Age and exploitation of obsidian from the Medicine Lake Highland,California

The relationship between major and minor elements, trace element composition, and age of obsidian sources within a volcanic field, is of considerable interest for obsidian source and artifact research in the New and Old World. The present study investigates this relationship in the Medicine Lake Highland of western North America. Geological evidence had indicated a very young age for all obsidian sources in the Highland, yet archaeological evidence suggested that obsidian was utilized for several thousand years. X-ray fluorescence analysis distinguished the latest flow (Glass Mountain) from the Cougar Butte, Grasshopper Flat, and Lost Iron Wells sources. Data obtained from two nearby archaeological sites showed that obsidian from the latter two sources was used by c. 7500 bc, while Glass Mountain material was not used (or available) until after 1360± 240 bp. These findings indicate that inferences of an extremely recent age for all obsidian sources in the volcanic field were unwarranted. Further analysis of major and minor elements indicated different hydration rates for these sources. The results argue that significant geochemical variability, as well as age differences, can exist between obsidian sources within the same volcanic field.     

Infra-red Photoacoustic and Secondary Ion Mass Spectrometry Measurements of Obsidian Hydration Rims

A procedure has been developed for measuring obsidian hydration rim thicknesses on archaeological artefacts using infra-red photoacoustic spectroscopy (IR-PAS). Calibration of the IR-PAS values with depth was completed using secondary ion mass spectrometry (SIMS) and optical microscopy to relate the quantity of diffused water to the measured thickness of the hydration layer. By monitoring the absorbance intensity at 1630 cm⁻¹wavenumbers, hydration rims between approximately 1 μm and 12 μm may be accurately measured and used for chronometric age estimates. SIMS depth profiling has the ability to measure layers less than 1 μm thick, extending the age calibration to samples of less than 100 years in age.     

Obsidian hydration at high elevation: Archaic quarrying at the Chivay source,southern Peru

We examine obsidian hydration as a means to date archaeological sites at high elevation in the central Andes, and in particular quarry sites that are difficult to date by radiocarbon means. The Chivay obsidian source lies in a volcanic depression above the Colca Valley in Arequipa, Peru (71.5355° S, 15.6423° E) at 4950 masl. We compare obsidian hydration readings from one quarry and two workshop locations. Ninety-one flakes from the quarry pit, and 61 and 33 flakes from the workshops were analyzed for hydration bands. Of these, 68 from the quarry, and 54 and 33, respectively from the workshops produced at least one culturally meaningful hydration band. As expected, obsidian appears to hydrate slowly at this high elevation. Yet, variation in hydration readings is low within stratigraphic contexts, suggesting relatively narrow windows of knapping activities in each excavation level. A small number of radiocarbon dates allow us to develop a preliminary hydration rate for Chivay obsidian in this high elevation location. Hydration data indicate that intensive quarrying began by 3800 cal. BC and stopped ca. 2300 cal. BC. By contrast, the two workshops appear to have been deposited 2900 and 1200 cal. BC, and 2700 and 2400 cal. BC. The data are consistent with an uptick in obsidian use by at least the Terminal Archaic period.     

Multiple origins of Bondi Cave and Ortvale Klde (NW Georgia) obsidians and human mobility in Transcaucasia during the Middle and Upper Palaeolithic

Using PIXE four types of elemental compositions were found among obsidian artefacts from the Bondi Cave and Ortvale Klde, Middle to Upper Palaeolithic sites in NW Georgia. One of those types corresponds to obsidians from the Chikiani source, whose compositions were determined with a very good agreement by PIXE and ICP-AES/MS. The composition of Chikiani obsidians is remarkably constant despite K–Ar and ³⁹Ar/⁴⁰Ar extrusion ages from ca 2.4 and 2.8 Ma. The compositions of two other groups of obsidian artefacts are similar to source materials from eastern Anatolia and Armenia, in particular Ikisdere, Sarikamis, Gutansar, and Hatis. Obsidian is only a minority component in the lithic assemblages at the Bondi Cave and Ortvale Klde. Both Neanderthal and Modern Human populations used obsidian in particular from Chikiani. Considering that the shortest walking distance to this nearest source is at minimum of about 180 km, and to other potential sources of more than 350 km it is suggested that this material reached these two sites mostly, if not exclusively, by a series of ‘down the line’ exchanges.     

Spatial variation of biologically available strontium isotopes (Sr/Sr) in an archipelagic setting: a case study from the Caribbean

This paper presents the results of strontium (Sr) isotope analysis of modern and archaeological animal remains and modern plant samples from the Caribbean region. The goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting. The range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems. The (is)landscape is divided into several sub-regions based on the age and lithology of underlying geology and the variability of ⁸⁷Sr/⁸⁶Sr ratios is reported as; mean ⁸⁷Sr/⁸⁶Sr ± 2 standard deviations, number of samples: 1) Volcanic and Intrusive rocks (0.7077 ± 0.0019; n = 162); 2) Cretaceous–Miocene Limestone (0.7085 ± 0.0009; n = 50); 3) Pliocene–Quaternary Limestone (0.7091 ± 0.0004; n = 54); 4) Sedimentary Deposits (0.7094 ± 0.0015; n = 16); 5) Metamorphic Deposits (0.7104 ± 0.0014; n = 6). There are substantial differences between expected ⁸⁷Sr/⁸⁶Sr values based on associated geology and measured ⁸⁷Sr/⁸⁶Sr in flora and fauna samples. These differences emphasize the importance of focusing on bioavailable strontium, as opposed to geological proxies, for estimations of Sr isotope ranges, especially in archipelagic environments. While some overlap exists between the ⁸⁷Sr/⁸⁶Sr ranges of certain sub-regions, other sub-regions possessed limited variation and could be distinguished based on strontium isotope data. This spatial patterning of biologically available strontium indicates that strontium isotope analyses can be successfully applied to the archaeological study of human mobility within the Caribbean region.     

Book Reviews

Abstract

Obsidian studies play an integral part in archaeology around the world, particularly in the Americas, but few archaeologists have employed obsidian studies to understand Native American life at historical archaeological sites. Yet, obsidian sourcing and hydration analysis can provide critical insights into site chronology and use, lithic recycling, and procurement and trade at contact and colonial sites. Obsidian geochemical sourcing and hydration analyses of a 19th-century rancho site in northern California have revealed new information on Native Americans who labored there in the second quarter of the 19th century. The obsidian data indicate a significant amount of lithic manufacture and use, a change in obsidian procurement in the 1800s, and an unprecedented number of obsidian sources represented on-site. The implications for general obsidian studies, as well as for regional archaeological issues, concern the problems with popular sourcing methods in northern California and the need to revisit current understandings of the first micron of hydration rim development.     

Historical ecology of late Holocene sea otters (Enhydra lutris) from northern British Columbia: isotopic and zooarchaeological perspectives

We examined the isotopic composition (δ¹³C and δ¹⁵N) of sea otter (Enhydra lutris) bone collagen from ten late Holocene (ca. 5200 years BP–AD 1900) archaeological sites in northern British Columbia (BC), Canada. Because sea otters are now extinct from much of this region and have not fully recolonized their former range (e.g. Haida Gwaii and most of northern BC) these data represent an important first step towards better understanding sea otter foraging ecology in BC. The isotopic data suggest a diet composed primarily of benthic invertebrates, with a very low reliance on epibenthic fish. There is very low isotopic and thus inter-individual dietary variability in Holocene BC sea otters during the late Holocene. Furthermore, zooarchaeological abundance data suggest that otters represented a widespread and significant focus of aboriginal hunting practices on the northern BC coast during the mid- to late-Holocene. The consistent reliance on a small number of low-trophic level prey and limited dietary variability in Holocene BC sea otters may reflect top-down impacts on otter populations by aboriginal peoples. As part of our assessment of sea otter diet, we review trophic discrimination factors (Δ¹³C and Δ¹⁵N) for bone collagen from published literature and find marked variability, with mean values of +3.7 ± 1.6 for Δ¹³C (n = 21) and +3.6 ± 1.3 for Δ¹⁵N (n = 15).     

New radiocarbon dating of the transition from the Middle to the Upper Paleolithic in Kebara Cave,Israel

The Middle to Upper Paleolithic transition (MP-UP transition) is considered a major technological and cultural threshold, at the time when modern humans spread “out of Africa”, expanded from the Levant into Europe and possibly into central and northern Asia. The dating of this techno-cultural transition has proved to be extremely difficult because it occurred sometime before 40,000 radiocarbon years before present (¹⁴C years BP), which is close to the end of the effective dating range of radiocarbon. Other dating methods such as Thermoluminescence (TL) or Electron Spin Resonance (ESR) are not sufficiently precise to date the recorded archaeological MP-UP transition in the Levant. Here we report a consistent set of stratified radiocarbon ages on freshly excavated charcoal from Kebara Cave, Mt. Carmel (Israel), that span the late Middle Paleolithic (MP) and Early Upper Paleolithic (EUP) This study applied novel strategies to improve sample preparation techniques and data analysis to obtain high-resolution radiocarbon models. From this study it is proposed that the MP-UP transition for this site can be placed immediately after 45,200 ± 700 ¹⁴C years BP and before 43,600 ± 600 ¹⁴C years BP or from 49/48 to 47/46 radiocarbon calibrated years before present (years Cal BP).     

Obsidian hydration dating by infrared spectroscopy: method and calibration

Low temperature (90–190 °C) hydrothermal experiments have been conducted on seven obsidians where composition of the glass varies significantly in the concentration of structural water within the unhydrated bulk material. Infrared transmission spectroscopy was used to track the diffusion of molecular water into the glass surface as a function of time and temperature. Long-term (60–360 days) hydration sequences at 90 °C show a t^0.6 time dependence for the mass uptake of molecular water that forms the hydration layer. The structural water concentration of the unhydrated bulk obsidian is highly correlated with the pre-exponential and activation energy and may be used to estimate the Arrhenius constants. In addition, secondary ion mass spectrometry (SIMS) hydrogen profiling of Napa Glass Mountain obsidian hydrated at 90 °C reveals that the early stages of diffusion exhibit a dynamic behavior that includes a fluctuating hydrogen concentration and a changing diffusion coefficient that slows with time.     

Provisioning Inka feasts at Tiwanaku, Bolivia: the geographic origins of camelids in the Pumapunku complex

While political integration can be achieved by many means, here we focus on the use of feasting and statecraft in the Inka Empire of the Andean Late Horizon (c. AD 1400-1532) in South America. In order to examine Inka political integration of the Lake Titicaca Basin of Bolivia, we examine paleomobility and paleodiet through radiogenic strontium and stable oxygen and carbon isotope data in archaeological camelid remains from the site of Tiwanaku. Mean radiogenic strontium isotope values from all archaeological camelid enamel and bone samples is ⁸⁷Sr/⁸⁶Sr = 0.70998 ± 0.00179 (1σ, n = 48), mean stable oxygen isotope values from a sub-set of archaeological camelid enamel and bone samples is δ¹⁸O_{carbonate (VPDB)} = −10.0‰ ± 2.6‰ (1σ, n = 18) and mean stable carbon isotope values from a sub-set of archaeological camelid enamel and bone samples is δ¹³C_{carbonate (VPDB)} = −9.0‰ ± 1.7‰ (1σ, n = 18). While many camelids consumed in these feasting events were likely local to the Lake Titicaca Basin, others came from a variety of different geologic zones, elucidating our understanding of Inka statecraft and the role of feasting in political integration in empires in the past.     

Obsidian procurement,least cost path analysis,and social interaction in the Mimbres area of southwestern New Mexico

For over 15 years chemical compositional analyses of obsidian artifacts recovered from archaeological sites in the southwestern United States have been increasingly used to address many research agendas. Despite this increasing interest in obsidian studies, few have attempted to synthesize the ever-growing amount of data generated from the numerous projects being conducted in the southwest. Here, we synthesize and present data for 923 sourced obsidian samples recovered from over 80 archaeological sites in the Mimbres area of southwestern New Mexico. We then use least cost path analysis as a means of investigating procurement patterns as well as networks of social interaction within the region.     

Obsidian hydration dating: accuracy and resolution limitations imposed by intrinsic water variability

Obsidian hydration dating typically yields a range of ages for a single chronometric measurement, even after controlling for source chemistry and effective hydration temperature. Previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water, and specifically hydroxyl ions, in the obsidian. Such variability exists within any given obsidian source, and even within any particular specimen. This paper analyzes the effect on age estimates of intrinsic water variability and concludes that if a controlled sample of obsidian yields a range of ages, there is no way to tell whether the range is due to long site use or to variations in hydroxyl concentration. At present there is no robust and cost-effective protocol for measuring hydroxyl concentration. Suggested guidelines for obsidian hydration dating are developed using a case study. These findings do not invalidate obsidian hydration as a chronometric technique, but they do suggest limits to the temporal resolution achievable.     

Migration and Viking Dublin: paleomobility and paleodiet through isotopic analyses

During the early medieval period in Ireland, Dublin was established as the largest Viking settlement on the island in the ninth century AD. A previous biodistance study has suggested that the population of the town consisted of a polyethnic amalgam of immigrant and indigenous. In this study, we use biogeochemistry to investigate paleomobility and paleodiet in archeological human remains from the ninth to eleventh century levels at the sites at Fishamble Street II (National Museum of Ireland excavation number E172), Fishamble Street III (E190) and John’s Lane (E173), as well as twelfth-century remains from Wood Quay (E132). Through radiogenic strontium isotope, stable oxygen, carbon, and nitrogen isotope, and elemental concentration analyses, we investigate the origins of the individuals who lived and died in early and late Viking Dublin. Mean archaeological human enamel and bone isotope values from Dublin are ⁸⁷Sr/⁸⁶Sr = 0.70975 ± 0.00139 (2σ, n = 22), δ¹³C_{carbonate(V-PDB)} = −14.8‰ ± 0.8‰ (1σ, n = 12), and δ¹⁸O_{carbonate(V-PDB)} = −7.2‰ ± 1.0‰ (1σ, n = 12). Archaeological human bone samples exhibit mean δ¹³C_{collagen(V-PDB)} = −20.8‰ ± 0.5‰ (1σ, n = 12) and mean δ¹⁵N_{collagen(AIR)} = +10.0‰ ± 1.7‰ (1σ, n = 12). Comparing these data with archaeological faunal data from Dublin and published data from northern Europe, we argue that there are no clear immigrants from other parts of the North Atlantic, although there is one clear outlier in both origins and diet. Overall, the relative homogeneity in both paleomobility and paleodiet may support models of acculturation in Viking Dublin, rather than a high number of first-generation immigrants or continued migration from Scandinavia.     

Residential mobility and social identity in the periphery: strontium isotope analysis of archaeological tooth enamel from southeastern Arabia

Strontium isotope analysis represents an effective means of assessing mobility and reconstructing geographic residence patterns in archaeological populations. This biogeochemical technique was utilized to test the hypothesis that burgeoning interregional exchange networks and the occurrence of exotic grave goods in local tombs would correspond with a highly mobile population and a considerable immigrant presence during the Umm an-Nar (2700–2000 BC) period in the UAE. This region has been considered peripheral relative to larger civilizations in Mesopotamia and the Indus Valley, but played an important role as a major supplier of copper for the Persian Gulf. Individuals (n = 100) from six monumental Umm an-Nar tombs (Mowaihat; Tell Abraq; Umm an-Nar Island I, II, V; Unar 1) were selected to evaluate the geographic origins of tomb members. Mean ⁸⁷Sr/⁸⁶Sr ratios from local individuals interred at Mowaihat (0.708863 ± 0.000014; 1σ, n = 12), Tell Abraq (0.708873 ± 0.000020; 1σ, n = 27), Umm an-Nar Island (0.708902 ± 0.000079; 1σ, n = 33), and Unar 1 (0.708805 ± 0.000065; 1σ, n = 25) all display little isotopic variability, indicative of a population that was not highly mobile. However, coupled with archaeological evidence, three immigrants from Tell Abraq (n = 2) and Mowaihat (n = 1) identified by deviant strontium values suggest that this region was actively engaged in interregional interaction. Despite claims that these tombs acted as visible markers of territoriality legitimized by local ancestors buried within them, the presence of non-locals suggests that as commerce became increasingly important, definitions of kinship and social identity may have become more flexible to better meet the needs of the local community and those with whom they interacted.     

Accuracy of obsidian hydration dating based on obsidian–radiocarbon association and optical microscopy

Most archaeologists using obsidian hydration dating (OHD) in the United States develop hydration rates from association of obsidian hydration rims with dates based on radiocarbon, subsequently using the rate for chronometric analysis. The overall accuracy of the process has never been quantified. This paper reports an accuracy analysis in which sources of uncertainty are defined and modeled and their effects quantified. A Monte Carlo simulation is used to quantify errors from rate development, while uncertainties in age resulting from chronometric analysis are calculated analytically. For typical ranges of error values, hydration rate errors of ∼5% or less are achievable in the absence of systematic errors, with errors of chronometric age estimates ∼20–30% or less.     

Geochemical composition of source obsidians from Kenya

Here we provide a reference resource to archaeologists interested in the sources of obsidian in Kenya, through electron microprobe analyses of 194 obsidian samples from 90 localities. Averaged analyses of each sample and eleven published analyses are categorized into 84 compositional groups of which only about 21 are known to have been used to produce artifacts, possibly because studies of artifactual material in the region are lacking. We also provide trace element analyses determined by XRF and LA-ICP-MS for these same obsidians. In northern Kenya 27 distinct compositions of obsidian have been found, including some of Miocene age, but the source of the most abundant obsidian found in archaeological sites in this part of Kenya remains obscure. The Baringo region contains at least 13 varieties of low-silica obsidian. The Naivasha–Nakuru region contains an abundance of obsidian with 38 compositional types recognized, and is the only region in Kenya apart from the Suregei (northern Kenya) that contains rhyolitic obsidian. Nine compositionally distinct types of obsidian are known from southern Kenya. Although Kenyan obsidians span the compositional range from phonolite to rhyolite, low-silica, nepheline-normative obsidians occur only south of 1°N latitude. One obsidian type, the Lukenya Hill Group, appears to have been derived from a regionally extensive ash flow tuff with a distribution of over 8000 km². From previous studies it is known that obsidians of lowest (Mundui) and highest iron content were used for tool manufacture, as were some obsidians (e.g., Kisanana) with the highest alkali content, and obsidians with both high (Njorowa) and low (Kisanana) silica content.     

Variability in the marine radiocarbon reservoir effect in Muscat (Sultanate of Oman) during the 4th millennium BC: reflection of taphonomy or environment?

Radiocarbon (¹⁴C) dating of archaeological coastal sites in arid areas is challenging because of the relative rarity of datable terrestrial artefacts. Marine artefacts provide an abundant source of carbon, which is technically easy to date but radiocarbon dates need to be corrected for local variations from the global average marine ¹⁴C reservoir age (ΔR). In archaeological sites, this is usually done by the comparison of the ¹⁴C age measured between coeval pairs of terrestrial and marine samples that have no inbuilt age. Here, we present the results of a study that aims to determine the local ¹⁴C marine reservoir effect (MRE) along the Eastern coast of the Arabic Peninsula during the 4th millennium BC, a period of important cultural, demographic and social changes in this region. Previous estimates of the MRE based on associated shells and charcoal vary by about 400 ¹⁴C yr and this is a serious limitation to the establishment of a precise chronology in the area based on marine material. In order to maximize the chances to obtain contemporaneous terrestrial–marine pairs for a new assessment of the MRE in this region we dated charcoal, shells, fish and turtle bones as well as human bones found in three recently and carefully excavated graves from Ra’s al-Hamra RH5. A large variability was found between charcoals (up to 240 ¹⁴C yr) and marine specimens (up to 785 ¹⁴C yr) present in the same grave. This variability was attributed to inbuilt ages, diagenesis and possibly environmental factors although taphonomic processes cannot be excluded. We discarded the oldest charcoals and used the ¹⁴C ages obtained on human apatite as a cut-off value to remove the marine outliers. Two out of the three graves provided terrestrial and marine assemblages which did not differ statistically and were used to calculate an average MRE of 645 ± 40 ¹⁴C yr (ΔR = 255 ± 55 ¹⁴C yr). This value is consistent with previous estimates based on the ¹⁴C dating of marine sediments off Pakistan and suggests stability of the MRE in the Arabian Sea since the 4^th millennium BC.     

Forensic Ar/Ar dating: a provenance study of Middle Stone Age obsidian artifacts from Ethiopia

Obsidian sourcing based on geochemistry is widely applied to reconstruct commerce patterns and dissemination of early hominid groups. Due to problems concerning potential intra-source variability or homogeneity of a geological source over large areas, parameters additional to this classical approach are desirable. Here we present the first ⁴⁰Ar/³⁹Ar investigation of Middle Stone Age (MSA) obsidian artifacts (i.e. debitage pieces) for this purpose, as well as of potential geological obsidian sources from Ethiopia. With the present pilot study we demonstrate that ⁴⁰Ar/³⁹Ar geochronology represents a reliable and powerful tool for archaeological provenance studies complementary to the geochemical approach and more recently applied techniques like fission track counting or Mössbauer spectroscopy. Two independent sets of debitage and potential source rock samples were dated by the ⁴⁰Ar/³⁹Ar method. Debitage pieces from the Kulkuletti excavation site and obsidian samples from the nearby obsidian outcrop Worja (central Ethiopia) exhibit basically identical age ranges as well as similar Ca/K and Cl/K ratios, supporting the debitage/source rock relationship previously inferred on geochemical grounds. A second small set of geochemically characterized debitage samples from the Porc Epic cave and potential source rocks from an obsidian outcrop at Kone (Eastern Ethiopia) however have different ⁴⁰Ar/³⁹Ar ages and Ca/K and Cl/K ratios. These results contradict the previous conclusion about a debitage/source rock relationship of the Porc Epic and Kone samples made on the basis of geochemistry [A. Negash, M.S. Shackley, Archaeometry 48 (2006) 1]. Additional sampling at the Kone outcrop as well as of other obsidian occurrences in the greater area is needed to unambiguously pinpoint the origin of these obsidian tools.     

Sources of Archaeological Obsidian on Sakhalin Island (Russian Far East)

Instrumental neutron activation analysis was performed on 79 obsidian tools and flakes from 35 sites on Sakhalin Island dating from Upper Paleolithic (c. 19,000 bp ) to Early Iron Age (c. 2000–800 bp ). Due to the absence of volcanic glass on Sakhalin Island, raw materials from the nearest obsidian sources on Hokkaido Island, such as Oketo, Shirataki, Tokachi-Mitsumata, and Akaigawa, were also analysed. A strong correlation between the chemical compositions of obsidian artefacts from Sakhalin and volcanic glass sources from Hokkaido was discovered. In particular, the Oketo and Shirataki sources were used for tool manufacturing throughout all of Sakhalin Island's prehistory. The distances between sources and archaeological sites range from 200–1000 km. The intensive exchange of raw materials continued and even intensified after the appearance of the La Pérouse (Soya) Strait between Hokkaido and Sakhalin about 10,000–8000 bp. The Sakhalin Island populations were deeply involved in the obsidian exchange network centered on Hokkaido.     

The Hungarian and Slovak sources of archaeological obsidian: an interim report on further fieldwork,with a note on tektites

This report describes the results of fieldwork carried out in the Zemplén Mountain area of north-eastern Hungary in 1975. The aim of this work was to locate and sample geological sources of obsidian which may have been used by prehistoric man. These sources are of increased importance since the work of Nandris (1975) showed that the Romanian “sources” do not produce workable obsidian. During the fieldwork three sources in Hungary were visited and sampled; one of these was the previously unlocated source of Csepegö Forräs. A number of other possible localities for geological obsidian are mentioned in 19th and 20th century geological and archaeological literature, and the present state of knowledge with regard to these is summarized. Further sources exist in central and in south-eastern Slovakia. These sources were not visited but material has been obtained from both areas. The central Slovak sources do not produce workable obsidian and are not therefore relevant to archaeological studies. Obsidian from three localities in south-eastern Slovakia is of good glassy quality and further fieldwork is now needed to check the validity of these localities as geological sources. Reference is made to obsidian sources in the western U.S.S.R., and the problem of the use of tektites in archaeological sites is discussed.The obsidian samples obtained during this work are currently being analyzed using neutron activation, in order to characterize the sources on the basis of their trace element analysis and thus to relate them to archaeological obsidian from central and eastern Europe.