Phytolith studies in Gran Barranca (central Patagonia, Argentina): the middle Eocene

ZUCOL, A. F. BREA, M.AND E. BELLOSI.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia

Cambridge University Press

Lugar: Cambridge; Año: 2010; p. 313 - 336

Zucol, A. F. Brea, M.and E. Bellosi. The sedimentary sequence of the southern escarpment of Lake Colhué Huapí (Gran Barranca locality, Chubut province, Argentina) is composed of Sarmiento Formation, Río Chico Group and Salamanca Formation. In the type profile (MMZ profile), the Sarmiento Formation comprises three successive stratigraphic units: Gran Barranca, Puesto Almendra and Colhué Huapí members, while Río Chico Group in the eastern extreme of the Gran Barranca (BCH profile) presents only two of its formations (Las Flores and Koluél Kaike formations). The sediments of this sequence, assigned by different indicators to the Eocene, were analyzed in their phytoliths content. The previous stages and the current state of phytolith analysis of this fossiliferous locality are summarized, with a preliminary analysis of MMZ profile. Phytolith analysis of the Río Chico Group formations (BCH profile) and Gran Barranca Member of Sarmiento Formation (MMZ profile) were implemented with satisfactory results regarding both their fertility and their variability. These results have allowed to establish a zonification of the sequence characterized by the presence of different structural features of their paleocommunities. The presence of botanical groups in each zone and their paleoenvironmental conditions are described. The oldest evidence of megathermic paleograsslands is reported for South American paleobotanical records.