which contains only a selected part of the full survey data. Copies of these 

 preliminary charts can be obtained from NOS on request and are a desirable 

 addition to the source material, not only for planning purposes, but for 

 interpretation of data and report preparation. 



125. Geomorphic features in the exploration area can best be displayed 

 by contouring the charts at the closest vertical scale practical with the 

 density of soundings. In most cases, geomorphic data from the charts will be 

 sufficient to locate and identify any existing inlet; estuarine, cape- 

 associated, or linear shoals; shoal retreat massifs, or other positive fea- 

 tures in the exploration area. Shoals are the primary prospects, and 

 exploration should be emphasized in these areas in terms of data coverage and 

 density. At the same time, the investigator should not neglect to obtain 

 sufficient coverage of intervening areas to identify large potential sources 

 such as relict stream channels that may lack geomorphic expression, and to 

 maintain continuity of data coverage throughout the exploration area. 



126. Geophysical tracklines are usually laid out either in a grid pat- 

 tern or in a continuous zig-zag onshore/offshore alignment (Figure 10) . Grid 

 lines (Figure 11) are used in areas where there seems to be a good possibility 

 of finding potentially usable material such as a shoal area. The zig-zag 

 alignment (reconnaissance lines) is used to connect grid areas to maintain 

 continuity and detect indications of possible sources that warrant further 

 investigation. The spacing of tracklines is based on an estimate of the prob- 

 able variability of bottom and subbottom features. Grid line spacing of 



0.8 km (0.5 mile) or less may be necessary in complex areas while spacing of 

 1.6 km (1.0 mile) may be adequate where conditions are more uniform. Configu- 

 ration and spacing of reconnaissance lines is also based on a judgment of the 

 complexity of the area. The configuration and spacing of tracklines need not 

 follow the grid and zig-zag patterns but can be varied in any fashion that 

 would be more appropriate for a particular area. The main objective is to 

 acquire comprehensive coverage that best reflects the surficial and sub-bottom 

 geology of the exploration area at an economically feasible cost. 



Schedule of Events 



127. Part of the planning procedure for borrow source exploration pro- 

 grams is scheduling of the individual phases of the operation. The schedules 



51 



