MATERIAL AND METHODS

One to two samples per section were systematically analyzed. For the last 500 k.y., a finer sampling resolution of 10–30 cm was used.

Smear slides were made directly from unprocessed samples and examined with a cross-polarized light microscope at 1000x resolution.

The total abundance of calcareous nannofossils for each sample was estimated as follows:

V = very abundant, >100 nannoliths per field of view.

A = abundant, 10–100 nannoliths per field of view.

C = common, 1–10 nannoliths per field of view.

F = few, <1 nannoliths per field of view.

Additionally, the abundance of calcareous nannofossil species in each sample was estimated as follows:

D = dominant, >50% of the total assemblage.

A = abundant, >10%–50% of the total assemblage.

C = common, >1%–10% of the total assemblage.

F = few, 0.1%–1% of the total assemblage.

R = rare, <0.1% of the total assemblage.

In regard to nannofossil preservation, etching and overgrowth are the most important features. In order to establish a ranking of preservation, we followed previous coding systems such as that used by Shipboard Scientific Party Leg 177 (1999), considering both effects (etching and overgrowth):

G = good (little or no evidence of dissolution and/or secondary overgrowth of calcite; diagnostic characters fully preserved).

M = moderate (dissolution and/or secondary overgrowth; partially altered primary morphological characteristics; however, nearly all specimens can be identified at species level).

Table T2 shows the semiquantitative results of this study. Only samples close to biostratigraphic events are displayed.