Sedidmentology and diagenesis of Mississippian (Kinderhookian and Osagean: Tournaisian and Visean) reefs in southwest Missouri, northwest Arkansas, and northeast Oklahoma

Abstract

Carbonate buildups (reefs) are present in the Kinderhookian Compton and basal Osagean Pierson formations in SW Missouri and adjoining Arkansas and Oklahoma. Their depositional origin, biota, and diagenesis are key to evaluating their potential as subsurface petroleum reservoirs. They formed on aggradational to progradational distally-steepened ramps. Those in the Pierson are mainly layered bafflestone, non- Waulsortian type reefs, they contain abundant fenestrate bryozoans and crinoids, and are capped by crinoid grainstones. They are interpreted to have been deposited in a moderate water depth environment that passed upward to a relatively shallow, highenergy environment, and locally they are oil-saturated. The older Compton reefs are characterized as Waulsortian and non-Waulsortian type. Non-Waulsortian type reefs are hybrid mud-dominated lithoherms/fenestrate bryozoan-crinoid muddy bafflestones that are associated with nodular-bedded, shaly mudstones. They are interpreted to have been deposited in low-energy, moderate water depth environments like those in the Pierson. One Compton reef examined is a Waulsortian reef with stromatactis-type vugs filled with abundant radiaxial fibrous calcite marine cements. The Compton bafflestone buildups were uplifted and subaerially exposed in mid-Compton time within an E-W trending belt in the study area. Meteoric-dissolution vugs formed and were subsequently occluded by internal vadose crystal silt (locally replaced by dolomite) and coarse pore filling calcite, and then the buildups were dislodged and re-deposited to the north within thick sections of upper Compton that downlap an intraformational exposure surface. Such allochthonous buildups might be mappable in the subsurface by thickness trends, lithologic recognition and seismic surveying.