BE-10 AND CHEMISTRY OF IMPACTITES AND TARGET MATERIALS FROM THE RIO-CUARTO CRATER FIELD, ARGENTINA - EVIDENCE FOR SURFICIAL CRATERING AND MELTING

We report in this study on the distribution of the cosmogenic isotope Be-10 and major and trace elements in impactites (clast-rich melt and glasses) and target materials (soil and loess) from the Rio Cuarto cra ter field in the Pampas of Argentina. The Be-10 concentrations and che mical composition of the impactites are comparable to that of the soil and loess. These results are in agreement with an origin of the impac t glasses by melting of a mixture of soil and loess, as also shown by comparison with experimentally fused loess samples. The Be-10 concentr ation of the impactites indicates that the melting and the excavation did not penetrate beyond the soil and loess package. The high content of the trace elements Cr and Ni in the impact glasses compared to the target materials suggest incorporation of small amount (< 1%) of the c hondritic impactor material.