Although Jacksonian deposits in the Mississippi Embayment have been recognized for many years, no detailed studies of these strata have been undertaken. Marine Jacksonian beds have been identified from small outcrops as far north as the latitude of Memphis, Tennessee, and the presence of upper Eocene strata beneath the alluvium of the Mississippi River Valley has been recorded, but the most accessible and representative Jacksonian section within the embayment occurs at the surface in an area of irregular shape in southeastern Arkansas. The present report is a result of studies of the Jacksonian outcrops in this region.

The outcrop area in southeastern Arkansas is situated in the western portion of the Desha basin, a partially enclosed structural depression formed as a result of the construction of the Mississippi structural trough by the Monroe uplift in the vicinity of the Arkansas-Louisiana boundary. The Jacksonian outcrops are inliers, completely isolated from the main body of Jacksonian sediments, which crop out in a belt roughly parallel to the coastline farther south.

*Includes: 125 pages, 2 plates, and 25 figures