Campanian Ignimbrite is a large-volume trachytic
tuff which erupted from the Phlegrean Fields (37-39 ka BP) and consisted of a fallout deposit overlain by ignimbrite.
West of Whangaroa Harbour, for example, is an area consisting of "Trachytic
breccia and basaltic conglomerates overlying tuffaceous sandstone with fossil plants which rest uncomfortably on green sandstones containing coal seams and Upper Secondary fossils".
Under thin section, the rock exhibits trachytic
Texture: P: porphyritic, VP: vesicular-porphyritic, and VT: vesicular trachytic
. Groundmass represents 60-90% of the rocks.
The Sabalan volcano consists of both late Miocene (old) and Quaternary (young) trachyandesitic and trachytic
to dacitic lavas with huge bodies of ignimbrites-density pyroclastic flows .
Groundwater comes mainly from Roque Nublo group and underlying Miocene trachytic
and phonolitic lavas.
Many samples preserve relict igneous or sedimentary textures, such as intergranular and trachytic
textures in mafic flows, eutaxitic banding in felsic flows, ffagmental texture in tuffaceous rocks, and bedding in epiclastic rocks.
loose, fragmental) know as local trachytic
basalt-andesite with an estimated age of 20000-30000 years BP (Asio 1996; Jahn and Asio 1998).
All Samoan tempers were derived alike from basaltic or associated trachytic
source rocks, but the beach sands, colluvial debris, and crushed rock that served as temper in other Samoan sherd suites are unlike the stream sands used for Pulemelei temper.
In thin sections, samples representative of the bulk of the upper sill show phenocrysts up to about 2.5 mm in maximum dimension, in a groundmass with a trachytic