High-resolution sclerochronological analysis of the bivalve mollusk Saxidomus gigantea from Alaska and British Columbia: techniques for revealing environmental archives and archaeological seasonality

The butter clam, Saxidomus gigantea, is one of the most commonly recovered bivalves from archaeological shell middens on the Pacific Coast of North America. This study presents the results of the sclerochronology of modern specimens of S. gigantea, collected monthly from Pender Island (British Columbia), and additional modern specimens from the Dundas Islands (BC) and Mink and Little Takli Islands (Alaska). The methods presented can be used as a template to interpret local environmental conditions and increase the precision of seasonality estimates in shellfish using sclerochronology and oxygen isotope analysis. This method can also identify, with a high degree of accuracy, the date of shell collection to the nearest fortnightly cycle, the time of day the shell was collected and the approximate tidal elevation (i.e., approx. water depth and distance from the shoreline) from which the shell was collected.Life-history traits of S. gigantea were analyzed to understand the timing of growth line formation, the duration of the growing season, the growth rate, and the reliability of annual increments. We also examine the influence of the tidal regime and freshwater mixing in estuarine locations and how these variables can affect both incremental structures and oxygen isotope values. The results of the sclerochronological analysis show that there is a latitudinal trend in shell growth that needs to be considered when using shells for seasonality studies.Oxygen isotope analysis reveals clear annual cycles with the most positive values corresponding to the annual winter growth lines, and the most negative values corresponding to high temperatures during the summer. Intra-annual increment widths demonstrate clear seasonal oscillations with broadest increments in summer and very narrow increments or no growth during the winter months. This study provides new insights into the biology, geochemistry and seasonal growth of S. gigantea, which are crucial for paleoclimate reconstructions and interpreting seasonality patterns of past human collection.     

REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ¹⁸O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ¹⁸O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ¹⁸O_shell appears to be strongly influenced by seasonal inputs of very low δ¹⁸O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.     

Seasonality and paleodiet in the Chiribaya polity of southern Peru

In the Andes, the complex Chiribaya polity, or señorío, was composed of economically specialized groups. Previous carbon and nitrogen isotope analyses of archaeological human bone from Chiribaya-affiliated sites have effectively demonstrated socioeconomic specialization and variability in paleodiet among different Chiribaya-affiliated sites. The present study complements earlier paleodietary analyses of Chiribaya populations by supplementing them with carbon and nitrogen isotope analyses of archaeological human hair from the two Chiribaya-affiliated sites of Chiribaya Alta and El Yaral. These new data demonstrate that seasonal variability in the consumption of marine products and C₄ plants such as maize was quite high for some individuals buried at Chiribaya-affiliated sites. In addition to elucidating the complex patterns of Chiribaya seasonality, this study contributes to the growing body of knowledge of archaeological analyses of human hair for paleodiet.     

Provenance analysis of Olivella biplicata shell beads from the California and Oregon Coast by stable isotope fingerprinting

While Olivella beads are a common component of archaeological sites in California, and were widely traded in prehistory, no method has been developed to trace individual beads to a point of origin. This study examines the potential of stable carbon and oxygen isotopes to source Olivella beads from the Pacific coast. The study shows that 1) the oxygen isotopic composition of modern Olivella biplicata shells faithfully varies with ambient sea surface temperature and local upwelling, lending themselves to sourcing studies; 2) oxygen isotope ratios in modern shells can be used to identify shells that grow north versus south of Point Conception, California; and 3) shell carbon isotope ratios may further subdivide these two regions into more spatially restricted source zones. Analyses on a small sample of 10 beads found at various archaeological sites within the interior of California suggest that all were made in southern California.     

Molluscan calendars: The use of growth-line analysis to establish seasonality of shellfish collection at the Mesolithic site of Morton,Fife

The technique of growth-line analysis is used to examine seasonal growth patterns in modern specimens of the edible cockle, Cerastoderma edule L. The modern control work provides a basis for the interpretation of seasonal collection in archaeological cockles, and is applied to shells from the Mesolithic site of Morton, Fife. The seasonal use of the site is shown to be clearly related to site function.     

Tracing the source of Late Neolithic Spondylus shell ornaments by stable isotope geochemistry and cathodoluminescence microscopy

Determination of the source of Spondylus objects is essential for the interpretation of Late Neolithic exchange systems and the social role of shell ornaments. We performed stable isotope analysis combined with cathodoluminescence microscopy study on ornaments (beads, bracelets) made of Spondylus shells excavated at the Aszód-Papi földek archaeological site in Hungary, to define their origin. For comparison Spondylus finds from Neolithic sites of Greece, modern Spondylus shells from the Aegean and the Adriatic, as well as fossil Spondylus and Ostrea shells from the Carpathian Basin were also examined. Oxygen isotope composition of Spondylus finds from Aszód ranges between ?1.9 and 2.1‰ and overlaps with the oxygen isotope range of shell objects from other Neolithic sites. Modern Spondylus shells from the Aegean and the Adriatic show overlapping δ¹⁸O values with one another and with the Neolithic objects; while recent shells of the Black Sea clearly are separate isotopically from the Mediterranean ones and most of archaeological artefacts. Spondylus shells from the Aszód site have Mediterranean origin; their source can be the Aegean or the Adriatic. Based on a former strontium isotope study the use of fossil Spondylus shells is excluded as raw material used for ornaments, however, in recent years the use of fossil shells was reintroduced. The shell ornaments from Aszód-Papi földek and the fossil oyster shells collected from the Carpathian Basin exhibit some overlapping oxygen isotope values; however, cathodoluminescence microscopy indicates that the Spondylus objects retained their original aragonite material. Diagenetic calcite, which occurs typically in the fossil shells, was not detected in the ornaments suggesting that the studied objects were made of recent shells. Calcitic parts observed in some Spondylus objects are not related to fossilisation.     

Mesolithic shellfish exploitation in SW Italy: seasonal evidence from the oxygen isotopic composition of Osilinus turbinatus shells

Oxygen isotope analyses were carried out on the topshell Osilinus turbinatus from archaeological sites with the aim to investigate the temporal exploitation patterns by Mesolithic groups inhabiting coastal caves in SW Italy. In order to assess the present day O. turbinatus intra-annual δ¹⁸O variability, living specimens were collected monthly at Marina di Camerota (SW Italian peninsula). Their shell-edges were analysed and the seasonal results were compared with archaeozoological material. Our findings show that Mesolithic O. turbinatus exploitation was carried out almost exclusively during the colder and intermediary seasons (e.g. autumn, winter, spring), with very sporadic harvesting during the warmer seasons. Results suggest a possible regional exploitation pattern of O. turbinatus by Mesolithic groups inhabiting this region.     

Seasonal stability in Late Holocene shellfish harvesting on the central California coast

Oxygen isotope determinations from 92 California mussel (Mytilus californianus) shells from ten archaeological sites in central coastal California show relatively stable seasonal harvesting patterns between 3600 CAL BP and historic contact (AD 1769). Coastal occupants harvested mussels nearly year-round and seem to have occupied individual residential bases throughout the seasonal cycle. Interior groups returned with mussels from the coast mostly in the spring and early summer, but almost never in the late summer/early fall when nut crops were harvested. These findings suggest two inter-dependent groups with distinct seasonal settlement strategies: inland people, reliant on acorns and other nut crops harvested in the fall, and coastal inhabitants who were less involved with acorns. This pattern is supported by accounts recorded by the first Spanish explorers in AD 1769. While some interior groups may have been seasonally migrating “collectors,” coastal populations were less mobile, inhabiting individual residential sites throughout the year, albeit not necessarily on a permanent basis. These findings highlight the strong influence of coastal environments and resources on hunter-gatherer mobility.     

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.     

In situ oxygen isotope micro-analysis of faunal material and human teeth using a SHRIMP II: a new tool for palaeo-ecology and archaeology

A Sensitive High Resolution Ion MicroProbe (SHRIMP II) has been used to make high spatial resolution in situ micro-analyses of oxygen isotopes in fish otoliths, and teeth from fossil herbivores and a Neanderthal. Large intra-tooth variations in the oxygen isotopic composition (up to 9‰) were observed in the enamel of herbivores from the Neanderthal fossil site of Payre, consistent with preservation of seasonal cyclicity. The range of isotopic compositions observed in Neanderthal tooth enamel was much smaller (∼3‰), possibly the result of a longer enamel maturation time averaging out variability. An archaeological otolith from a Preceramic site in Northern Peru exhibited marked changes in δ¹⁸O over life, due either to the fish occasionally migrating from the sea to a lower salinity habitat, or to short-lived rises in sea water temperature. A fish otolith from Australia's Willandra Lakes World Heritage Area showed clear seasonal variations, but also a general trend towards isotopically heavier and more saline water, as indicated by higher δ¹⁸O and Sr/Ca values resulting from increased evaporation. The results of these case studies are compared to results of oxygen isotope analysis using more conventional methods and demonstrate the ability of the SHRIMP II to provide precise high spatial resolution in-situ oxygen isotope analyses of a variety of biogenic materials. This approach has major advantages over conventional methods. It can provide rapid, micro-scale isotopic analyses of sub-permil precision without the need for chemical preparation of the sample.     

Oxygen isotope seasonality in a temperate estuarine shell midden: a case study from CA-ALA-17 on the San Francisco Bay,California

Seasonality determination using stable oxygen isotope (δ¹⁸O) analyses in archaeological mollusk shell has been largely limited to aquatic settings where one of the two factors that control shell δ¹⁸O – water δ¹⁸O (or salinity) and temperature – is assumed to be constant. Open coastal marine environments reflect the former situation, and tropical estuaries constitute the latter. In an effort to expand stable isotope seasonality to an ecological setting where neither variable remains constant, we present a model of annual shell δ¹⁸O cycle of aragonite deposition derived from instrumental data on salinity and temperature from San Francisco Bay, California. The predicted range of modeled shell δ¹⁸O is consistent with observed δ¹⁸O values in prehistoric and modern shells when local conditions are considered. Measurements of δ¹⁸O taken at 0 mm and 2 mm from the terminal growth margin were made on 36 archaeological specimens of Macoma nasuta from a late Holocene hunter-gatherer site CA-ALA-17, and season of collection was inferred using the shell δ¹⁸O model. We conclude that shellfish exploitation occurred through the year with the exception of fall, which may indicate scheduling conflicts with acorn harvesting or other seasonally abundant resources elsewhere. The model supports the feasibility of stable isotope seasonality studies in temperate estuaries, provided that instrumental records are available to quantify the relevant water conditions at appropriate spatial and temporal scales.     

Fast or feast: reconstructing diet in later medieval England by stable isotope analysis

In this pilot-study, which was designed to assess the range of isotopic variation in English medieval populations, we present the results of stable isotope analysis of carbon and nitrogen of human and animal bone collagen from three later medieval sites in Northern England.The isotopic values observed for the rural hospital of St. Giles by Brompton Bridge (N. Yorks.), the Augustinian Friary at Warrington and a mass-grave with casualties from the Battle of Towton (N. Yorks.) are significantly different from those reported for other archaeological populations in Britain, namely by their very enriched δ¹⁵N ratios which are combined with almost entirely terrestrial carbon signals. We discuss possible explanations for the unusual human data and argue on grounds of the available faunal data, that a mixed diet of terrestrial, marine and freshwater resources is most likely. This may indicate the significant impact of the medieval fasting regulations on everyday subsistence. We conclude that stable isotope analysis can complement the available historical information on diet in the Middle Ages.     

Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia

ABSTRACT

The residents of the Canary Archipelago consumed limpets since the arrival of humans ～2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (δ¹⁸O) and body size of the black limpet (Patella candei d’Orbigny, 1840) from archaeological sites in the Canary Islands to assess possible seasonal variability and intensity of shellfish collection throughout the late Holocene. The shell margin δ¹⁸O values of 100 shells (radiocarbon dated between ～500 and ～1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and was avoided in the cooler months (when SST?<?20°C). This pattern differs from most higher latitude Mesolithic and Neolithic human groups, which gathered shellfish year-round, targeting winter more heavily. Preliminary body-size measurements suggest shell sizes have experienced a decline from aboriginal times to the present, which possibly resulted from increasing anthropogenic pressures. During aboriginal inhabitation, maximum adult shell size remained stable, suggesting that present-day harvesting practices are more intense than harvesting from aboriginal human groups. This intensive collection has likely diminished the average adult size of limpet populations in the islands by ～27%.     

Determining Olmec maize use through bulk stable carbon isotope analysis

Bulk stable carbon isotope analysis on absorbed organic residues in ceramics can be an effective method for discerning patterns of maize use when the ceramics come from relatively uniform archaeological contexts. The bulk stable carbon isotope method is faster and less costly than the more commonly used compound-specific stable carbon isotope analysis. Moreover, the bulk stable carbon isotope method can determine the presence of C4 plant carbon in samples in which organic compounds have degraded. Bulk stable carbon isotope analysis was used to discern patterns of maize (Zea mays mays) use among a sample of 24 ceramic sherds from an Early Franco Period feasting deposit (ca. cal 650 B.C.) at the Olmec site of San Andrés, La Venta, Tabasco, Mexico. A comparison of the δ 13C results of different categories of ceramics showed that proportionally more maize was used in luxury beverage service wares than in utilitarian vessels, suggesting that maize-based beverages were prominent in this probable elite feasting episode.     

BULK STABLE LIGHT ISOTOPIC RATIOS IN RECENT AND ARCHAEOLOGICAL RESINS: TOWARDS DETECTING THE TRANSPORT OF RESINS IN ANTIQUITY?*

We have applied and refined methods for the determination of bulk hydrogen, carbon and oxygen isotope ratios in modern and archaeological resins. The modern resins have a wide range of isotopic values and vary within the same tree, between individual trees, with species and location. For all isotopes measured, there is a general trend of increasing depletion of the heavier isotope with increasing altitude. There is also a linear trend between depletion of δD and δ¹³C values with increasing latitude; this trend is less clear for oxygen, but is related to the meteoric water line. Two case studies using archaeological resins known or suspected to have been transported in antiquity have been investigated to determine whether isotopic signatures can assist in pinpointing the geographical origin of the resin: Pistacia sp. resin from Canaanite amphorae imported into Egypt from known geographical locations in the eastern Mediterranean during the Late Bronze Age, and Roman amphorae sherds lined with Pinus sp. resin from sites ranging from Britain to the eastern Mediterranean. These results show separate groupings between the two resin types (pine/pistacia) and between the modern/archaeological resins. Some archaeological samples are distinct from the others and the modern resins show differences between geographical areas. However, there are no clear patterns relating the different Canaanite fabrics or the suggested manufacturing site of the Roman amphorae.     

Assessing Prehispanic Herding Strategies through Stable Isotope Analysis: A Case Study from the Dry Puna of Argentina

ABSTRACT

The main goal of this work is to study the camelid herding and management strategies employed by the human groups that occupied the Dry Puna of Argentina during the late Holocene. Carbon and nitrogen stable isotope compositions were measured on bone collagen from domesticated South American camelids (llamas: Lama glama) recovered at two archaeological sites (Huirunpure and Chayal Cave). These results were interpreted using an already published data set of δ ¹³C and δ ¹⁵N values measured on bone collagen from modern herds of llamas managed in a traditional way. Our results showed that even though the archaeological sites of Huirunpure and Chayal Cave are located within different settings – at 4020 and 3700?masl respectively – and present different chronologies – 0–650 and 1300–1500 CE respectively – the llamas from both sites exhibit similar δ ¹³C and δ ¹⁵N values. This pattern was explained considering the characteristics of the vegetation communities that grow in the vicinity of both sites as well as the paleoenvironmental records of the Andean highlands. In sum, this work presents and discusses some preliminary results on the study of prehispanic herding practices in the Dry Puna of Argentina during the first 1500 years of the Common Era through stable isotope analysis.     

Stable hydrogen isotopes of bone collagen in palaeodietary and palaeoenvironmental reconstruction

The stable hydrogen isotope ratios (δD) of bone collagen in archaeological human and animal samples demonstrate a trophic level effect, with increasing δD from herbivores to omnivores to humans, in steps of 10–30‰. In addition the archaeological sites studied (Yarnton, Eton Rowing Lake, Danebury Environs–Suddern Farm, and Windmill Hill in the UK, Balatonszárszó in Hungary, and Huari in Peru) demonstrate geographical variation in δD. The detection of manuring in prehistory by comparison of δ¹⁵N to δD values in humans and a local herbivore (cattle) is also considered. This work is the first to measure δD in a large number and range of archaeological samples, with several animal species and humans. It demonstrates unequivocally that δD is different between species in ancient material, increasing from herbivores to omnivores to carnivores.     

Isotopic analysis of archaeobotanicals to reconstruct past climates: Effects of activities associated with food preparation on carbon,hydrogen and oxygen isotope ratios of plant cellulose

The cellulose fraction of botanicals recovered from archaeologically defined strata may be suitable for stable isotope-based palaeoclimatology in much the same manner as cellulose from tree rings has been utilized. However, manipulation by humans is a distinct possibility with such specimens and constitutes a potential source of isotopic alteration early in the post-mortem history of the samples. We studied the susceptibility of plant cellulose to isotopic alteration caused by manipulations related to food processing to determine if discarded plant foods recovered from archaeological contexts are suitable substrates for isotopic palaeoclimatic studies. The carbon and hydrogen isotope ratios of cellulose nitrate and the oxygen isotope ratios of cellulose were determined for Zea mays cobs, Helianthus annus seeds, Agave americana leaves, Pachyrrhizus erosus tubers and a cellulose standard before and after a variety of treatments, including boiling, roasting, fermentation, liming, molding and carbonization. The oxygen and hydrogen isotope ratios (which are climatically sensitive in all plants) and the carbon isotope ratios (which reflect climate only in certain plants) of all samples, except for Agave, were conserved during various food-processing steps. Thus, it appears that the isotope ratios of cellulose and cellulose nitrate prepared from many archaeological food plants, whether processed or uncooked, will reflect in vivo values and can be used to reconstruct aspects of palaeoclimate. Such isotopic palaeoclimatic studies will extend the utility and value of existing collections of ecofacts by opening a unique window for the study of the relationships among climate, plants and man.     

Alteration of Otolith Aragonite: Effects of Prehistoric Cooking Methods on Otolith Chemistry

Geochemical analyses of fish otoliths from archaeological sites are a valuable source of paleoclimate data. A common assumption in such research is that the otolith chemistry is unaltered from the time of capture until excavation. Although post-depositional diagenesis will vary between sites according to local burial conditions, the effects of common pre-depositional treatment such as cooking or trash disposal can be evaluated experimentally. Six Atlantic croaker (Micropogonius undulatus) and six gafftopsail catfish (Bagre marinus) were treated using five different methods to simulate cooking and trash disposal. The left sagittal otolith was removed as an experimental control prior to cooking or burning each fish. After cooking or burning, the remaining otolith was removed and each otolith pair was tested to measure changes in crystallography, carbon and oxygen isotope content, and elemental chemistry. Recrystallization and changes in isotope chemistry only occurred in burned otoliths. In contrast, elemental composition was altered during each treatment method. These experiments validate the use of carbon and oxygen isotope analyses of unburned otoliths in paleoclimate research, but suggest caution in the interpretation of elemental data.     

Systematic seasonal land use by late Pleistocene Tasmanian Aborigines

New research on the odontochronological (dental growth-increment) analysis of marsupial teeth provides opportunities to estimate with more certainty the time of the year Tasmanian Aborigines inhabited sites during the late Pleistocene. Here we focus on the Bennett's wallaby (Macropus rufogriseus) as a proxy for understanding seasonal human land use patterns and occupation of four southwest Tasmanian caves. The aim of the paper is to investigate whether caves at different altitudes were occupied in alternating seasons, and determine if the ‘Patch Model’ developed to explain the archaeological variability of late Pleistocene human behavior should be modified accordingly. The data presented here support the original observations that these sites, although reflecting extreme richness, were occupied in a punctuated seasonal manner with visits probably separated by a considerable time of unknown duration.