Leg 168 of the Ocean Drilling Program (ODP) was designed to document several fundamental aspects of hydrothermal circulation across the eastern flank of Juan de Fuca Ridge (Fig. 1), including: (1) the influence of basement topography, sediment thickness, and sediment permeability on thermophysical characteristics of fluid circulation; (2) the sensitivity of fluid composition to crustal age, temperature, and degree of sediment burial; (3) the nature and causes of physical, mineralogic, and chemical alteration of the igneous crust with increasing age and depth of burial; and (4) heat and element fluxes between the igneous crust and ocean water (Shipboard Scientific Party, 1997c). Upper Pliocene to Holocene sediment laps onto igneous basement within 20 km of the spreading axis of Juan de Fuca Ridge. Characterization of these strata becomes important if one's goal is to determine how the sediment cover influences the circulation and chemistry of hydrothermal fluids. As part of this characterization, we describe compositional data for turbidites and hemipelagic muds, interpret sediment provenance, and identify regional-scale pathways of sediment dispersal. By comparing interbeds of sand and mud, we also show whether or not the two types of sediment shared common detrital sources.