North American stratigraphic principles as developed by geologists mapping on continents can be applied to deep-sea sediments. The ability of the Deep Sea Drilling Project to obtain long cored intervals over extensive areas of ocean basins makes possible the establishment and lithologic correlation of rock-stratigraphic units (e.g., formations).

Deep-sea sediments should be divided and reported in terms of lithologic units which may be assigned rock-stratigraphic names if these units can be recognized at other sites. This practice is desirable in place of current stratigraphic practices in oceanography of defining rock-stratigraphic intervals by time-stratigraphic terms. The generally accepted North American usage of formation as a lithologic mappable unit devoid of any time connotation is recommended over the

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European usage of formation which often is actually a time-stratigraphic unit correlated across major facies changes.

Leg 9 of the Deep Sea Drilling Project recovered 1,500 m of core in eight sites (sites 77-84), a distance of 5,000 km, along the equatorial Pacific. Each site was cored to basement. Site 77 which was continuously cored 480 m was divided into several lithologic units that served as a standard of reference for Leg 9 sites. The consistent stratigraphic sequence and areal distribution of these lithologic units led to the adoption of four deep-sea formations: Line Islands Formation, Marquesas Formation, Clipperton Formation, and San Blas Formation. These formations are lithologically distinct, Tertiary, diachronous units that can be traced at least 4,000 km. The most useful and objective criteria to define these formations are color differences and to a lesser degree bedding characteristic . Color variations often are accompanied by textural, mineralogic, and biotic changes which further aid in the characterization of these formations.

Description of deep-sea sediments in terms of lithologic units and the establishing, tracing, and dating of oceanic formations can provide an improved basis for understanding the interrelations among rock-stratigraphic and time-stratigraphic units, lithologic and biologic sedimentation patterns, depositional processes, and subaerial dispersal patterns. It can also improve communication between oceanographers and continental stratigraphers.

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