Jacksonian Stage

ABSTRACT This is a paper about stratigraphic terminology. In it, Jacksonian is introduced as a time and time-rock unit replacing Jackson formation and Jackson group as a major division of the Eocene sediments of the Gulf and Atlantic Coastal Plain. The use of Jacksonian as an age and stage term reflects current trends toward definition of standardized chronological divisions in other regions, recognizes the natural basis for unit treatment of this sedimentary entity, and permits more accurate description of the upper Eocene portion of the stratigraphic column. The original type section of the Jackson group (exposures at Jackson, Mississippi) is designated as typical of the Jacksonian stage. More complete and better exposed sections in Clarke, Jasper, and Wayne counties, Mississippi, and in Clarke and Choctaw counties, Alabama, are designated as standard sections for comparison and partly for substitution of stratigraphic data supplied by the type locality. Suggestions for similar establishment of other natural divisions of Gulf Coast Tertiary sediments are made.