METHODS

Standard nannofossil smear-slide techniques were used to prepare samples. Unprocessed sediment was distributed on a glass coverslip using a mild (<3%) Calgon solution to achieve dispersal between the nannofossils and the clay fraction. Samples were dried and mounted on glass slides using Norland optical adhesive-61 mounting medium. The nannofossil biostratigraphy presented here is based on examination of each sample using a Zeiss photomicroscope III under 500× magnification, using phase-contrast and cross-polarized light. Relative abundance of each nannofossil species, overall preservation of the nannofossil assemblage, and the relative abundance of nannofossils were recorded for each sample using BugWin software (BugWare, Inc.).

Range charts presented in Tables T1, T3, and T5 were created using these measurements. Individual species abundance are represented by the following abbreviations:

V = very abundant; >100 specimens per 10 fields of view (FOV);

A = abundant; 11-100 specimens per 10 FOV

C = common; 6-10 specimen per 10 FOV;

F = few; 1-5 specimen per 10 FOV; and

R = rare; 1 specimen per >10 FOV.

The same definitions were used for estimations of total abundance of each sample, with the additional definition of "B" (B = barren of nannofossils). Preservation of the calcareous nannofossil assemblage was determined as follows:

G = good; individual specimens exhibit little or no dissolution or overgrowth; diagnostic characteristics are preserved and nearly all of the specimens can be identified;

M = moderate; individual specimens show evidence of dissolution or overgrowth; some specimens cannot be identified to the species level; and

P = poor; individual specimens exhibit considerable dissolution or overgrowth; many specimens cannot be identified to the species level.

For scanning electron microscope study, samples were prepared following the settling technique of de Kaenel and Bergen (1996), mounted on a glass coverslip taped to a specimen stub, and coated with a thin film of gold-platinum alloy in a vacuum coater.

Calcareous nannofossil species considered in this paper are listed in "Appendix," where they are arranged alphabetically by generic epithets. Bibliographic references for these taxa can be found in Perch-Nielsen (1985) and Bown (1998).