MAGNETIC SUSCEPTIBILITY ANALYSIS OF DRILL CUTTINGS DEPICT FINE-SCALE DEPOSITIONAL CYCLES IN THE ATOKA FORMATION, ARKOMA BASIN

Sedimentary basins are expected to store a record of detectable depositional cyclicity on Milankovitch scales: tens to hundreds of thousands of years. The Pennsylvanian-age Arkoma Basin is comprised mostly of the Atoka Formation, recognized by thick repeated intervals of sandstone and shale. The sedimentary alternations were controlled by tectonism, eustasy, subsidence, fluviodeltaic input into the basin, or a combination of these controls. The purpose of this project is to determine if cyclical Milankovitch-scale effects on sedimentation can be detected in the Atoka Formation. There is a paucity of physical rock evidence and biostratigraphic information of significance throughout the Atoka Formation. Here we utilize the geophysical rock property of magnetic susceptibility on drilled well cuttings and compare these readings to previously collected data of the same type from an outcrop proximal to the drilled well. Magnetic susceptibility readings were correlated to wire-line logs, cycles finer than the repeating sandstone- and shale-rich intervals were detected, and the periodicity of the cycles was visualized in the dataset. With future work, the timing of these cycles in the Atoka Formation and Arkoma Basin could lead to deciphering the timing of events in the basin despite the paucity of high-resolution relative and absolute age date information.