
feet thick of sand hardly hard enough to be called sandstone Above the conglomerate which is baked & altered by heat is a bed three hundred feet thick of lava and volcanic breccia differing every few feet horizontally and vertically in its exact composition
the lower part seem more like a cooked conglomerate of pieces of porphyrite with a basaltic matrix while the upper portion is composed in part of sharp fragments of porphyrite & dolerite cemented by a thin glossy vitreous lava.
This completes the key to the system of tertiary beds of the north part