and subbottom interfaces are received by one or more hydrophones. Return- 

 ing 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 navi- 

 gational 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), 



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

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

 tus 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-sectional 

 profiles showing all reflective interfaces within the subbottom. Selected 

 reflectors are then mapped to provide areal continuity or reflective hori- 

 zons 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 delivery 

 to CERC, these cores are sampled by drilling through the liners and remov- 

 ing samples of representative material. After preliminary analysis, a 

 number of representative cores are split in order to determine details of 

 the bedding. Cores are set up for splitting on a wooden trough. A circu- 

 lar power saw mounted on a base which is designed to ride along the top of 

 the trough is set so as to cut just through the liner. By making a cut in 

 one direction and then reversing the saw base and making a second cut in 

 the opposite direction, a 120-degree segment of the liner is cut. The 

 sediment above the cut line is then removed with a spatula, and the core 

 is logged, sampled and photographed. 



Samples from cores are examined under a binocular microscope, and 

 described in terms of gross lithology, mineralogy, and the type and 

 abundance of skeletal fragments of organisms. 



