Diagenesis of the fanglomerate of Little Florida Mountains (Miocene), southwestern New Mexico
— James M. Kiely and W. C. James

The Fanglomerate of Little Florida Mountains is mainly composed of gravel-sized rhyolite clasts with arenaceous portions of the matrix classified as volcanic arenites (Q₄F₄RF₉₂). The sand-sized rock fragment population is 96% volcanic and dominated by rhyolite grains (rhyolite 88%, intermediates 8%, basalt 4%). Authigenic products are diverse and primarily siliceous in composition (70% of total). Although there is overlap in the timing of some cement events, a paragenetic sequence is recognizable: (earliest) ( 1 ) limonite, (2) mixedlayer illite/smectite plus limonite, (3) megacrystalline quartz, (4) impure siliceous cements (silica ± limonite ± clay), (5) microcrystalline quartz, (6) illite, (7) opal, (8) calcite, (9) Ca-zeolite and (10) pyrite. Soil-forming processes and hydrothermal fluids may have had a major influence on cement type, amount and distribution.