Pleistocene glass in the Australian desert: The case for an impact origin

Irregular masses and flat slabs of vesicular, slaglike, and glassy melt (re ferred to herein as Edeowie glass) are locally abundant on a desert plain i n central South Australia, where the material appears to be associated with an old land surface being exhumed by deflation and water erosion. The slab s of melt are associated with outcrops of baked sediment having very simila r geochemistry, suggesting an origin by in situ surface fusion. Embedded cl asts displaying shock metamorphism in quartz suggest that the thermal sourc e may have been in some way associated with an impact event, although an ob vious crater is lacking. If Edeowie glass is related to impact, a different thermal mechanism from that generally ascribed to the production of impact melt is required because of evidence for in situ generation of melt distal from any crater. Ar-40/Ar-39 laser probe dating of two samples has produce d overlapping dates of 0.67 +/- 0.07 and 0.78 +/- 0.33 Ma.