http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Structural and Morphologic Study of Shatsky Rise Oceanic Plateau in the Northwest Pacific Ocean from 2D Multichannel Seismic Reflection and Bathymetry Data and Implications for Oceanic Plateau Evolution
Shatsky Rise is one of the largest oceanic plateaus, a class of volcanic features whose formation is poorly understood. It is also a plateau that was formed near spreading ridges, but the connection is unclear. The geologic structure and morphology of Shatsky Rise oceanic plateau provides key observations that can help understand its formation. Deep penetrating 2D multichannel seismic (MCS) reflection profiles and high-resolution multi-beam sonar data were acquired over the southern half of Shatsky Rise on R/V Marcus G. Langseth during two cruises. The MCS profiles allow us to image Shatsky Rise's upper crustal structure and Moho structure with unprecedented detail, and the multi-beam bathymetry data allow us to produce an improved bathymetric map of the plateau. MCS profiles and bathymetry data show that two of the volcanic massifs within Shatsky Rise are immense central volcanoes. Tamu Massif, the largest (~450 x 650 km) and oldest (~145 Ma) volcano, is a single central volcano with rounded shape and shallow flank slopes (<0.5°-1.5°), characterized by lava flows emanating from the volcano center and extending hundreds of kilometers down smooth, shallow flanks to the surrounding seafloor. Ori Massif is another large volcano that is similar, but smaller in size than Tamu Massif. The morphology of the massifs implies formation by extensive and far ranging lava flows emplaced at small slope angles. The relatively smooth flanks of the massifs imply that the volcanoes were not greatly affected by rifting due to spreading ridge tectonics. Several down-to-basin faults observed on the flanks of the massifs are not parallel to magnetic lineations, suggesting that they were not formed by seafloor spreading. The Moho of Shatsky Rise starts shallow (~6-7 km) beneath normal crust at the distal flanks and dips (~3°-5°) towards the center of plateau massifs, reaching maximum thickness of ~ 30 km. Shatsky Rise crustal structure is consistent with the Moho topography of isostatically compensated crustal structures, which is why the plateau exhibits a small free-air gravity anomaly signature. Shatsky Rise was built on young oceanic lithosphere with little rigidity, so the plateau formed in isostatic equilibrium with a deep crustal root. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152629
Doctor of Philosophy Texas A & M University 2014 http://hdl.handle.net/1969.1/152629