A volcanic complex preserved within a polygonal network of microsyenite ring-dykes, Goundai consists of a thick sequence of ignimbrites, peralkaline rhyolites and porphyries covering 15x10 km. To the northeast the complex is overlain by Cretaceous sediments. Tuffs at the base of the volcanic sequence are overlain by rhyolites and these in turn by 200-300 m of feldspar- and quartz-phyric rhyolites containing spongy arfvedsonite. Bowden et al. (1981) give chemical analyses of ignimbrites, including some trace element data.