Why a Standardization of Strontium Isotope Baseline Environmental Data Is Needed and Recommendations for Methodology

Abstract

Since initial applications of strontium isotope human sourcing in the early 1990s, the use of the method has steadily increased in archaeology and in anthropology more broadly. Despite this trend, the collection of necessary baseline environmental data has not been standardized and sometimes does not occur at all. A thorough environmental sampling strategy will ensure that all the variability within a selected region is documented, which is a critical step to improving the accuracy of sourcing studies. Furthermore, shared strontium baseline data collections are needed to improve the intercomparability of datasets and results. This paper provides a case study from a semiarid region in northwestern New Mexico, USA, highlighting the need for a bottom-up approach to baseline data collection (from bedrock to animal) and describes the methods of pre-field planning and collecting, including rationales for what samples to collect for Sr isotope baseline data. The authors hope that this paper will lay a foundation for the implementation and standardization of Sr isotope baseline data collecting, which does not currently exist.

Ølby Woman:

“…However, there is as yet no consensus regarding which type of proxy (e.g., surface waters, plants, soils, fauna, etc.) is the most suitable for delineating the isotopic range of bioavailable strontium signatures of an area (Grimstead et al 2017). For the area of Zealand (where the Ølby Woman was buried), several baselines have been established based on different types of environmental samples including surface waters, soil samples and faunal remains , Frei 2013, Frei and Price 2012, Price et al 2011, Price et al 2007).…”

87Sr/86Sr and trace element mapping of geosphere-hydrosphere-biosphere interactions: A case study in Ireland

“…To avoid contamination by modern day fertilisers, samples were taken from forested, non-agricultural land. The sampling methods followed in this study were adapted from those outlined by the British Geological Survey (BGS) (Johnson et al, 2005;Smyth, 2007) and adhere to the proposed standardised field methods specifically for 87 Sr/ 86 Sr (Grimstead et al, 2017).…”

Isotope values of the bioavailable strontium in inland southwestern Sweden—A baseline for mobility studies

“…The uptake of Sr in humans and animals is mainly controlled by Sr in plants, animals and drinking water coming from a certain area, or from a number of areas visited during a period of time. As discussed above, the Sr isotope ratios characteristic of these different sources can vary and so do the Sr concentrations ([ 82 ]: 187). Strontium concentrations are generally higher in plants than in meat, and some researchers argue that most Sr in humans originates from plants while the contribution from animals is of less importance [ 49 ].…”

“…There is at present little consensus on what proxy to use, and the choice of proxy material has been debated [ 28 , 31 , 49 , 72 , 76 , 82 , 84 ]. Ongoing methodological development, economical resources, availability and accessibility are some important factors in this choice.…”

“…Often, isotope studies include several different sample types. Grimstead, Nugent and Whipple [ 82 ] advocate a broad sampling strategy of soil, archaeological fauna, vegetation and water to map the Sr isotope system. However, these authors recognize and encourage that current provenance investigations have shifted away from utilizing animals to create baselines [ 82 ].…”