ABSTRACT
A detailed survey of the Oceanographer transform fault and
environs
at 35º N, 35ºW has yielded detailed information with
respect
to the generation and evolution of seafloor at a slowly accreting
plate
margin. From this data detailed bathymetric maps and maps of depth
to basement
have been constructed for a swath of seafloor 1800 km long and
100-200
km wide centered about the offset region. This data was used to
subdivide
major phases of seafloor spreading during the Tertiary. The ridge
crest
and all major topographic features near the transform appear to be
affected
by their proximity to the transform. The ridge crest widens and
deepens
towards the transform, and the rift valley walls are higher when
they lie
on the transform side of the valley than when they lie on the
fracture
zone side of the rift. Based upon the observed topographic effects
the
physical properties of the crust and upper mantle must vary
markedly near
the transform.
Constraints provided by a combined ALVIN/ANGUS field program in
the
summer of 1980 indicate that the present zone of decoupling
between the
North American and African plates is located in the center of the
transform
valley; the zone of decoupling is less than 2 km wide, and is
defined most
often by discontinuous, variable degraded elongate fault or
slump-degraded
fualt scarps in sediment.-Vertical tectonism and mass-wasting
processes
dominate near the axial deep whereas deposition and erosion
dominate in
the terraces and the upper wall province. The petrologic data and
the rock
distribution data confirm that the crust near the Oceanographer
transform
is thin and even, perhaps discontinuous and indicates that the
mode of
crustal formation is likely to change significantly near
transforms. Spectacular
bedforms including abyssal furrows, dunes, longitudinal and
transverse
current ripples, and wave ripples are abundant. Except for the
furrows
these bedforms are concentrated in the very rugged, upper wall
province
of the transform.
Chapter 3 presents a model for the formation of transform
topography.
This model hinges upon the assumption of a curved zone of
decoupling between
the plates near each ridge-transform intersection. This curvature
gives
rise to a geometric peculiarity which requires a gap to open
between the
plates. This gap conceivably should alter significantly many of
the physical
properties of the transform such as its depth, the height of the
crestal
mountains, the presence and width of any transverse ridges, and
gradients
of the seafloor into the intersection deep. Many of these
properties vary
in a fashion consistent with the model.
Moody, R.H., 1982. The geology of the Oceanographer Transform
Fault.
Unpublished MSc. thesis, State University of New York at Albany.
163 pp.,
+x.
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 40 Z899 1982 M66
thesis (scanned
text) - 9.5MB pdf file
Return to MS Theses completed in the
Geological
Sciences Program, University at Albany