Studies in Neotropical paleobotany. XI. Late Tertiaryvegetation and environments of southeastern Guatemala: palynofloras fromthe Mio-Pliocene Padre Miguel Group and the Pliocene HerreriaFormation.

Plant microfossils are reported from the late Tertiary Padre MiguelGroup and the Pliocene Herrería Formation of southeasternGuatemala. 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 Miguelflora, reveal the presence of a northern cool-temperate element. Theyounger Herrería flora is more lowland and warm temperate. Inthe absence of evidence for substantially higher elevations, thedifferences between the Neogene and modern vegetation are attributedmostly to climate. MAT (mean annual temperature) is estimated2°-3°C cooler than at present for the Padre Miguel flora,and ∼3.5°C warmer for the Herrería flora. There islittle evidence for arid vegetation, and the tropical rain forest wasabsent or poorly represented. These data are consistent with those ofother fossil floras in the region and with trends suggested by isotopicpaleotemperature analysis and global sea-level changes. The Guatemalaassemblages further provide evidence that the current version of thetropical rain forest is recent in origin and has undergone considerablechange in its range and composition throughout the lateCenozoic.