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An expanded record of the Cretaceous-Tertiary transition was discovered at Site 524. The transitional interval, in Core 20, Section 3 (large photo enclosed) is represented by red-mud deposits with intercalated turbidite sand layers. The muds immediately above the last Upper Cretaceous biogenic sediments are detrital clays and silts, mainly of volcaniclastic origin, with a minor amount of reworked plantonic fossils from the underlying Cretaceous formations. Rare occurrences of the chitinous nannofossils Thoracosphaera spp. And benthic foraminifera may be the only indigenous flora and fauna. The transition seems to record a sudden extinction of rich Cretaceous faunas and floras, and a gradual appearance of Tertiary species. Such a transition has been described on land sections, but the transition at Site 524 (Leg 73) is usually expanded to permit detailed investigations of the physical (temperature) and chemical (water chemistry) changes across the Cretaceous-Tertiary boundary.

An expanded record of the Cretaceous-Tertiary transition was discovered at Site 524. The transitional interval, in Core 20...