BRECCIAS RESEMBLING MELT BOMBS FROM THE ROTER-KAMM CRATER

Irregular, dark green to black, glassy-looking boulders are locally co mmon in the northwest portion of the rim of the Roter Kamm impact crat er in southern Namibia. Their smooth surfaces, flow-like textures, pre sence of folds, and their similarity to melt bombs have led to the int erpretation that these are molten impact ejecta. However, the samples we have examined are all fine-grained breccias composed of angular fra gments that show no evidence of melting. Meltlike surface textures of these rim breccias are largely a consequence of surface wind polishing of fine-grained rocks in a desert environment. These monomict breccia s were produced by impact-related brecciation of Gariep sediments (car bonaceous, siliceous shales) previously modified by low-grade Damaran metamorphism. Secondary quartz within the breccias is attributed to fl uid activity that postdates the impact.