Subsidence and Thermal History of Southern Oklahoma Aulacogen: Implications for Petroleum Exploration

Abstract

Reconstructed subsidence curves and the thermal history of the Southern Oklahoma aulacogen support the concept of thermally controlled isostatic subsidence for the formation of the basin and indicate the significance of this concept for petroleum exploration. Two mechanisms--initial elastic flexure, followed by detachment and differential subsidence of the aulacogen--are inferred from the subsidence curves. Two methods have been used for reconstruction of the thermal history. A tectonophysics model in combination with a history of basin evolution demonstrates that geothermal gradient and depth-of-burial were dynamic variables during the subsidence stage; maximum paleotemperatures were attained during Sylvan (Late Ordovician) time near the close of subsidence; and most of the Arbuckle Group had been subjected to the temperature conditions of oil formation (the oil liquid window) prior to the possible phase of fluid migration in Sylvan time. The second method, involving reconstruction of the geothermal history on the basis of geothermometry (palynomorph carbonization), suggests: (1) paleotemperatures exerted a significant effect on the level of organic metamorphism in the sedimentary rocks; (2) the geothermal gradient varied during the subsidence stage; (3) paleotemperatures were higher than those predicted by the theoretical model and support the hypothesis of formation of the basin by thermally controlled subsidence, and the application of this concept for petroleum exploration.