Aspects of Thermal Evolution of Anadarko Basin, Oklahoma

T. M. Harrison, M. T. Heizler, K. Burke

Individual microcline-bearing clasts in cores from depths of 2.17, 3.27, 3.34, 3.57, and 4.40 km provided to us by the Oklahoma Geological Survey yield ⁴⁰Ar/³⁹Ar age spectra showing a clear correlation for the Pennsylvanian-Permian granite wash between depth and radiogenic ⁴⁰Ar (⁴⁰Ar^{^sext}) loss, consistent with the expectation that the deeper parts of the Anadarko basin have experienced the higher temperatures. A less-expected result is that the initial ages in the five age spectra converge at ~100 Ma, indicating these samples were hot enough to cause diffusive loss of ⁴⁰Ar^{^sext} from the microcline lattice until as late as Albian times. Activation energies for this process are very similar to som of those involved in producing fluid hydrocarbons from organic matter. We therefore suggest that although there is good evidence of petroleum generation in the Anadarko basin by the end of the Permian, progressively larger volumes of source rock may have resided within the oil window in the Triassic to Early Cretaceous as the thick sediments of the basin warmed by conduction. Plateau ages indicate that temperatures as high as 180°C were obtained during the Mesozoic in rocks now lying at a depth of about 4 km. The coherence of the age spectra strongly suggest abrupt uplift of the basin beginning 100 Ma moving perhaps 2 km of sediment by erosion.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.