HR: 0830h
AN: OS11A-20    [Abstracts]
TI: A Late Holocene Record of Human Impact in the Tropical Lowlands of the Mexican Gulf Coast: Lago Verde.
AU: * Socorro, L
EM: mslozano@servidor.unam.mx
AF: Universidad Nacional A. de M‚xico Intituto de Geologˇa., Cd. Universitaria, M‚xico D.F., 14000 Mexico
AU: Sosa, S
EM: susosa@servidor.unam.mx
AF: Universidad Nacional A. de M‚xico Intituto de Geologˇa., Cd. Universitaria, M‚xico D.F., 14000 Mexico
AU: Caballero, M
EM: maga@tonatiuh.igeofcu.unam.mx
AF: Universidad Nacional A. de M‚xico Instituto de Geofˇsica., Cd. Universitaria, M‚xico D.F., 14000 Mexico
AU: Rodriguez, A
AF: Universidad Nacional A. de M‚xico Instituto de Geofˇsica., Cd. Universitaria, M‚xico D.F., 14000 Mexico
AU: Ortega, B
EM: bortega@tonatiuh.igeofcu.unam.mx
AF: Universidad Nacional A. de M‚xico Instituto de Geofˇsica., Cd. Universitaria, M‚xico D.F., 14000 Mexico
AB: Lago Verde is a maar lake (18 36 43 N; 95 20 52 W) located on the Gulf Coast of Mexico in "Los Tuxtlas" region. The area was cover by tropical rain forest and is part of the core area of the earliest Mesoamerican cultures. A 6 m sediment core was obtained in order to document vegetation and lake level history of this area. Lago Verde is a shallow, eutrophic lake (max. 4 m), the natural vegetation has been removed and grasslands with some tropical trees such Bursera grows around the lake. According with the radiocarbon chronology the sequence covers the last 2500 yr BP. At the base of the sequence low abundance of tropical trees is record, with intermediate lake levels. A sudden change in the pollen stratigraphy occurs at ca. 2000 yr BP, with important presence of Poaceae, Ambrosia and Cheno.-Am. along with Zea mays indicating human activity in the area. This is associated with a change in limnological conditions, recording turbid, shallow environments. This pollen signals correlates with dry phases in Yucatan, suggesting that this dry climatic signal probably had effect on an ample area of Mexico. However, at 1200 yr BP, no more Zea mays pollen is recovered suggesting the abandonment of the area. Lake levels recover as well as the tropical forest. The last 150 yr BP is characterized by the reduction in the pollen of tropical forest trees, presence of Zea mays, increased erosion rates, turbidity and eutrophication in the lake, all related to deforestation.
DE: 0400 Biogeosciences
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly