TECTONOSTRATIGRAPHY OF THE EXTERNAL FUEGIAN FOLD AND THRUST BELT, SOUTHERMOST ANDES, TIERRA DEL FUEGO, ARGENTINA

In this work, we combine extensive field data with detrital zircon U-Pb dating, calcareous nannofossils and dynocists analysis in order to constrain the tectonostratigraphy of the Fuegian Andes and have a better understanding of the evolution of the fold and thrust belt.

The Fuegian fold and thrust belt developed between the Danian and early Miocene at the southernmost tip of South America, caused by the closure of a prior back-arc basin. The external domain of this fold and thrust belt affects sedimentary rocks of a foreland basin (Magallanes-Austral basin and its extension to the Malvinas basin). In the eastern area, near the Atlantic Ocean where the cliffs have great outcrops, the stratigraphy and structures are quite well studied but the timing of deformation is resolved partially, because the sequences are not connected. However, The western area is characterized by few dispersed outcrops and therefore has a low stratigraphic resolution. Thus, it remains unclear which units are present in the area, their ages and their correlation with other units from the basin as well as how many deformation events can be identified in the study area.

This study allowed us to incorporate to the stratigraphic column, three new Cenozoic units, previously unknown at the area as well as to establish a deformation sequence with three contractional stages from the Danian to the Oligocene. These stages can be correlated with equivalent episodes recognized along the belt. These findings contribute to our understanding of the interaction between the tectonics and sedimentology of the Austral basin, an oil and gas exploratory frontier, with new elements that can enhance previous structural models.