Palynology and dinocyst biostratigraphy of ODP Leg 104 holes

Cores from ODP Leg 104 Holes 642A, 642B, 642C, 644A, and 644B were sampled at intervals of 40 cm to 100 cm for a detailed study of palynomorphs and palynodebris types in upper Cenozoic sediments of the Vetoing Plateau. Corecatcher samples were also studied from Hole 643A on the seaward flank of the plateau. Most of the 600 samples studied contained dinoflagellate cysts, pollen, spores, and various types of palynodebris. Total numbers of indigenous dinocysts and pollen-spore concentrations show cyclical variations which appear to correspond to climate fluctuations in Pliocene and younger sediments, and to either climatic changes or phytoplankton productivity cycles in the older sediments. Stratigraphic ranges for 68 cyst morphotypes were used to erect a provisional dinocyst zonation that can be correlated with other Northern Hemisphere high-latitude zonations. Four dinocyst zones are defined, with boundaries corresponding to biochronological or magnetostratigraphic ages of ca. 15 Ma, 9 Ma, 4.2 Ma, and 1.4 Ma. Environmental changes are interpreted in terms of (a) a progressive decline in species diversity due to the disappearance of subtropical species; (b) appearance of subarctic North Pacific taxa, presumably from the Arctic Ocean; and (c) an increase in heterotrophic protoperidinioid cyst species during the Pleistocene.