The distribution of all measured grain-size fractions with depth is diagrammed in Figure 3, Figure 4, and Figure 5 along with the pore-water chlorinity. Inspection of Figure 3, Figure 4, and Figure 5 points to the fact that the depth intervals, which encompass the chlorinity anomalies, are confined to the depth intervals where comparatively coarse-grained sediments occur. Two grain-size horizons bounding the zone of lowered pore-water chlorinity anomalies are clearly recognized in the column of Site 994 at depths in the regions of 250 and 400 mbsf (Fig. 3). The sediments in these horizons are enriched by particles >0.05, >0.01, >0.005, and >0.001 mm, compared to adjacent depths; the extent of the enrichment peaks are at approximately 2%, 10%, 12%-15%, and 8%-10%, respectively, which is distinctly larger than the upper 95% confidence limit of the standard deviation of the accuracy of our grain-size analysis (see Table 5). Similar horizons are more distinctly pronounced in the column of Site 995 (Fig. 4). In addition, the entire interval bounded by these horizons differs noticeably in this column from the underlying and overlying sediments by a rather high content of the fractions >0.005 and >0.001 mm. These two horizons do not stand out in the column at Site 997 (Fig. 5), but the entire interval under discussion is clearly discerned there by frequent interlayers characterized by a rather high content of the fractions >0.005 and >0.001 mm.
Individual chlorinity anomalies, which are attributed to gas hydrate-presence in situ, are also often, but not universally, controlled by rather coarse-grained sediments. Of a list of 61 of the most prominent anomalies in all three studied columns, 44 (77%) are more or less evidently confined to such sediments. Figure 6 provides an example of these anomalies.