Preliminary phytolith analysis of Sarmiento Formation in the Gran Barranca (Central Patagonia, Argentina).

ZUCOL, A. F.; M. BREA; E. BELLOSI; A. A. CARLINI & G. VUCETICH.

Plants, People and Places: Recent Studies in Phytolithic Analysis

Oxbow Books, Oxford, UK.

Lugar: Oxford; Año: 2007; p. 197 - 203

ABSTRACT The sedimentary sequence at Gran Barranca, the escarpment south of lake Colhué Huapí (Chubut province, Argentina), is composed mainly of pyroclastics of the Sarmiento Formation. In the MMZ profile, the Sarmiento Formation comprises three successive stratigraphic units: Gran Barranca; Puesto Almendra and Colhué Huapí members. The present contribution show the preliminary results of the phytolith analysis of this Formation in the MMZ profile, wherein the phytolith assemblages from the sequence are described. The phytolith assemblage throughout the entire sedimentary succession is characterized by the presence of different morphotypes, such spherical to aspherical spinulose to smooth phytoliths, pooid (festucoid), chloridoid and panicoid  phytoliths, elongate, point-shaped and fan-shaped  phytoliths. In addition, some levels also include spongy spicules and diatoms. Sarmiento Formation phytolith analysis show that assemblages are dominated by palm phytoliths during the Middle Eocene, that are replaced up-section by assemblages with more abundant graminoid phytoliths, with panicoid components dominant in the Late Eocene and chloridoid–pooid components dominant in the Oligocene – Early Miocene. The upper section of profile (Early Miocene) shows the presence of previously described floristic components although present in relatively smaller frequencies and oscillations or alternating abundances of the megatermic and meso-microtermic grass components. KEY WORDS. Phytolith analysis, Eocene – Miocene, Patagonia, Argentina.