Kaminski, M.A.; Armitage, D.A.; Coccioni, R.; (2008) Shocked diamonds in agglutinated foraminifera from the Cretaceous/Paleogene Boundary, Italy - a preliminary report. In: Kaminski, M. A. and Coccioni, R., (eds.) Proceedings of the Seventh International Workshop on Agglutinated Foraminifera. (pp. pp. 57-60). The Grzybowski Foundation: London, UK.



Abstract

Washed acid residues from rock samples taken at measured intervals across the Cretaceous/Paleogene boundary (KPB) section at Monte Cònero, Italy, were examined for agglutinated foraminifera to assess their ability to select heavy mineral phases. Examination with scanning electron microscopy (SEM) and electron microprobe has enabled us to identify minerals comprising the outer walls of several agglutinated foraminiferal species, including Psammosphaera fusca, and Reophax cf. parvulus. Modern representatives of these genera are known to preferentially agglutinate heavy minerals. Because of this curious behaviour, we postulated that heavy detrital minerals, including impact ejecta, would have been scavenged by these organisms and incorporated into their tests. We have identified microdiamond likely formed by impact, together with distinctive Ni-Co-rich mineral residues in agglutinated foraminifera from the KPB clay, and also from specimens sampled both above and below the boundary clay. This is the first reported occurrence of impact-related microdiamond associated with the KPB discovered outside North America. We conclude that scavenging of ejecta grains by agglutinated foraminifera is an important process for subsequent bioturbation and redistribution of the ejecta material. The grain-size distribution of the microdiamond is consistent with impact diamond formed uniquely as ejecta from the Chicxulub Crater, but further work is needed.

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