Basement lithostratigraphy, Deep Sea Drilling Project Hole 504B.

Abstract

The lithostratigraphy of the 1075.5m of basement drilled is described. A method of classifying basalts into lithologic types is proposed, and is used to construct a standardized lithologic column, modifying the lithology previously described. The oceanic basement at Hole 504B can be divided into three lithologic zones: an upper zone (the upper 571.5m of basement) consisting of a complex association of intercalated pillow lavas, pillow breccias, hyaloclastic, massive units (flows and sills), synflows, and localized flow and tectonic breccias; a transition zone (209m thick), consisting of pillow lavas, synflows, massive units, and dikes; and a lower zone (the deepest 295m cored and probably extending deeper) consisting predominantly of massive units and dikes. The lithostratigraphy of Hole 504B is essentially concordant with that of ophiolite complexes, and supports the ophiolite model for ocean crust structure. -from Author