The sedimentary units unconformably overlying the red granite at Angosto de La Quesera (Cordillera Oriental, Salta) and their stratigraphical interpretation: a critical revision more than 60 years after the pioneering work by J. Keidel

Abstract

After more than 60 years since the work by J. Keidel, the age and characteristics of the Paleozoic deposits that overlie the red granites of the Santa Rosa de Tastil pluton at Angosto de La Quesera (Cordillera Oriental, Salta province) are discussed. Recent work has questioned the unconformity described by that author and has reassigned part of the overlying sequence to the cambrian Mesón Group. This work focuses on the stratigraphical relationships and ratifies the discordant relationship between the overlying units and the granite basement and suggests their Ordovician age. Keidel (1943) not only described with certainty the stratigraphy and outcrop relationships in this area, but also did some detailed observations that even today cannot easily be discounted. The stratigraphical succession in the Angosto is composed of the Cardonal, the Devendeus and the Saladillo Formations. Their architecture and stratigraphical significance is discussed and compared with those of sequences cropping out in the adjacent regions, with the purpose of establishing a proper setting for the stratigraphical correlation. The presence of the Mesón Group within the Angosto is discounted and also the supposition of synsedimentary intrusive bodies. The particular situation of this region allows merging of the elsewhere separated Tilcaric and Iruyic unconformities in one same unconformity. In addition there was an important phase of later emergence related to the intra-Ordovician Tumbaya tectonism. The suggestion of a shortened hiatus within the Tilcaric unconformity is also rejected.