Francisco Bay. Krone's report also provides an excellent review of 

 techniques and considerations in radioisotope tracing. In addition to 

 the many field studies, some model work in the laboratory has been done 

 (Lean and Crickmore (19-63) and Taney (1962)). 



Most investigators used bundles of Geiger-Muller detectors mounted 

 on a sled, or drag. These detectors are large, rugged, and low in cost, 

 but they have measurement efficiencies of only about 1 percent. Other 

 investigators used scintillation detectors which have smaller active 

 volumes, but can be very efficient. In some cases, samples were taken 

 and autoradiographs made to provide a quantitative measure of sand tracer. 

 The value of taking sediment samples and laboratory determination of label 

 is limited by the number and size of the samples that can be taken, and 

 by the delay between sampling and analysis. 



The primary work accomplished to date in the vicinity of Point 

 Conception was done by Trask (1952, 1955). He studied the minerals 

 present in the stream sediments both north and east of Point Conception 

 and found that augite was present only in streams north of the Point. 

 Because augite was found to the east of Point Conception and because it 

 could not have been supplied by the local streams , he concluded that 

 sediments do indeed pass around the supposed barrier, the Point Conception 

 complex. 



The information available to. Trask, unfortunately, was incomplete. 

 No offshore samples were secured to the north and west of Point Conception 

 to determine whether augite was or was not present in those areas. If 

 augite did occur on the Continental Shelf to the north and west of Point 

 Conception as well as offshore east and south, then it would not be a 

 unique mineral species useful as a natural tracer. In fact, the possi- 

 bility of an offshore source of sand containing augite was eliminated on 

 the then held belief that sediments do not migrate toward the shore. 

 Another factor not fully considered is the difference of size parameters 

 on each side of the headland. Trask reported these differences, but 

 failed to realize that another source area could be the cause. 



Bowen and Inman (1966), partly based on the previous work by Trask 

 (1955), concluded that sediment moved around the Point Conception complex. 

 They also estimated the rate of drift at various locations around the 

 Point. Mineralogy, sedimentation, and transport in the area around 

 Pillar Point (northern California) were studied by Sayles (1965). He 

 concluded that the sands were locally derived and that there was no net, 

 long-term littoral transport of sand in this area. Similarly, Cherry 

 (1965) concluded that Point Reyes and Bodega Head are barriers to long- 

 shore transport . The geology and oceanic environment offshore of Point 

 Conception (San Miguel Gap) is discussed by Wright (1967). Lampietta 

 (19610 reports on the Ocean Science and Engineering, Inc. study of beach 

 configuration from Pismo to St. Augustin, California. Profiles 9 and 10 

 of that study are in the area of Surf, California, and profiles 12-1*+ cover 

 the area near Point Conception. Other studies of California sediments have 

 been made by Emery (195*0 and Cooper (1967). 



