Continental margin fluids and gases
Lead Scientist: Charles Paull
Project Manager: Bill Ussler
We propose a multi-year study of the processes
associated with movement of fluids and gases from their source, through
the seafloor, and into the ocean. Our efforts are similar to previous
MBARI projects associated with the investigation of seafloor seepage
We intend to focus on the following specific
(1) Biogeochemistry of Sub-Seafloor Fluids. We intend to focus on the
processes that affect fluid and microbial conditions where redox states
change at and near the seafloor. Where chemically reduced fluids discharge
onto the seafloor, focused seep communities occur.
However, similar horizons of rapid organic and inorganic change will
occur wherever there are sharp geochemical boundaries or accumulations of
microbial substrates in the subsurface. We will focus investigations on
(a) the sulfate-methane interface, and (b) hydrogen production and
consumption within continental margin sediments.
(2) Geomorphologic Significance of Fluid and Gas Venting. The escape of
fluids and gas through the seafloor are purported to influence the local
geomorphology. A number of geomorphic features are commonly considered to
be associated with fluid processes (including the development of
pockmarks, slumps, rills, and box canyon heads). Moreover, the role of
geologic structures (faults, canyon heads, slide scars, and laterally
truncated aquifers) in focusing fluid flow and the role of gas and gas
hydrates are poorly understood. Thus, we will conduct studies of the
sub-surface fluid chemistry in selected geomorphic regimes. This project
will be integrated with the companion canyon and continental margin
(3) Isotopes as Tracers of Mass Transport at Seafloor Seepage Sites.
Wherever exotic fluids discharge onto the seafloor, organic and diagenetic
reactions will occur which include chemosynthetic primary production and
formation of authigenic minerals (e.g. carbonates, barite, and sulfides).
To understand the processes that occur at these sites, we intend to
conduct selected detailed sampling, geochemical and isotopic measurements
on all significant fluid, gaseous and solid phases that contain carbon,
sulfur, and nitrogen at selected sites.
(4) Mass Flux at Seafloor Seepage Sites. The overall significance of
seafloor seepage is related to the total flux of fluids. The rates of
flow, the composition of the fluids and the surface area that is affected
determine the total flux. While in the long term we are interested in all
of these factors, we believe that the percent of the sea floor that is
affected by seepage is currently the least known factor within the
Monterey Bay region. Thus, we will initially try to determine the area
that is affected by studying the existing dive observations in the MBARI
video archives and combining them with other data to generate statistics
on the extent seepage affects this area.