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Abstract
Presented in this dissertation are various works related to crustal deformation on the Earth and Venus. Chapter 1, published in the Journal of Geophysical Research, presents relationships and techniques for determining the heights and slopes of discretely dipping surfaces, such as normal fault scarps, on the surface of Venus from measurements of their widths in Magellan stereo synthetic aperture radar images. The methods take into account radar distortion effects, and allow one to determine whether a slope is foreshortened, laid over, elongated, or in radar shadow. Chapter 2, co-authored with John Suppe, uses the techniques derived in Chapter 1 to measure the height and slope of 170 surfaces interpreted to be manifestations of normal faults to show that the mean topographic slope is about 36.4° ± 1.2°, regardless of height, suggesting that most faults have collapsed to tallus slopes, approximately at an angle of repose. Through the use of this mean topographic slope, we show that crustal extension due to faulting and folding for the most recent deformation in the Beta rift zone is <20 km. Chapter 3, co-authored with John Suppe, presents an analysis of compressive deformation in the Salinas Grandes basin of the Puna plateau of northwestern Argentina. A balanced cross section over the center of the basin documents a total of 4.8 km of Late Neogene shortening and 43.8 kin of Early Neogene shortening. Flexural modeling of the basal unconformity in basin suggests that the effective elastic thickness of the upper crust is about 5 km, and we infer that internal basin development in the plateau may be due to this weak crustal state in the Puna. In the Appendices are reproductions of two papers published in the Journal of Geophysical Research in which my contribution was less than that of the first authors. The works show that the many similarities in the topographic profiles of compressive mountain belts on Venus and the central Andes can be explained by modeling the mountains as critically tapered wedges where different parts of the wedge undergo a transition from brittle to plastic deformation with depth.
