DEEP-WATER LOWER ATOKA FORMATION, OUACHITA TROUGH, OK
From detailed studies along OK-2, mudrocks dominate the section with interstratified sandstone beds rarely exceeding 0.5-m thick. Both total and spectral GR logs have proven to be useful in correlating outcrop sections. Using conventional correlation approaches and total GR emissions, general correlation is possible, but ambiguous at the bed-to-bed scale. Because Th/K GR emissions is positively correlated with mica content in sandstones, detailed correlation of individual sandstone beds is unambiguous. Bouma Tc beds, with a thin Tb cap, are most common. Tc intervals are typically convoluted. Locally, Ta beds and thin Tb-c intervals are well developed. Paleocurrent indicators show a westward transport direction in the southern exposures and eastward transport direction in the northern exposures.
Exposures along OK-82 (~16 km. west of OK-2) are also being studied with large-scale correlation being possible using an airborne radar image. Some preliminary findings include the mapping of a very large submarine slump block(s). The southern section is much thicker and sandier compared the OK-2 and northern exposures; it also includes paleocurrent indicators showing northwestward transport. Other sections expose 1-m thick, Ta-e sandstones.