Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references.

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Thesis (Ph. D.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

The West Iberia (WIM) and Newfoundland (NFM) continental margins formed over a succession of rift events related to the opening of the North Atlantic between the Late Triassic and the Early Cretaceous. They are characterized by a variable width Ocean- Continent Transition (Zone) where exhumed and serpentinized mantle has been cored. Results from 1-D well backstripping along the Portuguese shelf suggest 40-45% greater extension factors (β) than previous estimates. In addition, the age and duration of both the Late Triassic-earliest Jurassic and the Late Jurassic rifting episodes have been better constrained. It appears, for example, that the Late Jurassic rift propagates northwards along the margin, as inferred for the continental break-up during the Early Cretaceous. Combined backstripping and gravity modelling techniques (POGM), together with new bathymetry and sediment thickness grids, have been used to estimate the effective elastic thickness, T_e, of the lithosphere. Results along closely space profiles in the WIM reveal that T_e decreases from 15-40 km over unthinned Variscan basement to ≤ 15 km over stretched continental and transitional crust. Along strike, a good correlation is found between the modelled mechanical structure and the segmentation of the Variscan basement onshore. Discrepancies between observed and calculated anomalies are discussed in terms of other processes that affected the margin, such as serpentinization and inversion. Thermo-mechanical rheological modelling techniques have also been tested. The compiled software inputs the β's constrained from POGM to determine the thermal structure of the margin, which, in turn, has been used to construct models of rheology and, hence, T_e. The models predict an increase in the T_e of thinned continental lithosphere with age since rifting, between < 20 and > 35 km, and suggest that processes such as ductile shearing and mantle serpentinization might have permanently weakened the lithosphere. Results from POGM along conjugate profiles off WI and NF reveal a greater longterm strength of extended continental and transitional basement in the NFM (T_e's of 10-40 km). This analysis further supports the hypothesis that the low T_e's modelled in the WIM might be related to its complex structural framework. In order to explain the large asymmetries observed in the amount of basement subsidence (500-1300 in) between the WI and NF margins a lithospheric-scale "simple shear" rift model is proposed for the latest stages of rifting and continental break-up.

At collisional mountain ranges the tectonic history of crustal shortening and subsequent post-collisional erosion is preserved in the form of the presently observed gravity anomalies. In this study, models of erosion and isostatic rebound at various stages of collision illustrate the evolution of crustal structure, topography, and resulting gravity anomalies. The Ouachita Mountains of Arkansas, which show a low/high Bouguer gravity couple characteristic of the initial stages of collision, have undergone just 8 km of erosion during the process of completely rebounding the syn-orogenic crustal root. This minor rebound means that the Ouachitas retain a crustal geometry similar to the continental margin prior to collision, including thin transitional and oceanic crust. At more advances stages of collision Bouguer gravity anomalies show a broad low reflecting a thickened crustal root. The width of this low, which relates directly to the amount of crustal shortening, is retained during subsequent erosion and elastic rebound, but the amplitude decays gradually. Thus, the width and amplitude of the low can be used to estimate the degree of convergence and amount of erosion, respectively, for a specific mountain range. For the Scandinavian Caledonides results are consistent with 20 km of erosion following 200 km of crustal shortening. Following a larger magnitude of convergence, about 300 km, the southern Appalachians are estimated to have undergone 28 km of post-collisional erosion. Bouguer gravity profiles across the recently-active Alps compare with a model of 200 km of crustal shortening and 8 to 12 km of erosion. While the Alps have undergone a similar amount of shortening as that estimated for the Caledonides, erosion and post-collisional rebound is at an initial stage, such that a thick section of exotic crust still overlies the underthrusted European Platform. The results of these model comparisons suggest that the crustal geometry ofa collisional mountain range should be viewed as a consequence of the degree of crustal shortening as well as the amount of erosion and isostatic rebound. In models at moderate to advanced stages of shortening ( 200 km), and mature stages of erosion (e.g., Caledonides, Appalachians), the geometry of the crustal "suture" between overthrusting and underthrusting crusts is present as a shallow, subhorizontal de collement beneath the foreland. In the hinterland the suture abruptly steepens, a result of differential uplift during isostatic rebound. This crustal geometry, characteristic of seismic-reflection profiles across many ancient mountain belts, suggests: (1) that the "low angle detachment" observed beneath collisional mountain ranges was originally much deeper and steeper than it is at present; and (2) that steep-dipping seismic reflectors towards the hinterland represent the thrusted contact between converging crustal blocks, but have been steepened as a result of isostatic uplift following erosion. / Graduation date: 1992

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Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 141-151) Also available in print.