Paper No. 35-1
Presentation Time: 8:00 AM-5:30 PM
EXHUMING THE SIERRA DE CULAMPAJÁ-PAPACHACRA: INTEGRATING APATITE (U-Th)/He AND FISSION-TRACK DATA
HAWKINS, Justin1, BECK, Charley1 and TYE, Alexander2, (1)Earth, Energy, and Environmental Sciences, Utah Tech University, 225 S University Avenue, St. George, UT 84770, (2)National Park Service, Zion National Park, State Route 9, Springdale, UT 84767; Earth, Energy, and Environmental Sciences, Utah Tech University, 225 S University Avenue, St. George, UT 84770; National Park Service, Geologic Resources Division, Post Office Box 25287, Denver, CO 80225
This study aims to address a critical gap in our understanding of the temporal and spatial dynamics of the convergent boundary and the associated orogenic processes that have shaped the central-southern Andes in NW Argentina. We used apatite (U-Th)/He dating and fission track thermochronometry to determine the age of exhumation of the Sierra de Culampajá-Papachacra, which forms the eastern margin of the southern Puna plateau. In this study, we collected two sets of samples from the Sierra de Culampajá-Papachacra and conducted new apatite (U-Th)/He dating on each. One set was collected along Argentina Rt. 43 near the village of Barranca Larga, while the other set of samples was collected near the village of Corral Quemado. The combination of the new apatite (U-Th)/He and fission-track data with the existing apatite fission-track (AFT) data from the area allows us to gain a more comprehensive perspective on the geological evolution of the region.
Our findings reveal that the apatite (U-Th)/He ages for the samples range between 6.3 and 28.6 Ma, indicating significant cooling and exhumation phases during this period. Additionally, the AFT ages for the Corral Quemado samples ranged from 16.5 to 20.3 Ma. Most of the thermal modeling results suggest that rapid uplift occurred from a range of 22 Ma to 15 Ma across both samples. In contrast with prior studies that yielded several Eocene-Oligocene apatite fission track ages (38-29 Ma), our new ages show that exhumation of the Sierra de Culampajá-Papachacra persisted into Middle Miocene time (15 Ma).
Our analysis of the Sierra de Culampajá-Papachacra, enhanced by the integration of new apatite (U-Th)/He data with existing AFT data, suggest that this region was tectonically active during Middle-Late Miocene deformation of the southern Puna plateau, and thrusting within this range may have been related to lithospheric foundering, rapid uplift across the southern Puna, and/or shallowing of the Nazca slab during Miocene time.
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