A Structural Investigation of the Arbuckle Anticline Related to the Appalachian-Ouachita Orogen
Hessert, Jenna M.
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The Arbuckle Mountains, south-central Oklahoma, record deformation associated with Appalachian-Ouachita Orogen along the southern margin of Laurentia at the end of the Paleozoic Era. Regional structures associated with this tectonism include (SW to NE) the Arbuckle, Tishimingo, and Hunton anticlines as well as regionally extensive west-northwest-trending faults with complex and poorly defined kinematic histories that separate the anticlines into distinct uplifts. Cross-sections throughout the orogen, often drawn at high angles to these faults and anticlines, assume plane strain and transport within the cross-section plane towards the northeast. However, published stratigraphic relationships and structural studies indicate significant post-Orodovician, left-lateral, oblique strike-slip motion along some of the faults. This research utilized large-scale geologic mapping (1:6,000 – 1:300 scale), fault kinematic analysis, and fracture analysis along a 7-mile (12 km) south-north corridor along U.S. Interstate 35 through the central Arbuckle Mountains to determine the relative contribution of dip-slip versus strike-slip motion along major faults, how folds and fractures vary with respect to these faults, and if outcrop scale structures are kinematically compatible with the larger model for the formation of the Arbuckle anticline. The results are as follows: (1) Outcrop-scale structures including folds, minor faults, opening mode fractures, and styolites are dominantly developed throughout the study area and contribute to the overall kinematics of folding and faulting associated with the Arbuckle anticline. These structures include outcrop scale parasitic disharmonic, intra-bed folds, map-scale imbricates and positive flower structures. (2) Outcrop-scale (minor) folds have shallowly plunging axes throughout the anticline and are parasitic to the northwest-trending Arbuckle anticline. (3) Kinematic analysis of fault-striae along the traverse display a transition from dominantly dip-slip faulting on the limbs of the anticline to oblique left-lateral, strike-slip faulting within the core. (4) Pre- and syn-tectonic fracture sets can be differentiated and indicate a maximum shortening direction of N340E throughout the anticline. (5) Outcrop scale structures are kinematically compatible across the Arbuckle anticline. These newly documented structures and patterns of deformation are consistent with transpression (transcurrent + contractional) distributed throughout structural domains within the Arbuckle anticline.