Sampling of Site 1014 for stable isotopic investigations was conducted at moderately high stratigraphic resolution to allow the development of a useful chronological framework for investigators studying the uppermost sections of this site. Four holes were drilled from 1164 to 1167 m, with sequences ranging from 19.5 to 404.4 m recovered from the site. Core recovery was excellent and exceeded 100% because of gas expansion as the sediments contained biogenic methane. Detailed comparisons between magnetic susceptibility, gamma-ray attenuation porosity evaluator density, and high-resolution color reflectance allowed splicing between cores from the four holes and demonstrated complete recovery of the sequence down to 160 meters below seafloor (Lyle, Koizumi, Richter, et al., 1997).
Two-centimeter samples of
10 cm3
volume were taken from Site 1014 at 5-cm intervals for the upper 20 meters
composite depth (mcd). The raw samples were disaggregated in warm water, washed
over a 63-µm sieve, and oven dried at 50°C.
The remaining coarse fraction was split, with one-half to be used for stable
isotope analysis and the other half kept intact for archival purposes. Benthic
foraminiferal stable isotope analyses were conducted on 194 samples.
Approximately eight to 10 clean, entire Uvigerina
spp. specimens were picked for benthic isotope analysis at 10-cm intervals in
the upper 20 mcd of the site (Table 1).
Uvigerina is a
benthic foraminiferal taxon frequently utilized for isotopic stratigraphic
studies of marine sediments. It precipitates its test close to oxygen isotopic
equilibrium (Shackleton, 1974) and thus provides reliable 
18O
records. Isotope analysis of the planktonic foraminiferal species Globigerina
bulloides was undertaken at 5-cm intervals in the upper 14.5 mcd
interval and at 10-cm intervals from 14.5 to 20.0 mcd on 284 samples (Table
1). The 18O
of G. bulloides
represents surface water conditions since this species lives in the near-surface
(0-20 m) (Pak and Kennett, 1997) and tolerates a wide temperature range (6°-26°C)
(Thunell and Sautter, 1992).
Specimens picked for
isotopic analysis were cleaned ultrasonically in reagent-grade methanol then
dried and roasted under vacuum at 350°C
for 1 hr to remove organic contaminants. The samples were reacted in
orthophosphoric acid at 90°C
with an on-line automated carbonate CO2
preparation device, and evolved CO2
was analyzed using a Finningan/MAT 251 light stable isotope mass spectrometer.
Instrument precision is 0.09
or better for 18O
and 13C.
All isotopic data are expressed using standard
notation in per mil ()
relative to Peedee belemnite (PDB) carbonate standard. Isotopic analysis is
related to PDB through repeated analysis of NBS-19, with values following Coplen
(1996) of -2.2 for 18O
and 1.95 for 13C.
