affected both institutionalized individuals and the medieval Danish community as a whole. Materials and Methods: We combine archaeology, historical sources, biological anthropology, isotopic analyses (δ¹³C, δ¹⁵N, δ³⁴S, ⁸⁷Sr/⁸⁶Sr) and radiocarbon dating, and further analyze bones with different turnover rates (ribs and long bones). Results: The δ¹³C, δ¹⁵N and δ³⁴S results indicate a C₃ terrestrial diet with small contributions of marine protein for leprosy patients and individuals from other medieval Danish sites. A similar diet is seen through time, between males and females, and patients with and without changes on facial bones. The isotopic comparison between ribs and long bones reveals no significant dietary change. The δ³⁴S and ⁸⁷Sr/⁸⁶Sr results suggest that patients were local to the regions of the leprosaria. Moreover, the radiocarbon dates show a mere 50% agreement with the arm position dating method used in Denmark. Conclusions: A local origin for the leprosy patients is in line with historical evidence, unlike the small dietary contribution of marine protein. Although only 10% of the analyzed individuals have rib/long bone offsets that undoubtedly show a dietary shift, the data appear to reveal a pattern for 25 individuals (out of 50), with elevated δ¹³C and/or δ¹⁵N values in the ribs compared to the long bones, which points toward a communal type of diet and reveals organizational aspects of the institution.

A Chronology of Ancient Earthquake Damage in the Modena Cathedral (Italy)

Tirelli, G., Bosi, G., Galli, A., et al. — Wed, 01 Feb 2023 05:06:23 +0100

The 15th century cross-vaults of the medieval Modena Cathedral (UNESCO site) consist of intricate patches of different masonry portions bound by three types of lime mortars and at least two types of gypsum mortars. Such anomalous structure suggests multiple repair works over time after damaging earthquakes. The absolute dating of lime mortars (¹⁴C) and bricks (TL) integrated with the pollen record of mortars allowed to clarify the construction and restoration history of the vaults and to link the repairs to the earthquake chronology for the area. The results reveal that the original construction of the vaults (1404–1454) was carried out using lime mortar binding reused Roman and medieval older bricks. Lime mortar was used also for later repairs caused by earthquakes in the 16th and 17th centuries. Gypsum mortars were then used to entirely rebuild some vaults and to repair others in the 18th and 19th centuries. The study indicates that unexpected damage could be revealed by the detailed chronology of masonry binders. These data represent fundamental steps to implement earthquake risk assessments and strengthening projects of ancient buildings.

The Nekselø Fish Weir and Marine Reservoir Effect in Neolithization Period Denmark

Fischer, A., Olsen, J. — Tue, 01 Jun 2021 05:06:23 +0200

The Nekselo Wickerwork provides an unusually solid estimate on the marine reservoir age in the Holocene. The basis for this result is a 5200-year-old fish weir, built of hazel wood with a brief biological age of its own. Oysters settled on this construction. They had lived only for a short number of years when the fence capsized and was covered in mud and the mollusks suffocated. Based on the difference in radiocarbon (14C) age between accelerator mass spectrometry (AMS) samples of oyster shells and wood, respectively, the marine reservoir age for this site is estimated to 273 ± 18 14C years. Re-evaluations of previously produced data from geological and archaeological sites of Holocene date in the Danish archipelago indicate marine reservoir ages in the same order as that of the Wickerwork. Consequently, we recommend the use of the new value, rather than the ca. 400 14C years hitherto favored, when correcting for the dietary induced reservoir effect in radiocarbon dates of humans and animals from the Late Mesolithic and Early Neolithic periods of this region.

Cosmogenic nuclide inheritance in Little Ice Age moraines - A case study from Greenland

Larsen, N. K., Søndergaard, A. S., Levy, L. B., et al. — Sun, 01 Aug 2021 05:06:23 +0200

Cosmogenic exposure dating is one of the most widely used methods to constrain the deglaciation history of former glaciated areas. In Greenland, more than 1000 cosmogenic ¹⁰Be exposure ages (¹⁰Be ages) have been published within the last two decades. However, a recurring problem is that many of these studies have reported variable amounts of nuclide inheritance making the ¹⁰Be ages too old and difficult to assess without large datasets or independent age control. In this study, we test the accuracy of ¹⁰Be dating of Holocene moraines using independent age constraints from threshold lake records. In Kangerlussuaq, West Greenland, the ¹⁰Be ages of the Ørkendalen moraine system are highly clustered with a mean age of 6.8 ± 0.3 ka (no outliers). In contrast, the nearby Little Ice Age (LIA) moraine yields scattered ¹⁰Be ages ranging from 2.5 to 0.1 ka but with a mean of 0.18 ± 0.06 ka after excluding outliers which coincides with independent age constraints from threshold lakes and boulder kill dates. At Gletscherlukket, Southeast Greenland, the ¹⁰Be ages of the LIA moraine range from 10.2 to 1.6 ka with a mean of 1.9 ± 0.2 ka after excluding outliers. This is ~1.7 ka older than recorded in the proglacial threshold lakes and suggests that all samples from this site contain a significant amount of nuclide inheritance. Our results are consistent with other reports of skewed ¹⁰Be age distributions in LIA re-advance moraines and it probably reflects nuclide inheritance from exposure during the Holocene Thermal Maximum when the glaciers in Greenland were inside the LIA extent. In contrast, there is no evidence of nuclide inheritance in the Ørkendalen moraines, most likely because the glacial erosion was more intense prior to the formation of the moraines i.e. sometime between the advance phase during Last Glacial Maximum position and the subsequent lateglacial and Holocene deglaciation. Our results highlight a potential pitfall related to dating re-advance moraines using cosmogenic exposure dating and we recommend using a multi-method dating approach.

A Roman provincial city and its contamination legacy from artisanal and daily-life activities

Holdridge, G. S., Kristiansen, S. M., Barfod, G. H., et al. — Tue, 01 Jun 2021 05:06:23 +0200

Roman metal use and related extraction activities resulted in heavy metal pollution and contamination, in particular of Pb near ancient mines and harbors, as well as producing a global atmospheric impact. New evidence from ancient Gerasa (Jerash), Jordan, suggests that small-scale but intense Roman, Byzantine and Umayyad period urban, artisanal, and everyday site activities contributed to substantial heavy metal contamination of the city and its hinterland wadi, even though no metal mining took place and hardly any lead water pipes were used. Distribution of heavy metal contaminants, especially Pb, observed in the urban soils and sediments within this ancient city and its hinterland wadi resulted from aeolian, fluvial, cultural and post-depositional processes. These represent the contamination pathways of an ancient city-hinterland setting and reflect long-term anthropogenic legacies at local and regional scales beginning in the Roman period. Thus, urban use and re-use of heavy metal sources should be factored into understanding historical global-scale contaminant distributions.

Comparison of thermal decomposition and sequential dissolution—two sample preparation methods for radiocarbon dating of lime mortars

Daugbjerg, T. S., Lindroos, A., Hajdas, I., Ringbom, Å., Olsen, J. — Thu, 01 Apr 2021 05:06:23 +0200

Dating lime mortar samples using the radiocarbon (14C) method can be difficult. This is because the contamination is similar to the primary dating material (CaCO3) and consequently difficult to remove. Mortar can also have late-in-formation pyrogenic carbonate from interactions with the environment after the initial hardening phase, such as recrystallization, fire damage or delayed hardening. When 14C dating a system of primary dating material, contamination and late-in-formation pyrogenic carbonate, one approach is multi-fraction dating with conclusiveness criteria. If a sample has sufficient contamination or late-in-formation pyrogenic carbonate, the criteria evaluate the result inconclusive. To improve inconclusive results from such samples, this study investigates sample preparation by thermal decomposition. Here samples that were inconclusively dated by the authors’ traditional method, sequential dissolution with 85% phosphoric acid, are investigated further. This study finds that CO2 thermally decomposed at low temperatures contains some late-in-formation pyrogenic carbonate. By rejecting CO2 decomposed at low temperatures, Kastelholm castle and Kimito church in Finland are conclusively and accurately dated. Furthermore, a preheating method removes some late-in-formation carbonate, but not enough for a conclusive result. Finally, thermal decomposition finds difficulty in discerning binder carbonate from limestone and marble contamination.

Ramped pyroxidation

Barrett, G. T., Keaveney, E., Lindroos, A., et al. — Sat, 01 May 2021 05:06:23 +0200

Current methodologies for radiocarbon dating of mortars typically use mechanical and chemical separation to isolate fractions of carbon dioxide from suitable lime binder carbonates. These methods have a moderate frequency of success, but difficulties are often encountered with (a) secondary crystallisation, (b) the presence of incompletely burnt limestone or limestone aggregate, and (c) more complex hydraulic mortars (e.g. pozzolana or cocciopesto mortars). An alternative approach to isolating CO₂ from mortar involves thermal decomposition of the sample. A new ramped pyroxidation (RPO) facility has recently been constructed at the ¹⁴CHRONO Centre. In RPO, samples are incrementally heated, with CO₂ produced as the sample undergoes thermal decomposition in the presence (oxidation) or absence (pyrolysis) of oxygen. The CO₂ evolved from different temperature fraction are collected cryogenically and radiocarbon dated. This method was applied to several lime mortars with expected ages to investigate if CO₂ fractions only associated with the setting of the lime binder could be isolated. For all samples tested, positive results were obtained. All but the first of six CO₂ fraction taken during the earlier stages of thermal decomposition were in statistical agreement and could be combined to provide an age that was in excellent agreement with the expected ages (for an Irish medieval round tower, and for a Finnish medieval castle and church). The lowest temperature fraction, not in statistical agreement, is significantly earlier and attributed to contamination from charcoal or coke from lime production. Positive results were also obtained from a piece of mortar that had undergone no pre-treatment. Modelling examining the potential of RPO to isolate lime binder CO₂ fractions, where either limestone (or incompletely burnt limestone) or secondary re-crystallised calcite are present as contaminants, further demonstrate the suitability of the approach.

Evidence for influx of Atlantic water masses to the Labrador Sea during the Last Glacial Maximum

Mon, 01 Mar 2021 05:06:23 +0100

The Last Glacial Maximum (LGM, 23-19,000 year BP) designates a period of extensive glacial extent and very cold conditions on the Northern Hemisphere. The strength of ocean circulation during this period has been highly debated. Based on investigations of two marine sediment cores from the Davis Strait (1033 m water depth) and the northern Labrador Sea (2381 m), we demonstrate a significant influx of Atlantic-sourced water at both subsurface and intermediate depths during the LGM. Although surface-water conditions were cold and sea-ice loaded, the lower strata of the (proto) West Greenland Current carried a significant Atlantic (Irminger Sea-derived) Water signal, while at the deeper site the sea floor was swept by a water mass comparable with present Northeast Atlantic Deep Water. The persistent influx of these Atlantic-sourced waters entrained by boundary currents off SW Greenland demonstrates an active Atlantic Meridional Overturning Circulation during the LGM. Immediately after the LGM, deglaciation was characterized by a prominent deep-water ventilation event and potentially Labrador Sea Water formation, presumably related to brine formation and/or hyperpycnal meltwater flows. This was followed by a major re-arrangement of deep-water masses most likely linked to increased overflow at the Greenland-Scotland Ridge after ca 15 kyr BP.

Age of black dogfish (Centroscyllium fabricii) estimated from fin spines growth bands and eye lens bomb radiocarbon dating

Hedeholm, R., Qvist, T., Frausing, M., Olsen, J., Nielsen, J., Grønkjær, P. — Thu, 01 Apr 2021 05:06:23 +0200

Accurate age estimates are key life history parameters for understanding growth, reproduction and susceptibility to exploitation. Using a combination of fin spine growth increments and bomb radiocarbon dating, we provide minimum age estimates for the small Atlantic squaloid shark, black dogfish (Centroscyllium fabricii) sampled in Greenland waters. Age estimates based on growth increments in the fin spine, just distal to the end of the pulp cavity, were obtained from males (N = 64) and females (N = 70), and von Bertalanffy growth curves were fitted. The maximum growth increment count was 36 in males and 35 in females. Males and females had similar growth rates, but females grew larger (L_{inf, females} = 68 cm, L_{inf, males} = 61 cm). To evaluate the fin spine age estimates, bomb radiocarbon dating on eye lenses were done on a selection of females. All individuals larger than 65 cm (total length) were older than the bomb pulse corresponding to an age of at least 53 years, while those smaller than 55 cm were younger. Therefore, we observe a discrepancy between age estimates obtained from fin spines and bomb radiocarbon dating, indicating that fin spines are unsuitable for ageing black dogfish, at least for the oldest individuals.

Changes in solar activity during the wolf minimum-new insights from a high-resolution ¹⁴c record based on danish oak

Fogtmann-Schulz, A., Baittinger, C., Karoff, C., Olsen, J., Knudsen, M. F. — Mon, 01 Feb 2021 05:06:23 +0100

We present a new biennial record of radiocarbon (14C) measured in Danish oak. The new record covers the years 1251-1378 CE, thereby spanning the Grand Solar Minimum known as the Wolf Minimum. Two oak samples from every other year were measured at the AMS facility at Aarhus University (Denmark), resulting in an average precision of 1.4‰ for the record. Spectral analysis of the new record revealed two peaks at 27 and 9.1 years, which could indicate the Hale cycle was lengthened and the Schwabe cycle shortened during the Wolf Minimum, but it is also possible that the amplitude of the Schwabe cycle was too small to be accurately identified with the acquired precision of this record. The record was bandpass filtered to investigate the variability of the amplitude in different bands, which showed a dampening of the amplitude during the second half of the Wolf Minimum in bands centered on the Schwabe and the Hale cycle, respectively. A reconstruction of the solar modulation function, Φ, also showed a periodicity of ca. 9 years, and indicated that the Wolf Minimum was preceeded by one cycle of decreased solar activity.

Batch processing of tree-ring samples for radiocarbon analysis

Fogtmann-Schulz, A., Kudsk, S. G.K., Adolphi, F., et al. — Mon, 01 Feb 2021 05:06:23 +0100

We here present a comparison of methods for the pretreatment of a batch of tree rings for high-precision measurement of radiocarbon at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. The aim was to develop an efficient and high-Throughput method able to pretreat ca. 50 samples at a time. We tested two methods for extracting α-cellulose from wood to find the most optimal for our use. One method used acetic acid, the other used HCl acid for the delignification. The testing was conducted on background 14C samples, in order to assess the effect of the different pretreatment methods on low-Activity samples. Furthermore, the extracted wood and cellulose fractions were analyzed using Fourier transform infrared (FTIR) spectroscopy, which showed a successful extraction of α-cellulose from the samples. Cellulose samples were pretreated at AARAMS, and the graphitization and radiocarbon analysis of these samples were done at both AARAMS and the radiocarbon dating laboratory at Lund University to compare the graphitization and AMS machine performance. No significant offset was found between the two sets of measurements. Based on these tests, the pretreatment of tree rings for high-precision radiocarbon analysis at AARAMS will henceforth use HCI for the delignification.

Younger Dryas ice margin retreat in Greenland

Funder, S., Sørensen, A. H.L., Larsen, N. K., et al. — Mon, 01 Mar 2021 05:06:23 +0100

To date the final stage in deglaciation of the Greenland shelf, when a contiguous ice sheet margin on the inner shelf transitioned to outlet glaciers in troughs with intervening ice-free areas, we generated cosmogenic 10Be dates from bedrock knobs on six outlying islands along a stretch of 300 km of the southwestern Greenland coast. Despite 10Be inheritance influencing some dates, the ages generally support a Greenland Ice Sheet (GrIS) margin that retreated off the inner shelf during the middle Younger Dryas (YD) period. Published 10Be-and 14C-dated records show that this history of the GrIS margin is seen in other parts of Greenland but with large variations in the extent and speed of retreat, sometimes even between neighbouring areas. Areas with a chronology extending into the Allerød period show no marked ice margin change at the Allerød-YD transition except in northernmost Greenland. In contrast, landforms on the shelf (moraines and grounding zone wedges) have been suggested to indicate YD readvances or long-lasting ice margin stillstands on the middle shelf. However, these features have been dated primarily by correlation with cold periods in the ice core temperature records. Ice margin retreat during the middle and late YD is explained by advection of warm subsurface water at the ice margin and by increased seasonality. Our results therefore point to the complexity of the climate-ice margin relation and to the urgent need for direct dating of the early deglaciation history of Greenland.

Early Neolithic occupation of the lowlands of south-western Iran

Darabi, H., Bangsgaard, P., Arranz-Otaegui, A., Ahadi, G., Olsen, J. — Mon, 01 Feb 2021 05:06:23 +0100

The lowlands of south-western Iran have been studied archaeologically since the mid nineteenth century. The Neolithic period, however, was mostly investigated in the 1960s and 1970s, when Early Neolithic settlements were reported in the western plains, positing the idea that the rest of the lowland plains had been populated after the Neolithic period. The excavation at Tapeh Mahtaj in 2015, however, has changed this view. This article provides inter-disciplinary results and discusses the nature of the Early Neolithic in the Iranian south-western lowlands, thereby enabling a better understanding of the emergence of early domestication and sedentism in the region specifically and in the Eastern Fertile Crescent.

Building a high-resolution chronology of a medieval urban site through Bayesian modelling*

Haase, K., Olsen, J. — Sun, 01 Aug 2021 05:06:23 +0200

This paper shows that combining stratigraphic information with dendrochronological and radiocarbon dating in a Bayesian model is a powerful tool in producing a high-resolution chronology for a medieval urban site. By using all available archaeological information, it is possible to construct a chronology of higher accuracy, transparency and reproducibility than that created through informal interpretation and ceramics chronologies. The example shows how a modelling process is also a valuable tool in validating and reassessing the stratigraphic interpretations. The model is used on two levels: (1) to establish the overall site chronology; and (2) to investigate the age and duration of individual events and structures. Finally, since the model is constructed independently of ceramics chronologies, it is suggested that the current local ceramics chronology could be revised.

The Roman amphitheatre in Mérida, Spain ˗Augustan or Flavian

Lindroos, A., Heinemeier, J., Ringbom, Å., Daugbjerg, T. S., Hajdas, I. — Wed, 01 Jan 2020 05:06:23 +0100

Four lime mortar samples from the Mérida amphitheatre in Spain were dated in 2001 and re-dated in 2019 with refined dating methods and focus on carbon dioxide that was released in late CO2 fractions when dissolved in phosphoric acid. The samples were difficult to date because they contained highly soluble, young carbonate contamination that dominated the carbon dioxide from the early stages of the reaction with the acid in the hydrolysis process. They were also rather hydraulic and rich in magnesium, which could have caused delayed hardening. However, there was very little dead carbon contamination so that late carbon dioxide fraction gave uniform 14C ages, pointing to a late 1st c. AD Flavian, or later age of the amphitheatre.

A field guide to mortar sampling for radiocarbon dating

Daugbjerg, T. S., Lindroos, A., Heinemeier, J., et al. — Fri, 01 Oct 2021 05:06:23 +0200

Radiocarbon dating of mortars is a method for absolute dating of historical mortared stone structures. Successful mortar dating studies have answered chronological questions, while other studies have revealed that mortar samples can have complications and contaminants. These can cause inconclusive results even with present state-of-the-art techniques. Previous research shows that adequate and proper sampling of mortar samples is of fundamental importance for a conclusive radiocarbon analysis. Therefore, this article thoroughly reviews the processes and environmental factors that may cause problems for successful radiocarbon dating of mortar samples, and presents best-practice sampling strategies for radiocarbon mortar dating.

Nye kalibreringskurver - betyder det noget?

Kanstrup, M., Olsen, J. — Tue, 01 Dec 2020 05:06:23 +0100

For at omregne målte 14C-aldre til kalenderår er det nødvendigt at bruge kalibreringskurver. Derfor er det vigtigt at
anvende så gode kalibreringskurver som muligt. Lanceringen af de nyeste kurver i august giver os anledning til at
forklare kort om historikken bag kalibreringskurverne og præsentere de mest relevante kalibreringskurver for danske
arkæologers vedkommende. Eksempler viser, hvor de nye kalibreringskurver kommer til at betyde mest. Med de nye
kalibreringskurver har vi især fået en langt højere opløsning, men der er også perioder og særlige hændelser vi bør
være ekstra opmærksomme på.

Urban Chronology at a Human Scale on the Coast of East Africa in the 1st Millennium a.d.

Wynne-Jones, S., Sulas, F., Out, W., et al. — Fri, 01 Jan 2021 05:06:23 +0100

This paper presents a new high-resolution excavation sequence of a house at the 1st millennium a.d. site of Unguja Ukuu, Zanzibar, with implications for a new and detailed understanding of the period between the 7th and 9th centuries a.d. on the East African coast. This is an important period associated with a broad and distinctive cultural tradition, often seen as a pre- or proto-urban phase. Household excavations at Unguja Ukuu revealed two occupation phases, spanning less than 40 years each. The results here thus present an unprecedented temporal resolution on the site, at the scale of human experience. Excavation and microstratigraphic analyses of multiple floor layers reveal decadal change in occupation at this house. Positioning this house into the broader settlement sequence, we argue for episodic settlement at the site of Unguja Ukuu and draw out detail on how we can explore change at this generational scale.

Constraints from cosmogenic nuclides on the glaciation and erosion history of Dove Bugt, northeast Greenland

Skov, D. S., Andersen, J. L., Olsen, J., et al. — Sun, 01 Nov 2020 05:06:23 +0100

The intricate interplay between subglacial topography and ice-sheet dynamics is key to the evolution of large ice sheets, but in Greenland as elsewhere the effects of longterm glacial history on landscape evolution remain poorly constrained. Here we measure abundances of cosmogenic ¹⁰Be and ²⁶Al in bedrock and transported boulders to unveil the glaciation and erosion history of Dove Bugt, northeast Greenland. In agreement with studies of west Greenland, we find that apparent exposure ages increase with elevation from 9 ka to 13 ka in low-lying valleys to 21 ka to 204 ka on high-elevation, blockfieldcovered plateaus. We employ a Markov chain Monte Carlo inversion framework to constrain the probability of various erosion histories, and we quantify the residence time of samples within the upper 2 m of the bedrock subsurface—a measure defined as the cosmogenic nuclide memory. This cosmogenic nuclide memory exceeds 600 ka on the highest plateaus but is limited to less than 500 ka in most other high-elevation samples and to less than 100 ka at low-elevations. Our results define maximum limits for the fraction of ice cover during the past 1 Ma to ~70% on the Store Koldewey peaks and ~90% farther inland at Pusterdal, respectively. Minimum limits to ice cover, however, cannot be reliably constrained by the data. Finally, we propose that limited erosion on the highest plateaus of Store Koldewey since 0.6–1.0 Ma indicates a minimum age for fjord-plateau formation within this area of northeast Greenland.