Figure F16. A. New sedimentary and volcaniclastic lithology naming conventions based on relative abundances of grain and clast types. Principal lithology names are compulsory for all intervals. Prefixes are optional except for “tuffaceous” lithologies. Suffixes are optional and can be combined with any combination of prefix/principal name. First-order division is based on abundance of volcanic-derived grains and clasts: >25% volcanic grains is either “volcanic” (>75% volcanic grains; named from grain size classification of Fisher and Schmincke, 1984 [orange]) or “tuffaceous” (25%–75% volcanic grains). Tuffaceous lithologies: if dominant nonvolcanic grain component is siliciclastic, the grain size classification of Wentworth (1922; green) was used; if not siliciclastic, it is named by the dominant type of carbonate, chemical, or biogenic grain (blue). 0%–25% volcanic grains are classified as nonvolcanic and treated similarly to tuffaceous lithologies: when nonvolcanic siliciclastic sediment dominates, the grain size classification of Wentworth (1922; green) is used; when the combined carbonate, other chemical, and biogeneic sediment dominate, the principal lithology is taken from the dominant component type (blue). Closely intercalated intervals can be grouped as domains to avoid repetitive entry at the small-scale level. (Continued on next page.)
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