Crustal structure of the high Andes in the north Pampean flat slab segment from geophysical data

MARCOS A. SÁNCHEZ; JUAN P. ARIZA; M. CECILIA WEIDMANN; DIEGO WINOCUR; ANDRES FOLGUERA; MYRIAM P. MARTINEZ

Santiago de Chile

Simposio; 1º Simposio de Tectonica Sudamericana; 2016

Asociacion de Tectonica Sudamericana

The Main Andes at the northern Chilean - Pampean flat slab segment were formed by the inversion of late Oligocene to early Miocene extensional depocenters in Neogene times. Their structure, size and depth are loosely constrained by field data since these sequences have amalgamated forming an almost continuous blanket with scarce basement outcrops and their base is limitedly exposed. From a wide geophysical database own of Instituto Geofísico - Sismológico Volponi (Universidad Nacional de San Juan) such as, satellite and aerial gravity and magnetic data, in this work we propose a 3D model that shows the basement structure at depth. Then a 2D structural section was adjusted across -29°30? S by using the 3D model and field data. The results indicate complex basin geometry with depocenters of variable size and depth buried beneath Mesozoic (?) -Paleogene and Neogene sections. Additionally, previously proposed crustal heterogeneities across this orogenic segment are geophysically constrained with a new crustal heterogeneity identified on the basis of a modeled 2D crustal section. We propose hypothetically, that this crustal discontinuity could have played a role in controlling Paleogene extension at the hanging wall of an asymmetric rift basin, explaining the locus and development of the Doña Ana Basin. Finally, this work provides new information about Cenozoic structure and Paleozoic basement architecture, presumably derived from amalgamation history of one of the highest and more inaccessible regions of the Andes