Using a high-resolution deep-towed seismic system, we have discovered a series
of contour-current bedforms at the base of the Sigsbee Escarpment in the Bryant Canyon
region of the northern Gulf of Mexico. We identify a continuum of bedforms that
include furrows, meandering furrows, flutes and fully eroded seafloor. These contourcurrent
bedforms are linked to current velocities ranging from 20 to upwards of 60 cm/s
based on nearby current meter measurements and similar flume generated bedforms
(Allen, 1969). We identify erosion and non-deposition of up to 25 meters of surface
sediment at the base of Sigsbee Escarpment.
Using 3-D and high-resolution seismic data, sediment samples, and submersible
observations from the Green Knoll area, we further define contour-current bedforms
along the Sigsbee Escarpment. The study area is divided into eleven zones based on
bedform morphology, distribution, and formation processes. We identify a contourcurrent
bedform continuum similar to that of the Bryant Canyon region, while the data
reveals additional features that result from the interaction between topography and
contour-currents. Three regional seismic marker horizons are identified, and we establish an age of ~19 kyr on the deepest horizon. The seismic horizons are correlated
with very subtle changes in sediment properties, which in turn define the maximum
depth of erosion for each of the individual bedforms.
Finally, we show for the first time that furrowed horizons can be acoustically
imaged in three dimensions below seafloor. Analysis of imagery of several horizons
obtained from 3-D seismic data from the Green Knoll region establishes the existence of
multiple paleo-furrow events. The contour current pattern preserved by the paleofurrows
is similar to the presently active seafloor furrows. And, based on the
morphology and development that we establish for the active seafloor furrows, we show
that paleo-furrows are likely formed by currents that are in the same range as those
measured today (20-60 cm/s), that erode into sediments with similar physical properties
to the fine-grained hemipelagic sediments of the present-day seafloor. We further
suggest the possibility that furrows are formed during inter-glacial highstands and buried
during glacial lowstands
