Impact at Ingalls? Evidence for a subsurface Ordovician meteorite impact near Ingalls, Oklahoma

A nearly circular subsurface structure 2 km in diameter has been identified in north-central Oklahoma near the town of Ingalls in Payne County. The structure lies beneath ∼1100 m of sedimentary rock, and stratigraphic information from well logs suggests that the structure developed from the Ordovician through the Devonian. Sedimentary units within the structure have widely varying thicknesses and abnormal characteristics. Rocks in the center of the structure have been uplifted nearly 100 m. The best explanation for these stratigraphic relationships is a meteorite impact, and the purpose of this study is to seek evidence supporting an impact origin for the Ingalls structure. Cuttings from wells drilled into the structure were investigated for evidence of shock metamorphism, the rock deformation caused by intense pressures generated only by meteorite impacts. Results indicate that the hypothesis of an impact at Ingalls is likely, but definitive evidence has not yet been found.