Ocean Drilling Program, United States

Late Cretaceous to Quaternary organic walled dinoflagellate cyst (dinocyst) events were recognized at two sites offshore Tasmania during Ocean Drilling Program (ODP) Leg 189. Detailed magnetostratigraphic results from this leg allow, for the first time in the Southern Ocean, a detailed calibration of such dinocyst events. This calibration permits a comparison of dinocyst events for selected species between the Northern and Southern Hemispheres. The independent age control compilation, based on data from stratotype sections and cores recovered during ODP (and other) drilling worldwide, shows that dinocysts are extremely sensitive temporal and spatial indicators. Spatially restricted dinocyst species can be grouped into low-, mid-, and high-latitude forms for both hemispheres, with the majority occurring in the mid- and low latitudes. Such taxa include Apectodinium homomorphum, which characterizes warm waters in the late Paleocene and early Eocene. Other taxa, such as Arachnodinium antarcticum, are found only in mid- or high latitudes and are known only from the Southern Hemisphere. A third group, including Spinidinium macmurdoense, is characteristic of high latitudes. By collating the ranges, we derive a sequence of dinocyst events that should greatly facilitate the use of these organisms for age determinations and correlations.