248 



Sediments 



parameters. Eighteen cores were collected 

 from thirteen basins, the continental slope, 

 and the deep-sea floor (Fig. 205). For com- 

 parison, the rate of deposition of sediments 

 at the top of the San Pedro Basin slope off' 

 Palos Verdes Hills based on radiocarbon age 

 determinations by the Magnolia Petroleum 

 Company (Emery, \95Sa) and the rate in 

 Ventura and Los Angeles Basins since the 

 Miocene Epoch are included. 



All cores were obtained with a piston 

 corer (Kullenberg, 1947) weighing 500 kg 

 and having a core tube 6.5 meters long and 

 about 10 cm in inner diameter. Piston cores 

 are far superior to simple gravity cores for 



this kind of work because of the shortening 

 of the sediment section produced by gravity 

 cores during their penetration of the bottom 

 (Emery and Dietz, 1941). The tripping de- 

 vice for the piston core was adjusted in such 

 a way that it tripped above the bottom, 

 allowing as much as a meter of water to be 

 drawn in before the core tube reached the 

 sediment surface. This procedure insured 

 that the topmost layer of sediment was 

 cored, although at the expense of not ob- 

 taining the maximum possible core length. 

 Evidence of recovery of the sediment sur- 

 face was provided by typical high contents 

 of interstitial water and even better by the 



SEA FLOOR OFF SOUTHERN CALIFORNIA 



STATUTE MILES 



CONTOUR INTERVAL — 1500 FEET 



3CX) FOOT CONTOUR ADDED 



Figure 205. Positions of cores used for determining rates of deposition of sediments from radiocarbon age measure- 

 ments. Rates of deposition in Ventura Basin, Los Angeles Basin, and Newport Bay are based on other data. 



