MATERIALS AND METHODS

Five sites were drilled during Leg 189 (Fig. F1), and at four sites (1168 and 1170-1172) Paleogene sediments were recovered. All sites were located at high latitudes in the Paleogene (see Fig. F2 for backtrack); thus, the nannofossil assemblages are similar to those of the southern high latitudes (e.g., Wei and Wise, 1990; Wei and Thierstein, 1991, Wei et al., 1992).

Smear slides were made from unprocessed sediments and examined with a light microscope at a magnification of 1000x. The abundance of selected nannofossil taxa on each slide was estimated using the following criteria:

V = very abundant, >10 specimens per field of view.

A = abundant, 1-10 specimens per field of view.

C = common, 1 specimen per 2-10 fields of view.

F = few, 1 specimen per 11-50 fields of view.

R = rare, 1 specimen per 51-200 fields of view.

For preservation of nannofossil assemblages

G = good, little evidence of etching or overgrowth.

M = moderate, etching and/or overgrowth is apparent.

P = poor, strong etching and/or overgrowth.

The bibliographic references of the species used in this study can be found in Perch-Nielsen (1985). Numerical ages discussed in this paper refer to the timescale of Berggren et al. (1995).