Simultaneous eruption of ash-flow tuffs resulted in a sequence of interbedded tuffs, sedimentary breccias and andesitic lavas.
More rarely clasts of streaky flow-banded or parataxitic material occur, derived from earlier welded tuffs.
In the massive tuffs, vitric to crysto-vitric varieties show delicately shaped glass shards and broken phenocrysts of euhedral quartz, plagioclase, muscovite, orthoclase, zircon and ilmenite.
The sequence comprises alternations of coarse tuff units that fine upwards and thinner lapilli-rich tuff horizons.
These two tuffs could have had the same parental magmas than the other tuffs and associated basalts.
Capstones also made of volcanic tuff covered the conduit for the length of its course, although differences in how the capstones were worked are apparent.
Pyroclastic products are widespread and include lapilli tuff, lithic tuff, agglomerate and pyroclastic breccia; compositionally similar lava flows are massive or blocky.
Since the chemical composition of the primary tuffs likely reflects their source material, the tectonomagmatic derivation of the volcanic ashes can be deduced.
