Pucallpa

At Pucallpa three small plugs are intruded into Cretaceous Vivian sandstones and are aligned northeast-southwest. The plugs comprise phonolite and alkali trachyte. The phonolites containalkali feldspar phenocrysts up to 1 cm long, groundmass alkalifeldspar, aegirine-augite, sometimes melanite, alkali amphibole and biotite; zeolite pseudomorphs are interpreted as dodecahedra after sodalite. Altered nepheline phenocrysts are found in some samples. Melanocratic fragments consisting of aegirine-augite, abundant apatite, biotite and a little melanite, sphene, iron oxides, carbonate and zircon are described. The alkali trachyte is composed of microperthite, albite, apatite and iron oxides, the latter probably after mafic minerals.