function of sediment depth to determine the depth profiles of metal 
concentrations. A gradient in the depth profile of a metal concentration can 
indicate the introduction or removal of the metal. Our first objective was to 
extend our search for drilling-related Ba to locations on the bank where data 
from seasonal cruises may not be available. Second, we hoped to make some 
inferences about the extent and rate of downward mixing of newly introduced Ba 
by benthic organisms and/or currents by examining profiles at stations 
adjacent to drilling operations. 
We examined the profiles of Ba and Ba/Al in four areas where the 
introduction of drilling mud was not expected (fig. 15A-D, location of samples 
shown in fig. 1). Although there is some scatter in the Ba values, 
particularly in sample M11-03-00-AX, the Ba/Al ratio is constant with depth at 
all four locations. This is a particularly important observation because it 
argues against the possibility that the naturally occurring Ba dissolves in 
response to reducing conditions in subsurface sediments and migrates upward 
into oxidizing sediments, where it precipitates. Sufficient reducing 
conditions in the sediments for the characteristic migration and precipitation 
of Mn has been observed in the interstitial water of core 83G9-B 
(K. O. Buesseler and E. R. Sholkovitz, Woods Hole Oceanographic Institution, 
pers. commun., July 1984) as well as in the total sediment phase (appendix 
table 4D). The absence of a gradient in Ba or Ba/Al at all four locations, 
which represent different sediment types, suggests that the gradients measured 
closer to drilling sites are not due to diagenetic reactions. 
An additional point regarding core 83G9-B, from 1,250 m water depth on 
the slope, is that concentrations of Pb are higher in the surficial sediment 
than in subsurface sediment (appendix table 4D). The source of this Pb is 
probably the burning of lead alkyls in gasoline in coastal metropolitan areas, 
52 
