Geology of the Illinois River and Lake Tenkiller, Oklahoma

The valley of the Illinois River and its impoundment at Lake Tenkiller in east central Oklahoma reveals excellent bedrock outcrops of Silurian through Carboniferous age. For a petroleum geologist, the romance of this scenic Ozark area is its abundance of exposures but with a scarcity of subsurface data. Despite having oil shows, mature Woodford-equivalent source rock, large en echelon faults, and facies similar to adjacent producing provinces, little exploration has been conducted. As a result, our knowledge of its geology relies heavily on legacy bedrock mapping by the Oklahoma Geological Survey as well as inference from more recent studies of adjacent producing areas (Arkoma Basin and Cherokee Platform). Using boats and a remotely controlled drone to view otherwise inaccessible outcrops, Doug and I will present some of the geological highlights of Lake Tenkiller. These include unconformities and faults, an island of Chattanooga (Woodford) black shale, complex clinoformal beds, sedimentary structures and fossils, Osage chat and tripolitic Miss Lime, and Atoka sandstone bluffs. John McLeod John McLeod is an independent geologist and geochemist and founder of Source Rocks International based in Tulsa, Oklahoma. He previously held petroleum geoscience positions with Mobil Oil, Oryx Energy, EOG Resources, Chesapeake Energy and SM Energy. John and his wife Mary own a weekend cabin near Lake Tenkiller that is built on the Osage chert/Hale sandstone unconformity. Doug Jordan Doug Jordan is a geologist with experience with Chesapeake Energy, Devon, EOG, Cities Services, and others. Specialties: Clastic sedimentology, sequence stratigraphy, hydrocarbon exploration and development, facies description and interpretation of conventional cores and outcrops, supervisory/mentoring roles.