Print this pageThe Connecting Splay Duplex: An Example Based on Geometry, Deformation History and Kinematics in the Footwall of the Canyon Range Thrust, Central Utah
SUSSMAN, AVIVA J.
A connecting splay duplex (CSD) is one which grows by emplacement of successive fault-bound slices between preexisting floor and roof thrusts. Development of a CSD is one mechanism for reactivation and taper growth in the hinterland portion of an orogenic wedge. Field studies and down-plunge projections of the Canyon Range culmination indicate an antiformal stack geometry with the Canyon Range thrust as the roof and the Pavant thrust as the floor. However, unlike a typical duplex in which the floor thrust grows during development of imbricate slices, timing relationships based on synorogenic conglomerate stratigraphy indicate that the Pavant thrust was present before development and propagation of hanging wall splays from the floor to the roof thrust, thus forming a connecting splay duplex. Microstructural studies within each of the fault-bound slices indicate that the higher, older horses deformed predominantly by plastic deformation while the younger, lower horses underwent more brittle deformation. This suggests that the horses were emplaced under a range of conditions and the structure was being progressively unroofed as it grew. I have used microstructural suites, as determined by point counts of microstructures, to distinguish between the connecting splays. While the resulting geometry is similar to previously described duplexes, evolution of connecting splay duplexes may prove to impact hydrocarbon distribution in such structures.