Named as lower series (of 2) of the Bendian period. Divided into two groups--Stanley (lower) and Jackfork (upper). Stanley includes (ascending): Tenmile Creek (new), Moyers (new), and Chickasaw Creek (new) formations. Jackfork includes (ascending): Wildhorse Mountain formation (new), Prairie Mountain formation (new) and its Prairie Hollow member (new), Markham Mill formation (new) and Wesley shale (new). Is found in the Ouachita Mountains of OK and AR in the Arkoma basin and Ouachita tectonic belt province. No specific type locality designated. Clastic facies are dominant and at intervals siliceous shales containing conodonts, spores, and Radiolaria were laid down; nearly all the shales have a "peculiar type of conglomerate." In southern Ouachita area, thickness is more than 13,000 ft. Overlies rocks of Chester series of the Mississippian period; underlies Morrow series of the Bendian period. Correlation chart. Of Carboniferous age.

Source: GNU records (USGS DDS-6; Denver GNULEX).