Goffer, Z. 2007 Sediments and Soils. In Archaeological Chemistry: Second Edition: 209-229 Middleton W.D. 2004 Identifying Chemical Activity Residues on Prehistoric House Floors: A Methodology and Rationale for Multi-Elemental Characterization of a Mild

Acid Extract of Anthropogenic Sediments. Archaeometry 46(1): 47-65 Knudsen K.J., Frink L., Hoffman B.W. 2004 Chemical characterization of Arctic soils: activity area analysis in contemporary Yup’ik fish camps using ICP-AES: Journal of Archaeological Science

31: 43-456

Functional Activity Characterization in Sanak and Unalaska Soils Using ICP-MS Michael Smuin, Idaho State University, CAMAS

Humans leave characteristic impacts within soils in areas where they live. Characteristic residues are left in middens, hearths and houses, among others. Such impacts include site structures and soil signatures. Other factors such as predation, grazing, occupation intensity and time, and other environmental factors also impact the signature. Phosphorus is a primary indicator of human habitation. Additionally, multiple element analysis has be used to characterize functional activities in sites. This enables archaeologists to have a better idea of what is going on at a site before excavating; minimizing the use of larger exploratory excavations. Archaeological excavations are expensive and destructive. Because it is not always possible to immediately see areas of occupation by house and storage pits, archaeologists may use exploratory test pits to try find these areas. Sanak Island (Figure 1) is separated from Unalaska by several hundred miles. Only one site on Unalaska was sampled while 32 sites were sampled on Sanak. The sites on Sanak Island are located along its coastline.

This research project was supported by funding from the National Science Foundation (BCS 0821783 and OPP 0722771) and the Idaho State University Office of Research

Data analysis is incomplete; however, the analysis has provided the following conclusions: • The largest variation in the soil samples is due to middens. Due to the strong signature of

middens, midden are easier to find than other functional activities in the soil record. • The second largest variation in the soil samples was the island on which the soil was

collected. This is due to how intensely the Unalaska site was occupied in relation to Sanak and the difference in elemental concentrations in the natural soils.

• Due to variation in site occupation intensity, formation processes, and human error, identification of site features such as houses, house berms, and other functional activities will be difficult. Additional data analysis is needed to test the validity of functional activity identification with these soil data.

PROJECT BACKGROUND

Objective: • To assess the ability of using ICP-MS to efficiently differentiate functional activities on Sanak and Unalaska. Hypotheses : • Functional activities will leave characteristic signatures. • Due to site formation processes and variation in soils, the soil

signatures of Sanak and Unalaska should be statistically significant.

OBJECTIVE AND HYPOTHESES

MATERIALS AND METHODS

RESULTS

CONCLUSIONS

BIBLIOGRAPHY

LOGO

• DFA of all middens irrespective site or island correctly classified 92% of samples. • DFA on all sites by house berms, houses, house middens, middens, non, and house

floors classified 59% of the soils correctly. This increased to 73.4% when looking at a single site.

Figure 4. Elemental Variation across Sites

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Figure 1: Sanak Island from Google Maps

Materials: A total of 959 soil samples were collected from 32 sites on Sanak Island and one site on Unalaska. These soils were then oven-dried at 200⁰C for 48 hours. They were then sieved with a 2mm screen to remove large bones, wood, and other elements. About 0.2 grams of soil was then digested in 20 ml of 1N hydrochloric acid. Standards: NIST standard 71A consisting of 42 elements Equipment: ThermoFisher X series II ICP-MS. Methods: Soil Preparation: 100 μl of digested soil sample was diluted in 9.8 ml of 2% trace metal grade nitric acid. ICP-MS: The diluted soil samples were placed in racks and introduced to the ICP-MS. A blank and standards at concentrations of 10ppb, 100ppb, and 500 ppb bracketed every 30 soil samples. Concentrations of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Sr, and Ba were measured. The concentrations of each element were then evaluated for normality and log transformed.

Element PC1 PC2 PC3

27Al -0.03 0.221 -0.24

31P 0.479 -0.225 -0.465

43Ca 0.563 -0.186 0.198

47Ti -0.068 0.271 -0.301

55Mn 0.151 0.455 -0.228

57Fe -0.046 0.228 -0.25

59Co 0.01 0.336 -0.218

65Cu 0.203 0.484 0.55

66Zn 0.311 0.353 0.234

88Sr 0.489 -0.153 -0.033

137Ba 0.216 0.194 -0.275

%Variation 63.1 14.6 8.1

Figure 2: Diluted Soil Samples

Figure 3: ThermoFisher X Series ICP-MS

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Figure 6 Principal Component Analysis by Midden.

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Figure 7 Principal Component Analysis Island

Table 1: Component Loadings in Principal Component Analysis.

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Figure 5: Discriminant Function Analysis Results on Mg, P, Al, K, Ca, Ti, Mn, Fe, Zn, Sr, and Ba

• The results from principal component analysis show that the most variation, 63.1%, in the soil is the presence of middens, due to the loadings on P, Ca, and Sr from principal component analysis (Table 1). Islands accounted for the second most variation.