Measurement of in Sz'tu Sediment Conductivity by means of a Bullard-type Probe

The heated-probe method of measuring sediment conductivity has been successfully adapted to making a multipoint determination in situ over the full gradient interval of a heat-flow measurement. A probe 2.3 m long and 1 cm in diameter can complete both the gradient and conductivity measurements in 30 min on the ocean floor. The first two stations show that agreement between the theory of the method and the experimental data is good, and that in situ sediment conductivity at 2.1 x 1O-j cal "C- ' cm- s- ' is consistent with representative values obtained by steady state laboratory methods. The original Bullard (1954) probe technique of thermal gradient measurement in the sediments on the ocean floor has the advantages of operational simplicity and ruggedness. The sensors and wiring are encased in the instrument shell and therefore rarely require repair or adjustment. The technique has, however, the minor dis-advantage of a relatively long probe time constant, and the major disadvantage of requiring either an outrigger probe to obtain a point value of in situ conductivit