) of total carbon measurements is 0.13%. The reproducibility (1) of organic carbon is 0.10%.
A total of 65 carbonate samples were taken as semi-indurated sediments (mostly with lighter color than surrounding sediments) or as solid carbonate pieces aboard the JOIDES Resolution.
Carbonate samples were washed with distilled water, dried, and ground in an agate mortar for analysis of total and organic carbon (used to calculate the total carbonate content) with a Carlo Erba elemental analyzer NA1500 at the IFM-GEOMAR Leibniz-Institute of Marine Sciences (Germany). Depending on the carbon concentration, 3–20 mg of sample was measured. Organic carbon is determined after removing carbonate carbon by acidification with 0.01-N hydrochloric acid. The reproducibility (1) of total carbon measurements is 0.13%. The reproducibility (1) of organic carbon is 0.10%.
A total of 62 carbonate samples were analyzed using XRD on a Philips PW 1820 instrument (CoK
) at the IFM-GEOMAR Leibniz-Institute of Marine Sciences. Instrument parameters were set to 40-kV accelerating voltage and 35-mA current. Samples were dried, crushed in an agate mortar, homogenized with ethanol, and prepared as randomly oriented powder slides. Scans were run from 20° to 60° 2
at a scanning speed of 0.01°/sec. The shift in the d(104) peak was used to determine the Mg content of magnesium calcite and dolomite minerals (Lumsden, 1979).
