IGEBA   23946
INSTITUTO DE GEOCIENCIAS BASICAS, APLICADAS Y AMBIENTALES DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
Comment on Impact structures in Africa: A review
Autor/es:
R.D. ACEVEDO, J. RABASSA, H. CORBELLA, M.J. ORGEIRA, C. PREZZI, J.F. PONCE, O. MARTÍNEZ, M. GONZÁLEZ-GUILLOT, M. ROCCA, I. SUBÍAS
Revista:
JOURNAL OF AFRICAN EARTH SCIENCES - (Print)
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2014 p. 1 - 4
ISSN:
1464-343X
Resumen:
Reimold and Koeberl (2014) published a detailed account of the African impact record. In the same paper they refer (on page 67) to recent reports of an entire impact crater strewn field in the volcanic Bajada del Diablo area of Argentina, where many crater-like features have been related to impact but, to date, no conclusive pro-impact evidence ? what-so-ever ? has been recognized; arguing that they may be related simply to volcanic processes. Later in their paper (on page 87) Bajada del Diablo is dismissed as an impact feature because it does not conform to the established criteria in Reimold et al. (2014). This expressed view dismissing an impact origin for Bajada del Diablo is also based on partial information and not on the entire data set provided in the paper by Acevedo et al. (2009). Reimold and Koeberl (2014) have omitted in the paragraphs noted above the main geologic argument of impact at Bajada del Diablo: the impact cratering reached two different but contiguous lithostratigraphic units (Acevedo et al., 2009). Therefore, they are overlooking the irrefutable evidence of craters, very close to each other, which have most likely been the result of impacts upon two dissimilar geologic environments. The authors have mentioned only the ancient volcanic environment, excluding the much younger sedimentary deposits which were also affected (Fig. 1). They have also ignored the proven fact that volcanic activity in the area ended several million years before these impacts took place. Moreover, the lack (so far) of findings of meteorite fragments or shock metamorphism in the Bajada del Diablo area does not necessarily mean that these crater-like features are not impact craters. As one of the mentioned authors stated just a few years ago: At present, however, meteorite components have been identified for less than one-quarter of the impact structures identified on Earth (C. Koeberl in Sites of impact, S. Gaz, 2009, p.15). Once more, the absence of evidence is not evidence of absence, but it may suggest instead that the impacting object could have been a blasting ice comet or its expansive waves. Furthermore, geophysical research on the Bajada del Diablo impact crater strewn field has been presented recently in Acevedo et al. (2012) and Prezzi et al. (2012, 2013) where electromagnetic, magnetic and gravity anomalies over both basalts and conglomerates of Bajada del Diablo (Fig. 1) are characteristic of those found at proven impact structures.