Using phytolith to track vegetation changes during the MMCO of the Santa Cruz Formation, Patagonia (Argentina)

CRIFO C.; KOHN M.J.; STROMBERG E.A.; KAY R.F.; A. F. ZUCOL; BARGO S.M.; VIZCAINO S.F.

Salvador

Congreso; XIV International Palynological Congress - X International Organisation of Palaeobotany Conference; 2016

International Organisation of Palaeobotany

The Santa Cruz Formation (SCF) of coastal Patagonia (17.5-16.8 Ma) represents the southernmost sedimentary record in the world spanning the onset of the middle Miocene climatic optimum (MMCO). It has yielded one of the most species rich and well-preserved Cenozoic vertebrate assemblages on Earth, which have helped demonstrate that the MMCO was a time of unusual faunal diversity in high-latitude South America. The SCF also contains paleobotanical evidence in the form of macrofossils and wood, and, above all, well preserved phytolith assemblages from the same strata as the vertebrate fossils. This combination of fossil records allows us to compare, for the first time, detailed records of faunal diversity and ecology, vegetation composition and structure, and local climate through middle Miocene global warming event in South America. Uniquely, variation in vegetation and faunal communities can be studied both in time and space, as several, well-dated stratigraphic levels of the SCF are traceable laterally along the Atlantic coast of Southern Patagonia for tens of kilometers. Here, I present preliminary results from phytolith analysis of the main stratigraphic section, recording vegetation change during the early part of the MMCO. I analyze variation in phytolith assemblage composition (i.e. Δ% of different plant functional types) in time, and interpret it in the light of the current climatic hypothesis derived from isotopic and and faunal data from the SCF.