| Continental fold-thrust belts, in general, are not linear features in map-view. Instead, they commonly display distinct curves; salients, which are convex-to-the-foreland, and recesses, which are concave-to-the-foreland, These features provide a research focus for geologists, in part because of the link between curve geometry and the geodynamic processes that generated them, and in part because of the apparent association between curves (salients, in particular) and petroleum provinces throughout the world.; The first chapter discusses the relationship between salient geometry and the process of salient formation. In order to efficiently discuss salient geometry, I first devised a vocabulary for describing salients efficiently. Using this vocabulary, I analyzed 20 salients from around the world, in order to characterize the natural variation of salients. Next, I performed a series of sandbox experiments to simulate the process of salient development. Four types of salients were analyzed: (1) basin-controlled salients, which form where the pre-deformational sedimentary basin is particularly thick; (2) indenter-controlled salients, which form as a response of a hinterland indenter; (3) margin-controlled salients, which form where fold-thrust belts mold to the preexisting irregular shape of the margin; and (4) detachment-controlled salients, which form due to variations in the lateral continuity of weak glide horizons. From this work, it is clear that structural trendline patterns in a salient depend on the mode of salient formation and on the direction of convergence. The second chapter presents numerical models, constructed using a finite-element program, designed to investigate stress and strain fields resulting from associated basin-controlled and indenter-controlled salients. This work demonstrated that the geometry of the salient causes development of significant stress and strain concentrations. The third chapter illustrates the spatial relationship between salients and oil fields, and speculates on reasons for this association. My overall results demonstrate how study of salient geometry provides insight into the pre-deformational setting in which the salient formed, and demonstrates that salient geometry may serve as a basis for prioritizing oil-exploration targets in fold-thrust belts. Basin-controlled salients are, in general, better prospects. |
