PALAEOLANDFORMS AND VOLCANIC IMPACT ON THE ENVIRONMENT OF PREHISTORIC CUICUILCO, SOUTHERN MEXICO-CITY

The Pedregal lava field covers an area of 80 km2 in the southern Basin of Mexico and includes the Cuicuilco archaeological site. Cuicuilco is considered an early urban centre in the Basin of Mexico, constructed during the Late Preclassic (a few centuries BC) and abandoned at the beginning of the first millenium AD. Three new radiocarbon ages, together with reinterpretation of previous ages and detailed analyses of the slopes of the Cuicuilco's ''pyramid'', support the hypothesis that Cuicuilco was abandoned long before the Xitli eruption. Xitli lavas followed several river valleys, damming some and causing them to silt up (Magdalena, Xocotitla, Puente Volado and Chicuautitla Rivers), subsequently deflecting the old drainage from Lake Xochimilco to Lake Texcoco. Upper and lower piedmont and river landscapes are reconstructed on the basis of soil characteristics and lithostratigraphic units. Palaeolandforms suggest an agricultural environment prior to the Xitli eruption.