HR: 16:00h
AN: B52F-01    [PDF]
TI: Relative Changes in C$_{3}$ and C$_{4}$ Biomass Recorded by Carbon Isotopes of Lipid Biomarkers in the Maya Lowlands of Pet\'{e}n, Guatemala
AU: * Newell, S D
EM: sdnewell@ufl.edu
AF: Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL 32611 United States
AU: Hodell, D A
EM: dhodell@geology.ufl.edu
AF: Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL 32611 United States
AU: Curtis, J H
EM: curtisj@ufl.edu
AF: Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL 32611 United States
AU: Brenner, M
EM: brenner@ufl.edu
AF: Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL 32611 United States
AU: Rosenmeier, M F
EM: mrosenme@pitt.edu
AF: Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL 32611 United States
AU: Rosenmeier, M F
EM: mrosenme@pitt.edu
AF: Department of Geology and Planetary Science, University of Pittsburgh, 200 SRCC Building 4107 O'Hara Street, Pittsburgh, PA 15260-3332 United States
AB: Forest disturbance in the Pet\'{e}n region of northern Guatemala, beginning approximately 3000 cal yrs BP, was associated with the agricultural practices of the Maya. Expansion of the Maya civilization during the Preclassic and Classic periods was accompanied by widespread deforestation of Pet\'{e}n watersheds and accelerated rates of soil erosion. Palynological data from the Pet\'{e}n region suggest the near elimination of high forest taxa during the period of Classic Maya occupation. The validity of pollen records has been questioned, however, because they represent only a small percentage of tropical vegetation that is pollinated by wind. To estimate changes in the proportion of C$_{3}$ to C$_{4}$ vegetation in the Maya forest, we measured the $\delta$$^{13}$C of long chain {\it n}-alkanes (C$_{29}$ and C$_{31}$) produced by higher terrestrial plants in a 4.1-m sediment core from Lake Sacnab, Guatemala. Deforestation during the period of Maya occupation is reflected in sediments cores by a distinct, clay-rich interval (termed the "Maya clay") that is characterized by low magnetic susceptibility and low organic carbon content. The $\delta$$^{13}$C of long chain {\it n}-alkanes average -28$\permil$ within the Maya clay, and decreases by 10$\permil$ above the clay unit following the demise of the Classic Maya civilization in the 9$^{th}$ century A.D. Our results suggest that vegetation was dominated by C$_{4}$ biomass during the Classic Maya period and is consistent with previous palynological interpretations. Reforestation following the demise of the Classic Maya is apparent in the pollen and compound-specific $\delta$$^{13}$C records and indicates a switch back to a C$_{3}$ dominated ecosystem once human pressures were curtailed. Compound-specific $\delta$$^{13}$C analyses of biomarkers in Lake Sacnab sediment provide further evidence that the Maya had a profound impact on their lowland neotropical environment.
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1055 Organic geochemistry
DE: 1699 General or miscellaneous
SC: Biogeosciences [B]
MN: 2003 Fall Meeting