Shipboard organic geochemical studies of cores from Site 1167 included monitoring of hydrocarbon gases, carbonate and OC, total sulfur (TS) and total nitrogen (TN) content, and Rock-Eval pyrolysis characterization of organic matter. Procedures are summarized in "Organic Geochemistry" in the "Explanatory Notes" chapter.
Cores recovered from Site 1167 were monitored for hydrocarbon gases measured by the headspace method. All reliable analyses were at background levels (4-10 parts per million by volume [ppmv]) for methane, and ethane was present in detectable amounts only in a few cores deeper than 350 mbsf.
Sixty-five sediment samples were analyzed for inorganic carbon (IC; calcium carbonate), and 27 selected (darker colored) samples from Site 1167 were analyzed for total carbon, OC (by difference), TN, and TS. The results are reported in Table T6. IC and OC contents are plotted against depth in Figure F27. Carbonate content is generally low (~0.1 wt% IC) with two samples having 0.4 wt% IC.
OC content averages ~0.4 wt% and shows no apparent trend with depth. Only two samples (at 279.03 and 409.04 mbsf) approach 1 wt% OC.
TN contents are generally <0.04 wt%, except for the two deepest samples analyzed (433.59 and 441.91 mbsf). These samples have carbon/nitrogen values (1.0 and 0.7) that are so low, it suggests that the slightly elevated TN contents are spurious measurements.
TS contents are uniformly low, with many samples having no detectable sulfur.
Nine samples from Site 1167 were characterized by Rock-Eval pyrolysis (Table T7). Samples with >0.5 wt% OC were selected for analysis. Pyrolyzable hydrocarbons (S2 yields) range from 0.09 to 0.21 mg of hydrocarbon/g of sediment. The pyrolyzable fraction of the OC is uniformly low (hydrogen index values of 17-38 mg of hydrocarbon/g of carbon). The elevated Tmax values (451°-534°C) and the broad S2 peak shapes in the pyrograms (not shown) indicate that all samples contain predominantly recycled and degraded thermally mature organic matter.