Radiocarbon dating of prehistoric hearths in alpine northern Sweden: problems and possibilities

The chronology of prehistoric Sami settlement sites has previously been established by conventional radiocarbon dating of bulk charcoal samples associated with hearths from sunken hut floors (stállo-foundations). Here we present results of a comprehensive dating exercise of stállo-foundations in the alpine area of northern Scandinavia using Accelerator Mass Spectrometry (AMS) radiocarbon dating of charcoal. Over a 3 km² study area, AMS calibrated ages of hearth charcoal from 22 stállo-foundations across 12 sites securely date these features to between cal. AD 640 and AD 1180. Only small variations in age were found between charcoal samples from different areas of a given hearth. Statistical analysis of all the charcoal AMS radiocarbon dates obtained reveals that 12 stállo-foundations across nine sites are contemporaneous and date to the Viking Period (AD 800–AD 1050). The tightly constrained AMS-based chronology of stállo-foundations contrasts with the existing chronology based on conventional radiocarbon analysis, which places these features within a significantly greater time-frame of between AD 600 and AD 1900, with most dates ranging between AD 800 and AD 1350.This discrepancy is likely to result from the necessity of collecting composite hearth charcoal particles, which may originate from different phases of occupation, in order to achieve the required final carbon content for conventional radiocarbon analysis. We argue that the new AMS-based radiocarbon chronology of stállo-foundations presented here supersedes the existing chronology based on conventional (Gas Proportional counting) radiocarbon analysis and we advocate the use of AMS radiocarbon dating in future hearth investigations.     

RADIOCARBON DATING OF MORTARS FROM ANCIENT GREEK PALACES

This study deals with radiocarbon dating of lime mortars which were used as supports for Mycenaean and Minoan paintings. The ¹⁴C dates are. on the whole, compatible with the historical data. and thus show that a large proportion of the Mycenaean surficial coatings can be dated by the radiocarbon method. However. in order to determine the age of the mortars accurately. it is necessary to evaluate the amount of sedimentary carbonate which may have been added to them. It is shown here that the oxygen and carbon isotope compositions of lime mortars are significant indicators that such a mixing actually took place.     

GEOCHEMICAL CHARACTERIZATION OF ARCHAEOLOGICAL LIME MORTARS: PROVENANCE INPUTS*

Chemical and mineralogical analyses were carried out on historical lime mortars from the parish church of Santa María La Real (Guipúzcoa). The study included various periods ranging from Roman to modern times and allowed the identification of various types of raw materials. In order to obtain pure binder, free of carbonate aggregates and charcoal particles, an innovative binder separation method was implemented. The chemical composition of the binder allows discrimination of different provenance areas for the raw materials, although those areas do not correlate with specific historical periods. In addition, the influence of burial processes on the primeval chemical features has been assessed and reveals that modern mortars display greater chemical modification than the Roman mortars.     

四川广汉三星堆遗址四号祭祀坑的碳十四年代研究

2020年,广汉三星堆遗址新发现祭祀坑的田野考古发掘工作正式启动,为解决祭祀坑的年代问题,四川省文物考古研究院委托国家文物局考古研究中心与北京大学考古文博学院考古年代学联合实验室对四号祭祀坑开展了碳十四年代研究,得到6个碳十四年代数据,经过贝叶斯统计树轮校正计算得到其埋藏年代有95.4%的概率落在距今3148—2966年的时间范围之内,属商代晚期。     

Technology,chronology and the role of crucible steel as inferred from iron objects of the ancient site at Junnar,India

Ordinary iron objects from an ancient habitation site at Junnar in India, dating to the 2nd BC to AD 2nd century, were examined for their microstructure, chemical composition and age. The objects were mostly made of high carbon steel with a homogeneous microstructure consisting of fine spherical particles of carbide in the ferrite background, free of non-metallic inclusions. Their carbon concentration ranged from 0.7% to over 1.6% with one exception at 0.2%. Some of them contained trace amounts of silicon, manganese and sulfur while one object retained cavities due to volume contraction during solidification reactions. These features indicate that the objects examined constitute an early example of Indian steel making in crucibles. Evidence was found that basic techniques needed for the success of crucible steel technology were mostly available at Junnar at the time. The radiocarbon measurement on carbon samples extracted from one of the iron objects placed its date between 176 BC and AD 20, in agreement with the radiocarbon dates of three charcoal samples from the same site. The forgoing results support that crucible steel was produced in India at a much earlier date than previously supposed, to serve as a material for specific needs arising in daily life.     

PLASTER AND MORTAR RADIOCARBON DATING OF NABATEAN AND ISLAMIC STRUCTURES,SOUTH JORDAN*

The study aims to use lime mortars and plasters to radiocarbon date Nabatean and Islamic structures from Petra and Udruh, south Jordan. Fifteen samples from seven structures were characterized by thin‐section, scanning electron and cathodoluminescence microscopy. The lime binders of all the samples and the organic inclusions from nine samples were AMS radiocarbon dated. The dates and the historical data of the samples were compared with each other. The results showed an agreement between the radiocarbon dates of the lime binders and the organic inclusions and the historical data for most of the samples. The radiocarbon dates of the lime binders supported by the radiocarbon dates of the organic inclusions and the archaeological data were helpful in reconstructing a rather precise chronology of the studied structures.     

Radiocarbon dating and the “old shell” problem: direct dating of artifacts and cultural chronologies in coastal and other aquatic regions

Archaeologists have long recognized the problem of the “old wood” effect in radiocarbon dating charcoal and wood samples, the age of which may be hundreds of years older than their use by humans. Such problems have resulted in significant changes in how most researchers select wood and charcoal samples for ¹⁴C dating, with many now using relatively short-lived carbonized materials for dating. Despite the significant strides made in our understanding of the potential biases of the “old wood” effect, little emphasis has been placed on the possible impacts of dating “old shell” in archaeological deposits. The use of marine shell for ¹⁴C dating is widespread in coastal areas around the world, including a growing emphasis on the dating of individual shell artifacts via Accelerator Mass Spectrometry (AMS). In dating shell artifacts, we have obtained several dates older than associated ¹⁴C dates for short-lived subsistence remains from the same deposits, including great disparities (>10,000 years) and more subtle differences (≥100 years). These discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts, including shells collected from fossil deposits, older archaeological sites, and beaches. The problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection, analysis of multiple ¹⁴C dates on a variety of materials, and proper calibration procedures.     

Dating Ancient Burial Mounds in Denmark – Revealing Problematic Ancient Charcoal

The National Museum of Denmark and the Department of Geography at the University of Copenhagen have collaborated on a project investigating burial mounds near early Medieval churches. The aim was to identify a possible continuity in cult sites across the shift to Christianity in the late Viking Age. Charcoal samples from 18 mounds were radiocarbon dated but the results showed they were far older than expected. Control dating undertaken on burial mounds of known age confirmed that charcoal in the mound fill can at least be up to 3000 years older than the mound itself. As charcoal can survive in the surface soil layer for millennia, in spite of ploughing, bioturbation and frost, it may also dominate the charcoal pool of the grass or heather turfs used in the mound construction. Therefore, the article concludes, charcoal cannot be used to securely date archaeological features built with turfs and it is important to be aware of the possible presence of very old charcoal when selecting material for dating archaeological features, even those which otherwise would be judged unaffected by material from earlier archaeological periods.     

RADIOCARBON DATING OF KILL SITES

Age determinations of kill sites, where charcoal is generally absent, has usually depended on radiocarbon analyses of bone material. However, it has been seen with known-age samples that these dates are often in error due to contamination by plant products or ground water carbonates. The use of soil samples from strata both above and below, as well as the level containing the artifacts, offers important advantages. The soil profiles present sequences of dates, whereas the bones are only individual samples. The distribution of the soil date values can indicate upper and lower limits for the age of the kill site. The Taima-taima paleo-indian site in the state of Falcón, Venezuela is presented as an illustration of the application of radiocarbon dating of soil to archaeological problems. A total of 22 samples were processed. It is seen that soils from two profiles indicate a dating of 13 000 years for the kill. Taking into account reasonable extents of error, uncertainties of ± 2000 years can be estimated. The non-carbonate fraction dates are in agreement with the earth samples, but this is probably due to the organic matter extracted from these materials being mostly soil contamination in the porous bone matrix. Fluorine measurements on the bones confirm the Pleistocene origin.     

Understanding the variability in freshwater radiocarbon reservoir offsets: a cautionary tale

Freshwater resources in past diets can lead to inaccuracies when attempts are made to ascertain their radiocarbon ages or those of the consumers. Radiocarbon reservoir effects may lead to significant age offsets when the bones or other tissues of these consumers are radiocarbon dated. A number of recent studies have investigated freshwater reservoir offsets. However no study thus far has satisfactorily obtained a ubiquitous freshwater reservoir correction due to variability in the ecosystems analysed. This study tests the possibility of predicting freshwater reservoir effects from the carbonate alkalinity of the water with measurements on modern fish bone and water samples. A predictive capability would be especially valuable in the absence of well-preserved archaeological fish bone. We surveyed samples from lakes and rivers in varying geological settings in Britain and Ireland. Modern fish bone and water samples were analysed to investigate modern radiocarbon offsets from the atmosphere. Archaeological fish bone was also analysed to examine past reservoir offsets at selected sites. Stable carbon and nitrogen isotope values were measured to aid in interpretation of any variability in the offsets. Large freshwater reservoir offsets were measured in some modern and archaeological samples (maximum offset = 1638 ¹⁴C years). The freshwater reservoir offsets in the fish bone were highly correlated with alkalinity of water in modern lake sites analysed. However, a high amount of variation within and between fish species was also evident in the results, precluding the possibility of providing regional corrections for freshwater reservoir offsets from alkalinity although this still may provide a general guideline. The variability is thought to be due to differences in the diet of individual fish.     

A Multidisciplinary Approach to the Study of Archaeological Mortars from the Town of Ammaia in the Roman Province of Lusitania (Portugal)

The Roman town of Ammaia (in Marvão Region) is considered one of the most important recent findings of the Roman presence in Portuguese territory. It was settled in Republican times and abandoned in the seventh century. In this research, 17 masonry mortars and renders from the West Tower (South Gate), the residential area near the West Tower, the macellum, the peristylium, the public bath building, the podium of the temple and the portico of the forum were analysed. The methodology of chemical, mineralogical and microstructural characterization has involved several complementary techniques, including stereomicroscopy, X‐ray diffraction, thermal analysis and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy. The results indicate that the mortars from the beginning of the town's edification were mainly composed of soil (clays). Later, during the main Roman building period, mortars were composed using a calcitic binder and the mortar composition varied according to their use and function. The samples from a period subsequent to the Roman occupation are based on a dolomitic binder. From the present study, relevant information has been acquired about the technological evolution of Roman construction in Ammaia, the historical context of the archaeological structures and guidelines for the conservation and restoration of mortars.     

Selective woodland exploitation for charcoal production. A detailed analysis of charcoal kiln remains (ca. 1300–1900 AD) from Zoersel (northern Belgium)

A detailed study of charcoal burning activities has been made for the Zoersel forest (Northern Belgium) based on an inventory of charcoal kiln remains, the analyses of wood charcoal and other charred botanical macroremains and radiocarbon dating of 10 of these kilns. Age determination of the youngest kilns was refined by dendrochronological analysis of trees growing on top of these kiln sites. The results show that, although many kilns were found, charcoal was produced in Zoersel only at certain moments during late and post-medieval times suggesting that charcoal burning was not a part of the regular management practice of these forests. The wood used for the production of charcoal mainly consists of taxa of alluvial (alder) forests while the kilns are situated on sites that currently are rather dry, with an oak dominated vegetation. For the older kilns, this contrast could be explained by an important change in local soil conditions. The younger kilns may be related to the conversion of alder woodland to grassland in the lower parts of the domain, with the kilns being constructed in the nearby dryer woodland areas.     

Paper 5: Historic Mortars from the Coudenberg Archaeological Site: Characterization and Source of Raw Materials

Abstract

The characterization of historic mortars by means of a concise methodology of material analyses can provide crucial information with regard to the origin of the raw materials and the ancient mortar technology. For the analysis of the historic mortars of the Coudenberg archaeological site, the methodology consists of optical and scanning electron microscopy, simultaneous thermal analysis, and an acidic treatment. These analyses were carried out on a total of seventeen samples lifted from various areas in the site, in function of the building chronology resulting from a historic built investigation. The type of binder and aggregate as well as their volumetric ratio were determined.

Both binder and aggregate present distinctive features, which made it possible to identify the probable geological provenance of the raw materials. The observations are verified with available historical records regarding the construction of the main banqueting hall — the Aula Magna — and the use of raw materials such as limestone and sand for the production of lime and construction purposes.     

The ancient pozzolanic mortars and concretes of <Emphasis Type="Italic">Heliocaminus</Emphasis> baths in Hadrian’s Villa (Tivoli,Italy)

The aim of this work is the physical and mineralogical-petrographic characterization of the mortars from the Baths with Heliocaminus, a special and unique architectural building in the complex of the Hadrian’s Villa in Tivoli. Thirty samples were investigated for composition and physical properties (density, porosity, water absorption, mechanical strength, particle size distribution of aggregate, etc.), representative of eight mortar groups: cubilia bedding mortar, brick bedding mortars, floor-coating and wall-coating bedding mortars, floor (rudus) and wall conglomerates (trullisatio), vault concretes, and lime plasters (arriccio). Physical parameters, together with the microscopic analysis and binder/aggregate ratio determined in three ways using image analysis (on thin sections and on specimens) and weight-data from dissolution of binder, have shown an interesting relationship between the physical-compositional characteristics and the function of mortars within the structure of the Heliocaminus baths. To identify the minerals and the reactant phases between binder and aggregate, as well as the hydraulic degree, selected samples were analyzed with x-ray powder diffraction, thermogravimetry, and differential scanning calorimetry techniques. The obtained results provide a close relation between pozzolanic characteristics and physical-mechanical properties of the mortars (i.e., punching strength index).     

Luminescence Dating of Monumental Stone Architecture at Chavín De Huántar,Perú

Optically stimulated luminescence (OSL) is applied to quartz extracted from mud mortar collected from Chavín de Huántar, an early Andean monumental center. The samples appear to have been only partially exposed to sunlight during construction, so a minimum age model is applied to equivalent dose distributions. Complications, including complex radioactivity, low sensitivity of the quartz, and limited sample, prevent high precision, but the 14 dates obtained cluster around 1000 BC largely in agreement with radiocarbon assays on charcoal also collected from the mortar. Results suggest a relatively rapid construction for the monument. This work develops OSL as a method for directly dating architectural mortar.     

Charcoal in alluvium of mountain streams in the Bieszczady Mountains (Polish Carpathians) as a carrier of information on the local palaeoenvironment

Fragments of charcoal are present in floodplain alluvium of the San and Strwi?? rivers in the Polish part of the Bieszczady Mountains, Polish East Carpathians. They occur as single clasts or in lenses in the basal part of fine-grained alluvium, together with unburnt wood debris, or in the middle part of the vertical sequence of the floodplain alluvium. 14 samples of charcoal from the upper courses of the San (ca. 50 km) and the Strwi?? (ca. 10 km) were dated with radiocarbon. The obtained dates fall mainly in the 15^th through 19^th century interval; only one sample is markedly older (9^th–10^th century). Taxonomic composition of the charcoal source wood was also studied and compared with that of coeval forests. Correlation of the charcoal age with the history of economic development of the studied region indicates that charcoal is of anthropogenic origin: older charcoal from intense slash-and-burn deforestation, while younger charcoal was produced by local industries.     

X-ray microtomographic imaging of charcoal

We assess the potential of X-ray microtomography as a tool for the non-destructive, three-dimensional examination of the internal structure of charcoal. Microtomographic analysis of a series of charcoals produced by the experimental pyrolysis of pine wood at temperatures from 300 and 600 °C in nitrogen only and in nitrogen mixed with 2% oxygen indicates that, despite substantial shrinkage, observed porosity, pore size and pore connectivity are all increased by pyrolysis and also by chemical oxidation. Analysis of a number of altered and unaltered archaeological and geological charcoals has demonstrated the capacity of the technique to identify and map the distribution of authigenic mineral contamination within charcoal fragments. The results are of significance to radiocarbon dating in that they provide insights into the mechanisms by which charcoal can be contaminated by extraneous carbon in the natural environment.     

Historical Mortars from the Fortified Upper Town of Eivissa (Balearic Islands,Spain)

Samples of mortars and stone of Portal de ses Taules from the Renaissance city walls of Eivissa (16th century) were characterized using thermal analysis— thermogravimetry and derivative thermogravimetry (DTG)—x-ray diffractometry, and scanning electron microscopy. The granulometric fraction of particle size <63 μm was selected as representative of the binder, while the fraction 0.5–1 mm was taken as representative of the aggregate in order to characterize mortar samples. The results show that local materials were used. Lime was the main component of most of the samples tested. Thermal analysis revealed the hydraulic nature of the lime mortars. High amounts of sodium chloride were found in the samples analysed.     

Kinetic effect of carbonic anhydrase enzyme on the carbonation reaction of lime mortar

The effect of carbonic anhydrase enzyme on the precipitation kinetics and phase transformations of calcium carbonate, and on the strength development of lime mortars has been investigated with saturated lime solutions, lime pastes and lime mortars under atmospheric conditions. The results clearly show that carbonic anhydrase catalyzes the reaction between carbon dioxide and aqueous lime, and increases the rate of calcium carbonate crystallization, the yield of the carbonation reaction and mortar strength at early ages. This is most likely a kinetic effect associated with the increased rate of carbonate ions supply to the solution by the enzyme. In addition, this enzyme favors the formation of stable calcite and significantly modifies its morphology by developing new crystal faces. These results suggest a novel approach for accelerating the hardening of lime mortars using carbonic anhydrase enzyme, which may offer a potentially novel approach with significant benefits on the applications of lime mortars in architectural heritage conservation as well as in construction.