and 5) and decreases at the time of cruises 6 through 10. Ba concentrations 
at station 5-29, 6 km to the west, continue to increase between the completion 
of drilling and cruise 8. This continued postdrilling increase and 
maintenance of high concentrations through cruise 12 may be caused by the 
transport and deposition of Ba-rich fine sediment originally deposited closer 
to the rig. These results suggest that Ba was being dispersed from the 
immediate vicinity of the drilling rigs. 
The question of how far the Ba from drilling mud could be traced was 
addressed by analyzing the fine fraction of sediment at stations 10 and 12, 
approximately 65 km west of the block 312 drill site, and stations 2 and 3, 
approximately 35 km to the east of the easternmost drill site. At stations 12 
and 10 we measured maximums in the Ba concentration at the time of cruises 8 
and 10, respectively (fig. 9A). We were surprised to record maximums in the 
Ba concentration at similar times, although of lower magnitude, at stations 2 
and 3. The maximum value at station 3 on cruise 7 is statistically higher 
than the mean of the first 6 cruises at the 99.5 percent level of confidence 
(t test). 
The Ba/Al ratio (fig. 9B) that was plotted for each sampling period is 
also used to show relative changes in the Ba levels. Typically Al is highly 
correlated with the percent of clay minerals in marine sediments and is used 
in the ratio to remove the variability introduced by different amounts of clay 
in the fine fraction on different sampling dates. The Ba/Al ratio also 
eliminates the small error introduced in making the chloride correction 
necessary to determine metal concentrations of the fine fraction in mass 
units. The Ba/Al ratio is at a maximum value at stations 2, 3, and 12 on 
cruises 7 or 8. The value for the relatively small maximum of station 3 is 
statistically higher (t test) at the 99.5 percent level of confidence than the 
mean of cruises 1-6. No Al data are available for samples from station 10. 
35 
