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DSDP Leg 63 recovered Neogene coccoliths from south of Point Conception, California (Site 467), to north of Cabo Corrientes, Mexico (Site 473), as part of a traverse exploring the sedimentary record of the California Current along the Pacific Coast. A combination of temperate and tropical zonations were used to date Leg 63 coccolith assemblages because of intergradations of warm and cool species along the transect. Variations in the abundance and the presence and absence of Discoaster species are useful in recognizing warm-cool intergradations. New taxa described in this report include Discoaster okadai n. sp., D. sanmiguelensis n. sp., Helicosphaera californiana n. sp., H. crouchii n. sp., H. gertae n. sp., and H. vedderi n. sp. INTRODUCTION Leg 63 of the Deep Sea Drilling Project recovered 398 cores at seven drilling sites, 467 through 473 (Fig. 1, A). These sites all lie south of DSDP Site 173 (Fig. 1, B), which is a standard reference for middle-latitude biostratigraphy along the Pacific Coast. Light-microscope techniques were used to study a set of 1100 coccolith smear slides. At most sites coccoliths provided the most continuous biostratigraphic record for correlation, however, gaps are indicated in the summary of coccolith zonal sequences (Figs. 2 and 3). Different sections in this chapter discuss zonation, site summaries, variation of assemblages along the traverse of sites, systematic paleontology, and species cited. ZONATION Low-latitude coccolith zonation (Bukry, 1971a, 1973a, 1975) can be applied to the lower middle Miocene at all of the Leg 63 sites. A significant change in assemblages at northern Sites 467 to 469 occurred in the middle Miocene Discoaster exilis Zone (Crouch and Bukry, 1979); low-diversity temperate assemblages became established and low-latitude guide taxon became sparse and sporadic. Temperate zones developed from Leg 18 (Bukry, 1973b), which span broader time intervals than do low-latitude zones, are used for the upper middle Miocene to lower Pliocene for Sites 467 and 468, with a minor change. The modification is that the earliest D. mendomobensis occurs in the D. neorectus Subzone correlative (in Leg 63 sites) instead of at the upper boundary of the D. neorectus Zone. The zone and subzone codes (CN12a . . . ) are from Okada and Bukry (1980) (Fig. 4). In the lower Pliocene of Holes 467, 468, 468A, and 469, a new local or limited middle-latitude subzone is recognized. The new Amaurolithus delicatus Subzone CNlOd is bounded by the first consistent Discoaster Initial Reports of the Deep Sea Drilling Project, Volume 63. asymmetricus Gartner at the base and by the last Amaurolithus spp. at the top. It is assigned to the top of the Amaurolithus tricorniculatus Zone CN10, above the Ceratolithus rugosus Subzone CNlOc. This unit is not part of the regular low-latitude zonation, because the Amaurolithus extinction typically precedes the first consistent D. asymmetricus populations; however, this unit has been identified previously as a Discoaster asymmetricus Zone by Gartner (1969) and Martini (1971). The sporadic occurrence of D. asymmetricus in the upper Miocene (Bukry, 1973a; Shafik, 1975) can cause problems with this subzone. The occurrence of this unit in tropical areas is questionable, because my slides from DSDP Hole 62.1, Core 10 (01°52.2'N), identified as D. asymmetricus Zone (Martini, 1971), show Ceratolithus rugosus Bukry and Bramlette and D. asymmetricus, but no Amaurolithus, which should signify the low-latitude Reticulofenestra pseudoumbilica Zone CNlla and b (compare Martini, 1971). The Leg 63 occurrences of the overlap between Amaurolithus and D. asymmetricus are in single samples or very short intervals of 1 or 1.5 meters at California Continental Borderland Sites 467 to 469. The brevity of this unit, which is also indicated by Gartner (1969) for Atlantic cores, may be a function of the sporadic occurrence of D. asymmetricus in the lower lower Pliocene and local variations in gradually increasing productivity near the extinction of Amaurolithus. This could account for the brevity or apparent nonoverlapping relation between these taxa in various regions. Detailed study of subsection intervals through the lower Pliocene in additional tropical and temperate cores should resolve this subzone correlation. The upper Miocene zonal boundary between the middle-latitude Discoaster mendomobensis Zone and D. variabilis Zone, when first described, was correlated with the boundary between the low-latitude D. quinqueramus Zone and D. neohamatus Zone (Bukry, 1973b). Studies of borderland dart cores and DSDP Site 469, Core 14, however, show that specimens of Discoaster mendomobensis Wise may occur earlier, in upper D. neohamatus Zone assemblages identified by the

Pacific Coast Coccolith Stratigraphy between Point Conception and Cabo Corrientes, Deep Sea Drilling Project Leg 63