Artículos

Landscapes antiquity of the Central Sierras Pampeanas (Argentina): Geomorphic evolution since the Gondwanas times

CARIGNANO, CLAUDIO ALEJANDRO; CIOCCALE, MARCELA ALEJANDRA; RABASSA, JORGE OSCAR

ZEITSCHRIFT FUR GEOMORPHOLOGIE. SUPPLEMENTBAND

Gebr. Borntraeger Verlagsbuchhandlung, Science Publishers, Stuttgart

Año:1999 vol.118 p.245-268

0044-2798

This paper discusses the significance of relict landforms eroded on Precambrian, Palaeozoic and Mesozoic rocks of the Sierras Pampeanas (Argentina), within the framework of Gondwanaland evolution. This paper discusses the significance of relict landforms eroded on Precambrian, Palaeozoic and Mesozoic rocks of the Sierras Pampeanas (Argentina), within the framework of Gondwanaland evolution. The geomorphological evolution of the Central Sierras Pampeanas is analyzed within the geological context of southernmost South America during the Mesozoic and Cainozoic times. The erosion surfaces which have successively levelled the regional relief are identified by using geomorphological, geometrical, structural and sedimentological criteria. The reconstructed morphogenetic evolution is as follows. During Jurassic times, a long period of tectonic quiescence and predominantly humid tropical climate enabled the progressive development of a broad, planation surface. The occurrence of corestones, bornhardts, tors, and deep weathering profiles are interpreted as residual landforms of that surface. The Late Jurassic-Late Cretaceous interval was marked by continental rifting and the ranges degradation under less humid, semi-arid climates. During this rifting interval, each major faulting event generated an erosional cycle. Thus, two planation surfaces were developed in a very long and complex denudation cycle. Remnants of these surfaces are still preserved around the nuclei of each of the larger blocks of the Sierras Pampeanas. Such surfaces were weathered during the Latest Cretaceous-Palaeocene lapse and, later, they were further worn down under semiarid climate from Early Eocene to Oligocene times, developing a fourth planation surface. During the Miocene a fifth planation surface was developed. Thick and mature calcretes remain as evidence of long-term, stability conditions. Due to the Pampean faulting and uplifting during the last 10 Ma, almost all surfaces have been broken and tilted.  The herein described Sierras Pampeanas planation surfaces are tentatively correlated with those of Eastern Brazil and Southern Africa.