Quaternary shortening at the Andean orogenic front (31°-33°s), Argentina: Current issues and challenges

 Carlos Costa¹, Emilio Ahumada¹, Benjamin Brooks², Andrew Meigs³, Lewis Owen⁴, Thomas Rockwell⁵, Lindsay Schoenbohm⁶, Carlos Gardini¹, Héctor Cisneros¹, Fabricio Vázquez^{1, 7}

1. Universidad Nacional de San Luis, Argentina. costa@unsl.edu.ar
2. U.S. Geological Survey, USA
3. Oregon State University, USA
4. University of Cincinnati, USA
5. San Diego State University, USA
6. University of Toronto, Canada
7. CONICET

Outstanding exposures, new data, and novel hypotheses developed during the last decade have turned the frontal deformation zone of the Andes between 31°S and 33°S (Fig. 1) into one of the most promising areas worldwide for improving the understanding on mountain building processes and seismic hazards related to thrust tectonics.

Because the Andes are relatively narrow in these latitudes, the geodetic signal in the backarc is dominated by the subduction zone locking process at the Chile trench. Nonetheless the geodetic analysis provides some useful constraints on the location and rates of modern backarc shortening, though not necessarily on the vergence. It is currently understood that backarc shortening occurs at rates of ~4-5mm/yr over a zone that is ~30km wide (across-strike) (Brooks et al., 2003; Kendrick et al., 2006). In the north (31°- 32°10° S) this would imply that the west-vergent, Eastern Precordilleran structures are the most likely to be active, while south of 32°10° S the east-vergent structures in the Southern Precordillera belt are likely to be most active (Fig. 1).

more