Advances In The Ordovician Palynology Of Argentina: biostratigraphy and paleobiogeography

RUBINSTEIN, C. V., DE LA PUENTE, G. S., SERVAIS, T., VECOLI, M. & ASTINI, R. A.

Tres Cantos, Madrid, España

Congreso; 4th European Meeting on the Palaeontology and Stratigraphy of Latin America; 2007

Instituto Geológico y Minero de España (IGME)

Because of their small size and their wide distribution in many marine and continental rocks, palynomophs are considered a useful tool for biostratigraphic and palaeogeographic purposes. Their potential for dating and correlations is largely recognized and consequently the interest on palynomorphs studies has increased together with the rise of the oil industry. In the last 10 years, the knowledge on Ordovician palynology in Argentina has increased notably, mainly concerning marine palynomorphs such as acritarchs and related algal forms. These studies focused mostly on the Ordovician basins of northwestern Argentina, including the Central Andean Basin extending into Bolivia and Perú and the Famatina Basin. Traditionally, the Puna region, the Cordillera Oriental, the Sierras Subandinas and the Sierras de Santa Bárbara, as well as the subsurface in the Chaco plains, were considered as separated basins derived from Cenozoic tectonism and the Andean growth, based on morphostructural criteria. Nevertheless, nowadays, no significant stratigraphical evidence neither palaeontological data support that these five geological provinces corresponded to different basins during the Ordovician, but to linked depositional systems within a broad foreland basin, developed within the upper plate across the western Gondwana margin. Lithological variations, local development of unconformities and slight palaeontological differences may represent a laterally continuous succession of adjacent depositional settings (including onshore-offshore gradients) occurring across the foreland (Astini, 2003, Astini et al., 2003). In the Famatina region, the Lower-Middle Ordovician succession of the Famatina Group is interpreted as part of a suprasubduction volcanic-arc, located along western Gondwana and developed prior to accretion of the Precordillera terrane (Astini, 1999; Astini and Dávila, 2004). In this particular depositional system, acritarch and chitinozoan integrated studies lead to constrain the age of the succession, to find out paleogeographical affinities and the relationship between the local variability in palynological assemblages and paleoenvironmental changes (Achab et al., 2006).The aim of this contribution is to show how palynological investigations, integrated to sedimentological and palaeontological studies together with facies analysis, can contribute to a better understanding of the evolution of such different geodynamic environments.This work is part of an international collaboration project carried out by the authors, concerning the evolution of the biodiversity of Ordovician marine and terrestrial palynomophs from the Gondwana margin.