Leg
6
Leg
Summary:
Leg 6 will be a
geological investigation of submarine canyon processes in the regions of
seafloor faulting off La Paz and Bahia Concepcion. The ROV will be used to
study tectonics and sedimentation as they relate to canyon formation.
Video imaging and manipulator sampling will be conducted in rock wall
areas, combined with core samples in areas of sedimentation. The
down-canyon transport of sediments will be documented using shallow water
rhodoliths as tracers. Onshore faults in these regions contain hot water
springs that suggest the possibility that submarine vents may be
discovered by the ROV offshore. If vent communities are present, they will
be compared with those examined during leg 4. The instrument package
deployed in Guaymas Basin during leg 2 will be recovered. The leg 6
coordinator is Dr. Gary Greene of MBARI, and the Mexican collaborator is
Dr. Jorge Ledesma Vazquez from the Universidad Autonoma de Baja
California.
History
& Purpose:
Leg
6 of the MBARI Oceanographic Expedition to the Gulf of California is
associated with studies of submarine canyon sedimentary processes and
tectonics. We plan to investigate submarine canyon formation along the
transcurrent fault boundaries of the southwestern parts of the Gulf in the
La Paz and Bahia Concepcion areas. These canyons are constrained by
wrench-fault tectonics, formed since the Gulf started to open in this
region 3-5 million years ago. Since the faults onshore in the vicinity of
our offshore investigation sites contain hot water springs, we anticipate
discovering submarine vents and possibly vent communities during our
dives.
In
addition, we will document the transport of sediment down the canyons
using naturally occurring shallow water red algae (rhodoliths) as tracers.
Rhodoliths were recovered in the past from deep-sea cores taken from the
submarine canyon offshore of La Paz and we suspect that these hard
coralline algae commonly occur within the submarine canyons that we intend
to investigate.
To
properly investigate the submarine canyons’ formation and processes we
will use the ROV Tiburon to observe and sample rock walls and
sediment within our study areas. Areas where seafloor seeps are found will
be sampled to determine fluid chemistry and any biological communities at
the seeps will be sampled to determine their genetic development.
Submarine canyons are major conduits for the transport of sediment to the
deep-sea floor. This process is not well understood. This investigation
will add considerable knowledge to submarine canyon processes in general,
using Baja canyons as a proxy or case study to document down canyon
transport using rhodolith tracers.
Click
here to visit the logbook from Leg 6.