Clams and Climate

On March 2, 2015 By suzannebirchIn Research1 Comment

Christine Bassett is currently a graduate student working with Fred Andrus in the Department of Geological Sciences at the University of Alabama and holds a B.A. in Anthropology and a B.S. in Geology from the University of Georgia, US. This post is based on research for her M.S. in Geology at Alabama.

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Sclerochronology and Paleoenvironmental Reconstruction in the North Pacific Ocean

The archaeological record reflects fluctuating marine conditions from the Aleutian Islands to the Northwest coast of North America during the Late Holocene (Wanner et al., 2008). Though not widely tested, recent research suggests that conditions may have cooled enough during the Late Holocene cold phase to allow sea ice to accumulate as far south as the Northern Pacific Ocean. My research is focused on establishing sclerochronological analysis of Saxidomus gigantea as a means of detecting differences in sea surface temperatures in the Northern Pacific Ocean. Sclerochronological and isotopic analysis of skeletal carbonates can provide a proxy for sea surface temperatures as well as the length of seasons during the recent geological record. My research will contribute to a larger project focusing on human and animal adaptation to climate change led by Fred Andrus (Univerisity of Alabama), Catherine West (Boston University), and Mike Etnier (Portland State University) by providing an additional proxy for reconstructing environmental conditions in the Late Holocene.

Figure 1. Cross-section of mature shell, age seven years, magnification 10x. The arrow denotes the distance between two annual winter growth lines (modified from Hallmann et al., 2009).

Sclerochronology is the study of the growth of invertebrate skeletons. I work exclusively with bivalves, whose distinct growth lines mark regular biologically and environmentally controlled growth intervals (Hallmann et al., 2009). Isotopic analysis of oxygen (δ18O) from growth lines can identify winter growth bands between successive growing seasons. Nadine Hallman and her colleagues (2009) examined the life history of S. giganteus and compared shell precipitation during the organism’s life with oxygen isotopic analysis. They determined that dark bands (Fig. 1) largely co-occurred with peaks in δ18O (Fig. 2). These dark bands mark the beginning and end of a season of growth and the interval between them represent the length of one growing season.

Oxygen isotope variation — Figure 2. Upper: Shell oxygen isotope record (δ18O, black bars) compared with reconstructed temperature (Tδ18O, light grey curve) and sea surface temperature (SST, dark grey curve) data collected from http://www.cdc.noaa.gov. Lower: Daily growth increment width time series (n = number of increments per year. The blue bars represent the annual winter growth lines measured in (A). Positive δ18O values correspond with winter growth lines while negative δ18O were sampled from the portion of the shell between winter growth lines. Oxygen isotope data confirms annual winter growth lines. Specimen collected September, 9 2007 (modified from Hallmann et al., 2009).

Measuring and comparing the lengths of seasonal shell growth from shells collected at higher latitudes with shells collected from slightly lower latitudes could provide a means of assessing changes in the length of growth seasons, possibly indicating differential sea surfaces temperatures between latitudes. Applying this method to ancient archaeological shells would allow me to test for changes in the length of growing season and by extension, the presence of cold conditions – and possibly sea ice – in the Northern Pacific Ocean during the Late Holocene.

Map of the study area (Alaska) — Figure 3. Collection sites have not yet been determined. Potential site candidates are located along the Gulf of Alaska and include Unalaska (A) and Kodiak Islands (B), Alaska and Dundas Island, B.C. (C) (modified from NASA satellite image).

Winter growth line in S. gigantea — Figure 4. Image of winter growth line in an acetate peel made from S. gigantea cross-section at 40X magnification (Personal image by Bassett, 2014).

To accomplish this, I plan to collect samples of Saxidomus gigantea from Alaska and Northern British Columbia (Fig. 3). I will analyze δ18O profiles across the organism’s second or third year of growth, the most ontogenetically reliable period of growth, to determine that winter growth bands correspond to peaks in δ18O so that later sclerochronological analysis can be performed. For sclerochronological analysis, I will prepare acetate peels (Fig. 4) so that I can then count lunar-daily growth lines between winter growth bands to quantitatively measure the length of the growing season. Assuming I can detect a difference in the length of the growing season between samples collected at different latitudes, I will apply the same method to ancient samples from the same regions. If the method tested here is successful, sclerochronological analysis of bivalves may be able to contribute to δ18O data interpretation and comparative studies with other organisms to provide a more comprehensive view of changes in SST through recent geological history. Understanding climate in the past contributes greatly to archaeological research that seeks to understand how human behavior, particularly the exploitation of floral and faunal resources, changes as components of the environment change.

REFERENCES

Hallmann, N., Burchell, M., Schone, B.R., Irvine, G.V., Maxwell, D., 2009, High-resolution sclerochronological analysis of the bivalve mollusk Saxidomus gigantea from Alaska and British Columbia: techniques for revealing environmental archives and archaeological seasonality. Journal of Archaeological Science, v. 36, pp. 2353-2364.

Wanner, H., Beer, J., Butikofer, J., Crowley, T.J., Cubasch, U., Fluckiger, J., Goosse, H., Grosjean, M., Joos, F., Kaplan, J.O., Kuttel, M., Muller, S.A., Prentice, C., Solomina, O., Stocker, T.F., Tarasov, P., Wagner, M., and Widmann, M., 2008, Mid- to Late Holocene climate change: an overview. Quaternary Science Reviews, v. 27, no. 19-20, pp. 1791-1828.

From the Balkans to Barbuda

On June 26, 2014 By suzannebirchIn ProjectsLeave a comment

A number of new and exciting projects are focused on incorporating several techniques in zooarchaeology, including stable isotope analysis, to better understand the complex and intertwined history of humans and certain animals. In this post, Dr. Holly Miller shares some of the goals of one such ongoing research scheme: The Fallow Deer Project.

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The Fallow Deer Project

The Fallow Deer Project is an AHRC-funded multi-disciplinary study looking at the cultural history of Dama dama dama, the European fallow deer. As one of two Research Fellows on the project, my role is to investigate the biogeography and management of fallow deer through time. To do this, I am using a combination of isotope analyses (C, N, Sr, S, O) to look in depth at the archaeological remains of ancient and modern fallow deer populations, investigating questions related to the importation of animals, founding herds and changing management practices. Were fallow deer domesticated? Under what circumstances were fallow deer established across Europe? How do human-Dama relationships reveal worldview?

The Fallow Deer Project Logo

No other species of deer has a closer relationship to people than the European fallow deer, and it is becoming clear that this has been the case for millennia. Since the Neolithic, humans have selectively transported and maintained these elegant animals, moving herds from their native, post-glaciation, range in the eastern Mediterranean, across Europe and eventually the globe. Fallow deer are now one of the world’s most widely-naturalised animals. Wherever they have been introduced they have altered the physical and psychological landscape, and their distribution is a direct record of human migration, trade, behaviour and ideology. In combination with studies of archaeology, history, geography, anthropology, genetics, and osteological research, isotope analysis is being used reveal the cultural significance of the fallow deer as they moved from the Balkans to Barbuda, and everywhere in between.

The project is led by Dr Naomi Sykes (University of Nottingham) Prof. Rus Hoelzel (University of Durham) and Prof. Jane Evans (British Geological Survey). The team are working with researchers from a number of fields and institutions up and down the UK- from archaeologists and art historians, to musicians and deer stalkers.

Web: http://www.fallow-deer-project.net

Tweet: @DeerProject

Make use of/contribute to our deer bone database: http://www.nottingham.ac.uk/zooarchaeology/deer_bone/search.php

Climate in Your Dinner

Our latest contributor is Georgia Roberts. Georgia is currently in the second year of her PhD at La Trobe University, Melbourne, Australia, and holds a Masters in Archaeological Science from Australian National University.

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Investigations of Seasonality in the Archaeological Record of Southwestern Tasmania, Australia

Stable isotope analysis can support a range of zooarchaeological research. One such application is investigating seasonality – assessing the season of death of individual animals. When these animals are associated with archaeological sites, we can use this data to infer season of site use.

The rugged limestone karst landscape of southwestern Tasmania, Australia, contains several archaeological cave sites with exceptional preservation. This region has been described as an archaeological ‘province’ sharing many characteristics, including distinctive faunal collections, dominated by Bennett’s wallaby (70% by Minimum Number of Individual [MNI] counts) and the Common Wombat (27% MNI). The current project focusses on two of these sites – Warreen Cave and Bone Cave.

Related archaeological sites in southwestern Tasmania. Adapted from Cosgrove et al. 2010.

The wilderness of southwestern Tasmania.

Wombat teeth are continuously growing, capturing the isotopic signature of the surrounding environment in the enamel as it forms. The mandibular incisor is the longest tooth (6-7cm) and records approximately 18 months of isotopic data. By sequentially sampling the enamel, a high-resolution record of local climate (δ¹⁸O) and vegetation (δ¹³C) can be retrieved. By assessing seasonal variation in modern analogues, the data can be used to determine season of death and thus inferred season of site use.

Sequential sampling of tooth enamel along the mandibular incisor from a modern Common wombat.

Dr Anne Pike-Tay and colleagues (Pike-Tay et al. 2008) used odontochronological analysis to identify that Bennett’s wallabies, the primary prey species, had been killed in the same season throughout the chronology of each site – autumn/winter for Warreen Cave and summer for Bone cave. My PhD uses stable isotopic analysis of Common wombat (Vombatus ursinus) teeth to test this trend, investigating when and how wombats were being utilised by Tasmanian Aboriginal people at the end of the Pleistocene (35,000 to 11,500 years ago).

Tasmanian Common Wombats – female with joey.

This research is supported by the La Trobe University Faculty of Humanities and Social Sciences Internal Funding Scheme, the Australian Archaeological Association Research Grant Scheme and Dr Michael Gagan of the Earth Environment Stable Isotope Laboratories (Australian National University).

References

Cosgrove, R., Field, J., Garvey, J., Brenner-Coltrain, J., Goede, A., Charles, B., Wroe, S., Pike-Tay, A., Grün, R., Aubert, M., Lees, W., O’Connell, J., 2010. Overdone overkill – the archaeological perspective on Tasmanian megafaunal extinctions. Journal of Archaeological Science 37, 2486–2503.

Pike-Tay, A., Cosgrove, R., Garvey, J., 2008. Systematic seasonal land use by late Pleistocene Tasmanian Aborigines. Journal of Archaeological Science 35, 2532–2544.

On May 27, 2014 By suzannebirchIn ResearchLeave a comment

Introducing the i-bone Project

On April 30, 2014 By suzannebirchIn ProjectsLeave a comment

This contribution comes from Dr. Thomas Doppler, who is based at the University of Basel, Switzerland, at the Integrative Prähistorische und Naturwissenschaftliche Archäologie (IPNA) (Integrative Prehistory and Archaeological Science) and the Department of Environmental Sciences. We’ve also added the IPNA to our list of stable isotope facilities-get in touch if we’re missing yours!

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Isotope analysis of well dated cattle and red deer bones from Swiss Neolithic lakeshore settlements as indicator for herd management, dairying, environment and human impact

The project (April 2013 to March 2016, based at the University of Basel, Switzerland) aims at studying cattle economy and cattle management on one hand and human impact on the red deer population on the other, as represented in the archaeology of the Swiss lakeshore dwellings.

Organic remains are well preserved at the site of Arbon Bleiche 3. Photograph: © Amt für Archäologie Thurgau, Daniel Steiner.

These dwellings – dated between 4300 and 2400 BC – have the richest and most detailed archaeological record in Europe, and provide a unique background for the examination of models of subsistence, intensification, cultural adaptations to climatic changes and human impact to the prehistoric environment. Waterlogged deposits have preserved many organic remains such as wood, seeds, animal dung; and hundreds of thousands of animal bones have been recovered. Based on dendrochronology the archaeological finds can be dated precisely at least to decades but even to single years, allowing a longitudinal study with unprecedented time resolution.

We focus our research on the eastern area of Switzerland, especially on the lakeshore settlement of Arbon Bleiche 3 at Lake Constance and sites in the lower Lake Zurich region, where vast and well documented archaeozoological collections cover a long chronological sequence of settlements in a small and clearly defined region.

Map showing the location of the study sites in Switzerland, including Arbon Bleiche 3 at Lake Constance and a range of sites in the lower Lake Zurich region. Figure: © IPNA, Thomas Doppler.

The research questions will be addressed using carbon, nitrogen, oxygen and strontium isotope analyses on animal bones and high-crowned cattle and deer molars.

The project is financed by Swiss National Science Foundation and supported by different institutions in Switzerland, Germany and Great Britain. For further information see www.i-bone.ch

Rethinking Mycenaean Economy

On March 19, 2014 By suzannebirchIn ResearchLeave a comment

Stable isotope analysis in zooarchaeology is an exciting–and growing–research area, with the potential to inform and expand on a multitude of questions about humanity in the past, present, and future.

Part of the mission of the working group and the purpose of our blog is to share ongoing research in this area with a wider audience. To that end, we’re launching a series of posts on current projects combining zooarchaeology and stable isotope analysis in innovative ways around the world and in all time periods. If you would like to contribute a post on your research, you can email suzanne_birch [at] brown.edu. Comments and questions on posts are welcomed and encouraged!

Our first post is by Gypsy Price, who is currently a PhD candidate in the Anthropology Department at the University of Florida. Her research uses stable isotope analysis to reveal differences in faunal economies in early complex societies, specifically Late Bronze Age (LBA) Mycenae, Greece. Thanks Gypsy!

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Faunal Economy at Petsas House

View of Mycenae, with a plan of the citadel and location of Petsas House indicated by the red circle.

Five years ago I got involved with the Petsas House Project, a domestic/industrial structure located downslope from the citadel of Mycenae dating to the Late Helladic III A2 (circa 1300 BC). Around the same time I had become increasingly captivated by Galaty and Parkinson’s “Rethinking Mycenaean Palaces” series which critically examined the extent, degree, and manner of economic authority engendered by Mycenaean palaces. Bottom line, the majority of our knowledge about Mycenaean economy is based on Linear B tablets, which are geographically, temporally, and topically restricted: they have only been recovered from a handful of palatial sites, and record only transactions of interest to palatial administration occurring in the months prior to their deposition. As a result, economic models have been constructed from the top down, resulting in a myopic sense of the movement of resources within the larger society and an artificial inflation of the influence of the palace.

Through isotopic survey, we can discern feeding groups that may be indicative of disparities in provisioning or foddering strategies, and patterns of importation of animals. It was here where I realized that the extremely well-preserved and extensive faunal assemblage at Petsas House could offer a unique, micro-scalar perspective on management and distribution of faunal resources in an extra-palatial industrial/domestic context with a palatial settlement. Furthermore, there was an available contemporaneous faunal assemblage which had been previously excavated from the Cult Center, an ideological complex located within the walls of the hilltop citadel.

Gypsy Price with Petsas House materials.

Thus, with the invaluable support of Dr. Kim Shelton (UC Berkeley) and my committee chair, Dr. John Krigbaum (University of Florida), my PhD research was born. My sample set includes four main species known to have been purposefully managed during the LBA: goat, sheep, cow, and pig/wild boar. I am using carbon (δ¹³C), nitrogen (δ¹⁵N), and oxygen (δ¹⁸O) ratios from bone collagen and bone apatite fractions to identify discrete inter- and intra-taxonomic feeding groups. Strontium (⁸⁷Sr/⁸⁶Sr) and oxygen (δ¹⁸O) isotope ratios from bone and serially sampled teeth are being used to identify season movement patterns and to look for evidence of extra-local individuals which may be indicative of importation. I am currently in the process of interpreting the structured variation in these data to elucidate some of the nuances of LBA Mycenaean faunal economy, allowing us to develop a “ground-truthed” model of management and distribution between disparate sectors of a single LBA Mycenaean palatial settlement for the first time.

Stable Isotopes in Zooarchaeology

Tag: oxygen