STRATIGRAPHY AND STRUCTURE OF THE GUARGUARÁZ COMPLEX, FRONTAL CORDILLERA, ARGENTINA

Detailed mapping of the Mendoza Frontal Cordillera basement in the Río de las Tunas area indicates the presence of previously unrecognized metamorphic facies such as quarzitic schists, marbles and calcareous mudstones. The protoliths were deposited in active marginal basins, with siliciclastic and carbonate platforms, and slope facies. All of them show clear primary sedimentary structures, such as lamination, crosscutting structures and sigmoidal bodies, due to bar migration.

Deep submarine channels occupied by turbiditic flows, which display an east-west paleoflow, incised the carbonate platform. Transitional relationships between carbonate platform, now represented by marbles and crystalline carbonates, and turbiditic flows, represented by micaceous schists, can be recognized in the upper levels of the turbidic sequences. At the same time, basic submarine volcanism occurred in the basin. The volcanic products include pillow lava, lava flows, basic dikes and sills. Their emplacement and paleogeographic setting is still unclear.

Basement rocks were metamorphosed under greenschist and amphibolite facies, whereas turbiditic facies show very low-grade metamorphism. Structure of the Frontal Cordillera basement is not simple, and most of its setting is unknown. Schists and calcareous mudstones developed crenulation cleavage and SC cleavage. In the eastern area, marbles and interbedded schists are folded in wide structures with large curvatures, whereas the turbiditic sequences, preserving their original arrangement, form thick (more than 400 m) sedimentary piles in nearly horizontal structures.