摘要：Microfaunal and foraminifera1 oxygen isotope data from the Chukchi Plateau, the Alpha-Mendeleev Rise and the Lomonosov Ridge deep-sea cores (Table 1) representing the last 4.5-5 million years, yield evidence of significant paleoceanographic and paleoclimatic changes. Uranium series isotopes and magnetic stratigraphy provide the time frame for these Late Neogene sequences (Herman & Osmond 1984). The similarity in faunal and floral patterns as well as in lithology allows cor- .relation of cores over widely separated regions. Several datum levels were recognized. They include the Globigerina egelida acme zone between -1.8 and -1.6Ma, the Globigerina quinqueloba acme zone 0.7 Ma and -0.34-0.24 Ma, the Stetsonia horuarhi acme zone between -1.66 and - 1 Ma and the Orthopithonella acme zone between -1.66 and -0.73 Ma (Fig. 1).
