Studies in neotropical paleobotany. XI. Late tertiary vegetation and environments of southeastern Guatemala: Palynofloras from the Mio-Pliocene Padre Miguel Group and the Pliocene Herreria formation

Plant microfossils are reported from the late Tertiary Padre Miguel Group and the Pliocene Herreria Formation of southeastern Guatemala. The most abundant palynomorphs are cf. Acrostichum (maximum 45%), Cyperaceae (29%), cf. Antrophyum (27%), monolete fern spores (16%), and Pinus (11%). Pollen grains of Picea, Juglans, Quercus, and Ulmus, primarily from the Padre Miguel flora, reveal the presence of a northern cool-temperate element. The younger Herreria flora is more lowland and warm temperate. In the absence of evidence for substantially higher elevations, the differences between the Neogene and modern vegetation are attributed mostly to climate. MAT (mean annual temperature) is estimated 2 degrees-3 degrees C cooler than at present for the Padre Miguel flora, and similar to 3.5 degrees C warmer for the Herreria flora. There is little evidence for arid vegetation, and the tropical rain forest was absent or poorly represented. These data are consistent with those of other fossil floras in the region and with trends suggested by isotopic paleotemperature analysis and global sea-level changes. The Guatemala assemblages further provide evidence that the current version of the tropical rain forest is recent in origin and has undergone considerable change in its range and composition throughout the late Cenozoic.