CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
artículos
Título:
PHYTOLITH ANALYSIS OF THE KOLUEL-KAIKE FORMATION (EARLY-MIDDLE EOCENE), PATAGONIA, ARGENTINA
Autor/es:
ZUCOL, A.; BREA, M.; RAIGEMBORN, M. S.; KRAUSE, J. M.; MATHEOS, S
Revista:
INTERNATIONAL JOURNAL OF PLANT SCIENCES
Editorial:
UNIV CHICAGO PRESS
Referencias:
Lugar: CHICAGO; Año: 2011
ISSN:
1058-5893
Resumen:
The major evolution of the flowering plants occurred before Gondwanaland began to break up, and has continued on the different fragments (Whitmore 1990). It is possible to identify three critical times to understand the radiation, adaptation and diversification of the early angiosperms. The first arisen at the Cretaceous-Paleogene boundary (K/P); the second in the Earliest Paleocene; and the third, as the most critical time, during the Eocene-Oligocene Transition (EOT) in the boundary of the Oligocene glaciations. During the two first periods, marked changes in the floral composition took place, which would originate the ancestral pool that development during the drastic changes of the EOT. This geological time range coincides with the major tectonic activity and the volcanism associated with the Gondwanaland supercontinent breakup (Behrensmeyer et al. 1992). Such a break up is of special significance for the tropical biogeography because all tropical extant regions lie on its fragments (Whitmore 1990). Since the floristic groups that come later to Miocene are the principal lineages that compound the South American Quaternary paleofloras, to know about the pre-breaking up Gondwanaland paleoflora is essential to understand the development of both climate and vegetation changes of the different constituents parts of this supercontinent. In this sense, and particularly referred to Central Patagonia, diverse paleobotanical studies were made in the sedimentary sequences of the Paleogene of the San Jorge basin on the last 10 years, thus contributing to the knowledge of the floristic composition during the Paleocene-Eocene interval (Matheos et al. 2001, 2005; Zucol et al. 2004a, 2004b, 2008, 2010; Brea et al. 2005a, 2005b, 2008a, 2008b, 2009, 2011; Brea and Zucol 2006; Prámparo et al. 2008; Raigemborn et al. 2009). Taking into account the multidisciplinary studies that are being carried out regarding the Upper Paleocene-Middle Eocene, in this contribution we make reference to the phytolith assemblages from Koluel-Kaike Formation in the Chubut province, Argentina (fig. 1). We present a phytolith analysis of the Río Chico Group and discuss the importance of the angiosperm phytoliths in the reconstruction of the Lower Paleogene paleoflora in the Golfo San Jorge Basin (Chubut and Santa Cruz provinces, Argentina). Especially an intermediate terms between arboreal dominated paleocommunities (such that found in Salamanca and Las Flores Formations (Zucol et al. 2008; Brea et al. 2008 a; Raigemborn et al. 2009)) and the mixed herbaceous/arboreal paleocommunities or savannah types (described in lower levels of Gran Barranca Member (Zucol et al. 2010)). Which involve the first records of grasses - dominated ecosystems, which will then be more abundant from the Neogene. A phytolith analysis is a useful tool to reconstruct paleoenvironment recorded from volcanic ash, since the sediments under such condition are poor in organic fossils, for example pollen and wood, but rich in phytoliths (Kondo et al. 1988). These types of analysis have provided some valuable information about palaeovegetation of these sedimentary sequences originated under great volcanic and tectonic activity.