Research Article Geochemical Characterization of Bolivian Formative Earthen Architecture by Wavelength-Dispersive X-ray Fluorescence Melissa A. Goodman-Elgar, 1, * Nichole S. Bettencourt, 1 and Richard Conrey 2 1 Department of Anthropology, Washington State University, Pullman, Washington 2 School of the Environment, Washington State University, Pullman, Washington Correspondence * Corresponding author; E-mail: mage@wsu.edu Received 5 June 2013 Revised 29 July 2014 Accepted 30 July 2014 Scientific editing by Steven Shackley Published online in Wiley Online Library (wileyonlinelibrary.com). doi 10.1002/gea.21500 In this study, we employ wavelength-dispersive X-ray fluorescence (WDXRF) to characterize construction materials from Formative civic architecture (1000 B.C.E.–C.E. 400), ethnographic mudbricks, and off-site controls from the Taraco Peninsula, Bolivia. The preparation of earthen construction mate- rials for civic buildings can shed light on aspects of community development such as labor organization, resource management, and architectural technolo- gies. We apply geochemical results to reconstructing how public buildings were made as communities moved toward socio-political complexity in this region. However, there are few geochemical studies in the Andes, and little prior sci- entific analysis of earthen architecture. We therefore tested the efficacy of WDXRF for this region, and developed control materials. Our archaeological samples were selected from two Formative villages, Chiripa and Kala Uyuni. In this study, we performed WDXRF analyses on 63 archaeological and con- trol samples including archaeological floors, walling, plasters, and mortars, as well as contemporary ethnographic walling and topsoils. Elemental signatures for 28 elements clearly distinguished the archaeological flooring, walling, plas- ter, and mortars from ethnographic and off-site controls. More subtle varia- tions were detected that distinguish study sites and the different material types. Laboratory-calibrated multi-element XRF effectively supports efforts to recon- struct the pathways to social complexity in the Titicaca Basin. C  2014 Wiley Periodicals, Inc. INTRODUCTION In this study, we determined geochemical signatures of archaeological and ethnographic earthen building mate- rials from the Taraco Peninsula, Bolivia by wavelength- dispersive X-ray fluorescence (WDXRF). The Taraco Peninsula was home to the Chiripa culture, which un- derwent dramatic social changes during the Formative period from small foraging communities to large villages with monumental architecture (Hastorf, 1999, 2003; Stanish, 2003; Bandy, 2004, 2006; Hastorf et al., 2008). In this region, pathways to social complexity are evi- dent in increasingly elaborate material culture, partic- ularly polychrome ceramics, found in association with civic-ceremonial architecture including courtyards, tell mounds, and special purpose rooms (Chavez, 1988; Has- torf, 1999; Bandy & Hastorf, 2007; Roddick, 2009). The earthen materials used to build these structures are an- thropogenic media that were prepared according to cul- turally proscribed traditions of practice. We sought to quantify observable differences in different classes of con- struction material and to compare these between two ma- jor sites, Chiripa and Kala Uyuni. In reconstructing the composition of these materials, we hope to contribute to reconstructions of the social changes Taraco communi- ties underwent as they became more populous and cen- tralized during the period in which they developed social hierarchies. In the absence of prior geochemical studies of ancient architecture, this study marks the first application of geo- chemical approaches to the characterization of earthen construction materials for the Andes. We therefore initi- ated this project with a well-established bulk technique in order to determine if the geochemical characteristics 32 Geoarchaeology: An International Journal 30 (2015) 32–58 Copyright C  2014 Wiley Periodicals, Inc.