Middle Eocene deformation-sedimentation in the Luracatao Valley: Tracking the beginning of the foreland basin of Northwestern Argentina.

PAYROLA BOSIO, P.A., DEL PAPA, C., POWEL, J., HONGN, F.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam ; Año: 2009 vol. 28 p. 142 - 158

0895-9811

The Andean foreland basin overlaps the Cretaceous-Paleogene Salta rift basin in northwestern Argentina.Knowledge of the relationship between rift and foreland basins is key to understanding the initial stagesof foreland basin development related to Andean shortening. We present a new stratigraphic scheme forthe Luracatao Valley, revealing that the Quebrada de los Colorados Formation (Payogastilla Group) liesover the Santa Bárbara Subgroup (Salta Group) through an erosional unconformity that turns into anangular unconformity close to folds and faults recorded in the Santa Bárbara Subgroup. The base of theQuebrada de los Colorados Formation shows growth strata along the west frontal limb of an anticlinewith Santa Bárbara units in its core. The finding of a mammalian fossil at the base of the Quebrada delos Colorados Formation allows us to assign a Middle-Upper Eocene age to the sedimentation; therefore,the time elapsed between the deposition of the final postrift strata and the beginning of Andean sedimentationwas brief and constrained to the Lower-Middle Eocene. This data indicates that the Eocene deformationphase described in other portions of the Puna-Cordillera Oriental transition (e.g., the northernCalchaquí Valley and Aguilar range) is also present in the Luracatao Valley, offering new tools for interpretingthe ages and distributions of the initial episodes of sedimentation and deformation related to theAndean shortening. Thus, the Luracatao Valley provides new evidence for tracking the distribution of thePaleogene deformation in northwestern Argentina.