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.

Sociopolitical organization, landscape change, and hydraulic engineering in the Teotihuacan Valley, Mexico: 1250 B.C.–A.D. 1810

“…As such, precise environmental conditions during the settlement of the Teotihuacan Valley in the Formative Period (1500 B.C.-A.D. 100) remain unclear. Firm evidence for the Teotihuacan/Classic Period (A.D. 100-650) climate is also scarce, but grass phytoliths from radiometrically dated contexts in the surrounding valleys suggest that the climate was similar but possibly drier than it is today (Cordova, 1997;Solleiro-Rebolledo et al, 2006). Meanwhile, speleothem and dendrochronological evidence suggest that the modern timing of monsoonal rains has been present since at least one century after the city's collapse (Kennett & Marwan, 2015;Lachniet, Bernal, Asmerom, Polyak, & Piperno, 2012;Stahle et al, 2011).…”

“…Furthermore, every known irrigation canal dating to the Teotihuacan period is floodwater based-that is, rainfed-and exists up-valley from the springs (Aguilera Muñoz, 1997; Armillas, Palerm, & Wolf, 1956;Cabrera, 2005;Cabrera & Gómez, 2008;Charlton, 1977Charlton, , 1978Charlton, , 1979aCharlton, , 1979bGómez & Gazzola, 2004;Mejía Ramón, 2016Millon, 1957;Nichols, 1987aNichols, , 1988Nichols et al, 1991;Sanders, Nichols, Storey, & Widmer, 1982;Sanders, West, Fletcher, & Marino, 1972). The missing data may be due to the exceptionally deep soils downstream from the springs (Cordova, 2017;Skopyk & Martínez-Yrizar, 2012), although excavations near the springs have failed to find such permanently fed hydraulic features for maize agriculture (Gómez & Gazzola, 2004;González Quintero & Sánchez Sánchez, 1991).…”

“…Aztec tribute lists suggest that amaranth (Amaranthus hypocondriacus) was just as important (Berdan & Anawalt, 1997;Glocker Rossainz, 2018;Mohar Betancourt, 1976;Sauer, 1967). Teotihuacan's limited paleobotanical evidence suggests that amaranth was fundamental, but wild amaranth's ubiquity in the environment makes it difficult to assess the contribution of domesticated amaranth to the Teotihuacano diet (Cordova, 1997;Vázquez et al, 2014). In colonial times, the Spanish outlawed amaranth cultivation, so modern traditional amaranth farming is rare (Bravo Vázquez & Molotla Molotla, 2007;Santamaría Llerandi, 2014;Sauer, 1967) making productivity data almost nonexistent (Hoidal, Gallardo, Jacobsen, & Robles, 2018;Ortiz-Torres et al, 2018).…”

“…Such changes in the social order precipitated episodes of landscape degradation as terraces fell into disrepair and former ways of life disappeared. Potentially a lack of maintenance led to system collapse and a third period of significant erosion (Cordova, ; McClung, Rubio, et al, ; McClung, Tapia‐McClung, & Gorenflo, ). This erosion would have been exacerbated by the introduction of agro‐pastoralism and large‐bodied livestock, which have been associated with severe erosive events elsewhere (Barton et al, ).…”

A Geoarchaeological Investigation of the Street of the Dead at the Tlajinga District, Teotihuacan, Mexico

“…Estimates of potential agricultural productivity implied that the region could sustain dense populations (Charlton 1970; Lorenzo 1968), although later population estimates for the urban zone alone suggested that a significant proportion of basic subsistence resources had to have been acquired from a much broader area (McClung de Tapia 2012). Recent research indicates that prior estimates of agricultural potential were based on modern soils, which developed on redeposited sediments (Cordova 2016; González-Arqueros et al 2013; Sánchez-Pérez et al 2013). A black soil with vertic properties overlying the tepetate, the volcanic bedrock in this region, had been observed by archaeologists in different sectors of the region (Charlton 1972; Nichols 1987; Widmer 1987); its significance, however, was unrecognized at the time.…”