Tropical Pacific silicoflagellate zonation and paleotemperature trends of the late Cenozoic.

Abstract

Quantitative study of late Cenozoic silicoflagellates at tropical Pacific DSDP Sites 572 and 575 shows that the greatest amplitude of fluctuation in relative paleotemperature values occurred in the late Miocene. The coolest minimum paleotemperature values (near Ts = 30) also occurred in the late Miocene. The warmest intervals (Ts = 80-100) occurred in the middle Miocene and late Pliocene to Quaternary. In detail, the silicoflagellate relative paleotemperature curve correlates fairly well with the eustatic sea-level curve and deep-sea hiatus sequence. The only upper Cenozoic low-latitude biostratigraphic units not identified are the Distephanus speculum haliomma Subzone and Naviculopsis quadrata Zone, owing to the absence of the nominative species, which probably had non-tropical ecologic preference. Several Naviculopsis occurrence events within the Naviculopsis ponticula Zone correlate between DSDP Hole 575A and DSDP Hole 495 off Guatemala. Many local and regional biostratigraphic events are recognized. New taxa identified from DSDP Leg 85 include Dictyocha nola Bukry, n. sp., Distephanus stradneri var. grandis Bukry, n. var., Mesocena elliptica var. rhomboidea Bukry, n. var., and Naviculopsis obtusarca var. acicula Bukry, n. var.-Author