Resumo

BARREDA, Viviana D.; OTTONE, Eduardo G.; DAVILA, Federico M.  e  ASTINI, Ricardo A.. Age and palaeoenvironment of the del Buey Formation, Famatina range, La Rioja, Argentina: sedimentological and palynological evidences. Ameghiniana [online]. 2006, vol.43, n.1, pp.215-226. ISSN 1851-8044.

Sedimentary facies and palaeoenvironments are described and interpreted from the del Buey Formation, Famatina Range, La Rioja Province. Miospores and algae are reported for the first time in this unit. The del Buey Formation is mainly composed by pinkish to reddish shales, some conglomerates, and conspicuous levels of mudstones, interpreted as braidplain and lacustrine deposits. The palynological assemblage, recovered from the lacustrine facies, is scarce and low-diversified. It is composed by probably allochtonous Podocarpaceae, together with Malvaceae and mostly halophytic-xerophytic herbs and shrubs of Chenopodiaceae, Ephedraceae, Convolvulaceae and Asteraceae, as well as tropical taxa such as Magnaperiporites (Convolvulaceae?) and Senipites (Symplocaceae). The assemblage also contains Pteridophyta, Bryophyta and Chlorococcales ( Botryococcus and Pediastrum ). Species of Malvaceae and Sparganiaceae/Thyphaceae would represent the vegetation of a freshwater lake, a habitat adequate to the development of planktonic green algae, whereas the remaining taxa could have developed in lacustrine marginal environments. The record of xerophytic and tropical taxa coupled with the development of calcretes and intrasedimentary gypsum suggest semiarid and warm to warm-temperate climate conditions. Recent isotopic data indicate a Middle Miocene age for the del Buey Formation, palynological evidence supports this temporal assignment.

Palavras-chave : Argentina; Famatina range; Miocene; Sedimentology; Palynology.