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Mountain building processes at the orogenic front. A study of the unroofing in Neogene foreland sequence (37ºS)

Article

Authorship
SAGRIPANTI, LUCIA
Date
2012
Publishing House and Editing Place
SERVICIO NACIONAL GEOLOGIA MINERVA
Magazine
ANDEAN GEOLOGY, vol. 39 (pp. 201-219) SERVICIO NACIONAL GEOLOGIA MINERVA
Summary Information provided by the agent in SIGEVA
The orogenic front at 37ºS has been mainly formed through at least two ontraccional stages, as inferred from the exhumed major angular unconformities at the Late Eocene and the Late Miocene times respectively. A Late Cretaceous event is restricted to the hinterland zones in the Main Cordillera. A series of syntectonic sedimentary packages, that thin to the east is identified through a detailed description of the cannibalized westernmost Neogene foreland basin associated with the Sierra de ... The orogenic front at 37ºS has been mainly formed through at least two ontraccional stages, as inferred from the exhumed major angular unconformities at the Late Eocene and the Late Miocene times respectively. A Late Cretaceous event is restricted to the hinterland zones in the Main Cordillera. A series of syntectonic sedimentary packages, that thin to the east is identified through a detailed description of the cannibalized westernmost Neogene foreland basin associated with the Sierra de Reyes. Their detrital microscopic and macroscopic descriptions reveal that the Neogene basin was fed from the west and particularly from the eastern Sierra de Reyes slope at the time of mountain incision. Detrital composition of the upper section reveals that a metamorphic component is present, implying that a domain further east has been exhumed, and therefore that the westernmost foreland basin has been cannibalized. This also implies that exhumation previous to Miocene times should have been minimum in the area, since the Neogene succession represents a complete unroofing. The structural cross sections show Neogene shortening of about 20%, leaving in comparison Eocene contraction as negligible.
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Key Words
Synorogenic depositsForeland basinMalargüe fold and thrust beltCentral Andes