CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
artículos
Título:
Comment on ??Impact structures in Africa: A review?? by Reimold and Koeberl [J. Afr. Earth Sci. 93 (2014) 57?175]
Autor/es:
ACEVEDO, R.; RABASSA, J.; CORBELLA, H.; ORGEIRA, M.J.; PREZZI, C.; PONCE, J.F.; MARTÍNEZ, O.; GONZÁLEZ GUILLOT, M.; ROCCA, M.; SUBÍAS PÉREZ, I.
Revista:
JOURNAL OF AFRICAN EARTH SCIENCES - (Print)
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2014
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 (Koeberl, 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.