9709114 Gregory The history of Andean uplift is highly pertinent to climatic studies. The Andes forms the only major barrier to zonal atmospheric circulation in the Southern Hemisphere. They extend throughout the tropics, a sensitive zone where small changes in climate impact on a global scale. As of now, the development of Andean elevation is poorly constrained. Under the previous proposal "Uplift History of the Bolivian Andes" to which this is a renewal, the 14-20.8 Ma Potosi and 10.35 ( 0.06 Ma Jakokkota floras from the Altiplano were estimated to have paleo mean annual temperatures (MATs) of 24.8 and 21.3 (C, respectively, using foliar physiognomic analysis of Wolfe (1993, 1995). The similarity of these estimates suggests that uplift occurred before the first flora was deposited and after 10 Ma, but not between the two floras. The objective of this study is to constrain the absolute paleoelevation at 10 Ma by estimating the paleoclimate and paleoelevation of two newly discovered floras from Bolivia: the 8-10 Ma Yecua flora, which grew near sea level in eastern Bolivia, and the 10.35 Ma Calunchullpa flora from the Altiplano. Analysis of the Yecua flora will constrain the sea-level paleoclimate at 8-10 Ma. Using MAT and enthalpy-based paleoaltimeters, the Yecua paleoclimate can be compared to that of the previously studied Jakokkota flora and the new Calunchullpa flora to derive absolute paleoelevations for the Altiplano sites. To improve the paleoclimate estimates, modern analogous vegetation will be collected from eastern Bolivia for addition to the database of Wolfe (1995). This study fits the objectives of Earth Systems History because it will provide 1) well-dated, quantitative, terrestrial paleoclimate proxy data which can be used to evaluate the results of general circulation models, 2) topographic and vegetation boundary conditions for general circulation models, and 3) an improved calibration between leaf physiognomy and climate, which will increase the accuracy of the foliar physiognomic climate proxy.
