Methods for Laboratory measured Physical Properties, Gearhart-Owen Well Logs, and the Uyeda Down-Hole Temperature Probe, Leg 61, Deep Sea Drilling Project

Abstract

In the laboratory, we measured heat conductivity, sound velocity, 2-minute GRAPE wet-bulk density, gravimetric wet-bulk density, wet-water content, and porosity on the same sample, when possible.An attempt was made to obtain an undisturbed sample. This is a serious problem in the upper 200 meters of the hole, where the sediments are soft, as the drill bit is 25 cm in diameter, with the ~ 6-cm-diameter coring hole within this cutting bit. Most soft sediments are literally "squirted" into the core barrel and completely disturbed.Because of this core disturbance, few discrete samples for physical-property measurements were taken in the upper part of the hole; however, the continuousanalog GRAPE was always run. Also as a result of the degree of core disturbance in the upper part of the hole, and stiffness of samples which were not disturbed, vane shear strength could be measured on only a small number of "semi-soft" samples.The criterion for an undisturbed sample is undistorted bedding or laminae in the sample. The obvious problem with this criterion is that a completely homogeneous soft-sediment core would not be sampled, even if it were undisturbed.In general, sediment remained in the core liner for about 2 hours. The core section was split, and samples were selected immediately for heat-conductivity measurement, which was done immediately (2-5 minutes). Then a D-shaped sample was cut for the sound-velocity measurement, and a smear slide was made; this sample was wrapped in plastic and placed in a small plastic box with a wet sponge. The sample was then removed from the plastic wrapper, and its surface cleaned with either a spatula or file. Distilled water was squirted on these surfaces, and the velocities were measured; then the GRAPE 2-minute wet-bulk-density determination was made. Afterward, a sub-sample was cut for gravimetric determination of wet-water content, wet-bulk density, and porosity; this sample was cleaned and wrapped in plastic, then sealed in a plastic vial with a wet towel. The vial was placed in a refrigerator above freezing until it could be processed. Initial Reports of the Deep Sea Drilling Project, Volume 61.Basalt samples were handled differently, because of DSDP's official curatorial process. Basalt was not in a plastic liner; therefore, it was necessary to select soundvelocity samples when the cores arrived on deck and were brought into the laboratory. These core segments were wrapped in plastic until the samples were processed by the DSDP curator and eventually split. After the core segment was split, heat conductivity was measured immediately (2-5 minutes) on the split core. Then a minicore (~2 cm diameter) was drilled out of this 1/2 core segment. This mini-core was wrapped in plastic and placed in a plastic vial with a damp sponge until velocity and a 2-minute GRAPE were measured. Velocity was measured across the axis of the mini-core, and 2-minute GRAPE was measured parallel to the axis of the minicore. The mini-core was then wrapped in plastic and sealed in a vial with a wet sponge...