Convergent Wrench Fault and Positive Flower Structure, Ardmore Basin, Oklahoma
1983. "Convergent Wrench Fault and Positive Flower Structure, Ardmore Basin, Oklahoma", 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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A seismic profile from the Ardmore basin illustrates a positive flower structure and demonstrates important criteria for identifying convergent (or transpressional) wrench faults with seismic control. Positive flower structures are linear antiforms that are cut longitudinally along their apex by the upward-diverging strands of a wrench fault. Some of the fault strands have important reverse separations. These flower structures are to be distinguished from the negative flower structures discussed elsewhere in this atlas (Harding, 1983). Negative flower structures are complex, linear synforms displaced by inward-dipping strands of a wrench fault that have mostly normal separations.
In the discussion that follows, we first briefly outline the setting and the geologic history of the region in which the profile was taken. Then the general characteristics of positive flower structures and the flower structure features observed on the Ardmore basin profile are described. Lastly, the controls and mechanisms for the development of positive flower structures are discussed.
The Ardmore basin lies in the foreland of the Ouachita fold and thrust belt and within the splays of the Washita Valley wrench system. The Ardmore basin underwent initial subsidence in the latest Precambrian through Middle Cambrian as part of the southern Oklahoma aulacogen (Figure 1; Hoffman et al, 1974). The aulacogen was oriented transverse to the early Paleozoic continental margin (approximated by the Ouachita geosyncline on Figure 1) and became narrower toward the northwest. In the Late Cambrian through Pennsylvanian, basin subsidence took the form of a broad syncline.