METHODS

Smear slides of raw sediment were examined at 1000x using standard light microscope techniques under crossed polarizers, transmitted light, phase-contrast light, and differential interference contrast light in order to estimate relative calcareous nannofossil abundance and preservation. A JSM-5900 scanning electron microscope was employed to take digital images for more precise species identification.

Estimates of overall nannofossil abundance were given the following letter codes:

V = very abundant (>10 nannofossils/field of view).

A = abundant (1-10 nannofossils/field of view).

C = common (1 nannofossil/2-10 fields of view).

F = few (1 nannofossil/>10-100 fields of view).

R = rare (1 nannofossil/>100 fields of view).

The average state of preservation of the nannofossil assemblage in each sample is designated as follows:

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

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

P = poor (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).

Relative individual species abundance estimations follow the procedure of Hay (1970) and are indicated in the following manner:

V = very abundant (>10-100 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.

Oxygen and carbon isotopes were measured on bulk carbonate by grinding dried sediment to a homogenous powder and reacting ~60 µg of untreated sample in orthophosphoric acid at 70°C using a Finnigan-MAT Kiel III carbonate preparation device. Evolved CO₂ gas was measured online with a Finnigan-MAT 252 mass spectrometer at the University of Florida. All isotope results are reported in standard delta notation relative to Vienna Peedee belmenite (Coplen, 1996). Analytical precision for isotope analyses was ±0.03 for ¹³C and ±0.06 for ¹⁸O.