Introduction
The Chimú polity, active between AD 900 and 1470 on Peru’s northern coast, was one of the last major pre-Inca polities. Current models of research agree that the Chimú polity was a centralised state and possibly even an empire (Moseley & Day Reference Moseley and Day1982; Moore & Mackey Reference Moore, Mackey, Silverman and Isbell2008). Chimú elites organised and governed the 30 000-person strong, urban centre of Chan Chan, which included extensive economic, political and religious infrastructure in the Moche Valley (Topic Reference Topic, Moseley and Cordy-Collins1990). To feed this population and concentrate a sufficient surplus, Chimú elites employed a series of geopolitical and biopolitical strategies. The expansion of agricultural production in the Chicama Valley was one such strategy (Moseley & Cordy-Collins Reference Moseley and Cordy-Collins1990), and construction of the Chicama-Moche canal was an attempt to intensify agricultural production (Ortloff Reference Ortloff2021: 132). This monumental 70km-long hydraulic project connected the northern Moche Valley to the Chicama Valley through aqueducts and multiple feeder canals (Keatinge Reference Keatinge1974: 72).
There is debate in the academic community about whether this state-sponsored canal was ever functional (Pozorski & Pozorski Reference Pozorski and Pozorski1982; Ortloff et al. Reference Ortloff, Moseley and Feldman1983), with the conclusion ultimately central for understanding the Chimú administration of Chicama. The canal may have functioned at least up to Quebrada del Oso (Figure 1) (Kus Reference Kus1972, Reference Kus1984: 409; Keatinge Reference Keatinge1974).
Figure 1. The location of Quebrada del Oso and Chan Chan (image © Programa Arqueológico Chicama–PRACH, based on Google Earth).
Three moderately well preserved architectural compounds sit adjacent to a large number of agricultural fields at Quebrada del Oso suggesting one of several possibilities: 1) the site was fully functional (and therefore the canal was operational); 2) the site was built but not functional during the Chimú administration (as the canal was not operational); or 3) the site was lightly occupied and subsequently abandoned due to the failure of the canal to function effectively. Excavation of two of the main structures in 1974 revealed a post-primary occupation (Keatinge Reference Keatinge1974: 75), but a detailed record was never published. The main structure, with three niches, was identified as an ‘Audiencia’ (Keatinge Reference Keatinge1974: 75)—possibly a ‘Rural Audiencia’ (Andrews Reference Andrews1974: 248)—a type of Chimú administrative structure.
Our study combined drone-based remote sensing, systematic surface survey, excavations in the architecture sector and test pits in agricultural fields. Excavation units targeted irrigation furrows, cultivation areas and architecture. We collected over 1200 diagnostic pottery fragments, obtained a sample for radiocarbon dating and analysed soil at the Universidad Peruana Cayetano Heredia. This multiproxy approach aimed to determine the function of this Chimú agricultural centre through integrated archaeological and archaeobotanical data.
Results and discussion
The total area of the Quebrada del Oso site, including architecture and agricultural fields, is identified as around 60ha, 10ha larger than previously reported (Kus Reference Kus1972: 155) (Figure 2). Our multiproxy approach enabled the identification of previously unrecorded areas of the site and the detailed documentation of Chimú agricultural fields, which will be published in a separate study.
Figure 2. Google image of Quebrada del Oso showing architectural components, agricultural fields and Casma ceramics (orange dot), with inset detail of Component 2 (A) and fields (B) (image © PRACH).
Excavations in Architectural Component 2 (‘Structure B’; Kus Reference Kus1972) revealed a C-shaped structure, confirming the presence of an ‘Audiencia’ (Figure 3). The stratigraphy corroborates a brief early occupation composed of two formal floors, each 20mm thick, separated by a 30mm layer of semi-compact soil. An intrusive fire pit in the C-shape structure also confirms a later, post-primary occupation (Keatinge Reference Keatinge1974: 75). A sample from this fire pit provides a radiocarbon date of cal AD 1463–1628, Chimú-Inka to early Colonial period (Table 1), consistent with prior dates from the nearby canal sector (Kus Reference Kus1972; Pozorski & Pozorski Reference Pozorski and Pozorski1982) (Figure 4).
Figure 3. Aerial view of the excavations in the C-shaped structure of architectural Component 2 (image © PRACH).
Table 1. Radiocarbon dating of Quebrada del Oso.
Figure 4. Radiocarbon dating of Quebrada del Oso site (QO-1), and the closest section of the Chicama-Moche Intervalley Canal. Calibrated using OxCal 4.4 software with SHcal20 curve (image © PRACH).
Analysis of the pottery identifies Chimú and Casma domestic wares (Figure 5) (Melissa Vogel and David Pacifico, pers. comm.). The presence of these sherds suggests a Chimú resettlement strategy, involving the relocation of populations from the Casma polity, located several kilometres away. Ceramics recovered in the survey of the agricultural fields provide relative dating (after Caramanica et al. Reference Caramanica, Huamán, Morales, Huckleberry and Quilter2020) of intensive field use from AD 1350–1400, based on the consistent presence of Late Chimú ceramic types (Prieto Reference Prieto2008; Vogel Reference Vogel2016: 80).
Figure 5. Ceramics from Quebrada del Oso: a & b) Chimú ceramics; c) incised Casma; d) painted Casma; e) moulded Casma (image © PRACH).
Microbotanical analysis of soil from the agricultural fields reveals phytoliths from Zea mays (maize) and Phaseolus sp., as well as from invasive species and common weeds typically associated with cultivated landscapes. Furthermore, the identification of diatoms indicates sufficient water for cultivation (Figure 6). These data strongly support field use and underscore the need for a comparative study of diatoms from the canal and the fields.
Figure 6. Microbotanical remains identified in the agricultural fields: a) Zea mays; b) Phaseolus sp.; c) diatoms (image © PRACH).
Conclusions
Our research identifies three occupational phases at the site. The first, corresponding to radiocarbon dates by Kus (Reference Kus1972) and Pozorski and Pozorski (Reference Pozorski and Pozorski1982), marks the construction of architectural compounds. Linked to the first floor of the C-shaped structure, this phase likely reflects a planned strategy in which local agricultural production sustained the workforce engaged in building the Chicama-Moche Intervalley Canal.
The second phase likely dates to the fourteenth century and is characterised by the remodelling of the C-shaped structure’s floor, expansion of the agricultural fields and increased population density in this section of the valley. The presence of Casma ceramics across several fields suggests that Chimú elites mobilised populations from Casma to sustain agricultural production at Quebrada del Oso. The final phase reflects an opportunistic use of the agricultural complex in the fifteenth century (Caramanica et al. Reference Caramanica, Huamán, Morales, Huckleberry and Quilter2020).
Our results support the interpretation that the site was built and occupied since cal AD 1045–1415 (95.4% probability) (Kus Reference Kus1972: 227), during the Chimú period, with microbotanical remains suggesting that the agricultural fields were successful. Our multiproxy study therefore confirms that Quebrada del Oso was an example of the complex economic and political strategies of the Chimú Empire.
Funding statement
This research was supported by the Universidad Nacional Mayor de San Marcos (RR Nº 007572-R-23, project code E23150111i), the University of South Florida and the University of California-Santa Barbara.
Author contributions: CRediT Taxonomy
Carito Tavera-Medina: Conceptualization-Lead, Data curation-Lead, Formal analysis-Lead, Funding acquisition-Lead, Investigation-Lead, Methodology-Equal, Project administration-Equal, Resources-Equal, Supervision-Equal, Writing - original draft-Lead, Writing - review & editing-Lead. Henry Tantaleán: Conceptualization-Lead, Data curation-Equal, Formal analysis-Equal, Funding acquisition-Equal, Investigation-Lead, Methodology-Equal, Resources-Equal, Supervision-Equal, Writing - original draft-Lead, Writing - review & editing-Equal. Charles Stanish: Data curation-Equal, Funding acquisition-Equal, Resources-Equal, Writing - original draft-Equal. José Roman: Data curation-Equal, Investigation-Equal, Visualization-Equal. Juan Quispe-Baquedano: Data curation-Equal, Formal analysis-Equal, Investigation-Equal, Methodology-Equal. Diana Huachaca: Data curation-Equal, Investigation-Equal. Alicia Boswell: Resources-Supporting.
