Exempel på tuff

• The formation of the clay minerals can be divided into three different stages in the tuffs.

• The results show that the fluid compositions varied significantly between the different tuffs.

• Toward the inlet of the conduit, the capstones consisted of extremely heavy, river-worn, shaped slabs of tuff.

• From the data available on the tuff samples so far, the recognition of species has proven problematic due to the fragmentary nature of the fossils.

• Since the chemical composition of the primary tuffs likely reflects their source material, the tectonomagmatic derivation of the volcanic ashes can be deduced.

• Pyroclastic products are widespread and include lapilli tuff, lithic tuff, agglomerate and pyroclastic breccia; compositionally similar lava flows are massive or blocky.

• 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.

• These two tuffs could have had the same parental magmas than the other tuffs and associated basalts.

• The sequence comprises alternations of coarse tuff units that fine upwards and thinner lapilli-rich tuff horizons.

• 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.

• More rarely clasts of streaky flow-banded or parataxitic material occur, derived from earlier welded tuffs.

• Simultaneous eruption of ash-flow tuffs resulted in a sequence of interbedded tuffs, sedimentary breccias and andesitic lavas.