Marine Sonoprobe system, a low-frequency seismic system which generates a pulse of sound energy with a dominant frequency of 3,800 cycles per second, is described. Marine Sonoprobe profiles are presented which illustrate various geologic features. Among these are examples of buried channels, reefs, anticlines, faults, facies changes, and sedimentary pinch-outs. Bottom-sediment sampling and coring have shown that the reflections observed on Marine Sonoprobe records are correlative with changes in sediment type. The various factors which have an effect upon the quality of the records and the depth from which reflected signals may be recorded are: (1) boat speed and course with respect to the direction of movement of waves and currents; (2) instrument installation; (3) domin nt frequency, pulse shape, and pulse energy; (4) water depth; and (5) geologic conditions such as thickness and depth of the reflecting horizon, and possibly the moisture content.

Marine Sonoprobe information is most useful in a coring and sediment analysis program.