(1) Lenses incorporate varicoloured tuffaceous cherts intercalated with tuffaccous mudstone and tuff .(2) Increasing proximity to a subduction zone during plate convergence is indicated by the appearance of felsic tuff .(3) The lower series consists of alternating basalt lava, tuff breccia, tufite, and siliceous rock, whereas the upper one is dominated by diabase.(4) It also follows that there are differences in age between grains, which is consistent with the impression of resorption given by the grain morphology: possibly all grains predate the final tuff volcanism.(5) Among the 30 different types of stone recognized are varieties of diorite, granite, bedded tuff , sandstones, limestones, and tufa.(6) Further up section the geology is dominated by a succession of unmetamorphosed but strongly fractured and veined blocky andesites, basalts and tuffaceous rocks.(7) In addition, there are tuffaceous (volcanic ash) layers at various horizons throughout the Green River Formation.
