Development and Distribution of Hypogenic Caves and Paleokarst Features in the Arbuckle Mountains of South Central Oklahoma, USA
The Arbuckle Mountains are a complex geologic province, characterized by thick sequences of intensely folded and faulted carbonates, sandstones, and shales of the Late Cambrian through Pennsylvanian. Cave, karst and paleokarst features occur in relatively high densities within several limestone and dolostone formations and play a significant role in the storage and transport of fluids in the subsurface. Knowing the origins, morphology and distribution of these karst features is necessary for understanding the karst porosity in production horizons in oil and gas fields. Traditionally, the origins and morphology of these karst features has been viewed as being epigenic, developing from the surface downward; however, recent studies have provided compelling evidence for a more complex evolutionary history for the carbonates. Analyses of more than 1,530 caves, karst and paleokarst features indicate that multiple physical and chemical processes may have taken place, with at least 70 of the features displaying classic signatures for having occurred as a result of hypogenic origins, developing from upwelling corrosive fluids. Hypogenic karst signatures can be found in caves throughout the Arbuckle Mountains, but occur most commonly in the regimes where deformation is most severe, such as the north flank of the Arbuckle anticline. However, there is evidence that hypogenic speleogenesis may have occurred on the south flank of the Arbuckle anticline where the semi-confining Simpson Group overlaid the upper Arbuckle Group, producing maze-like caves which are indicative of such processes. Hypogenic karst development appears to be continuing today where the soluble carbonates are overlain by confining units along the edges of the anticline where fresh and saline waters mix and microbial interactions with hydrocarbons provide the fluid geochemistry allowing carbonate dissolution. Hypogenic karst processes may also be responsible for the origin and development of cavities and conduits in these same formations, encountered during drilling in the deeper subsurface, that have otherwise been attributed to eogenetic processes during Paleozoic sea level fluctuations.
AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015