INTEGRATING SUBSURFACE DATA INTO A SEQUENCE STRATIGRAPHIC FRAMEWORK OF THE ORDOVICIAN BROMIDE FORMATION, SOUTH-CENTRAL OKLAHOMA

The Ordovician Bromide Formation in south-central Oklahoma was deposited along a mixed carbonate-siliciclastic ramp in the Oklahoma Basin and in close proximity to the subsiding Southern Oklahoma Aulacogen. Previous work has focused on outcrop correlation of important bounding surfaces and the identification of three third order sequences that record the depositional history of the Bromide Formation. Here, we focus on identifying the same bounding surfaces in the subsurface by linking outcrop gamma ray profiles into the subsurface. Fifteen well logs were processed in PETRA to construct a 150 mile northeast-southwest transect ranging from Muskogee to Carter County. All three depositional sequences were identifiable in the subsurface, primarily based on gamma-ray and inferred minerology from PE, bulk density, and neutron-porosity curves. Sequence 1 is characterized by illitic-chloritic shales interbedded with marly packstones and sandy grainstones. Sequence 2 in the subsurface shows a regular gamma ray variation consistent with the limestone-shale rhythmite package in the Mountain Lake Member. The surface of forced regression and sequence boundary of sequence 2 lies just below the large chloritic-illitic shale unit that is interpreted as a lowstand deposit at the base of sequence 3. Sequence 3 is carbonate dominated, and shows gradually declining API values consistent with the outcrop interpretation as a highstand deposit shallowing into the major unconformity with the Viola Formation at the top of sequence 3.