Further comment to ??Reply to Comment on impact structures in Africa: A review (Short Note)?? by Reimold and Koeberl [J. Afr. Earth Sci. 100 (2014) 757?758]

ACEVEDO, R.; RABASSA, J.; ROCCA, M.; GONZÁLEZ GUILLOT, M.; MARTÍNEZ, O.; SUBÍAS PÉREZ, I.; CORBELLA, H.; PREZZI, C.; ORGEIRA, M.J.; PONCE, J.F.

JOURNAL OF AFRICAN EARTH SCIENCES - (Print)

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 100 p. 1 - 2

1464-343X

In a Comment on Reimold and Koeberl (2014a) to JAES, Acevedoet al. (2014) claimed an impact origin for Bajada del Diablo craterstrewnfield (BdD), a remote locality in Central Patagonia. Suchgenesis had been denied by Reimold and Koeberl (2014a), whorejected its relationship to any impact-cratering process since, intheir opinion, Acevedo et al. (2009, 2012, among other papers)had not found direct evidence of impact. Neither Professor WolfUwe Reimold nor Professor Christian Koeberl had visited the sitenor contacted us before about the nature of our investigations. Itwould have been nice to exchange information with theseresearchers, before they so strongly criticized our work, particularlywhen they have used, unnecessarily, quite offensive and bellicosewords, which we believe we do not truly deserve.Indeed, so far, meteorite fragments have not been found there yet,though in its place Fe?Ni- and lawrencite-bearing microsphereswere collected. Likewise, proof of shock metamorphism has not beenobserved, though some hints may have been unveiled. However, anew element of valid analyses for identification of possible astrobleme-strewn fields such as the case in question has been revealed:the fact that many similar, circular and problematic structures arediscovered over contiguous but different geological environments.In the countless discussions proposed up to now concerning definitiveevidence for impact origin of problematic structures it has neverbeen taken into account that a multiple collision of a fragmentedbody could affect different environments, thereby providing in itselfevidence for impact. That is what we think we have proven to havetaken place in Bajada del Diablo.In reply to our original Comment in JAES, Reimold and Koeberl(2014b) discarded for a second time the slightest possibility thatBdD might be an impacted area because, in a few words, the newinstance of impact identification does not appear within theirown scheme of impact evidence (French and Koeberl, 2010;Reimold and Koeberl, 2014a; Reimold et al., 2014), ignoring thatin the scientific world nobody should claim to be the unique ownerof the truth. Nevertheless, this is an interpretation which meritsbeing investigated, appealing to a presumption iuris tantum, inwhich incorrectness may be demonstrated only when enoughappropriate data are provided.Our research team that has studied this critical and remote localityhas been the only one working in situ; at the least, we think thatwe should be allowed the benefit of doubt. Our multidisciplinaryworking group has provided a clear, field based, geomorphologicalrecord hitherto unknown in other astrobleme-strewn fields inplaces where neither fragments of meteorites nor other elementswhich may unquestionably prove the existence of impacts havebeen found: that is, the presence of craters which formed simultaneouslyover two different geological substrata and regional landformssuch as basalt tablelands and piedmont gravels of clearlydifferent age.Arthur Conan Doyle used to say: ??When you have eliminatedthe impossible, whatever remains. . .must be the truth??. Duringour endless discussions, we have eliminated the impossible (e.g.volcanism, phreatomagmatism, ground subsidence, karst features,eolian deflation, biological origin, etc.). Thus, in scientific terms, itis reasonable to state that all bowl shaped depressions with raisedrims and stony ejecta blankets at Bajada del Diablo (with a total ofalmost 200), which equally affected volcanic and sedimentaryrocks are in fact impact craters. In other words, there is no neednow to discuss which has been the impactor, either a dismemberedasteroid or a comet, to recognize impact craters as such because noother known origin may be attributed to them. The fact that theyare affecting two geological environments and regional landformsof different age makes them the result of a unique event, which isnone other than an impact, unless Reimold and Koeberl have informationabout Bajada del Diablo that is unknown to us, which theseauthors are now reluctant to expose.Therefore, we suggest that basic geological aspects (whichshould not be ignored particularly if one has not done in situ observations)should never be left aside when geological dilemmas likethis need to be resolved. Likewise, we support that general anddetailed studies of regional geomorphological features should notbe overlooked in the study of astrobleme-strewn fields.Finally, the last paragraph of Reimold and Koeberl (2014b) haswrongly quoted one of our comments, namely that ??the absenceof evidence is not evidence of absence?? (Acevedo et al., 2014),not ??the absence of evidence is absence of evidence?? [sic] as theyhave paraphrased, which suggests an airily dismissive reading ofour paper.