METHODS

Calcareous nannofossils were examined using standard light microscope techniques, under crossed polarizers, transmitted light, and phase contrast light at 1562× magnification. Preservation and abundance of calcareous nannofossil species may vary significantly because of etching, dissolution, or calcite overgrowth. It is not uncommon to find nearly pristine specimens present in the same sample as specimens exhibiting overgrowth or etching. Thus, a simple code system to characterize preservation has been adopted and is listed below:

VG = very good preservation; no evidence of dissolution and/or overgrowth; no alteration of primary morphological characteristics and specimens appear diaphanous; specimens are identifiable to the species level.

G = good preservation; little or no evidence of dissolution and/or overgrowth; primary morphological characteristics only slightly altered; specimens are identifiable to the species level.

M = moderate preservation; specimens exhibit some etching and/or overgrowth; primary morphological characteristics sometimes altered; however, most specimens are identifiable to the species level.

P = poor preservation; specimens are severely etched or exhibit overgrowth; primary morphological characteristics largely destroyed; fragmentation has occurred; specimens cannot be identified at the species and/or generic level.

Six calcareous nannofossil abundance levels are recorded as follows:

V = very abundant (11-100 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 11-100 fields of view).

R = rare (1 specimen per 101-1000 fields of view).

B = barren.

Calcareous nannofossil species considered in this paper are listed in "Appendix" where they are arranged alphabetically by generic epithet. Bibliographic references for these taxa can be found in Perch-Nielsen (1985) and Bown (1999).