The slower rate of barite disappearance from the upper 2 cm measured 
after cruise 8 is probably related to the effect of downward mixing into the 
sediment. This process decreases the concentration in the surface O to 2-cm 
layer by dilution rather than actual removal. Consequently, the removal 
process is actually slowed by mixing processes since larger storms (which are 
less frequent) are necessary to erode sediments to the increasing depths of Ba 
penetration. 
The slower rate of barite disappearance after cruise 8 could also be 
caused by the accumulation of sediments having lower Ba concentration on top 
of the sediments having higher Ba concentrations. 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 which is discharged by drilling operations 
and subsequently eroded from the sediments near the drill rigs? Some of the 
barite may dissolve into seawater which is undersaturated 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 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 processes. 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 the surface sediment higher than in sediment at greater depth. At both 
stations 10 and 12, we have observed peaks in the Ba concentration of 
postdrilling samples. At coring stations 50 km west of transect III (0C140- 
39, 41), we observed an enrichment of the Ba/Al ratio in surface sediments and 
65 
