The present work includes a palynofloristic synthesis of Tertiary research carried out at marine and continental basins with particular emphasis on stratigraphy of the Balsas Group sensu Fries (1960). Also it includes palynostratigraphic information related with San Gregorio Formation (Baja California Sur State) and Cuayuca Formation (Puebla State) assemblages. Taxa of chronostratigraphic and ecologic importance are emphasized at every paleobasin. The numerical and cladistic correlation showed that palynological assemblages of units belonging to the Balsas Group are closely related to San Gregorio flora. The results indicate that since the Paleocene, under a tropical regime, an evergreen forest was present together with warm temperate elements. Later, in the Eocene epoch, the tropical floras remained as the principal components of the vegetation. In the Late Eocene - Early Oligocene, the assemblages are a mixture of temperate and desert taxa prevailing over tropical elements at the Sierra Madre Occidental Province. But the subtropical and tropical floras continued as the main components in the Gulf Coast Province where the tropical vegetation stayed up to the Holocene. In contrast, in the western basin localities (Sierra Madre Occidental Province) it was detected a desertification since the Oligocene where savannas and grasses became established. Afterwards, in the Miocene, at the same region, the xerophitic flora dominates the assemblages, proving the existence of a desert at that time.It is evident that the coniferous forest and oak communities inhabit the mountain ranges since the Eocene becoming more abundant in the Oligocene, but they became the dominant taxa in the pollen assemblages from the Neogene to Quaternary.According with the Tertiary flora analyzed in this survey the actual vegetation present in Mexico is a response to climatic changes and active volcanism throughout the Tertiary. Finally, different types of vegetation began to be recognizable in the fossil assemblages since the Oligocene. The historical development of Mexico (tectonic, rifting, volcanism) explains the richness and endemism of Mexican flora.
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- Tertiary Palynofloristic correlations between Mexican Formations with emphasis in dating the Balsas Group
- Springer Netherlands
- Chapter 2