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Structural and Stratigraphic Development in the Early Stages of the Andean Broken Foreland, Famatina Ranges, Western Argentina

F. M. Davila
CONICET and Catedra de Estratigrafı´a y Geologı´a Histo´rica, Universidad Nacional de Co´rdoba, Argentina

The early evolution of the Andean mountain chain is a matter of debate and constitutes a crucial topic to be addressed. The timing of the onset of regional contraction and mountain building is unconstrained in the central-southern Andes, a complex region with significant basement involvement, known as the “broken foreland” in west Argentina. The Famatina Ranges are located on the boundary between the classic fold-and-thrust belt and this broken foreland area, and has a thick Tertiary stratigraphy that needs to be understood in order to better address the depositional environments and the structural setting and evolution.

Andean shortening is usually based on balanced cross-sections that comprise late Oligocene to Recent stratigraphy. Nevertheless, some researches have suggested orthogonal convergence between the Nazca Plate and western South America since the Paleocene. The latter implies that regional contraction should have been active during the growth of the Andes with hypothetically coeval development of Paleocene foreland basins. These foreland basins were segmented and almost completely reworked during the last stages of the Andean Mountain building. So far, no evidence of Paleocene sedimentation and early Tertiary uplifting and deformation has been proven in the western Argentina. However, on the basis of fission-track analysis and a recent stratigraphic survey on the Del Creston Formation in the thrust belt that the Famatina Ranges reveals the possibility of this 1500 m thick coarse clastic succession represents an early “lostlink” of the foreland basin evolution.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid