A FAILED AULACOGEN? CONCEPTUAL ORIGIN OF THE WICHITA MOUNTAINS AS A FAILED CONTINENTAL RIFT

Shatsky (1946) first identified the Wichita (and Arbuckle) Mountains of the central United States as an “aulacogen”, or a “feature born of a furrow”, consisting of a linear zone of deformed basement and overlying strata sitting within a stable continental interior. Such features were increasingly noticed by Soviet geologists of the time, long before the advent of plate tectonics. Subsequent workers (e.g. Hoffman et al) during the development of plate tectonics linked the aulacogen concept to the failed arm of a triple junction of spreading centers invoked to explain continental rifting and creation of new ocean basins. Accordingly, the “Southern Oklahoma Aulacogen” became a type example of a failed continental rift, and has widely been interpreted as such since. Upon further inspection, the Wichita Mountains, consisting of a suite of mafic and felsic intrusive rocks and felsic extrusive rocks of Cambrian age, do not exhibit many of the characteristics now associated with preserved, failed continental rifts. For example, the Triassic rift basin system of Eastern North America consists typically of structurally-linked, asymmetric half grabens filled primarily with mafic extrusive rocks along with proximally derived conglomerates and lacustrine basin fill. As a minimum, a re-evaluation of the origin of the “Southern Oklahoma Aulacogen” as a failed rift system seems appropriate.