Circular Natural Geoforms, Sierras Pampeanas and Chacopampeana Plain, Argentina

Abstract

Structural geoforms often allow us to interpret the processes that gave rise to them. Circular geoforms are normally associated with meteorite falls, with the volcano caldera or the intrusion of igneous bodies, and elliptical geoforms with tectonic processes. We describe eight circular morphological features representing depressed areas based on visual interpretations from satellite and radar scans images. Three geoforms are located at the northern of the Sierras Pampeanas and the others five in Chacopampeana plain in Argentina. The La Ciénaga circular structure is 15 km in diameter, Las Cejas is 34 km in diameter and Schaqui is 21 km in diameter. The semicircular structures of the Chacopampeana plain (Las Víboras, El Fadeté, La Irma and Laguna de los Cisnes) are between 15 and 31.5 km in diameter. The elongated Campo del Cielo structure connected to the El Fadeté structure has an E-W strike, 12 km long and 4km wide, similar characteristics to those described in the literature. These studied structures have no associated volcanic rocks and no evidence of tectonic activity is observed. The La Ciénaga structure is a depression covered by quaternary sediments. The Schaqui structure is formed in an environment of intrusive rocks and its morphology is marked by the contact between them. In the Las Cejas structure, seismic profiles show the normal fault of one of its edges and the basin generated in its center. In Campo del Cielo several structures were found associated with the fall of meteorites; the structures described there seem to be formed by the impact of an object and contrast with the monotony of the rest of the area. Until now rings of these characteristics, magnitudes and diameters are unknown and unheard of in Argentina.