mission, especially in terms of Continental Shelf structure (Meisburger 

 and Duane, 1969), Continental Shelf sedimentation (Field, Meisburger and 

 Duane, 1971), and its potential application to historical geology and 

 engineering studies of the shelf, the sand inventory program is now re- 

 ferred to as the Inner Continental Shelf Sediment and Structure Program 

 (ICONS) . 



2. Field and Laboratory Procedures 



The exploration phase of the ICONS program uses seismic reflection 

 profiling supplemented by cores of the marine bottom. Additional support- 

 ing data for the studies are obtained from USC^GS hydrographic boat sheets 

 and related published literature. Planning, and seismic-reflection pro- 

 filing, coring, positioning, and analysis of sediment obtained in the 

 cores are detailed in Geomorphology and Sediment Charaoteristios of the 

 Nearshore Continental Shelf ^ Miami to Palm Beach ^ Florida (Duane and 

 Meisburger, 1969) . However, a brief description of techniques is germane 

 to this paper and follows. 



a. Planning - Survey tracklines were laid out by the CERC Geology 

 Branch staff in either of two line patterns: grid and reconnaissance 

 lines. A grid pattern (line spacing about 1 statute mile) was used to 

 cover areas where a more detailed development of bottom and subbottom con- 

 ditions was desired. Reconnaissance lines are one or several continuous 

 zigzag lines followed to explore areas between grids, and to provide a 

 means of correlating sonic reflection horizons between grids. Reconnais- 

 sance lines provide sufficient information to show the general morphologic 

 and geologic aspect of the area covered, and to identify the best places 

 for additional data collection. 



Selection of core sites was based on a continuing review of the 

 seismic profiles as they became available during the survey. This proce- 

 dure allowed core-site selection based on the best information available; 

 it also permitted the contractor to complete coring in one area before 

 moving his base to the next area. 



b. Seismic Reflection Profiling - Seismic reflection profiling is 

 a technique in wide use for delineating subbottom structures and bedding 

 planes in sea floor sediments and rocks. Continuous reflections are 

 obtained by generating repetitive high-energy, sound pulses near the water 

 surface and recording "echoes" reflected from the bottom-water interface, 

 and subbottom interfaces between acoustically dissimilar materials. In 

 general, the compositional and physical properties which commonly differ- 

 entiate sediments and rocks also produce acoustic contrasts. Thus, an 

 acoustic profile is roughly comparable to a geologic cross section. 



Seismic-reflection surveys of marine areas are made by towing sound- 

 generating sources and receiving instruments behind a survey vessel which 

 follows predetermined survey tracklines. For continuous profiling, the 

 sound source is fired at a rapid rate, and returning signals from bottom 



