Organic carbonate mud mounds in the Prairie Grove Member of the Hale Formation developed on a shallow shelf swept by competent tidal currents. The mounds were stabilized by crustose red algae and fostered a sheltered setting where phylloid algae and marine invertebrates could thrive. The mounds supplied skeletal sediment locally to the intermound areas as well as regionally along the stable platform. This sediment mixed with quartz sand to form a major mixed carbonate-siliciclastic system in northwestern Arkansas.
Ryan, John M. and Zachry, Doy L.
"Development of Organic Mud Mounds in a Mixed Carbonate-Siliciclastic Depositional Environment,"
Journal of the Arkansas Academy of Science: Vol. 46
, Article 9.
Available at: http://scholarworks.uark.edu/jaas/vol46/iss1/9