FISHERY BULLETIN: VOL. 72. NO. 2 



SANTA BARBARA BASIN C-2S2-I 

 TH-BES/TH-B3B ACTIVITY 



\ 



Q_ 



O 1-00. 



LD 

 D 



_| O-BO.. 



SANTA BARBARA BASIN C-^39B2-S 

 PB-210 ACTIVITY 



iaSB-1300 



000 e-oo <oo 600 



1-00 10-00 1^-00 14.00 16-00 16.00 50-00 



0.00 4-00 B'OO 12-00 lB-00 20-00 24-00 



1-00 3E-00 3E-00 40-00 



DEPTH IN CENTIMETERS IN SEDIMENT 



DEPTH IN CENTIMETERS IN SEDIMENT 



Figure 4a,b-— Santa Barbara Basin Th-228/Th-232 activity and Pb-210 activity at sediment depth. An excess of both the thorium 

 isotopic ratio Th-228/Th-232 and the lead isotope Pb-210 are present in coastal surface sediments (Koide et al, 1972, 1973). In the case of 

 Pb-210 (22-3 yr half life), the varve age estimate and the radiometric age estimate may be directly compared- The thorium ratio on the 

 other hand cannot be directly estimated as function of time but may be calibrated against the accepted varve age. 



BAJA CALIFORNIA C-E44 Bl-4 

 TH-P2a/TH-B32 ACTIVITY 



BAJA CALIFORNIA C-B44 Bl-4 

 PB-210 ACTIVITY 



0-00 2-00 4-00 G-00 8-00 lO-OO 15-00 14-00 lB-00 lfi-00 50-00 



0-00 4-00 B-00 12-O0 ie-00 ao-oo ?4.oo ae-oo ^-oo 3B-oo 4o-oo 



DEPTH IN CENTIMETERS IN SEDIMENT 



DEPTH IN CM- (MINUS SLUMP) 



Figure 4c,d.— Soledad Basin Th-228/Th-232 activity and Pb-210 activity at sediment depth. The information gained from the study of 

 these radiometric tools in the Santa Barbara sediment may be applied to the anaerobic sediment of the Soledad Basin. Here, despite the 

 absence of consistent laminae, the radiometric ages provide the basis for a time framework- It should be noted that the scatter of Pb-210 

 points at the lower end (circa 1880) signals the merging with the supported background activity (U-238 series)- 



262 



