What We Do: Investigations

Final Report: Rio Nuevo Archaeology, 2000–2003

This report presents summaries and interpretations of the archaeological features, artifacts, and historical data uncovered during the Rio Nuevo Archaeology program conducted in downtown Tucson between 2000 and 2003 for the City of Tucson. Several major archaeological sites were investigated, including the San Agustín Mission and Mission Gardens, the Tucson Presidio, the Tucson Brickyard, the prehistoric Clearwater site, and numerous historic and prehistoric canals. The report includes 22 chapters and several appendices. Each chapter and appendix is self-contained—including text, figures, tables, and references—and can be downloaded individually.

Individual chapters and appendices can be cited by their titles as sections in the volume:
2006 – Rio Nuevo Archaeology Program, 2000–2003: Investigations at the San Agustín Mission and Mission Gardens, Tucson Presidio, Tucson Pressed Brick Company, and Clearwater Site. Technical Report No. 2004-11. Center for Desert Archaeology, Tucson, Arizona.
J. Homer Thiel and Jonathan B. Mabry (editors)

Front Matter (PDF format, 197.11 KB)

  • Rio Nuevo Archaeology Program, 2000–2003: Investigations at the San Agustín Mission and Mission Gardens, Tucson Presidio, Tucson Pressed Brick Company, and Clearwater Site.
  • Edited by J. Homer Thiel and Jonathan B. Mabry
  • Contributions by Jenny L. Adams, Judi L. Cameron, Sergio F. Castro-Reino, Owen K. Davis, Robert Dayhoff, Beth DeWitt, Michael W. Diehl, Elizabeth Eklund, Douglas Gann, Gwen Harvey, James M. Heidke, Jennifer Kahn, Thomas Klimas, Vince M. LaMotta, Carlos P. Lavayen, Jonathan B. Mabry, John McClelland, Kyle McKoy, Elizabeth J. Miksa, Caroline Ogasawara, Manuel R. Palacios-Fest, Barnet Pavao-Zuckerman, Annamarie Schaecher, Peter D. Schulz, M. Steven Shackley, R. Jane Sliva, Susan L. Stinson, J. Homer Thiel, Arthur W. Vokes, Jennifer A. Waters, and Caramia Williams.

Chapter 1 – An Overview of the Rio Nuevo Archaeology Project, 2000–2003 (PDF format, 41.59 MB)

  • Between October 2000 and January 2003, Desert Archaeology, Inc., conducted archaeological investigations at seven locations for the City of Tucson as part of the Rio Nuevo Archaeology project. Hundreds of cultural features were excavated, with more than 160,000 artifacts recovered. This work documented 4,100 years of occupation and 3,500 years of irrigated agriculture in the floodplain of the Santa Cruz River just west of downtown Tucson, Arizona. Some well-preserved remains of the late eighteenth century Spanish period mission and mission gardens were also revealed on the western side of the river, as was a portion of the Tucson Presidio—founded in 1775—on the eastern side. These findings establish Tucson as one of the oldest continuously occupied settlements in the United States.

Chapter 2 – Excavation Methods (PDF format, 113.93 KB)

  • From October 2000 through February 2003, archaeological testing and excavations at seven major locations within or close to downtown Tucson were conducted by Desert Archaeology, Inc. Two of the areas—one at the southeastern corner of Congress Street and Interstate 10 (I-10), and the other on the southern side of Congress Street west of I-10—are scheduled to be developed for new residences, businesses, and museums. The City of Tucson plans to create cultural parks at the three other locations—the San Agustín Mission, the Mission Gardens, and the Tucson Presidio, AZ BB:13:13 (ASM).The archaeological research conducted for the Rio Nuevo Archaeology project had several goals, including the mitigation of archaeological resources in areas where development was to occur. Work in the planned cultural parks documented the range of cultural resources present, and identified areas damaged by previous ground-disturbing activities. Selected features were also sought that would guide the planned reconstructions. Finally, artifacts and historical information was sought that will be used in future exhibits.

Chapter 3 – Cultural History of the Tucson Basin and Project Area (PDF format, 147.56 KB)

  • Over the past 100 years, archaeologists have documented the long history of human activities in southern Arizona. Excavations ranging from Paleoindian mammoth kill sites to 1940s trash dumps have allowed reconstruction of the prehistory of the region and added depth to understanding of the Historic period. A basic outline of the cultural history of the region and a discussion of previous research in the project area are presented in this chapter.

Chapter 4

Chapter 5 – Artifact Summaries and Analysis Sampling Strategies (PDF format, 146.78 KB)

  • A large number of artifacts were discovered over the course of the Rio Nuevo archaeological fieldwork, ranging in age from about 4,100 years old to the 1950s. Unfortunately, many of the artifacts were discovered in poor contexts—features damaged by rodents or later human activities, or truncated by the historic-period plowzone. A decision was made to limit analyses to samples from the best-preserved features that would provide data to address the research questions raised in the proposal submitted to the City of Tucson.The numbers of artifacts recovered from excavated features are provided in this chapter, including overall counts by site locus and time period. The sample sizes relative to the total numbers of artifacts recovered are summarized in Table 5.1. Contexts and research issues are identified for the analyzed samples from each temporal component at each site locus. Chapters 6 through 18 provide additional information about the artifacts, plant remains, faunal bone, shell, and human remains recovered during the Rio Nuevo Archaeology project.

Chapter 6 – Petrographic Analysis of Pottery for the Rio Nuevo Project, with a Case Study of Temporal Trends in Historic Period Native American Pottery Production (PDF format, 2.41 MB)

  • Petrographic modal analysis, or point counting, is a detailed microscopic analytical technique used to establish the mineralogical composition of a rock or sediment. It has been used extensively to establish composition and provenance of archaeological ceramics, especially in the Greater Southwest. For the Rio Nuevo Archaeology project, 56 sherds from the Clearwater site, AZ BB:13:6 (ASM), and the Tucson Presidio, AZ BB:13:13 (ASM), were selected for petrographic analysis to establish their provenance and to verify the temper characterizations provided by ceramicist James M. Heidke. The sherds are a subset of the 2,373 sherds chosen for detailed ceramic analysis (Chapter 7, this report). They comprise plain and red wares from prehistoric and historic contexts.

Chapter 7 – Native American Pottery (PDF format, 5.89 MB)

  • Prehistoric and Historic Native American pottery was recovered from three archaeological sites investigated as a part of the Rio Nuevo Archaeology project. A total of 17,073 sherds was recovered from the Clearwater site, AZ BB:13:6 (ASM), with 9,790 of those sherds recovered from features located at the San Agustín Mission locus of the site, 4,226 sherds from the Mission Gardens locus, and 3,057 sherds from the Congress Street and Brickyard loci. Another 950 sherds were recovered from canal features at AZ BB:13:481 (ASM). Finally, a total of 8,704 sherds was recovered from features located at the Tucson Presidio/Block 181, AZ BB:13:13 (ASM). Analysis focused on identifying sherds of Early Agricultural period incipient plain ware pottery, regardless of recovery context, and temporally unmixed deposits of prehistoric, Spanish, Mexican, and American Territorial period O’odham pottery.

Chapter 8 – Human Figurines (PDF format, 106.12 KB)

  • The Rio Nuevo sites yielded a total of 49 fired-clay objects, including 44 artifacts that could be identified as portions of fired clay human figurines. These artifacts were recovered from both an early site, Clearwater, AZ BB:13:6 (ASM), and a site occupied later in time, the Tucson Presidio site, AZ BB:13:13 (ASM). The majority, however, were found at the Clearwater site. Stylistically simple and with little decoration, researchers often link such figurines with fertility or cult rituals that may have been based in the household, or on a larger community-wide scale. Other possible functions included use as charms in healing rituals, use in rituals honoring family ancestors, and as toys.

Chapter 9 – Ground Stone Artifacts (PDF format, 1.63 MB)

  • The stone items considered in this chapter include traditional tools such as manos, metates, and axes, as well as the raw materials selected for tool manufacture, pigments, and minerals collected for pigment production or ornament manufacture – that is, anything that has been shaped through impaction or grinding, and anything that has been used to impact or grind, essentially any stone item not considered flaked. A total of 1,206 items thought to fit this definition were recovered during the Rio Nuevo Archaeology project. Of this total, 260 (22 percent) items were chosen to examine the nature of the activities that involved the use of ground stone artifacts and their raw materials at the Clearwater site, AZ BB:13:6 (ASM), and the Tucson Presidio, AZ BB:13:13 (ASM).

Chapter 10 – Flaked Stone (PDF format, 1.8 MB)

  • The Rio Nuevo flaked stone analysis focused on materials recovered from several loci of the Clearwater site, AZ BB:13:6 (ASM): (1) the earliest occupations at the Congress Street locus; (2) two Agua Caliente phase features from the Mission Gardens locus; and (3) one Spanish period O’odham feature at the Mission locus. The earliest assemblage is the most recent addition to the large body of data about the Unnamed interval of the Early Agricultural period (2100–1200 B.C.). The Clearwater site artifacts provide the first opportunity to investigate technological behaviors from different locations within the floodplain of the Santa Cruz during this previously inadequately understood interval. Similarly, literature about the flaked stone technology utilized by Pima populations in the Tucson area is virtually nonexistent; the Piman lithic assemblage is limited, but it is significant for beginning explorations of this time period.

Chapter 11 – Shell Artifacts (PDF format, 273.86 KB)

  • Recent excavations at sites within the Rio Nuevo development area in the west-central Tucson Basin—the Clearwater site, AZ BB:13:6 (ASM); the Tucson Presidio, AZ BB:13:13 (ASM); and AZ BB:13:481 (ASM)—resulted in the recovery of an assemblage of 1,366 pieces of shell, estimated to represent approximately 867 individual items. Although much of the collection is dominated by freshwater and terrestrial mollusks, a number of marine specimens are also present. This collection reflects an occupation that extends back to the Early Agricultural period, and that continued intermittently into recent historic times.

Chapter 12 – Historic Era Artifacts (PDFformat, 5.67 MB)

  • A large number of Historic-era artifacts were recovered during archaeological work at the San Agustín Mission locus, AZ BB:13:6 (ASM), and the Tucson Presidio site, AZ BB:13:13 (ASM). Analysis focused on three assemblages: 1) Spanish- and Mexican-period artifacts from the Tucson Presidio; 2) American Territorial period items from the Tucson Presidio; and 3) the artifacts found in a well filled in by Chinese gardeners at the Mission locus.

Chapter 13 – Faunal Remains (PDF format, 914.55 KB)

  • Large numbers of animal bones were found during the Rio Nuevo Archaeology project. Analysts examined a sample of the bones to determine how humans utilized animals over the course of the last 4,000 years. Analyses focused on animal bone from: 1) prehistoric contexts at the Clearwater site, AZ BB:13:6 (ASM), and the Tucson Presidio, AZ BB:13:13 (ASM); 2) features at the Tucson Presidio dating to the Spanish, Mexican, and American Territorial periods; 3) an 1890s Chinese gardeners’ well at the San Agustín Mission locus, AZ BB:13:6 (ASM); and 4) Spanish-period Piman (O’odham) features at the Mission locus.

Chapter 14 – Plant Remains from the Clearwater Site (PDF format, 158.65 KB)

  • The archaeological effort associated with the Rio Nuevo Archaeology project resulted in the recovery and analysis of plant remains from 274 flotation samples. The data collected from this project provided an opportunity to test previous studies that document a series of trends in plant use spanning an interval of approximately 3,200 years. The plant assemblage discussed in this report substantiates earlier findings that Early Agricultural period (2100 B.C.–A.D. 50) subsistence efforts incorporated a wide range of wild plant taxa in an effort to minimize risks associated with floodplain farming. During the first millennium A.D., crops quickly displaced wild foods as subsistence efforts became highly focused on floodplain farming, reducing or eliminating the use of previously important wild plants. Upon the arrival of colonizing Spaniards and, later, emigrating Euro-Americans and Chinese, a host of new crops, ornamental trees, and weeds were brought in. These newly introduced Old World taxa greatly expanded the range of resources available to people living in the Tucson Basin.

Chapter 15 – Pollen Analysis of the Clearwater Site (PDF format, 245.98 KB)

  • Pollen analysis of 52 sediment samples from the Clearwater site, AZ BB:13:6 (ASM), was conducted as part of the Rio Nuevo Archaeology project. The analysis confirms some patterns in the regional archaeological pollen record and also identifies some new features. Some shifts in the represented plant taxa indicate fluctuations in water table levels related to climatic changes or intensive irrigation.

Chapter 16 – Analyses and Interpretations of Canal Ostracodes (PDF format, 1.63 MB)

  • In the Santa Cruz floodplain near downtown Tucson, the Rio Nuevo Archaeology project documented several canals dating between 1500 and 100 B.C., as well as later prehistoric, protohistoric, and historic canals. In this study, ostracode analysis is used to reconstruct the history of irrigation operations at AZ BB:13:481 (ASM), the site number assigned to the canal segments at the base of A-Mountain.

Chapter 17 – Sources of Obsidian Artifacts (PDF format, 298.05 KB)

  • A total of 32 flaked obsidian artifacts was recovered by the Desert Archaeology, Inc., investigations at the Clearwater site, AZ BB:13:6 (ASM), and the Tucson Presidio, AZ BB:13:13 (ASM). The elemental concentrations in 20 obsidian artifacts were analyzed by the energy dispersive X-ray fluorescence (EXRF) method to match them to the compositions of known obsidian sources in the Greater Southwest. The types of obsidian artifacts, their contexts, the ages of those contexts, and identified sources are summarized in this chapter.

Chapter 18 – Human Burials (PDF format, 144 KB)

  • A total of 25 inhumations, 6 cremations, and 7 partial skeletal remains were discovered during the Rio Nuevo Archaeology project. These ranged in date from the Early Agricultural period to the Protohistoric period. An additional 13 Spanish-period burials previously discovered at the San Agustín Mission and Tucson Presidio were also examined.

Chapter 19 – Radiocarbon Dating of Early Occupations (PDF format, 167.51 KB)

  • The chronology of prehistoric occupations at the Clearwater site, AZ BB:13:6 (ASM), and associated canals, AZ BB:13:481 (ASM), earlier than about A.D. 550, the beginning of the Hohokam ceramic chronology, is based on 34 radiocarbon dates, including 16 new dates obtained during the Rio Nuevo Archaeology project. This combined set of radiocarbon dates also provides a chronological framework for the early portion of the alluvial sequence at the base of A-Mountain. In this chapter, the age ranges of pre-A.D. 550 occupations in various strata of the floodplain are estimated using the pooled probability method.

Chapter 20 – Geomorpholopgy and Stratigraphy (PDF format, 1.1 MB)

  • The alluvial deposits exposed in trenches at the Clearwater site, AZ BB:13:6 (ASM), during the Rio Nuevo Archaeology project can be related to alluvial deposits identified in several previous trenches excavated in the Holocene floodplain of the Santa Cruz River, on the western side of the present channel below A-Mountain. The new exposures of alluvium and additional radiocarbon dates reported here allow refinement of the stratigraphic model of the Holocene terrace at the base of A-Mountain. This chapter provides a synthesis and interpretation of the information currently available.

Chapter 21 – Public Outreach (PDF format, 3.41 MB)

  • An important component of the Rio Nuevo Archaeology project was the participation of members of the Tucson community. Desert Archaeology, Inc., used volunteers on several excavations, had guides to provide tours of the digs, and large open houses at the end of each project. More than 5,000 people viewed the work in person and thousands more saw or heard media reports on the television, radio, or newspapers. Several programs were focused on reaching a wider audience through the use of computer animation, outreach to students and teachers, and through exhibits at local museums. Each of these programs is briefly described here.

Chapter 22 – Summary: The Archaeology of a Changing Community (PDF format, 4.16 MB)

  • Between the twenty-first century B.C. and the arrival of the railroad in 1880, the series of communities that developed in Tucson’s birthplace at the base of A-Mountain and in the downtown area shared characteristics that define communities everywhere. Because each type of community shared these characteristics and developed from the previous one, the history of Tucson communities has a trajectory that can be traced through time. Here, we use the lens of archaeology and the discoveries of the Rio Nuevo Archaeology project to examine (1) how Tucson initially developed as one of the earliest oasis communities in the Southwest; (2) survived for millennia as an irrigation community operating extensive systems of canals; (3) transformed into both a mission and military community during the Spanish and Mexican periods; (4) and then, after becoming part of the United States in the mid-nineteenth century, rapidly evolved into an ethnically diverse frontier community providing supplies, services, and transportation links for miners and ranchers in southern Arizona. These identities sometimes overlapped for decades or for centuries, giving Tucson a diverse character through much of its history.

Appendix A – Supplementary Data on Rio Nuevo Shell Artifacts (PDF format, 112.27 KB)

Appendix B – Supplementary Data on Rio Nuevo Project Macrobotanical Samples (PDF format, 161.11 KB)