Definición litoestratigráfica de la Formación Ciénaga del Río Huaco (Cretácico) Precordillera central, San Juan, Argentina

LIMARINO, C.O; NET, L.; GUTIÉRREZ, P.R.; BARREDA, V. D.; CASELLI, A.; BALLENT, S.

Revista de la Asociación Geológica Argentina

Sigma

Lugar: Buenos Aires; Año: 2000 vol. 55 p. 83 - 99

1851-8249

Lithostratigraphical definition of the Cienaga del Río Huaco Formation (Cretaceous), Precodillera Central, San Juan, Argentina. A thick sequence of red beds, which has received different stratigraphical interpretations, crops out along the Eastern flank of the Precordillera to the north of the Huaco river, San Juan Province. In this paper, the name Ciénaga del río Huaco Formation is proposed for the middle part of that sequence. The Ciénada del Río Huaco Formation lies unconformably on Permian red beds of the Patquía Formation, and is covered by Tertiary (Oligocene?) conglomerates and sandstones. On the basis of its lithological characters, the Ciénaga del Río Huaco Formation is divided into three sections: lower, middle and upper. Sedimentological data suggest that the unit was deposited in a variety of continental environments. The basal part of the lower section probably originated in deep-gravel-bed braided rivers, whereas the upper part is from a san-bed meandering fluvial system. The middle section is interpreted a having been deposited by poorly channalized ephemeral floods closet o small lakes and eolian dunes. Finally the upper section comprises clastic and evaporitic sediments deposited in an ephemeral hypersaline lake. The age of the Ciénaga del Río Huaco Formation is discussed on the basis of palynomorphs and ostracod remains. Both lines of evidence are consistent and point to a Late Cretaceous (Maastrichtian) age for the red beds.