Phytolith studies in Gran Barranca, Central Patagonia, Argentina

ZUCOL, A.; BREA, M.; RAIGEMBORN, M. S.; MATHEOS S. D.

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

Cambridge University Press.

Lugar: Cambridge (UK); Año: 2007;

In the Golfo San Jorge basin, central Patagonia, Argentina, during the Upper Paleocene-Eocene?, an important fluvial cycle is developed whose sediments have been called the Río Chico Group. This Group is formed by three units: the Peñas Coloradas, Las Flores and Kaluél Kaike formations. In the present contribution were analyzed the sedimentary samples obtained in the BCH profile (45° 43´ 26 ´´ LS and 68° 37´ 14 ´´ LW) of the Gran Barranca locality, where Las Flores and Koluél Kaike formation outcrop. Four phytolith assemblages were recognized characterized by the abundance of angiosperm and palm phytoliths, associated with Poaceae, Cyperaceae and Podostemaceae phytoliths. Sponge siliceous spicules, Chrysostomataceae cycts and diatoms also have been found in these assemblages. Ten families and one Order were recognized (Arecaceae, Chrysobalanaceae, Mimosaceae, Magnoliaceae, Annonaceae, Burseraceae, Boraginaceae?, Poaceae, Cyperaceae, Podostemaceae and Zingiberales). The palaeovegetation would have conformed humid tropical and subtropical forests, some dominated by woody angiosperms and others for palms. These forests would have been developed under climatic warm and humid conditions. The existence of these climatic conditions for Upper Paleocene-Eocene? is also support by the paleoxylologic records as well as the climatic inferences obtained by means of the sedimentological characteristics.