Abstract

The Desmoinesian Oswego of the Marmaton Group in the Putnam Field of Oklahoma is equivalent to the surface Fort Scott Formation consisting of five members: in ascending order, Breezy Hill Limestone, Excello Shale, Blackjack Creek Limestone, Little Osage Shale and Higginsville Limestone. The Oswego is the most widespread Pennsylvanian limestone in the Mid-Continent. The Oswego in the Putnam Field is an 80-foot thick northwest-southeast trending phylloid-algal mound complex developed on the shelf edge (hinge line) of the Anadarko basin. Basin equivalent is a black carbonaceous shale deposited in a sediment-starved basin.

The Oswego represents several marine transgressive-regressive sequences of cyclic deposition. The Breezy Hill was deposited during a marine transgression over the deltaic sediment of the Cherokee (Cabaniss) Group. The overlying Excello Shale was deposited in a deep euxinic marine sea. The basal and middle part of the Blackjack Creek was deposited by a transgressive sea. The Little Osage Shale was deposited in a deep marine sea similar to the sea that deposited the Excello. The Higginsville was deposited during a regression, but in the study area only the basinal terminus of the Higginsville is represented. The remaining Marmaton carbonates followed this pattern, until clastic detritus from the south filled in the basin.

The Oswego in the Putnam Field is a prolific petroleum producer. Estimated gas reserves from all producing formations in the field suggest that the Putnam Field is a potential giant.