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.

取自大洋钻探计划（Ocean Drilling Program, ODP）第104航次642A、642B、642C、644A与644B孔的岩芯，以40 cm至100 cm的间距取样，用于细致研究韦廷高原（Vetoing Plateau）晚新生代沉积物中的孢粉类化石（palynomorphs）与孢粉碎屑（palynodebris）类型。本研究还针对该高原向海侧643A孔的岩芯捕获器样品展开了分析。本次研究涉及的600份样品中，绝大多数均含有沟鞭藻囊孢（dinoflagellate cysts）、花粉、孢子及多种类型的孢粉碎屑。本土沟鞭藻囊孢总数与花粉-孢子浓度均呈现周期性变化，该变化在上新统及更年轻的沉积物中与气候波动相契合，在较老沉积物中则与气候变化或浮游植物生产力周期相关联。研究基于68种囊孢形态类型的地层延限，建立了一套临时性沟鞭藻分带方案，该方案可与北半球其他高纬度地区的沟鞭藻分带进行对比。该方案共划分出4个沟鞭藻带，其边界对应的生物年代学（biochronological）或磁地层学（magnetostratigraphic）年龄分别约为15 Ma、9 Ma、4.2 Ma与1.4 Ma。本研究从三方面解读环境变化：（a）因亚热带物种灭绝导致的物种多样性逐步降低；（b）疑似源自北冰洋的北太平洋亚北极类群的出现；（c）更新世时期异养型原多甲藻类（protoperidinioid）囊孢物种丰度的提升。