Middle Eocene-Oligocene broken-foreland evolution in the Andean Calchaqui Valley,NWArgentina: insights fromstratigraphic, structural and provenance studies

C. DEL PAPA; F. HONGN; J. POWELL; PATRICIO PAYROLA; M. DO CAMPO; M, STRECKER; I. PETRINOVIC; A. SMITH; R PEREYRA

BASIN RESEARCH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 25 p. 574 - 593

0950-091X

Two end-member models have been proposed for the Paleogene Andean foreland: a simple W-Emigrating foreland model and a broken-foreland model. We present new stratigraphic, sedimentologicaland structural data from the Paleogene Quebrada de los Colorados (QLC) Formation, in theEastern Cordillera, with which to test these two different models. Basin-wide unconformities,growthstrata and changes in provenance indicate deposition of the QLC Formation in a tectonicallyactive basin. Both west- and east-vergent structures, rooted in the basement, controlled the depositionand distribution of the QLC Formation from the Middle Eocene to the Early Miocene. Theprovenance analysis indicates that the main source areas were basement blocks, like the PaleozoicOire Eruptive Complex, uplifted during Paleogene shortening, and that delimits the eastern boundaryof the present-day intraorogenic Puna plateau. A comparison of the QLC sedimentary basin-fillpattern with those of adjacent Paleogene basins in the Puna plateau and in the Santa Barbara Systemhighlights the presence of discrete depozones. These reflect the early compartmentalization of theforeland, rather than a stepwise advance of the deformation front of a thrust belt. The early Tertiaryforeland of the southern central Andes is represented by a ca. 250-km-wide area comprising severaldeformation zones (Arizaro, Macon, Copalayo and Calchaquı) in which doubly vergent or asymmetricstructures, rooted in the basement, were generated. Hence, classical foreland model is difficult toapply in this Paleogene basin; and our data and interpretation agree with a broken-foreland model.