- Gregory-Wodzicki, K.M., submitted to Paleo-3, A late Miocene subtropical-dry
flora from the northern Altiplano, Bolivia.
A variety of
evidence suggests that the Altiplano of the Central Andes, the second highest
and largest plateau on earth, underwent significant uplift in the late
Miocene-Pliocene. The most important datum supporting recent uplift is
a collection of the 10.66 ± 0.06 Ma Jakokkota flora from west-central
Bolivia, which implies a paleoelevation no more than 1600 ± 1200
m; today the site has an elevation of almost 4000 m. In order to test
the reliability of this estimate, the present study analyzes a new collection
of the Jakokkota flora from a lacustrine unit that is 0.2-0.5 million years
younger than the previously analyzed collection from a fluvial unit. Climate
estimates based on leaf morphology for the two collections are statistically
indistinguishable; the combined flora has a mean annual temperature =
21.5 ± 2.0 °C and a mean annual precipitation = 550 ±
180 m.. The similarity of the climate estimates for the two floras suggests
that there was not a significant climate change between them, nor a significant
bias in the leaf morphology due to differing taphonomic processes. The
climate estimate for the combined flora thus presents a representative
picture of the late Miocene climate of the northern Altiplano. If one assumes
that the climate of the tropics has not changed significantly since the
late Miocene, as is suggested by marine isotopic data, then the paleoclimate
of the Jakokkota flora implies a paleoelevation of 1160 ± 600 m.
Thus, the Jakokkota flora supports the hypothesis of a young age for the
Altiplano.