Silicoflagellate and Diatom Stratigraphy, Leg 16, Deep Sea Drilling Project

Abstract

The stratigraphic and paleoenvironmental significance of middle Miocene to upper Pleistocene silicoflagellate and diatom assemblages from the Panama Basin area of the eastern tropical Pacific Ocean is presented. The assemblages are dominated by warm-water open-ocean species. Paleotemperatures indicated by silicoflagellates are higher for the Pleistocene than for the Pliocene, and higher temperature correlates with lower productivity. Up welling is believed to have been a persistent Oceanographic feature in the basin, but it was probably reduced when higher surface temperature prevailed, as during the Pleis-tocene. Seven tropical silicoflagellate biostratigraphic zones are newly described or emended: Dictyocha epiodon Zone, Mesocena elliptica Zone, Distephanus boliviensis Zone, Cannopilus major Zone, Dis-tephanus crux Zone, Distephanus longispinus Zone, and Diste-phanus octacanthus Zone. Five tropical diatom biostratigraphic zones are newly described or emended; Roperia tesselata Zone, Chaetoceros sp. Zone, Hemidiscus cuneiformis Zone, Coscinodis-cus plicatus Zone, Craspedodiscus coscinodiscus Zone. Two new silicoflagellate species, Cannopilus quintus Bukry and Foster and Dictyocha vanandelii Bukry and Foster, and one new replacement name, Distephanus quinquangellus Bukry and Foster, are presented.