Abstract

RAIGEMBORN, María Sol; KRAUSE, Javier M; BELLOSI, Eduardo  and  MATHEOS, Sergio D. Stratigraphic redefinition of Río Chico Group (Early Paleogene) in the north of the Golfo San Jorge basin, Chubut. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.2, pp.239-256. ISSN 0004-4822.

The Río Chico Group (Late Paleocene-Middle Eocene), which is continental in origin and outcrop in Golfo San Jorge basin, has not got a suitable lithostratigraphic scheme yet which considers variations and spatial relationships of its internal units. In this paper, restricted to the north of the basin, four formations are redefined from base to top: Las Violetas, Peñas Coloradas, Las Flores and Koluel-Kaike. The lower relationship of this group with Salamanca Formation is transitional and it is resolved in a stratigraphic interval called in this paper transitional levels. Las Violetas Formation is restricted to the center of the study area, north edge of the basin, where it probably has a lateral relationship with Peñas Coloradas Formation. The last unit shows an important development in the coastal and western study and it disappears to the central area. Las Flores Formation has its greatest thickness in the central area (more coarse facies) and decreases towards the east and west (more fine facies). Koluel- Kaike Formation has its typical facies and greatest thickness towards the west of the study area. Whereas towards the center and east the thickness decreases until it disappears towards the north edge of the basin. The relationship of the last unit with the upper lying Sarmiento Formation is transitional.

Keywords : Stratigraphy; Río Chico Group; Paleogene; Golfo San Jorge Basin.

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