--> ABSTRACT: Structural Models of Foreland Basement-Involved Structures, by S. Mitra and V. S. Mount; #91021 (2010)

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Structural Models of Foreland Basement-Involved Structures

MITRA, SHANKAR, and VAN S. MOUNT

Basement-involved structures occur as chains of uplifts in foreland basins and commonly contain significant hydrocarbon accumulations. Most fields are located on the broad crests of these structures; however, the search for complex traps in deeper targets requires an improved understanding of fold-fault relationships. On the basis of geometric and kinematic modeling, case studies of well-constrained structures, and field observations, we propose two main types of structures: model 1, in which basement deforms primarily by movement on a major fault, and model 2, in which basement deforms both by faulting and the development of a downward-propagating deformation zone. For both models, the geometry and deformation of the cover units and the nature of fault propagation are dependent on the relative competencies of the stratigraphic units. Case studies of well-constrained structures from the Bighorn basin, the Uinta basin and the Central Basin Platform demonstrate the role of mechanical stratigraphy in controlling the structural geometry. in the Bighorn basin, the major fault breaks through the predominantly competent Paleozoic section after only limited deformation in Cambrian shales. Mesozoic shales exhibit significant internal deformation on the steep forelimbs of the anticlines. In the Uinta basin, the major fault breaks through the Paleozoic to Jurassic section, with the Cretaceous Mancos shale absorbing most of the deformation. Finally, in the Central Basin Platform, the deformation is concentrated within the incompetent Ordovician Simpson group, between the competent Ellenburger and younger Paleozoic units. The characteristic features defined in these models will be useful in interpreting basement structures in areas of poor or limited data coverage. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.