Cretaceous volcaniclastic rocks from the lower part of Deep Sea Drilling Project Hole 462 (Cores 14-80) were studied under the microscope. X-ray study of clay minerals and authigenic zeolites and amphiboles was also made. Altered hyalobasalts and palagonitized (or replaced by Fe-Mg-smectite) sideromelanic glass are predominant in the rock composition. Acid to basic plagioclases, basic volcanic glass, biotite, pyroxene, hornblende, and olivine were recognized in sediments. Accumulation of sediments took place in relatively deep-water environments, whereas transportation of volcaniclastic material was by turbidite flows. In the zone of doleritic sills, the volcaniclastic rocks were subjected to hydrothermal and contact-metasomatic alteration, resulting in formation of authigenic zeolites (analcime, wairakite [?], thomsonite) and monoclinic amphiboles (tremolite, actinolite). Geochemical study of volcaniclastic sediments shows them to be products of transportation of tholeiitic basalt material which interacted with sea water. An increase in content of Fe 3+ , K, Mn, and heavy metals (Cu, Ni, Co, V) is observed in this succession: tholeiitic basalts, their hyaloclastites, smectitic clays. A similar tendency is observed in a transitional zone from the lower horizons of the sequence (Barremian) to the upper ones (Cenomanian).