Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: www.elsevier.com/locate/jasrep The lay of land: Strontium isotope variability in the dietary catchment of the Late Iron Age proto-urban settlement of Basel-Gasfabrik, Switzerland David Brönnimann a, ⁎ , Corina Knipper b , Sandra L. Pichler a , Brigitte Röder c , Hannele Rissanen c,d , Barbara Stopp a , Martin Rosner e , Malou Blank f , Ole Warnberg g , Kurt W. Alt a,h , Guido Lassau d , Philippe Rentzel a a Integrative Prehistory and Archaeological Science, Basel University, Spalenring 145, 4055 Basel, Switzerland b Curt Engelhorn Centre Archaeometry GmbH; D6, 3; 68159 Mannheim, Germany c Ur- und Frühgeschichtliche und Provinzialrömische Archäologie, Departement Altertumswissenschaften, Basel University, Petersgraben 51, 4051 Basel, Switzerland d Archäologische Bodenforschung des Kantons Basel-Stadt, Petersgraben 11, Postfach, 4001 Basel, Switzerland e IsoAnalysis UG, Gustav-Müller-Straße 38; 10829 Berlin, Germany f Department of Historical Studies, University of Gothenburg, Box 200, 405 30 Gothenburg, Sweden g Institute of Anthropology, Johannes Gutenberg University, 55099 Mainz, Germany h Center of Natural and Cultural History of Man, Danube Private University, Steiner Landstr, 124, 3500 Krems, Austria ARTICLE INFO Keywords: Strontium isotopes Environmental samples Isotope mapping Biologically available strontium Land use patterns Iron Age ABSTRACT Basel-Gasfabrik (Switzerland) comprises an extensive La Tène (chiefly Lt D, 150–80 BCE) settlement and two associated cemeteries at which strontium ( 87 Sr/ 86 Sr) isotope analysis of human and animal teeth investigated regional and supra-regional contacts. The interpretation of the analytic data, however, requires information on the isotopic baseline values around the site. Using 102 modern vegetation and 9 water samples from 51 lo- calities, this study characterizes the isotopic ratios of the biologically available strontium of geological units and watercourses around Basel and compares these to 28 human infant, 6 pig, and 5 dog teeth from the site. Furthermore, pedological criteria evaluate the suitability of landforms for crop and pasturelands. The 87 Sr/ 86 Sr ratios of the environmental samples from geological units in up to 50 km distance varied between 0.70776 and 0.71794. Human infant teeth exhibited much more homogeneous 87 Sr/ 86 Sr ratios (0.70847–0.70950), which coincided largely with those of potential arable soils around Basel and indicate targeted exploitation of land- scapes for agriculture. The more variable values of the faunal teeth suggest more widely ranging habitats or imports from the site's hinterlands. Two local isotope ranges were defined based on archaeological enamel samples and modern vegetation data from a confined radius around Basel. The study documents the complexity of distinguishing local and non-local individuals in a geologically heterogeneous region as well as the potential of isotope analyses to explore prehistoric land-use patterns. 1. Introduction Strontium isotope ratios ( 87 Sr/ 86 Sr) are widely used to investigate mobility and migration in (pre-) historic communities (e.g. Chenery et al., 2010; Knipper et al., 2012; Neil et al., 2016; Nehlich et al., 2009), the origin of single human individuals and animals (e.g. Alt et al., 2013; Müller et al., 2003; Lamb et al., 2014; Tütken et al., 2004) or animal husbandry and land-use around settlements (e.g. Knipper, 2011; Stephan et al., 2012; van der Jagt et al., 2012). Strontium is a trace element, which commonly occurs in rocks (Bentley, 2006). It has four stable isotopes, of which the radiogenic isotope 87 Sr results from β- decay of 87 Rb (rubidium). Depending on the original rubidium content and the age of bedrock formations, the relative amount of 87 Sr varies among geological units, which is expressed as 87 Sr/ 86 Sr ratios. Due to weathering, strontium is released into the soil and ground water. From there it is biologically available, meaning that it can be taken up by plants and transported along food chains with very little isotopic frac- tionation. In humans and animals, strontium substitutes for calcium in the biogenic hard tissues of teeth and bones. While bones are constantly remodelled and also fairly prone to postdepositional alteration of the https://doi.org/10.1016/j.jasrep.2017.11.009 Received 28 July 2017; Received in revised form 5 November 2017; Accepted 8 November 2017 ⁎ Corresponding author. E-mail addresses: david.broennimann@unibas.ch (D. Brönnimann), corina.knipper@cez-archaeometrie.de (C. Knipper), sandra.pichler@unibas.ch (S.L. Pichler), brigitte.roeder@unibas.ch (B. Röder), hannele.rissanen@bs.ch (H. Rissanen), barbara.stopp@unibas.ch (B. Stopp), martin.rosner@isoanalysis.de (M. Rosner), malou.blank.backlund@gu.se (M. Blank), warnberg@uni-mainz.de (O. Warnberg), kurt.alt@unibas.ch, kurt.alt@dp-uni.ac.at (K.W. Alt), guido.lassau@bs.ch (G. Lassau), philippe.rentzel@unibas.ch (P. Rentzel). Journal of Archaeological Science: Reports 17 (2018) 279–292 2352-409X/ © 2017 Elsevier Ltd. All rights reserved. T