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Tectonic and climatic controls on seafloor sedimentary processes from analysis of multi-beam sonar and multi-channel seismic data collected during the Galicia 3D seismic experiment

AuthorsGibson, James; Shillington, Donna; Sawyer, Dale; Morgan, Julia; Ranero, César R. ; Reston, Timothy; Dash, Ranjan K.; Payne, Barton
Issue Date12-Dec-2016
PublisherAmerican Geophysical Union
Citation2016 AGU Fall Meeting (2016)
AbstractDue to a very low sedimentation rate, the deep Galicia Basin provides a unique opportunity to gain insight into the control by recent tectonic and/or climatic processes on deep-sea sediment delivery. In order to study the sediment delivery system we use morphological and geophysical attributes drawn from multi-beam (MB) sonar bathymetry/backscatter data supplemented with 3D multi-channel seismic (MCS) surface seismic attributes collected using R/V Marcus G. Langseth during the Galicia 3D seismic experiment (2013). We observe a submarine canyon that is controlled by rift-block geometry and connected to the Galicia Bank. Relatively low reflectivity is associated with the canyon, but a large (~125 km2) tongue-shaped area of high reflectively is seen in the deep abyssal plain seaward of the canyon mouth. This suggests that processes such as flow stripping are taking place resulting in relatively coarse grain deposition in the basin. This interpretation is further supported by the presence of variable wavelength (400m-5km) sediment waves and discrete linear bands of high reflectivity. Spectral analysis of the sediment waves reveals short-wavelength overprinting of relatively long-wavelength features suggesting a relatively recent shift in the flow regime. The spectrums also provide quantitative measurement of the wavelength, amplitude, and phase of the reflectivity relative to the bathymetry from which we make estimations as to grain size and flow velocity. Additionally, attributes drawn from MB (e.g., slope, aspect) and MCS (e.g., instantaneous frequency) spanning the sediment wave field are used for multivariate least squares analysis of the spatial distribution of reflectivity in respect to the morphology of the sediment waves, which further supports the spectral analysis. The large tongue shaped high reflectivity feature extending ~30km into the basin is analyzed in respect to geometry and variable reflectivity. The results of the above analyses along with interpretation of seafloor seismic surface attributes such as dip illumination and spectral decomposition provide insight into recent sediment delivery. From the combined analysis/interpretation we make estimations as to the most recent source process i.e. turbidity current vs debris flow in the framework of tectonic and/or climatic controls
DescriptionAmerican Geophysical Union Fall Meeting, 12-16 December 2016, San Francisco
Publisher version (URL)https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/167119
Appears in Collections:(ICM) Comunicaciones congresos
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