Primer registro palinológico de la Formación Puerto Madryn, Mioceno de la provincia del Chubut, Argentina

PALAZZESI, L.; BARREDA, V.

AMEGHINIANA

Lugar: Buenos Aires; Año: 2004 vol. 41 p. 355 - 362

0002-7014

Abstract. First palynological record from Puerto Madryn Formation, Miocene of Chubut province, Argentina. A diverse and well preserved palynological assemblage is described for the first time from Puerto Madryn Formation, Puerto Pirámide outcrops, peninsula Valdés. A Middle Miocene or  Late  Miocene age was suggested based on fossil remains or radiometric records. The recovered palynologic assemblage has palynomorphs of marine and continental origins, present in similar frequencies. Freshwater algae are abundant. The spore-pollen assemblage is dominated by herbaceous and shrubby elements, which suggest a halophytic and xerophytic vegetation. Chenopodiaceae (Chenopodipollis chenopodiaceoides (Martín) Truswell), Ephedraceae (Equisetosporites spp.), Convolvulaceae (Tricolpites trioblatus Mildenhall y Pocknall), and Asteraceae (Tubulifloridites spp.) are the dominant families, with subordinate Poaceae (Graminidites sp.), Malvaceae (Baumannipollis spp.) and Anacardiaceae (Striatricolporites spp.). The presence of Restionaceae (Milfordia sp.), Sparganiaceae/Typhaceae (Sparganiaceaepollenites barungensis Harris), Azollaceae (Azolla sp.) and Cyperaceae (Cyperaceaepollis neogenicus Krutzsch) indicates the development of a hydrophytic community. Arboreal components are poorly represented by Podocarpaceae, Araucariaceae and Fagaceae, briophytes and pteridophytes are also very scarce. The palynological assemblage suggests a shallow costal marine environment, with high continental input. The spore-pollen assemblage indicates salt marsh vegetation with littoral ponds of brackish to fresh water setting. A Late Miocene age is indicated by the presence of  the key species Tubulifloridites pleistocenicus Martin and T. simplis Martin. No evidence of warm to warm-temperate climatic conditions were recognized from the palynological assemblage, however dry environments would have prevailed as was pointed out by the dominance of shrubby and xerophytic elements.