Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1997
Description:
Pelagic sedimentation is the primary modifier of topography generated by ridge-associated
volcanic and tectonic processes. This thesis represents an effort to understand the
processes of, and the general distribution of, pelagic sedimentation on rough topography,
particularly in the Atlantic Basin but with applications to the world ocean as a whole.
This study utilizes a simple numerical model of sedimentation which, when applied to
models of rough basement topography, allows us to study sedimentation effects in terms of
commonly-measured stochastic parameters including seafloor RMS height, abyssal hill
spacing, and slope distribution. We also address the effect of sediment compaction on
seafloor morphology, and the impact of long-wavelength topography on stochastic
measures of sedimented seafloor.
Understanding gained allows the construction of inverse problems to obtain information
about sediment distribution and basement morphology from multibeam bathymetric data in
regimes where backscatter from rough, reflective basement highs obscures returns from
wide-beam seismic systems. By using maximum likelihood estimation to compare slope
distribution functions calculated from data to those from filtered model topographies, we
estimate average sediment thickness L, basement RMS height H, and a measure of
sediment mobility K.
Using data from near-ridge surveys and off-axis transit lines, we invert for L, H, and K for
3-29 Ma seafloor from the western flank of the Mid-Atlantic Ridge (MAR) near 26°N, 2-
45 Ma seafloor from the western flank of the MAR near 26°S, 2-40 Ma seafloor from the
eastern flank of the MAR near 25°S, and 1-38 Ma seafloor from the western flank of the
MAR near 35°S. Variations in L with seafloor age allow us to constrain sediment rain rate
and the corrosivity of bottom waters to calcite since the Oligocene. We hypothesize that
sediment rain rates during much of the early and middle Miocene were only 10-50% of the
average rate for the past -10 m.y. Variations in H suggest correlation between tectonic
setting and topographic variability. A relatively narrow range of K is needed to describe
intrahill sedimentation patterns.
Description:
Financial support for this thesis was provided by ONR grants NOOO 14-90-J-1584,
N00014-93-l-0344, and N00014-93-1-0896 as part of the Acoustic Reverberation Special
Research Project (ARSRP), and by an NSF Graduate Fellowship.
Keywords:
Sedimentation and deposition
;
Geomorphology
;
Submarine topography
;
Maurice Ewing (Ship) Cruise EW9208
;
Maurice Ewing (Ship) Cruise EW9011
;
Robert D. Conrad (Ship) Cruise RC2711
;
Robert D. Conrad (Ship) Cruise RC2802
;
Thomas Washington (Ship) Cruise
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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