Archaeological Science Techniques
Behind the science
Diatoms species are indicative of a wide variety of environmental conditions (e.g. marine, brackish or freshwater) that reflect temperature, salinity (level of common salt in solution), pH (potential hydrogen), oxygen and mineral content (e.g. silica, phosphate, nitrate and iron). Their taxonomy and ecology are well known, with different species occupying the bottom of (benthic), or floating within (planktonic), water bodies (e.g. oceans, lakes, ponds, rivers, salt marshes, ditches), and living in soil and on trees.
Mollusca are preserved on land (e.g. soil and mires), and in freshwater (e.g. lakes), brackish water (e.g. high salt marsh) and marine (e.g. estuaries) sediments where there is an adequate amount of calcium carbonate. Mollusca have the potential to provide broad palaeoenvironmental reconstruction and may provide useful information on woodland clearance and land-use and human economy and diet.
Insects provide valuable information on regional and local environmental conditions, the local human environment, human and animal diet, and the function of archaeological features, condition of human and animal mummified remains, and the contents of offerings. These applications require detailed records of modern groups of insect species and their ecological preferences, and the ability to differentiate between those species indicative of the general environment (allochtonous species) and local area (autochtonous species).
Palynology provides valuable information on vegetation composition, structure and succession, plant migration, climate change, human modification of the natural vegetation cover and land-use and diet. They enable us to record vegetation succession due to natural processes, such as competition and climate change, and human activities, such as woodland clearance and cultivation.
Wood preserved by waterlogged conditions provides primary data on woodland composition, and hence vegetation history, woodland management, agricultural practices (e.g. fodder and bedding for animals), woodland exploitation for domestic fires (fuel), human impact on the natural environment, catastrophic, natural wild fires, material culture (wooden artefacts), time of woodland exploitation, local environmental conditions, preservation and bias in wood assemblages and technological sophistication.
In peat and alluvium, seeds are almost exclusively preserved in a waterlogged state. The seeds and their components (e.g. stems, leaves, buds) in peat and alluvium will represent either plants growing locally (autochthonous) or plants growing at an uncertain distance from the point of deposition (allochthonous). Analysed in conjunction with other proxies (e.g. pollen, insects), they may provide valuable information on climate change or vegetation history.
The presence of charcoal in archaeological and geological archives often provides useful information on natural wildfires (including climate history), human-induced woodland clearance, agricultural practices and woodland management. Distinguishing between human and natural fires is problematical, and often relies on supporting information from pollen and sedimentological studies.
Ostracods are aquatic invertebrates. Species are divided into two groups, those occupying the bottom of a water body and those within the the open water body. The benthic ostracods are found in freshwater and seawater, while the pelagic species are almost exclusively marine. They are highly sensitive to changes in salinity with three main assemblages identifiable: freshwater (<0.5‰ lakes, rivers and ponds), brackish water (0.5-30‰ lagoons and salt marshes) and marine (30-40‰ oceans and seas), as well as rainfall, temperature and alkalinity.
Phytoliths are produced by plant cells from silica and water. They have characteristic shapes which, for certain plant taxa, enables their identification. They are small and preservation occurs in dry, alkaline and aerobic conditions. These conditions may be found in several archaeological contexts, namely hearths and the sediment fills of caves, pits and coprolites. Phytoliths may provide valuable information on grassland (e.g. the presence of meadow and pasture), cultivation of crops (e.g. maize) and the presence of herbivores (e.g. within dung).
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. A wide variety of geochronological tools or methods can be employed to estimate quantitative and qualitative dating of rocks and sediments. Techniques exist to date all geological materials, from billions of years to historical records. U-series dating is the most reliable method for dating Quaternary (the last 2 million years) sedimentary carbonate, silica, and fossil material. Radiocarbon dating (14C) dates material with organic carbon, and has a maximum range of 100,000 years. Thermoluminescence (T-L dating) provides ages within a range of 100-800,000 years. Lead 210 (210Pb) has a short half-life, and dates material from the past 150-200 years.
Tephrochronology uses discrete layers of tephra (volcanic ash) from a single eruption, to create a chronological framework in which paleoenvironmental or archaeological records can be placed. Each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker. Tephra layers are deposited relatively instantaneously over a wide spatial area. This means they provide accurate temporal marker layers which can be used to verify or corroborate other dating techniques, linking sequences widely separated by location into a unified chronology that correlates climatic sequences and events.
Foraminifera are unicellular organisims and comprise a shell (test) composed either of secreted organic matter (tectin) and secreted minerals (alcite, aragonite or silica). All but a very few are aquatic and most are marine, the majority of which are marine and live on or within the seafloor sediment (benthic) while a smaller variety are floaters in the water column at various depths (planktonic). A few are known from freshwater or brackish conditions and some soil species have been identified. Over 10,000 species are recognized, both living and fossil. They are usually less than 1 mm in size. Formainifera are therefore useful indicators of changes in water depth, salinity and climate.
Archaeozoology or zooarchaeology is the analysis of animal remains within the archaeological record. The most common animal remains found within archaeological and geological archives are bones (e.g. fish, small and large mammals). Archaeozoology is the interpretation and association of animal remains with artefacts and people. It is focused around the recovery and analysis of animal remains in order to examine the physiology and ecology in relation to cultural activities. Major themes are animal domestication, exploitation, use patterns, butchery practices, and dietary contributions. Archaeozoology therefore focuses on human use of and impact of ancient animal populations, provides data on subsistence, dietary patterns and animal domestication.
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Quaternary Scientific, School of Archaeology, Geography and Environmental Science (SAGES),
The University of Reading, Whiteknights, PO Box 227, Reading, RG6 6AB, UK