Pre‐Hispanic and Colonial Flood Plain Destabilization in the Texcoco Region and Lower Teotihuacan Valley, Mexico

Abstract

Stratigraphic sequences in the flood plains of the eastern Basin of Mexico reveal episodes of intense flooding in the past 3000 years, represented by the deposition of alluvial units C, D, and E, and their respective soil horizons. Unit C correlates with the initial growth of population and clearance of vegetation in the piedmont during the Formative period, followed by a stable period ca. 200 B.C. to A.D. 800 represented by a dark A‐horizon (soil S3). Unit D is associated with land use changes in the Late Classic and Early Toltec periods, sometime between approximately A.D. 800 and 1100. A relatively stable period occurred during the Toltec and Aztec periods, marked by an A‐horizon (soil S4). Unit E represents rapid sedimentation that occurred during the Spanish Colonial period. Previous research in this area suggests that flood plain destabilization in the Early Colonial period occurred as a result of rapid abandonment of terraces, check dams, and settlements in the watersheds of the main rivers. It is possible that the previous period of stabilization (unit D) was influenced by the abandonment of previously managed environments. In the three rapid sedimentation phases, it is possible that climatic fluctuations played an indirect role, if at all.