ABSTRACT: Side-Scan Sonar and Submersible Observations: New Techniques for Gleaning More Information from Sea-Floor Outcrops

Jerome Kendall, J. E. Hams, S. P. Buck

Advances in high resolution side-scan sonar imaging technology are so effective at imaging sea-floor geology that they have greatly improved the efficiency of a bottom sampling program.

The traditional sea-floor geology methodology of shooting a high-resolution seismic survey and sampling along the seismic grid was considered successful if outcrops were sampled on 20% of the attempts. A submersible was used sparingly because of the inability to consistently locate sea-floor outcrops. Side-scan sonar images have increased the sampling success ratio to 70-95% and allow the cost-effective use of a submersible even in areas of sparse sea-floor outcrops.

In offshore basins this new technology has been used in consolidated and semiconsolidated rock terranes. When combined with observations from a two-man submersible, SCUBA traverses, seismic data, and traditional sea-floor bottom sampling techniques, enough data are provided to develop an integrated sea-floor geologic interpretation.

On individual prospects, side-scan sonar has aided the establishment of critical dip in poor seismic data areas, located seeps and tar mounds, and determined erosional breaching of a prospect. Over a mature producing field, side-scan sonar has influenced the search for field extension by documenting the orientation and location of critical trapping cross faults. These relatively inexpensive techniques can provide critical data in any marine basin where rocks crop out on the sea floor.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990