Reconstructing the formation and land use history of the Mound 2 depression at Río Viejo, Oaxaca, Mexico

Abstract

Archaeological and geoarchaeological work in the lower Río Verde Valley, Oaxaca, Mexico reveal a varied spatial relationship between the prehistoric inhabitants and this dynamic floodplain region over the last 3000 years. Significant demographic expansion occurred by the Late Formative period following floodplain aggradation resulting from a change in stream hydrology and morphology. During the Classic and Postclassic periods, major shifts in settlement and land use occurred, primarily from the productive floodplain to the piedmont. The archaeological site of Río Viejo has played a pivotal role in the political and social history of the valley. Archaeological data indicate the site was occupied from the Middle Formative to the Early Postclassic and was an urban center and the political seat of the region during the Terminal Formative and again in the Late Classic. Four large depressions are associated with mounded architecture at the site. We collected paleoenvironmental and geoarchaeological data from the Mound 2 feature. A synthesis of this multi-proxy data has enhanced our understanding of site formation, occupation, and land use from the Late Formative to Postclassic times. The analysis indicates that the depression associated with Mound 2 was originally a borrow pit on the floodplain that was enhanced and augmented by monumental mound building. The area around Mound 2 was the focus of domestic and agricultural use during the Terminal Formative. An apparent cessation of activity around Mound 2 occurred during the Early Classic, which is consistent with a significant contraction in population at the site at this time. Activity resumed at Mound 2 in the Late Classic and continued until at least the Early Postclassic. These changes in occupation history appear to have resulted from political developments within the valley.