The evolution of Cenozoic floras in southern South America, and associated environmental changes

ARI IGLESIAS

Punta Arenas

Congreso; VIII Southern Connection Congress; 2016

Here I revised the vegetation record through the early Paleogene‒Neogene in southern South America, based on a compilation of paleobotanical records. I will discuss the onset of neotropical floras, when Andean temperate forest begun, and how Patagonia changed into an arid steppe. At the beginning of the Paleogene, the strengthening of the zonal climatic model at high latitudes was reinforced by global warming. During this time, high diversity angiosperm floras can be recognized in Patagonia. The presence of cycads, palms, and tree ferns are consistent with warm temperatures. High precipitation in Patagonia is in accordance to an Andean Cordillera still not raised to modern elevations. Podocarpaceae forests wereextended, and the presence of mangroves, swamp woodlands, mossy forests are recorded in Patagonia. Although they had their own features, some taxa are linked with Australasia. The global increase in temperature ended at the mid Eocene when Antarctic Circumpolar Current was activated, declining global temperatures. A major phytogeographical change occurred in the Oligocene and then extended into the Neogene: all biogeographical regions migrated to lower latitudes. In Patagonia, cool temperate forests ? with conifers and deciduous angiosperms? developed. Sub-Antarctic Nothofagus floras expanded their distribution in southern Argentina and Chile. For the Miocene, the first expansion of herbaceous shrub and typical arid elements is noticed, when the Andes began their maximum rate of ascent. If the richness were higher in the high-middle latitude, and arid biome was developed in south-tropic areas, then the diversity gradient should have had a different pattern than modern Neotropic.