Abstract

VERGEL, María del Milagro; ACENOLAZA, Guillermo F.  and  ARAOZ, Lucía. The Casa Colorada Formation at the Quebrada de Moya (Cambrian-Ordovician): contributions to the chronostratigraphy of a classical locality in the Cordillera Oriental of Jujuy (Argentina). Ameghiniana [online]. 2007, vol.44, n.3, pp.621-630. ISSN 1851-8044.

The Casa Colorada Formation is represented by a thick siliciclastic sequence that crops out in the mid-sector of the Quebrada de Humahuaca, Jujuy Province. Trilobites, conodonts, brachiopods, echinoderms, trace fossils and palynomorphs are recorded in the strata and allowed, with some minor differences, to a general chronostratigraphic understanding of the Cambrian-Ordovician transition in the region. The Casa Colorada Formation was formally defined in the 1960´s on the basis of an informal nomination done in the 1950´s. During the last years, an increasing amount of publications in the area leaded to the creation, use and missuse of stratigraphic nominations, generating some inconsitencies in the literature. This contribution proposes a new stratigraphycal frame for the above mentioned situation, and presents palynological data for the Casa Colorada Formation that crops out at Quebrada de Moya in Chucalezna. Early Ordovician acritarchs include Buedingiisphaeridium tremadocum Rasul, Cymatiogalea cristata (Downie) Rauscher, C. membranispina Deunff, Dasydiacrodium tremadocum (Gorka) Tongiorgi in Bagnoli et al., Polygonium symbolum Rasul, Saharidia downie Combaz, Solisphaeredium akrochordum (Rasul) Moczydlowska y Stockfors, S. lucidum (Deunff) Turner, and Vulcanisphaera britannica Rasul, among the most important forms recorded in the upper levels of the unit, and represents the earliest Tremadocian association in the South American Central Andean Basin.

Keywords : Casa Colorada Formation; Cambro-Ordovician; Stratigraphy; Palynomorphs; Jujuy; Argentina.