Ordovician 485.4 Mya - Named for a Celtic tribe, Ordovices

Carbonates

OKLAHOMA

The Arbuckle Group of Late Cambrian and Ordovician age was deposited in the Oklahoma basin in a broad epicontinental sea that extended across the southern Mid-Continent. The region was stable throughout Arbuckle deposition, as evidenced by the lateral continuity of the strata (Johnson, 1991a). In fact, the Arbuckle was deposited as part of an even larger carbonate (limestones and dolomites) platform that extended from West Texas to eastern North America. The Arbuckle and its equivalents are all composed of very thick, almost pure carbonate successions that are often dolomitized. These successions consist of several hundred upward-shoaling, meter-thick, tidal-flat cycles or parasequences (Wilson, 1994). Extensive karst and solution-collapse brecciation (ancient cave systems) developed within these carbonates as a result of meteoric water infiltration during the widespread post-Sauk unconformity (Wilson, 1994). It is these karsted zones that contain significant amounts of porosity and permeability in what are otherwise low-porosity and low-permeability rocks.