Las Capas Archaeological Project: Field Methods, the Retention Basin, and Extramural Feature Descriptions

Summary

Field methods and extramural feature descriptions are presented in this report from archaeological investigations at the prehistoric site of Las Capas, AZ AA:12:111 (ASM), situated in the Tucson Basin of southern Arizona. Testing and data recovery excavations at Las Capas were conducted by Desert Archaeology, Inc., from August 2008 through September 2009, with smaller phases of fieldwork in 2012 and 2013, as part of Pima County's Regional Wastewater Reclamation Department Regional Optimization Master Plan (ROMP). This massive project involved major upgrades and expansion of wastewater facilities at the Tres Rios Wastewater Reclamation Facility (WRF). Funding was provided by Pima County, and the excavations were conducted under the supervision of their Office of Cultural Resources and Historic Preservation, which requires all projects to adhere to the Federal standards of Section 106 of the National Historic Preservation Act of 1966 (as amended).

Las Capas is located in the northern Tucson Basin, situated on the eastern bank of the Santa Cruz River, just downstream from the confluences of the river with Rillito Creek and Cañada del Oro Wash. This is the point in the Santa Cruz River Valley where all major tributaries in the surrounding watersheds converge because of the terrain and the gradient, making it an ideal location for agriculture due to high water table levels and predictable streamflow. The great majority of features recovered at Las Capas dated to the San Pedro phase (A.D. 1200-800 B.C.) of the Early Agricultural period (2100 B.C.-A.D. 50).

The archaeological excavations allowed the singular opportunity of investigating a large area of the site in detail and intensity, providing the most comprehensive look at a San Pedro phase farming community conducted, to date, in southern Arizona. Backhoe trenches were excavated over most of the wastewater facility area to document the extent of archaeological deposits. Following this effort, intensive excavations were conducted in loci where new plant facilities were to be constructed (identified as Loci AE; Loci F-H were only treated during the exploratory phase of the project).

Data recovery resulted in the identification of more than 5,500 prehistoric features, of which 3,455 were excavated or tested. Investigated feature types included 53 pithouses, 8 possible pithouses, 22 extramural surfaces, 610 bell-shaped pits, 49 large pits, 2,099 small pits, 490 roasting pits, 40 pits of unknown or other function, 20 inhumations, 2 cremations, and 11 animal burials. The excavations resulted in the recovery of more than 113,000 artifacts and 7,300 samples of various kinds, representing the largest quantity of San Pedro phase material recovered yet from the Tucson Basin. A large agricultural field system was also discovered containing primary and lateral canals that delivered irrigation water from the Santa Cruz River to hundreds of small fields. This field system has now been well-documented, and its history of development and modification through time reconstructed in detail.

Primary research issues investigated at Las Capas include chronology, artifact analyses, irrigation technology, subsistence systems, and syntheses of Early Agricultural lifeways. In short, the excavations at Las Capas have provided an ideal opportunity to study an Early Agricultural irrigation community in detail from the "production" end—fields, canals, and their contexts — to the "consumption" end of domestic living.

The results of the Las Capas investigations are presented in a series of Anthropological Papers, Technical Reports, and a book published, variously, by Archaeology Southwest and Desert Archaeology. The two Anthropological Papers provide a broad overview and synthetic examination of the site, with a specific emphasis on the reconstruction of prehistoric life in the northern Tucson Basin during the Early Agricultural period San Pedro phase. One volume (Anthropological Papers No. 50) provides the environmental and cultural context of the Las Capas project area. The environmental setting is discussed in detail, as it is the "stage" on which all cultural behavior is enacted. The complex mix of environment and culture defines the "Anthropogenic Landscape," the overarching research theme of the Las Capas Archaeological Project. The other volume (Anthropological Papers No. 51) explores the cultural and behavioral components of the San Pedro phase Las Capas occupation and the Early Agricultural period occupation of the Tucson Basin in general.

The five Technical Reports focus on more specific research issues, providing data that may be of interest to a more limited or specialized audience. The Technical Reports include discussions of the field methods, feature descriptions and descriptions of the mortuary assemblage, and an experimental analysis examining Early Agricultural period agriculture and ground stone tool production. A map packet is also iv Abstract included as a Technical Report, with areal maps showing the project area and feature location by individual locus. Finally, the book is available that presents the first comprehensive study of Early Agricultural period projectile points in the greater Southwest United States, including both typological and behavioral interpretations.

This Resource is Part of the Following Collections

• Desert Archaeology DAHA Resources   •
• Digital Archive of Huhugam Archaeology (DAHA)

Keywords

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Individual & Institutional Roles

Contact(s): Desert Archaeology, Inc.

Contributor(s): James M. Vint; Office of Cultural Resources and Historic Preservation

Sponsor(s): Pima County

Prepared By(s): Desert Archaeology, Inc.

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