Vane Shear Strength and Index Properties . The vane strengths and 

 index properties are plotted in Figure 19. The original strength profile 

 varies considerably throughout its length. This rather erratic tendency 

 seems to correlate with a zone of substantially lower liquid limits. 

 Although the water contents in the zone decrease (as the plastic indices 

 remains relatively constant), a loss in original strength is recorded at 

 the 60- to 70-centimeter increment. This behavior suggests disturbance 

 to the sample. The lowest two sample intervals exhibit similar charac- 

 teristics. The plasticity indices are relatively consistent, while the 

 water contents decrease. Unfortunately, the strength also decreases. 

 The most obvious explanation is again sample disturbance. However, this 

 unique behavior might also be attributed to the mineralogic composition 

 of the material. The author tends to favor the former explanation. 



Station 



Geologic Considerations . Station is located on the distal portion 

 of the Ganges Cone in the Indian Ocean. The site, approximately 250 miles 

 southeast of Ceylon, has a water depth of 2,350 fathoms. Sediments are 

 usually terrigenous in origin (Fairbridge, 1966). An extrapolation of 

 data presented by Siddquie (1967) suggests that many sediments are silts 

 and clays. The percentages of carbonate compound are usually less than 

 25 percent. Similar sediments on the continental slopes are generally 

 plastic and soft in consistency (Fairbridge, 1966). These Continental 

 slope sediments are composed of clay minerals and microorganisms such as 

 foraminifera and radiolaria. 



Sediment Identification . A 90-centimeter gravity core and a 70- 

 centimeter trip core were obtained from Station 0. The upper 50 centi- 

 meters of both samples was composed of a tan silty clay. The sediment 

 became grayer below that depth. Both materials were classified (Unified 

 Classification System) as inorganic silts of high r ompressibility (MH) . 

 The Trilinear System categorized the materials as silty clays. The tan 

 silty clay had a median diameter equal to 0.0022 millimeter, while the 

 gray silty clay's median diameter was 0.0028 millimeter. The percentages 

 of sand, silt, and clay size particles in the tan soil were 20, 19, and 

 61, respectively. The gray soil, in turn, was composed of 187o sand size 

 particles, 217» silt size, and 617o clay size. Carbonate carbon and organic 

 carbon constituted approximately 8.57, of each sample. 



Vane Shear Strength and Index Properties . The vane strengths and 

 index properties are plotted in Figures 20 and 21. The gravity core 

 strengths generally increase with depth as expected. A large increase 

 in strength occurs in a zone where plasticity indices are changing con- 

 siderably. The trip core exhibits strengths that are usually higher than 

 the measurements made on gravity core samples. However, the index prop- 

 erties of the two samples correlate quite well. The bottom portion of 

 the trip core is thought to be disturbed. 



32 



