Constraints on post-Oligocene deformation and unroofing of the central Puna Plateau at ~23°S latitude, northwestern Argentina

ALICE LETCHER, RICARDO N ALONSO, ISABELLE COUTAND, TREVOR DUMITRU, PAUL R RENNE, MANFRED R STRECKER, MASA SUDO, GEORGE HILLEY

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012

0895-9811

Abstract We present new field observations, Apatite Fission Track (AFT), Apatite Helium thermochronometry (A-He), and 40Ar/39Ar geochronometry from the Susques Basin on the Puna Plateau of northwestern Argentina that provide time constraints on the post- Oligocene exhumation and deformation history of this area. Thermal modeling of three AFT samples from this area indicates that they were exhumed through the AFT total annealing temperature (TA) between 26 and 20 Ma. Exhumation of the ranges bounding the Susques Basin thus appears to have started slightly earlier than, and continued contemporaneously with, exhumation of the eastern margin of the Puna Plateau, as recorded by transects across this margin farther south. A-He ages were consistently older than AFT ages and simulation of many randomly generated thermal histories showed that these two datasets are irreconcilable. It therefore appears that the A-He data from the basin-bounding ranges cannot be relied upon to provide unambiguous constraints on the thermal history of this region. Our new 40Ar/39Ar ages from deformed sedimentary strata within the Susques Basin constrain the timing of intrabasin shortening to approximately 6.5 Ma, after which tectonism appears to have ceased. If these samples can be viewed in the same tectonic context as samples along a transect at ~25° S lat, our results and those previously reported indicate that in this region deformation initiated within the plateau realm during Oligocene to early Miocene time and affected the eastern plateau margin between approximately 21 and 18 Ma.