Cirriped assemblage zones of the eocene claibornian and jacksonian stages, southeastern Atlantic and Gulf Coastal Plains
Abstract Two Eocene cirriped assemblage zones are recognized in the Gulf Coastal Plain of Alabama and Mississippi. The Arcoscalpellum subquadratum Zone is characterized by A. subquadratum (Meyer and Aldrich), Aporolepas americana (Withers), Euscalpellum eocenense (Meyer), and Solidobalanus antiquus (Meyer), and ranges through the upper Claibornian Stage. The Arcoscalpellum jacksonense Zone is characterized by A. jacksonense Withers, A. choctawensis Weisbord, Aporolepas howei Cheetham, and Solidobalanus sp. aff. S. antiquus (Meyer), and ranges through the Jacksonian Stage. Representative species of one or both of these cirriped zones are found also in Texas, Georgia, South Carolina, and North Carolina, and afford an additional means for correlating Claibornian and Jacksonian marine units between the Atlantic and Gulf Coastal Plains. The Arcoscalpellum subquadratum Zone is represented in the Cook Mountain Formation of Texas and Mississippi, the upper Lisbon Formation and overlying Gosport Sand of Alabama, the McBean Formation of Georgia, and the Cubitostrea sellaeformis beds of the restricted Santee Limestone of South Carolina. The A. jacksonense Zone is represented in the Moodys Branch Formation of Mississippi and Alabama, the Cocoa Sand of Alabama, the Pachuta Marl of either Mississippi or Alabama, the Shubuta Clay equivalents in Alabama, the Clinchfield Sand and Dry Branch Formation of Georgia, the Cross Formation of South Carolina, and the biosparrudite and biomicrudite members of the Castle Hayne Limestone in North Carolina. Some cirriped species found in these zones in the southeastern Atlantic Coastal Plain are not represented in the Gulf Coastal Plain. Solidobalanus n. sp. 1, a species unrelated to the S. antiquus group, occurs in the McBean Formation of Georgia ( Arcoscalpellum subquadratum Zone). Kathpalmeria georgiana Ross is found in the Griffins Landing Member of the Dry Branch Formation of Georgia and has tentatively been identified from the Inglis Formation of northern Florida ( Arcoscalpellum jacksonense Zone). Euscalpellum carolinensis Zullo and Baum and Solidobalanus n. sp. 2 (related to Solidobalanus n. sp. 1) are found in the Cross Formation of South Carolina and the Castle Hayne Limestone of North Carolina ( Arcoscalpellum jacksonense Zone). Recognition of the A. jacksonense Zone in the Cross Formation and the Castle Hayne Limestone supports recent conclusions based on calcareous nannofossil zonation and radiometric determinations that these units are Jacksonian rather than Claibornian in age.