Interstitial water samples
were obtained using conventional methods (Manheim and Sayles, 1974). Chloride
concentrations were measured on the ship (Eberli, Swart, Malone, et al., 1997)
using methods described by Gieskes (1973, 1974). Oxygen and hydrogen isotopic
measurements of the pore waters were made in the Division of Marine Geology and
Geophysics at the University of Miami. Hydrogen isotopic data were only analyzed
on one hole as a result of operational problems. Oxygen isotopic data were made
in duplicate on most samples from Sites 1003 through 1007. As the methods for
the measurement of both isotopes are different from the conventional techniques
(Epstein and Mayeda, 1953; Friedman, 1957), they will be elaborated here. Both
measurements were made using a water equilibration system (WEST) attached to a
Europa GEO. In the WEST, the oxygen isotopic composition is determined on CO2
that has been injected into serum bottles at slightly above atmospheric pressure
containing 1 cm3 of sample. The samples are subsequently equilibrated
at 40°C for 4 hr without shaking. The process is entirely automated: the CO2
is injected into the sample bottles and retrieved using an autosampler, and the
gas is transferred to a dual-inlet mass spectrometer through a cryogenic trap
(-70°C) to remove water. The precision of this method for oxygen, determined by
measuring 59 samples of our internal standard, is ±0.07
(Fig. 4). The relatively large
standard deviation is a result of a 0.3°C temperature variation in the
equilibration bath. The hydrogen isotopic composition is determined using the
same device as employed for CO2. Equilibration with hydrogen gas
takes place in the presence of a platinum catalyst (Hokko Beads) at 40°C (Coplen
et al., 1991). As a result of the above-mentioned stability problems with the
temperature bath, precision using this method is ±1.5
(Fig. 4). All data are calibrated
using Vienna Standard Mean Ocean Water (SMOW) and are reported in parts per
thousand (
) according
to the conventional notation.