profiling, the soimd source is fired at a rapid rate, and returning 

 signals from bottom and subbottom interfaces are received by one or more 

 hydrophones. Returning signals are amplified and fed to a recorder 

 which graphically plots the two-way signal travel time. Assuming a 

 constant velocity for sound in water and shelf sediments, a vertical 

 depth scale can be constructed to the chart paper. Horizontal location 

 is obtained by frequent navigational fixes keyed to the chart record by 

 an event marker, and by interpolation between fixes. 



A more detailed discussion of seismic profiling techniques can be 

 found in a number of technical publications (Miller et al., 1967; 

 Ewing, 1963; Hersey, 1963; and Moore and Palmer, 1968). 



Geophysical work for the present study was accomplished with a 

 seismic system using compressed air as a sound energy source. Two "air 

 guns" were used simultaneously during the survey. A low energy, high 

 resolution gun source with a 1-cubic-inch chamber was used to produce a 

 signal which provides good resolution but limited penetration. . Returns 

 from this source were recorded directly on 8-inch-wide electronsensitive 

 paper using a recorder sweep speed of 125 milliseconds. The second gun 

 had a 3-cubic-inch chamber, and its returns were recorded on magnetic 

 tape and later played back through a recorder for display on 19- inch- 

 wide recorder paper. The latter source provides greater penetration, 

 but resolution is reduced because of its longer pulse time. 



c. Coring Techniques - A pneumatic vibrating hammer-driven coring 

 assembly was used for obtaining cores from the survey area. The appa- 

 ratus consists of a standard core barrel, liner, shoe and core catcher 

 with the driver element fastened to the upper end of the barrel. These 

 are enclosed in a self-supporting frame which allows the assembly to 

 rest on the bottom during coring, thus permitting limited motion of the 

 support vessel in response to waves. Power is supplied to the vibrator 

 from a deck-mounted air compressor by means of a flexible hoseline. 

 After the core is driven and returned, the liner containing the cored 

 material is removed and capped. 



d. Processing - Seismic records are analyzed to establish the 

 principal bedding or structural features in upper subbottom strata. 

 After preliminary analysis, record data is reduced to detailed cross- 

 section profiles showing all reflective interfaces within the subbottom. 

 Selected reflectors are then mapped to provide areal continuity of 

 reflective horizons considered significant because of their extent and 

 relationship to the general structure and geology of the study area. 



If possible, the upper mapped reflector is correlated with core data 

 to provide a measure of continuity between cores . 



Cores are visually inspected and logged aboard ship. After de- 

 livery to CERC, these cores are sampled by drilling through the liners 

 and removing samples of :cepresentative material. After preliminary 

 analysis, a number of representative cores are split to determine 



