Late quaternary environmental changes of the central part of the Basin of Mexico; correlation between Texcoco and Chalco basins
Por:
Lozano-Garcí M.D.S., Ortega-Guerrero B.
Publicada:
1 ene 1998
Resumen:
A 10.8 m core was collected from Lake Texcoco to investigate paleoenvironmental changes for the late Quaternary in the central Basin of Mexico. Results from pollen, magnetic susceptibility and loss-on-ignition analyses reveal important fluctuations. A time scale has been established from five AMS 14C dates and tephra correlation. A humid period is recorded from at least 34,000 to ca. 23,000 yr B.P. where mesophytic and wetland taxa are important. A trend of dry and cold conditions began during the late glacial maximum, reflected by an expansion of the pine forests and lowering of pollen diversity and concentration. This trend continued during the late glacial when grasslands developed, and culminated at ca. 14,000 yr B.P. Volcanic activity was particularly noteworthy during this time in association with this environmental change. A major hiatus marks the culmination of the dry period. Wetter conditions during the early (?) Holocene-mid-Holocene allowed Texcoco to be a persistent saline lake. Correlation between Chalco and Texcoco sub-basins based on 14C dated pollen assemblages suggests that the major environmental changes affecting both sites are of climatic origin. However, volcanic eruptions also have played an important role in modeling the landscape as well as the evolution of vegetation and the lacustrine systems within the basin, and some of the limnological changes in the lakes could be explained by volcanism rather than by climatic causes.