ABSOLUTE TIMING AND RELATED FLUID FLOW ASSOCIATED WITH THE WASHITA VALLEY FAULT SYSTEM AFFECTING THE ARBUCKLE MOUNTAINS

The Arbuckle Mountains, Oklahoma, correspond to an inverted aulacogen uplifted during the Pennsylvanian (330--290 Ma) and affected by a large-scale strike-slip fault system: the Pennsylvanian Washita Valley Fault System. Based on stable (O, C) and radiogenic Strontium isotope approaches, previous studies have attempted to resolve the syn-tectonic diagenetic and fluid-flow history of the Arbuckle Mountains. Results from these studies suggest that the diagenetic alteration of carbonate exposed within the Arbuckle Mountains was structurally controlled by fault systems and dominated by meteoric fluid.

Although the principal tectonic phase is linked to the Arbuckle Orogeny (Pennsylvanian), two other deformation events have been documented on the field, suggesting a long lasting and complicated tectonic history, opening debate about the exact timing of the sinistral Washita Valley Fault System and related fluid-flow.

In order to resolve the exact timing of the Washita Valley Fault System activity, we performed detailed field-based structural analysis coupled with in-situ U-Pb analyses on fault related carbonate veins. In addition, we used conventional O and C stable, and ∆47 clumped isotope analyses on carbonate veins and their direct host rocks to document the associated diagenetic alteration. Our preliminary results suggest that the Washita Valley Fault was active during Early Cretaceous (140-116 Ma), contradicting previously proposed Pennsylvanian ages (320-290 Ma) estimated by either stratigraphic correlation or from seismic data interpretation. In addition, our new stable isotope dataset also suggest that the Washita fault system acted as a closed hydrological fluid system involving formation water at 85-120 ˚C during its activity.