Archaeology and Prehistory of Northwest Mexico: A "Rough Essay"

David Phillips

The Trincheras Culture Area

Sometime in the first centuries of the common era, the Early Agricultural people of the Concepción basin began making pottery, becoming the Trincheras culture (Sauer and Brand 1931). The tradition extended from the basin east to the Rio San Miguel (Braniff 1978, 1985), northeast into the Santa Cruz Valley (Phillips and Swann 1984), and south to below Puerto Libertad. Two hallmarks of the Trincheras Culture are its distinctive painted pottery and cerros de trincheras (terraced hills that supported houses).


The characteristic Trincheras pottery is a smooth brown ware. Some of this pottery was painted, with or without a slip for background. "Purple" (dark but reddish) paint, based on ground hematite (at least sometimes including specular hematite), was painted directly over the brown pottery ( Trincheras Purple-on-plain ) or on an intervening red slip ( Trincheras Purple-on-red ). Some vessels were also painted with a lighter red iron-based paint; the resulting polychrome designs mostly alternated the red and "purple" paints. If the polychrome design appears on a white slip, the type name is Nogales Polychrome. If the design appears on an unslipped surface, the type name is Altar Polychrome.

Cerros de Trincheras

Cerro de Trincheras
Cerro de Trincheras, Sonora. Right-click for source.

Those not familiar with the archaeological literature should be aware that the word trinchera refers to several types of prehistoric feature, depending on its context and exact usage.

Why build homes on the sides of hills, when better locations are invariably present? In a long-simmering debate, some archaeologist see cerros de trincheras as primarily defensive while others see them primarily as expressions of deeply held beliefs. (There are, of course, archaeologists who acknowledge both possibilities.) In fact, cerros de trincheras are poorly designed from the standpoint of defense tactics (compared to many sites of central Arizona, for example, they are too "porous"), so the "social expression" hypothesis seems more likely (to me, at least). The basic structure of the northwest Sonora cerros de trincheras is of a series of hillside terraces used as living and work sites, while the top of the hill was reserved for rituals. The ritual space includes a large (8–24 m diameter) stone circle that defines an open-air or possibly covered sacred room, plus smaller (2–5 m diamter) stone circles that may have been shrines (like the Huichol "god houses") or rooms for the storage or investment of ritual paraphernalia (S. Fish and P. Fish 2008).

Culture History

Despite recent work, the Trincheras chronology remains murky. Randall McGuire and Elisa Villapando have modified Thomas Bowen's (1976) sequence for the culture, based on their survey work in the Altar Valley, and their sequence (McGuire and Villapando 1993) will be followed here. Villalpando's (2000:532–533) revised dates for the sequence are also provided.

The Atil phase corresponds to Bowen's Phase 2, which Bowen dated from A.D. 200(?) to 800. (Bowen's Phase 1 was a preceramic phase.) McGuire and Villapando allow that the Atil phase could have begun as early as A.D. 200 but may have started as late as A.D. 700. They decline to fix an end date for the phase. Villalpando (2000:532) has since dated the phase from A.D. 700 to 1150. "Bowen was impressed that his Phase 2 sites appeared to be Cochise sites with the addition of pottery. Our data certainly do not contradict this observation" (McGuire and Villalpando 1993:71). The phase is characterized by plain brown and Trincheras Purple-on-brown (unslipped) pottery, by small pit house villages, and by an inferred use of agriculture.

A single low hill (SON F:10:34) ... is a convincing candidate for a trincheras site dating to an initial plainware horizon.... No painted pottery was found.... A few rock rings occur in conjunction with small numbers of stone walls and rudimentary terraces surrounding a large central cleared area on the summit. Trincheras sites of an initial plainware horizon also are reported in southwestern New Mexico [Roney 1999] and in southern Arizona [Wallace et al. 2007]. A substantial chronological hiatus is probable between this initial plainware [trincheras] site and those later in the sequence with Trincheras painted [pottery] (S. Fish and P. Fish 2008:54).

The Altar phase corresponds to Bowen's "Phase 3," which Bowen dated from A.D. 800 to 1300. Pottery of the phase included plain brown, Trincheras Purple-on-red, Trincheras purple-on-brown, and Trincheras and Nogales Polychrome. The phase ends when the decorated varieties of Trincheras pottery ceased to be made, but there is no agreement on when that happened. Based on the occurrence of the decorated Trincheras types in U.S. sites, McGuire and Villapando (1993:72) suggest that the phase ended by A.D. 1100–1150 rather than 1300. Villalpando (2000:533) has since dated the phase from A.D. 1150 to 1300. Beatriz Braniff (1985) drew on her work in the San Miguel Valley to push the end of decorated Trincheras pottery into the 1400s and possibly into the 1500s. Braniff's arguments hinge on a single radiocarbon date, however, which is always risky.

The Altar phase saw an intensive occupation of the Trincheras culture area. The making and trading of shell ornaments was important, as was irrigation farming. Part of the occupation of the La Playa site (Johnson 1963, 1966) dates to this period, and included shallow pit structures (McGuire and Villalpando 1989) and extensive shell workshops (Woodward 1936). McGuire and Villapando (1993:72) believe that cerros de trincheras first appeared locally in the Altar phase, contrary to Bowen's conclusion that they appeared later. They are supported in this claim by Suzy and Paul Fish (2008), who identify six evenly spaced, fairly tightly clustered cerros de trincheras as dating to this period.

The El Realito phase corresponds to Bowen's Phase 4, which Bowen dated from A.D. 1300 to 1450—but if McGuire and Villapando are correct about the Altar phase, the El Realito phase began no later than A.D. 1150. Villalpando's (2000:533) revised dates for the phase are A.D. 1300 to 1450, matching Bowen's original dates. The Trincheras decorated wares were no longer made, and the local pottery was now plain brown and red ware. Imported pottery, previously absent, was now found and included Salado and Casas Grandes types.

During the El Realito phase the most famous Trincheras culture site, Cerro de Trincheras (O'Donovan 1997, 2002), was an undoubted regional center that included a number of houses as well as ceremonial precincts. The immediate area also included nine "secondary" cerros de trincheras (S. Fish and P. Fish 2008). Only one of the Altar phase cerros de trincheras, El Cerrito, went out of use by El Realito phase. "It was the probable precursor to Cerro de Trincheras, apparently eclipsed and replaced as that emerging center consolidated its primate position" (S. Fish and Paul Fish 2008:56).

Bowen's Trincheras sequence ends at A.D. 1450, but occupation of the Concepción drainage basin continued. The Santa Teresa phase (A.D. 1450–1690) was marked by plain pottery, small arrowpoints with basal notches, and cobble outlines for brush houses. The Oquitoa phase (A.D. 1690–1840) was marked by Oquitoa Plain and Oquitoa Red-on-brown (Hinton 1955) and was a period of native population movement and decline, coupled with missionization and European settlement. In the Tohono O'odham phase (1840s–early 1900s), a remnant native population lived on the fringes of local Mexican society. Native material culture included Papago Plain and Papago Red pottery and Euroamerican goods. In the early 1900s the last identifiable Native Americans withdrew from the Altar Valley (McGuire and Villalpando 1993:72–74). For the period after A.D. 1450, Villalpando's (2000:533) revised dates match those provided by McGuire and Villalpando.

Extent and Contacts

Based on survey and limited excavation along the Rio San Miguel, Braniff (1978, 1985) described a settlement pattern for a valley outside the "core" occupation in the Concepción basin. "Hamlets" had one or more rectangular rooms, marked by cimientos, and overlooked the valley floor. Low trash mounds were sometimes present. Cerros de trincheras were also present. The third type of site consisted of traces of structures built against tuff outcrops. The fourth site type was pictographs (both prehistoric and historic) in overhangs along the river bed near Cucurpe (Braniff 1978, 1985). As I commented in 1989, "These data are consistent with a ranchería settlement pattern; based on early historic accounts, I suspect that small villages were also present but were obscured by later mission activity" (Phillips 1989:391).

The spatial contiguity of the Hohokam and Trincheras cultures, along with certain close similarities (for example, in rock art [Ballereau 1987; P. Schaafsma 1980:100–101]) have led researchers to posit some sort of relationship between the two. If so, that relationship probably had to do with a shared cultural and linguistic background (the Cochise culture and Piman language) and with trade, not with formal political ties. Villalpando's (2000) essay in the Braniff Homenaje summarizes (among other things) the important Trincheras role in the manufacturing and trade of shell ornaments.

Link: In Flight: Adriel Heisey's Images of Trincheras Archaeology

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Last revised November 7, 2009.
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