Routine monitoring of hydrocarbon gases was performed on one sample of every core recovered at Site 1101 (Table T12). Inorganic carbon analyses were performed on one sample of every other section, and elemental analyses were performed on a subset of these samples (Table T13). Additional samples were collected specifically to examine suspected carbonate-rich intervals between 50 and 140 mbsf. This constitutes a strong bias in the sampling pattern.

Methane concentrations remain low (<100 ppm) in the upper 120 mbsf. At greater depths, methane increases to ~20,000 ppm (Table T12; Fig. F19). Small amounts of ethane were detected below 150 mbsf (Table T12).

The inorganic carbon record at Site 1101 (Fig. F20) distinguishes clearly the lithostratigraphic Units I, II, and III (see "Lithostratigraphy"). Calcium carbonate concentrations range from 0.3 to 3.1 wt% in Unit I (0-53 mbsf), from 0.2 to 46.7 wt% in Unit II (53-143 mbsf), and from 0.0 to 0.8 wt% in Unit III (143-215 mbsf). Most notably, Unit II includes a series of centimeter- to decimeter-scale layers of carbonate-rich (3-28 wt%) silt and mud that contain well-preserved foraminifers and calcareous nannofossils (see "Biostratigraphy"). These layers occur exclusively, but not consistently, within bioturbated intervals of inferred interglacial-age sediment, separated by intervals of laminated silt and clay deposited presumably during glacial periods. A similar pattern of carbonate variability characterizes Unit I; however, the peak carbonate concentrations remain low (<4 wt%) compared to those observed in Unit II.

The Brunhes/Matuyama boundary, identified at 55.1 mbsf using paleomagnetic data (see "Paleomagnetism") and coeval with oxygen isotope Stage 19, coincides with a carbonate-rich layer near the top of Unit II (Fig. F20). This supports the idea that these layers represent interglacial periods. Other factors that may have influenced the variability of carbonate accumulation include changes in productivity, preservation, sedimentation rate, and dilution by terrigenous sediment. Also, a carbonate-cemented (>45 wt%) silt layer occurs near the base of Unit II (see "Lithostratigraphy"), where methane concentrations begin to increase and possibly play a role in precipitating calcium carbonate (see "Inorganic Geochemistry").

Total organic carbon concentrations (Fig. F21) remain low (<0.4 wt%) throughout Unit I and the upper part of Unit II and decrease essentially to zero in the lower part of Unit II, perhaps as a result of greater terrigenous input. Total organic carbon returns to low (<0.4 wt%) but slightly increasing values with depth in Unit III.