Exploring Accumulation Rates of Shell Deposits Through Seasonality Data

Shell middens are often analysed as the result of short- or long-term depositional activities. In order to confidently interpret such deposits, it is necessary to have accurate estimations of shell accumulation rates, most commonly produced by radiocarbon dates. This paper introduces the application of seasonality data as a temporal measurement of short-term shell deposition. This gives access to an additional estimate of shell accumulation rates, which work on a shorter timescale than can be analysed through radiocarbon dating. We focus on shell deposits on the Farasan Islands, Saudi Arabia, which comprise over 3000 shell midden sites dating to the mid-Holocene (6500–4500 calBP). One site (JW1727) was chosen to (1) explore the potential of seasonality data to reconstruct accumulation rates, (2) analyse the intensity of exploitation and (3) assess the visibility of short-term shellfish deposits. Stable oxygen isotope values (δ¹⁸O) were obtained from the marine gastropod Conomurex fasciatus (Born 1778), representing 72 % of the shell weight of JW1727, to reconstruct season of capture. Seasonality data was grouped by their spatial distribution, which allowed successive episodes of deposition within a stratigraphic sequence to be connected. This allowed us to make an estimation of exploited shell meat of ～200 kg over a 7-month period (～400 shells/day). We argue that excavation methods and low resolution stratigraphic data cause imprecision in the seasonality data and the low visibility of rapidly accumulated shell deposits. Also, an increase of analysed shells per layer is key to understanding the seasonal brickwork of more middens in the future.     

Exploring Oyster (Crassostrea virginica) Habitat Collection via Oxygen Isotope Geochemistry and its Implications for Ritual and Mound Construction at Crystal River and Roberts Island,Florida

Research at Crystal River and Roberts Island Shell Mound Complex, on the western coast of Florida, USA, offers a quantitative assessment of the temporality of shell deposit construction, Native subsistence practices, and mobility patterns through stable oxygen isotope data from eastern oyster (C. virginica). The δ¹⁸O_water values of oysters vary synchronously with salinity, assuming relatively constant δ¹⁸O_water/salinity gradients since the time of occupation, allowing for an examination of shifts in oyster habitat exploitation over time. Our previous (Thompson et al. 2015) study indicated that midden accumulation occurred throughout the year, while oysters from mound deposits were collected in colder months. New data indicate that in addition to differential season of collection, habitat exploitation also varied. During early occupation at the site, oysters were collected primarily from lower saline habitats, while in later phases oysters were obtained from higher salinity waters; we relate this to a lower sea level and concomitant settlement shift seaward. Additionally, oyster from later mound contexts was collected from higher saline habitats relative to those in midden contexts; Native people may have targeted specific bioherms at certain times for the year for feasting-related mound construction.     

Stability in the South Pacific surface marine C reservoir over the last 750 years. Evidence from American Samoa, the southern Cook Islands and the Marquesas

Although minor climatic and sea-level changes have been documented for the South Pacific during the late Holocene, our understanding of the consequent impact of these changes on the marine ¹⁴C reservoir, and therefore the ¹⁴C content of shellfish, is limited. Ultimately, this has implications for documenting the chronology of human movement and adaptation in this region. In this paper we compare marine reservoir (ΔR) data obtained from tightly controlled archaeological proveniences with known-age, pre-AD 1950 shells from the southern Cook Islands, American Samoa, and Marquesas Islands. Results indicate that there has been no significant change in the near-shore marine reservoir in these three locations over the last ca. 750 years. Furthermore, known-age, pre-AD 1950 shell samples provide more precise ΔR values for use in sample calibration than archaeological paired shell/charcoal samples. This is attributed in part to the limitations of assigning provenance and age to material from archaeological sites. On the basis of these results we conclude that the known-age, pre-AD 1950 shell derived ΔR values can be used to calibrate shell ¹⁴C results from deposits of late Holocene age.     

Possible Wild Boar Management during the Ertebølle Period. A Carbon and Nitrogen Isotope Analysis of Mesolithic Wild Boar from Fannerup F,Denmark

This paper presents a stable isotope and radiocarbon study on a total of 85 samples of wild boar (Sus scrofa), humans (Homo sapiens), dogs (Canis familiaris), red deer (Cervus elaphus) and roe deer (Capreolus capreolus) from four Late Mesolithic sites in Jutland, Denmark. Four of the eight Sus scrofa samples from one site, the shell midden of Fannerup F, show markedly enriched carbon and nitrogen isotope values, indicating a dietary intake of a substantial amount of marine food. In contrast to standard interpretations of Late Mesolithic animal economy, we suggest that the enriched values of Sus scrofa may be an indication of management by Ertebølle groups in the area that facilitated access to substantial amounts of marine foods for these wild boars compared to contemporaneous conspecifics. The ¹⁴C dates of the Sus scrofa range from 5290 to 4335 cal BC, suggesting that the management of Sus scrofa developed independently of contact with Neolithic societies. Although the sample size remains small, the interpretation of Late Mesolithic animal management adds to the growing evidence for political and economic complexity in the Ertebølle culture.     

Radiocarbon Marine Reservoir Effect in Human Remains from the Kitakogane Site,Hokkaido, Japan

Accelerator mass spectrometry (AMS) was used to measure radiocarbon (¹⁴C) in bones excavated from the Late Jomon shell midden at the Kitakogane site, Hokkaido, Japan. Comparison between ¹⁴C ages of terrestrial and marine mammals from the same site showed systematic age differences which could be attributed to the ¹⁴C marine reservoir effect in the western North Pacific Ocean. Furthermore, this effect was clearly observed in human remains from this site, indicating a heavy dependence on seafood. Dietary habit was estimated from δ¹³C and δ¹⁵N measured in the same human remains. Apparent ¹⁴C ages indicated 79% of protein originated from marine sources.     

Stratigraphic and spatial variability in shell middens: microfacies identification at the ethnohistoric site Tunel VII (Tierra del Fuego,Argentina)

Based on ethnographic accounts from the eighteenth to the twentieth century, functional areas have been identified within Fueginian shell middens. In this context, archaeological microfacies acquire a functional meaning when the microscopic record is compared to information gathered from ethnology, macroscopic observations made during excavation, and experimental modern analogues. All these lines of evidence were combined for the first time at Tunel VII, an eighteenth/nineteenth century shell midden occupied repeatedly by Yamana people, the last hunter–gatherer–fisher groups of the Beagle Channel. The sampling strategy involved three sets of samples: (1) two stratigraphical columns taken from the hut “entrance” and from a portion of the shell midden (i.e., the surrounding refuse shell ring), (2) thin sections from five hearths representing successive phases of frequentation of the hut, and (3) experimental burnt valves of Mytilus edulis, the main malacological component of the site. Comparison of microfacies from groups (1) and (2) provided microscopic indicators to distinguish between shell dumping areas and occupation surfaces. Comparison of microfacies within columns from group (1) allowed recognizing periods of site abandonment and periods of more intense/longer site frequentation. The experimental samples from M. edulis served as a reference to characterize the five central hearths in terms of maximum burning temperatures reached. Different burning structures were correlated to the season of hut frequentation and to their location (and function) within different portions of the hut. The intra-site micromorphological comparison strategy within a well-documented ethnohistorical context provides valuable indicators for the identification of functional areas in archaeological contexts when ethnographical information is not available.     

THE BEAD MAKER’S MIDDEN: EVIDENCE OF LATE PREHISTORIC SHELL BEAD PRODUCTION ON OSSABAW ISLAND,GEORGIA

Abstract

In 2005, archaeological excavations were undertaken in a single shell midden at a late prehistoric Irene phase (circa A.D. 1380) site on Ossabaw Island, Georgia. The excavations were designed specifically to collect information on the fabrication of shell beads and other shell ornaments. A considerable amount of stone was recovered, almost all of which is petrified wood used specifically in the production of “microdrills” for perforating shell beads. Also recovered were large quantities of fragmented knobbed whelk (Busycon carica), the principal raw material used for shell beads, as well as examples of shell beads in all stages of manufacture. The excavations of this midden, designated the Bead Maker’s Midden, produced abundant information bearing on shellworking technology, including the full range of tools and raw materials used and the sequences involved in the production of shell beads. Replication experiments were conducted to validate the archaeological findings. The collected data provide direct evidence of the process of shell bead production during the Late Mississippi period.     

The earliest evidence of domesticated wheat in the Crimea at Chalcolithic Ardych-Burun

Abstract

This paper reports the discovery of the earliest evidence of domesticated wheat in the Crimean peninsula from the Ardych-Burun shell midden site, Ukraine. The Ardych-Burun site dates to middle of the 4th millennium cal b.c. For the first time, the chronology of a Ukrainian Chalcolithic period site has been established through direct radiocarbon dating of cereal grains retrieved from it. This discovery allows for a wider discussion of the chronology and geographical origins of domesticated plant species in Ukraine and the role the Caucasian corridor may have played in the spread of agriculture into eastern Europe. The presence of cereal crops in the southern Crimea enriches our understanding of the subsistence strategies of the coastal population, which was previously linked only with pastoralism, hunting, and the exploitation of marine resources.     

Comparison of mangrove oyster shells lengths harvested in Cuba during the pre-Columbian era and the present day

Abstract

The Mangrove oyster [Crassostrea rhizophorae (Guilding, 1828)] was intensely harvested in the pre-Columbian era by an aboriginal group of hunters and gatherers known as the Ciboney who lived exclusively in Western Cuba. During a comprehensive study of mangrove oyster fishing areas it was of interest to compare the population characteristics under contemporary exploitation with those in pre-Columbian times and for that purpose two samples were used: one from a Ciboney midden in an archeological site 3 km inland from the Jaruco River mouth and another from a commercially exploited population in the ecologically similar Tacajó River. The samples were studied with a ‘shell classifier’ of original design resulting in a mean length of 51.8 ± 2.5 mm for the midden shells and 51.0 ± 3.1 mm for the contemporary sample. Both values were not statistically different for any P > 0.10 meaning that the two populations they came from had similar characteristics. It was also concluded that the Ciboney's manual harvesting exerted less negative anthropogenic pressure on the mangrove oysters’ populations than the contemporary commercial practices based on the use of metal instruments to gather the oysters along with the mangrove aerial roots they are attached to. This latter conclusion is based on the fact that oyster shells 41–80 mm long from the midden are 12% more abundant than in the modern sample, in spite of 500 years of weathering.     

Prehistoric Shellfish Exploitation in Coastal New York

Abstract

Sectioning studies of marine bivalves are broadening our understanding of prehistoric shellfish exploitation along the Atlantic coast of North America. We review the evidence for the timing of shellfish exploitation in coastal New York and present the results of a recent sectioning study of Mercenaria mercenaria from the Sungic Midden site on Shelter Island, New York. The results compare favorably with the harvesting patterns of other north Atlantic Sites, indicating that shellfish exploitation took place during more than one season of the year. The implications of these findings are examined in relation to current subsistence-settlement models of coastal New York.     

Shellfish exploitation in Stone Age Arctic Norway: procurement patterns and household activities

Archaeological evidence for coastal shellfish exploitation in Arctic Norway mostly dates from 5300 to 1500 BC, encompassing the terminal Mesolithic, the Late Stone Age, and the beginning of the Early Metal Period. Shell middens are generally associated with semi-subterranean houses, but may also occur as free-standing deposits. The primary shellfish taxa exploited were Littorina littorea, Arctica islandica and Mytilus edulis. Most of the species utilized were available in the littoral zone and were easily procured in the course of daily household activities, but sub-littoral A. islandica would have required greater investment in procurement technology and time, as well as labor cooperation. Shellfish were an occasional dietary supplement and could also serve as fishing bait. Spatial and temporal variation in shellfish assemblages reflects local marine ecology, sea-level changes, household dynamics, and perhaps field processing. Interpretation of the existing data is constrained by inadequate midden sampling and documentation methods.     

MARINE RESOURCES IN THE MESOLITHIC AND NEOLITHIC AT THE GROTTA DELL’UZZO (SICILY): EVIDENCE FROM ISOTOPE ANALYSES OF MARINE SHELLS*

Oxygen isotopes in shell carbonate samples from the marine rocky‐shore intertidal gastropod Monodonta turbinata (Born) are investigated in both modern analogue specimens and in archaeological specimens from the Grotta dell’Uzzo (Sicily). Variations in shell edge values of δ¹⁸O in living specimens collected monthly over two years are closely correlated with monthly seawater temperatures measured at the time of collection, showing that the species can be used for palaeoseasonality studies. Analyses of shell edge δ¹⁸O values in archaeological specimens, from Mesolithic through to early Neolithic phases at the Grotta dell’Uzzo, enabled the inference of various seasons of collection of shellfish and how such seasonality varies between the different phases of occupation. Interesting similarities and differences exist between the seasons of marine shellfish exploitation and the seasons inferred from the vertebrate zooarchaeological assemblages. A major inference drawn from the analyses and discussion is that the exploitation of all marine resources (fish and shellfish) increased in the later Mesolithic and early Neolithic periods.     

‘The Conscience of the Community’: the Au Vaine of Rarotonga

ABSTRACT

The Au Vaine (‘several women’ in Cook Islands Māori), grassroots women’s committees, worked to promote agricultural efforts and food security in Rarotonga during the 1920s and 1930s. A unique organization, the Au Vaine actively encouraged the growing of commercial crops alongside subsistence plantings at a time when women were being pushed towards the home and hearth, and men pulled to wage labour jobs. These women illustrate the powerful and often unheard voices Pacific women retained throughout this period, as well as the critical role of food in Pacific history. In this article I examine the context within which the Au Vaine emerged, discuss what distinguished them from other women’s committees in Polynesia, highlight their purpose and impact on Cook Islands foodways, and explore some of the reasons they declined by the 1940s.     

Archaeological Site or Natural Marine Community? Excavation of a Submerged Shell Mound in Ninigret Pond,Rhode Island

ABSTRACT

Submerged shell midden sites and natural shell deposits can have similar characteristics and can be difficult to distinguish archaeologically. We excavated two test units from a large (at least 35 m×70 m) submerged shell mound in Fort Neck Cove in southern Rhode Island to assess whether it was natural or cultural in origin. This mound had been recognized as a potential archaeological feature as early as the 1970s. Excavation, radiocarbon dating, and subsequent laboratory analysis of excavated materials suggest that the mound was a natural oyster reef rather than a submerged archaeological site. No artifacts were found; there was no clear evidence for human modification of any shells; small species that would not have been targeted as food were present; and δ¹³C values of oyster shells from the mound were consistent with freshwater input into their growth environment, suggesting that they grew in an estuarine environment that did not exist prior to the inundation of the ponds. The stratigraphically oldest radiocarbon date we could obtain (430–190 cal BP, 2σ range), from 70 cm below the pond floor, placed deposition of shells at least 3,000 years after the inundation of the pond. The excavation methods that we used and the process of testing, irrespective of whether the feature is cultural, are valuable contributions to the methodological literature on submerged site archaeology and help provide insight for other researchers working to discern natural from cultural shell midden sites.     

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.     

Oxygen isotope analysis of California mussel shells: seasonality and human sedentism at an 8,200-year-old shell midden on Santa Rosa Island,California

To evaluate coastal settlement and land use strategies among maritime hunter-gatherers, we analyzed oxygen isotope (δ¹⁸O) data from 131 marine carbonate samples from 21 California mussel (Mytilus californianus) shells obtained from a large ～8,200-year-old shell midden (CA-SRI-666) on California’s Santa Rosa Island. Seasonal distributions of the isotopic data were assigned using a paleo-sea surface temperature model created by comparing modern sea surface temperatures (SST) to a fully profiled ～8,200-year-old shell. For 20 additional shells, we used two sampling strategies to compare season-of-harvest inferences and explore whether the Early Holocene site occupants were sedentary. Estimated season-of-harvest differed by 35 % between the two sampling methods, corroborating recent isotope analysis of an 8,800-year-old shell midden on San Miguel Island. Shellfish appear to have been collected year-round at CA-SRI-666 from intertidal or subtidal water temperatures similar to modern SST in the vicinity of eastern Santa Rosa Island. The isotope results are consistent with other evidence from CA-SRI-666 that suggest that the site served as a residential base for relatively sedentary maritime people.     

Stable isotopic analysis of human and faunal remains from the Incipient Chulmun (Neolithic) shell midden site of Ando Island,Korea

We analyzed stable carbon and nitrogen isotope ratios of human and animal remains from the Ando shell midden, South Korea. The Ando site is a rare Incipient Chulmun (Neolithic) site (ca. 6000–5000 BC), which contains well-preserved human and animal bones in shell mounds. The stable isotope results for humans (average δ¹³C = −13.5 ± 0.5‰ and δ¹⁵N = 15.2 ± 0.5‰) indicate that Ando people in the Incipient Chulmun period strongly depended on marine resources. There were no isotopic differences between humans of different sex and age at this site. We compared our data with other previous published isotopic data from the Chulmun sites and found that the Ando people had similar isotope values to the southern Chulmun people (Tongsamdong and Daepo), but different isotopic ratios than the western Chulmun people (Daejukri and Konamri). These results indicate that marine foods were the main food resources in the southern coastal regions, but not in the western coastal regions in Chulmun Korea.     

Palynological study of a Mi'kmaw shell midden,Northeast Nova Scotia,Canada

Before now, no palynological studies were made on shell midden deposits in Nova Scotia, despite a long history of archaeological research. A test study of samples taken from the shell midden at Maligomish (Indian Island) on the Northumberland Strait was conducted to determine if sufficient pollen, fern and moss spores, and other non-pollen palynomorphs (NPP's, including fungal remains, algal spores) could be recovered to allow interpretation of environmental conditions at the time of deposition. Several pollen processing methods were tested: sieving and swirling, chemical treatment with cold HCl, 5% KOH and brief exposure to 5% NH₄OH, and treatment with acetolysis solution. We recovered variable amounts of pollen, spores and NPP's from samples taken at 3–5 cm, 5–15 cm and 15–25 cm below surface. Abundant microcharcoal fragments prevented effective use of the swirling technique, but sufficient palynomorphs were recovered by chemical treatments to allow assessment of down-section changes in assemblages. Three radiocarbon ages from Mya arenaria and Crassostrea sp., and measurements of sediment grain size, moisture, organic and inorganic carbon, provide a framework for analysing palynological assemblage changes and context for interpreting differential palynomorph preservation. Despite some oxidation and microbial degradation of palynomorphs in the time interval (ca. 380–1600 cal yr BP), the midden assemblages correlate with pollen zones from marine and lake core sites within ca. 50 km of Maligomish. Shifts in abundances of algal spores, testate amoebae and aquatic plant pollen also indicate changes in depositional conditions during the time of midden use. The study provides the first reference for archaeologists attempting to use palynology for analysis of samples from Nova Scotian shell-bearing contexts.     

Terrestrial hermit crabs (Anomura: Coenobitidae) as taphonomic agents in circum-tropical coastal sites

Hermit crabs are ever alert for more suitable shells to inhabit, but what this may mean for coastal shell middens has rarely been considered. Here, the impact of the most landward-based of hermit crab families, the tropical Coenobitidae, upon archaeological shell-bearing deposits is assessed using a case study: the Neolithic Ugaga site from Fiji. At Ugaga, hermit crabs were found to have removed the majority of shells from the midden and had deposited their old, worn shells in return. The behavioural ecology of genus Coenobita suggests a mutualistic interaction whereby humans make available shell and food resources to hermit crabs, which in turn provide a site cleaning service by consuming human and domestic waste. Diagnostic indicators of terrestrial hermit crab wear patterns on gastropod shells are outlined and the conditions under which extensive ‘hermitting’ of shell midden deposits may occur are investigated. The ability to recognise hermit crab modification of shells is considered not only important for archaeomalacologists analysing tropical shell deposits, but also for field archaeologists wishing to select suitable shell samples for radiocarbon dating.     

Focus: sulphur isotope variation in archaeological marine fauna from northern Europe

We undertook combined stable carbon, nitrogen and sulphur isotope analysis of marine and terrestrial faunal remains from two prehistoric coastal shell middens in Denmark. The aim of the investigation was to establish whether sulphur isotopes were useful in discriminating terrestrial and marine consumers in this region. We found that sulphur isotopes do separate marine and terrestrial fauna but, contrary to our expectations, we observed a negative correlation between δ³⁴S and δ¹³C values for marine fauna. We conclude that similar studies over a broader geographical range are needed before sulphur isotopes can be reliably used to study coastal resource exploitation.