The volcanic succession in the area is 1300 m thick and comprises a lower sequence
of felsic tuffs and ignimbrites, a middle sequence of andesite to andesite-basalt flows
and fragmentals capped by felsic tuffs and flows. These sequences are intruded and
discordantly overlain by basalts of reported Paleogenic age. The volcanic rocks
unconformably overlie and intrude folded Jurassic sediments