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Geology of Culebra Island, Puerto Rico
Culebra Island, located about twenty miles east of Puerto Rico, is composed of undated andesite and spilitic volcanics which are intruded by diorite plutons. On the basis of the ages of similar rocks on Puerto Rico and the ...
Geological and geophysical studies of a portion of the Little Llano River Valley, Llano and San Saba counties, Texas
A geologic study of the Precambrian Valley Spring gneiss was made in the Babyhead-Wilberns Glen area in northern Llano County, Texas, Magnetic and gravity surveys were made over this and the surrounding areas to determine ...