May 13th, 2003; Leg 6, Port Stop
two groups of local high school and university students visited the R/V
Western Flyer. Our morning group (see right), led by Gary
Greene and Mike
Foster, included students from
Jose Maria Morelos y Pavon High School and their instructor Alejandra
Angeles-Perez; 4 graduate students from Carmona from Instituto Politecnico
Nacional, Centro Interdisciplinario de Ciencias Marinas (CICIMAR) and
their professor Dr. Gustavo Hernandes; and 2 undergraduate students from
Universidad Autónoma de Baja California Sur (UABCS) and their instructor
Dr. Rafael Riosmena-Rodriguez.
and Bill Ussler led
the afternoon group (see left), who were from two departments at the Universidad Autonomas
California Baja Sur (UACBS): 17 students
from the Departamento de Ingeniería en Pesquerías and their instructors
Cervantes Díaz and MC Jesús Fiol; and one student from the Departamento
de Geología Marina and Professor Mara Yadira Cortés Mtz.
Charlie Paull explains textures found in the carbonate rock slabs collected during Leg 5. These rocks contain large quantities of authigenic carbonate produced by the activity of methane-oxidizing archaea in methane-rich sediments.
There is a new
makeup to the science crew for Leg 6. New faces include Gary
Foster, Dave Caress,
Debra Stakes, Meg
Tivey, Antoine Page,
Ledesma-Vasquez, and Alejandra
Chee. Charlie Paull,
Bill Ussler, and Rendy
Keaten are the only veterans of the previous leg.
– Bill Ussler,
Leg 6 objectives
are primarily geological and exploratory in nature. Gary Greene has
prepared the following discussion of our dive objectives and of our
interest in rhodoliths.
On a Roll: The
canyons will be investigated along the southeastern margin of Baja
California to determine their sedimentary activity and significance as
conduits for transporting terrestrial and other materials to the deep
basins of the Gulf of California. These canyons are of particular interest
to both geologists and biologists as their heads lie in close proximity to
extensive rhodolith beds, patches of living red algae that have a unique
spherical or ball-like shape. This shape facilitates them to roll around
the bottom, which is needed to keep them living, and thus allows them to
easily roll downslopes or submarine canyons. Since rhodoliths grow in
relatively shallow waters, in the photic zone of primarily tropical to
sub-tropical environments, they are potentially excellent indicators of
climatic conditions and marine depositional environments. Our intent is to
use rhodoliths as natural tracers to document downslope sediment transport
from known rhodolith banks or source areas.
What is a
Our intent is to
collect cores of sediment on the slope and in the active channels of
submarine canyons where rhodoliths may have rolled downslope or were
carried down canyons in debris flows. It has been postulated that many
rhodoliths are carried away from their growing grounds by severe storm
events such as hurricanes. If that were the case, we would expect to see
concentrations of rhodoliths in distinct layers within the cores we
collect. We will look for such stratigraphy to document not only the past
occurrences of hurricanes but also the periodicity of major sediment
transport events along the western flank of the Gulf of California.
thought to live about six months after they have been removed from their
growing environment. Therefore, if a living rhodolith were found in one of
our cores we would have a good timeline for determining the age of the
sediment cored. The last major storm event in the southern Gulf was a
hurricane in September of 2001. We are hopeful that we will see that event
represented in one of our cores by the concentration of rhodoliths. This
will also give us a timeline that we can use to determine recent
sedimentation rate along the western marine margin of Baja California.
In addition, we
will collect rock samples along the steep fault scarps that form the
eastern submarine margin of the Concepcion Peninsula and Espiritu Santo
Island. These rocks should tell us much about the geologic history of the
region, as they may represent rocks that were in existence prior to the
rifting of Baja California from the Mexican mainland. As Baja ripped away
from the North American continent, tear faults and other faults were
produced that exposed the upper crust of the earth in this region. Our
hope is that we will be able to collect rocks from these exposed fault
faces that can then be used to determine the geological conditions that
existed prior to and during rifting or seafloor spreading.
A third objective of our cruise is to examine areas where we believe hot mineral-rich fluids are venting on the seafloor. For example, shallow nearshore faults in the Concepcion Bay area are venting hot (90° C) fluids and gas that have attracted a unique biological community, which are concentrated along the trend of the fault. We will investigate a major fault face offshore of the Concepcion Peninsula that may be associated with the same hot water source area. If vents or seeps are found, we expect to find chemosynthetic communities and other biology that are attracted to such seeps.