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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Journal of Archaeological Science 39 (2012) 23e32 Contents lists available at ScienceDirect Journal of Archaeological Science journal homepage: http://www.elsevier.com/locate/jas Phosphates, plowzones, and plazas: a minimally invasive approach to settlement structure of plowed village sites Christopher I. Roos a,*, Kevin C. Nolan b a Department of Anthropology, PO Box 750336, Southern Methodist University, Dallas, TX 75275-0336, United States b Applied Archaeology Laboratories, Department of Anthropology, Ball State University, Burkhardt Building, Room 314J, Muncie, IN 47306, United States article info abstract Article history: Inferences about settlement structure play an important role in explanations of social and political Received 25 February 2011 change in Late Prehistoric eastern North America, but ethical and logistical challenges posed by extensive Received in revised form horizontal excavations mean that archaeologists must develop low cost, minimally invasive methods for 17 June 2011 investigating key properties of village structure. There are two important components of most villages in Accepted 23 June 2011 the region: 1) the peripheral distribution of middens; and 2) the size and location of formal communal spaces or plazas, each of which leaves traces in soil chemistry. In shallowly buried, plowed village sites Keywords: where artifacts have been physically displaced, the chemical signature of middens may be more resistant Phosphates Plowzone to disturbance and provide an enduring signature of ancient settlement structure. We conducted Fort Ancient a systematic soil phosphorus survey at the Reinhardt Site (33PI880) in central Ohio, the primary occu- Soil chemistry pation of which occurred during the Late Prehistoric Period (ca. AD 1200e1450), to test for the presence Middens and approximate size of a central plaza and the shape and distribution of peripheral midden deposits. Plazas Soil samples from the modern plowzone (N ¼ 131) were analyzed for Mehlich II extractable phosphorus Site structure using molybdate colorimetry. The interpolated phosphorus distributions indicate a clear ring midden approximately 90 m across with an internal plaza that is roughly 30 m  40 m. Artifact distributions from a shovel test pit survey and interpolations of plowzone magnetic susceptibility measurements identify the location of the village but are ambiguous with regards to village size and do not clearly distinguish the central plaza. Our results suggest that systematic surveys of soil phosphorus are a rapid, minimally invasive, and inexpensive method for generating data on the size and shape of villages and their plazas. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction (Bawaya, 2007), extensive horizontal excavations are increasingly unfeasible and undesirable. It is incumbent upon archaeologists to Settlement structure and village layout feature centrally in develop reliable methods for inferring settlement structure that archaeological inferences about past social organization. This is reduce the amount of destructive sampling needed to generate especially true for the Late Prehistoric Period (AD 1000e1600) in relevant data. the Ohio Valley (e.g., Cook, 2008; Means, 2007; Pollack and In many parts of the central, midwestern, and eastern United Henderson, 1992). Reconstructions of these features often rely on States, the long history of cultivation has destroyed many shallowly extensive horizontal excavations that reveal structures, features, buried (<60 cm deep) structures and features. Such post- and their spatial relationships. Such investigations are expensive, depositional disturbance can remove unambiguous traces of time-consuming, and may run counter to conservation ethics features within the plowzone and redistribute artifacts vertically (Lipe, 1974) and the principle of Stewardship espoused by the and laterally across the site (Dunnell and Simek, 1995; Lewarch Society for American Archaeology (Lynott and Wylie, 1995). and O’Brien, 1981). Although the impact of tillage on lateral arti- Indeed, in a post-NAGPRA world where archaeologists regularly fact movement can be profound (e.g., Navazo and Diéz, 2008), many engage with descendant communities (e.g., Mills et al., 2008)and experimental studies indicate that surface artifacts on plowed sites in which further collections only add to the “curation crisis” still provide valuable information (e.g., Dunnell and Dancey, 1983; Roper, 1976), including estimates of village location and size (e.g., Hawkins, 1998). In general, however, the lateral mobility of arti- * Corresponding author. Tel.: þ1 214 768 2753; fax: þ1 214 768 2906. facts, particularly large artifacts (e.g., Dunnell, 1990; Dunnell and E-mail addresses: [email protected] (C.I. Roos), [email protected] (K.C. Nolan). Simek, 1995; Lewarch and O’Brien, 1981; cf. Odell and Cowan, 0305-4403/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2011.06.033 Author's personal copy 24 C.I. Roos, K.C. Nolan / Journal of Archaeological Science 39 (2012) 23e32 1987), suggests that in order to identify intrasite patterns, such as 2. Background the size and shape of internal plazas, plowzone artifact distribu- tions should be complemented with datasets that are strongly 2.1. Settlement structure and society in the upper midwest linked with human activity and less vulnerable to lateral disturbance. Nucleated villages scattered across the floodplains and terraces In this paper, we describe geochemical survey techniques that of river systems were common during the Late Prehistoric Period in offer a valuable, minimally invasive approach for inferring settle- eastern North America. These sites vary in size and details of ment structure at shallowly buried, subsequently plowed sites. We organization, but throughout the Upper Midwest most are char- begin by briefly describing the importance of settlement structure acterized by a generalized doughnut shape with a domestic area for inferring social changes in Late Prehistoric eastern North surrounding a central open plaza (Cook, 2008; Dunnell, 1983; America followed by discussion of anthropogenic soil phosphates Dunnell et al., 1971; Graybill, 1981; Hart et al., 2005; Henderson, and their association with midden deposits. We suggest that 1992, 1998; Kennedy, 2000; Means, 2007; Pollack and Henderson, because anthropogenic phosphates are associated with fine-grained 1992, 2000; Redmond, 1994, 2003). Among the Late Prehistoric sediments, the phosphate record is less vulnerable to lateral trans-egalitarian societies of the Middle Ohio River Valley (i.e., Fort disturbance by tillage than are artifacts. Through a central Ohio case Ancient; Griffin, 1966), villages generally displayed a plaza- study (Reinhardt Site, 33PI880) we illustrate the value of systematic centered structure with socially important structures and features sampling of plowzone sediments for reconstructing key settlement in proximity to the village center. This is a pattern that is also features in a Late Prehistoric village (AD 1000e1600). We conclude exhibited by contemporaneous villages at on the fringes of nearby by discussing the implications of our strategy for improving Middle Mississippian chiefdoms (Fig. 1). At Fort Ancient sites, regional-scale knowledge of Late Prehistoric village size and layout. however, there is no clear evidence that political hierarchies Fig. 1. Approximate distributions of Middle Mississippian societies with hierarchical socio-political structures and trans-egalitarian Upper Mississippian societies in the eastern United States. Author's personal copy C.I. Roos, K.C. Nolan / Journal of Archaeological Science 39 (2012) 23e32 25 (Henderson, 1998; Schroeder, 2004) accompany variation in decomposes, organic P rapidly becomes “fixed” relative to other settlement size in the region (but see Cook, 2008: 126). ions as it is adsorbed on the surfaces of clay minerals or bound with Most of the well known Middle Ohio River Valley villages share iron or aluminum (in acidic soils) or calcium (in calcareous soils) to a distinctive internal structure. They are composed of concentric form Fe-, Al- or Ca-phosphate minerals (Bethell and Máté, 1989; rings of features and, although there is some organizational vari- Holliday and Gartner, 2007:344;Proudfoot, 1976). Allogenic ability within the habitation ring, refuse disposal was either con- phosphates from anthropogenic or natural inputs are most closely strained between the habitation ring and the palisades linked to the fine fraction of soils (Crowther, 1997: 99, 2002: 405; (Carskadden and Morton, 2000; Graybill, 1981), or interspersed Wells, 2010: 226). Therefore isolation of fine fraction improves the with the habitation ring around the plaza (Cook, 2008; Dunnell, likelihood of identifying anthropogenic