Exhumation of the Precordillera and northern Sierras Pampeanas and along-strike correlation of the Andean orogenic front, northwestern Argentina

Roxana Safipour, Barbara Carrapa, Peter G. DeCelles, Stuart N. Thomson

Research output: Chapter in Book/Report/Conference proceedingChapter

11 Scopus citations

Abstract

In NW Argentina (∼26°S), adjacent to the Puna Plateau of the central Andes, exhumation and deformation propagated from west to east across the Puna Plateau and Eastern Cordillera during early-late Cenozoic time. Presently existing data do not indicate a clear eastward younging trend in exhumation in the Precordillera and northern Sierras Pampeanas at the southeastern flank of the Puna Plateau at ∼28°S. In this study, we mapped an ∼80-km-wide transect at a latitude of ∼28°S in the Sierra de Las Planchadas and the Fiambalá Basin. Apatite fission-track (AFT) ages from six samples from thrust fault hanging walls are between 20 and 14 Ma, and apatite helium (U-Th)/He ages from five samples range from 21 Ma west of the Sierra de Las Planchadas to 2 Ma in the Fiambalá Basin. Several samples record mixed apatite (U-Th)/He ages and pre-Cenozoic AFT ages, indicating partial resetting through the 120-60 °C temperature window and suggesting a depth of exhumation between ∼6 and 3 km. Thermal modeling of AFT and (U-Th)/He ages indicates cooling from ca. 22 Ma until 2 Ma and a younging trend to the east. These ages are consistent with previously published AFT ages in the Fiambalá region and AHe ages in the Eastern Cordillera to the northeast and suggest Miocene exhumation and deformation in the Precordillera at 28°S and the Eastern Cordillera at 26°S. From a kinematic standpoint, the region of the Precordillera at 28°S may be considered a continuation to the south of the Eastern Cordillera at 26°S, implying a single continuous SW-NE-striking deformation front along this portion of the central Andes. Detrital zircon U-Pb ages from Upper Miocene strata in the Fiambalá Basin suggest that Permian-Miocene rocks in the Sierra de Las Planchadas are the primary source of the Miocene basin fill. This is consistent with previously published eastward-directed paleocurrent data and other provenance proxies and indicates that uplift of the Sierra de Las Planchadas began no later than ca. 9 Ma.

Original languageEnglish (US)
Title of host publicationGeodynamics of a Cordilleran Orogenic System
Subtitle of host publicationThe Central Andes of Argentina and Northern Chile
EditorsMihai N. Ducea, Mihai N. Ducea, Peter G. DeCelles, Paul A. Kapp, Barbara Carrapa
PublisherGeological Society of America
Pages181-199
Number of pages19
ISBN (Electronic)9780813712123
DOIs
StatePublished - Jan 1 2015

Publication series

NameMemoir of the Geological Society of America
Volume212
ISSN (Print)0072-1069

ASJC Scopus subject areas

  • Geology

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