Basalts and silcretes on the coast near ulladulla, southern New South Wales

Abstract

Silcretes on the N.S.W. coast near Ulladulla have long been attributed to. a sub-basaltic origin, but field evidence is at odds with all variations of the sub-basaltic hypothesis, and one site shows good evidence that the basalt post-dates the silcrete. K-Ar ages averaging 29.7 ± 0.5 Ma from the basalts provide a minimum age for silcrete development in this area. Furthermore, the K-Ar dates, together with evidence for an erosional rather than tectonic origin of the coastal lowland, demonstrate that the adjacent tablelands reached their present elevation prior to the mid-Oligocene. Show more