Structural Styles, their Plate Tectonic Habitats and Hydrocarbon Traps in Petroleum Provinces
T.P. Harding, J.D. Lowell, 1983. "Structural Styles, their Plate Tectonic Habitats and Hydrocarbon Traps in Petroleum Provinces", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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Broadly interrelated assemblages of geologic structures constitute the fundamental structural styles of petroleum provinces. These assemblages generally are repeated in regions of similar deformation, and their associated hydrocarbon traps can be anticipated prior to exploration. Styles are differentiated on the basis of basement involvement or detachment of sedimentary cover. Basement-involved styles include wrench-fault structural assemblages, compressive fault blocks and basement thrusts, extensional fault blocks, and warps. Detached styles are decollement thrust-fold assemblages, detached normal faults ("growth faults" and others), salt structures, and shale structures.
These basic styles are related to the larger kinematics of plate tectonics and, in some situations, to particular depositional histories. Most styles have preferred plate-tectonic habitats: (1) wrench faults at transform and convergent plate boundaries; (2) compressive fault blocks and basement thrusts at convergent boundaries, particularly in forelands and orogenic belts; (3) extensional fault blocks at divergent boundaries in all stages of completion and certain parts of convergent boundaries; (4) basement warps in a variety of plate-interior and boundary settings; (5) decollement thrust-fold belts in trench inner walls and foreland zones of convergent boundaries; (6) detached normal faults, usually in unstable, thick clastic wedges (mostly deltas); (7) salt structures primarily in interior grabens that may evolve to completed divergent boundaries; and (8) shale structures in regions with thick overpressured shale sequences.
Important differences in trend arrangements and structural morphologies provide criteria for differentiation of styles. These differences also result in different kinds of hydrocarbon traps. Wrenchrelated structural assemblages are concentrated along throughgoing zones and many have en echelon arrangements. The basic hydrocarbon trap is the en echelon anticline, in places assisted by closure directly against the wrench fault itself. Compressive and extensional fault styles typically have multiple, repeated trends, which combine to form zigzag, dogleg, or other grid patterns. Their main trap types are fault closures and drape folds above the block boundaries. Basement warps (domes, arches, etc.) are mostly solitary features and commonly provide long-lived positive areas for hydrocarbon concentration in broadly flexed closures.