Cerro Medina (Yarigua' A-Mi)
A phonolite plug in the Caanabe Valley intruding Jurassic and Silurian sandstones.
A phonolite plug in the Caanabe Valley intruding Jurassic and Silurian sandstones.
A conical hill apparently of an alkaline character. No further information.
An essexite stock. A large area of alkaline rocks is shown on Plate 1 of Milton and Eckel (1959) but this is an error, most of the area being occupied by Silurian sandstones with only a small area of essexite, about which there is little detail available.
An intrusion of essexite is emplaced in Silurian sandstones. It is similar to the essexite of Soto-Rugua (No. 12) but lacking syenite veins.
A shonkinite plug forms a conical hill 500 m in diameter. A modal analysis gave alkali feldspar 26%, nepheline 29.7%, augite 31.6%, olivine 4.5% and ore 8.2%; a chemical analysis is also available.
Described as diabase by Putzer (1962) but is in fact essexite and shonkinite (Vera Maringo, personal communication, 1981). No other details are known.
A group of small plugs are intruded into sediments of the Pennsylvanian Tubarao Series which are little known but appear to include essexite, shonkinite and nepheline syenite.
This is an essexite and shonkinite plug with veins of syenite.
A 4 m thick biotite porphyry dyke cuts sandstones in an area east of Villarica and passes into a sill within the sandstones. Brown biotite phenocrysts are set in K-feldspar, (?)nepheline and opaques.
A Quaternary volcanic field lies to the north of Lake Yojoa and comprises a lava field of about 100 km2, with a number of scoria cones and domes in the central part, the whole lying within the Sula Graben.