Detailed Report of Leg One
The R/V Edwin Link with the Johnson Sea Link 1 research submersible
departed Port Fourchon, LA, at 7:40 pm on August 16, 2000, and arrived on station in Green
Canyon block GC-185 (Bush Hill) in the early morning hours of Aug. 17.
August 17-19, 2000
Dives 4224 to 4230
During the first three days, Dr. Roberts deployed and retrieved equipment at Green
Canyon 185 (Bush Hill) as part of another project.
August 20, 2000
Dive 4231
Steamed overnight from GC 185 to GC 286/287/331. This dive surveyed Traverse 1, running
NE to SW. Depth ranged from 2750 ft. to 2950 ft. Along the route, the submersible found
and video taped bacterial mats, clam beds, and a number of small-to-large carbonate rocks,
which agreed well with the amplitude maps. A calcium carbonate hardground sample was
collected along the route.
Dive 4232
Surveyed Traverse 2 on GC 286/287. Depth ranged from 2713 to 2749 ft. Found several
large carbonate boulders, some erosional features which appeared to result from brine
seeps, and a large crater (approximately 20-30 ft. across and 10 to 15 ft. deep). The
crater had a fractured carbonate crust all around the rim. A couple of samples were taken
on the rim of the crater, and the second released hundreds of droplets of oil, followed by
a steady stream of gas bubbles. A gas sample was taken, and formed hydrate in the top of
the clear sample tube.
August 21, 2000
Dive 4233
After steaming overnight, this dive surveyed Traverse 2 on GC 204/249. Depth ranged
from 2839 to 2957 ft. This traverse went from a muddy, hemipelagic burrowed bottom to a
white shell hash area. Several small ridges and gullies were observed.
Dive 4234
Surveyed Traverse 3 on GC 204. Depth ranged from 2658 to 2960 ft. A dormant mud vent
was observed, and a sample was taken of the numerous clam shells present around it; came
up on a mound with numerous dead mussels, and a few live ones. A large area of carbonate
hash with some large carbonate rocks was observed, which agreed very well with the
amplitude maps.
Following this dive, the R/V Edwin Link put back into Port Fourchon, LA, and a
scientific crew change was made. The vessel sailed on the evening of August 22nd, and
arrived on station on the morning of August 23rd.
For more information, contact Keith Good.
