TABLE 2.—Analysis of sediment standard and replicate sediment samples—Continued 
Sample Al Ba Cd Cr Cu Fe Mn Ni Pb V Zn 
replicate _(%) (ppm) (ppm) __ (ppm) (ppm) (4%) (ppm) (ppm) ___ (ppm) (ppm) _ (ppm) 
a 3.86 200 138 74 18.8 2.86 378 37 26.2 126 77 
o---------- 8.9 0 008 1.4 5 5.5 8 1 1.3 5.5 2 
w(%)! 203 0 6.1 1.9 2.4 1.9 2 Dell 5.0 4.3 2.6 
lCoefficient of variation. 
2values reported by the Marine Analytical Chemistry Standards Program, National Research Council, Canada. 
observed in the gravel fraction at the drill sites 
in blocks 312 and 410. A few cuttings were found 
during both year 2 and year 3 at station 17, 2 
km to the east of the drill site in block 410. On 
cruise 9, cuttings were observed at all stations 
within 500 m of the drill site in block 312. The 
cuttings are angular, range in size from 2 to 8 
mm, and are primarily gray in color. By using X- 
ray diffraction analysis on a few cuttings, L. J. 
Poppe (USGS, written commun., 1984) identified 
calcite as the predominant mineral with lesser 
amounts of dolomite and layered silicates. These 
minerals are common throughout the subsurface 
Jurassic and Cretaceous sediments (Arthur, 
1982). The highest concentrations of cuttings, 
which were localized at the drill sites, represent 
less than 1.5 percent of the total sample weight. 
The cuttings did not occur in a recognizable pile 
in the vicinity of the drill site in block 312, accor- 
ding to R. A. Cooper, National Marine Fisheries 
Service (written commun., Oct. 14, 1983), who 
conducted visual and photographic surveys of 
the drill site from a submersible. 
TRACE METALS IN BULK SEDIMENTS 
During the first year of this program, we estab- 
lished that the concentrations of trace metals in 
sediments collected before drilling began were 
low compared to their average concentrations in 
crustal rocks and that they were characteristic 
of uncontaminated coarse-grained sediments. We 
found the variability in trace-metal concentra- 
tions from station to station to be closely cor- 
related with the content of fine-grained material 
and organic carbon in the sediments, as com- 
monly occurs (Crecelius and others, 1975). Pb 
values higher than average crustal abundances 
were measured only at the location south of Mar- 
tha’s Vineyard where fine-grained sediments are 
11 
accumulating and where previous studies (Bothner 
and others, 1981) have suggested tetraethyl lead 
from gasoline as a source of the elevated Pb found 
in this area. 
Throughout the 3 years of monitoring, the con- 
centrations of Ba in bulk sediments from the 
upstream control stations (transect I, stations 1- 
3) were fairly consistent with time (fig. 4, appendix 
table 4A). On the basis of these data, we judge that 
no increase in Ba had occurred at these stations. 
We found no increases in the concentration of other 
metals as a result of drilling at these upstream loca- 
tions during the 3 years of monitoring. 
. In contrast, there were measurable changes in the 
concentrations of Ba in block 410 (stations 16, 17, 
and 18, fig. 5). Drilling began in this block immedi- 
ately after the first sampling cruise in July 1981 
and continued (with some interruptions) until 
March 31, 1982. The mean current flow on this part 
of the Continental Shelf is to the west, although 
tidal and storm currents can reverse the mean flow 
(Butman and others, 1982a). Relative to the mean 
current flow, stations 17 and 18 are upstream and 
downstream of the rig position, respectively (fig. 5). 
At station 16, located within 200 m of the drill 
rig in block 410, average Ba concentrations ap- 
parently increased steadily from a predrilling con- 
centration of 32 ppm to the maximum concentra- 
tion of 172 ppm measured on cruise 6, an increase 
by a factor of 5.9. Drilling was completed before 
cruise 4, and we expected that the maximum con- 
centration of Ba would be found on the fourth 
cruise. However, no statistical difference exists in 
the Ba concentration between cruises 4 and 6 at the 
95-percent level of confidence (a=0.05) because of 
the large within-station variability in the Ba 
distribution (fig. 5). 
The concentration decreases at the time of cruise 
7 remain at a fairly constant level of about 80 ppm 
from cruises 8 through 12, except for cruise 11. The 
