Archean spherule beds : Impact or terrestrial origin ?

We agree with Glikson [1] that the identification of Precambrian impact deposits is an important and largely unresolved problem, and thank him for providing us with an opportunity to further discuss our mineralogical and geochemical results [2] on the enigmatic spherule layers in the Barberton Mountain Land of South Africa. We note, however, that unfortunately Glikson has not been able to name definitive criteria for the identification of such Archean impact deposits either, and, thus, has also been unable to establish an impact origin for the Barberton spherule layers with any degree of certainty. We also would like to note that we [2] did not categorically exclude an impact origin. Rather, we found the arguments in favour of such an origin, as presented by Lowe et al. [e.g., 3-5], inconsistent, unconvincing, and incomplete. Before summarizing our arguments against an impact origin, we would like to comment on some of Glikson's observations. He comments that it is pertinent to compare the Barberton spherule layers with the Bunyeroo ejecta in Australia, which are connected with the Precambrian Acraman impact structure, and lists the occurrence of "shatter coned volcanic fragments, planar defor-