3D SEISMIC EXPRESSION OF PALEOKARST: AN EXAMPLE FROM OSAGE COUNTY, OKLAHOMA

Karst terrain is a landscape formed by dissolution of carbonate rock through the action of meteoric water, hydrothermal fluids or biogenic sulfuric acid. A karst landscape represents an unconformity event and can include buried hills, sinkholes, collapse features, paleocaves and solution valleys. Paleokarst is ancient karst that has experienced tectonic subsidence and burial.

Interpretation of three dimensional (3D) seismic data from Osage county, northeastern Oklahoma shows evidence of paleokarst in lower Cambro-Ordovician Arbuckle Dolomite. The lower Arbuckle is underlain by granitic basement rocks. The Arbuckle formation can be subdivided into upper (U), middle (M) and lower (L) based on 3D seismic analysis. Specifically, subtle unconformity surfaces exist between U/M and M/L Arbuckle sections.

The M/L unconformity surface is approximately 100 m above granitic basement and shows negative amplitude anomalies indicating an extensive paleocave system. The paleocave system has an areal extent of 2.7 square kilometers and an average passage width of 260 m. Proximity to the basement suggests the paleocave system is due to aggressive hydrothermal waters dissolving Arbuckle limestone that was later dolomitized. This system could also be an amalgamation of collapse sinkholes, similar to those found in the Tarim Basin, China. The variance seismic attribute highlights basement faults that may have served as hydrothermal fluid pathways related to carbonate dissolution forming a paleocave system, now buried and collapsed but mappable with 3D seismic data.