60 
50 
40 
30 
PERCENT OF TOTAL Ba 
20 
>1000 
1000-500 500-210 210-105 
[05-60 
STATION 5-2 
M4=X—— 
MI0zO—— 
60-30 30-10 
SEDIMENT-SIZE CLASSES, IN ym 
FIGURE 12A.—Relative amount percent of total barium in different size fractions of bottom sediment collected on cruises 4 
and 10 at site-specific station 5-2 on Georges Bank. 
Although Georges Bank as a whole is considered 
to be eroding, processes of sediment redistribution 
and local accumulation have been identified 
(Twichell, 1983). 
What is the fate of the barite that is discharged 
by drilling operations and subsequently eroded 
from the sediments near the drill rigs? Some of the 
barite may dissolve into seawater that is under- 
saturated with respect to BaSO, (Chow, 1976; 
Dehairs and others, 1980). However, the rate of 
dissolution is likely to be slow, and the Ba released 
by dissolution may be reprecipitated by certain 
planktonic organisms or reprecipitated during the 
decomposition of suspended-organic matter 
(Dehairs and others, 1980). 
The fate of Ba added to Georges Bank seems, 
at present, to be linked to sediment transport proc- 
esses. We have found small Ba increases in the fine 
fraction of sediment at distant stations both to the 
west and to the east of the drilling area. To the west 
at station 12, we have found Ba concentrations in 
25 
the surface sediment that are higher than those at 
greater sediment depth. At both stations 10 and 
12, we observed peaks in the Ba concentration of 
postdrilling samples. At coring stations 50 km 
west of transect III (OC140-39, 41), we observed 
an enrichment of the Ba/Al ratio in surface 
sediments and interpret this as evidence for a small 
recent addition of Ba. Also to the east, along 
transect I, we measured Ba increases in some of 
the postdrilling samples, although these are of 
smaller magnitude than those at stations 10 and 
12. There is no evidence of an increase in Ba at sta- 
tions 13 or 138A from the analysis of surface 
samples or from sediment cores, although a small 
signal is more difficult to identify here because of 
a higher predrilling Ba concentration. 
A rough calculation made in an earlier report 
(Bothner and others, 1984b) suggested that 69 per- 
cent of the barite discharged by all eight explora- 
tory wells could be accounted for in the sediments 
within the western half of a circle 130 km in 
