Sequence stratigraphic studies of the Alabama Tertiary have resulted in the delineation of approximately twenty depositional sequences, which are interpreted to reflect distinct eustatic sea-level cycles of varying magnitude. The PI recently completed detailed studies of two of these sequences. Significant variations in degree of bioturbation, general ichnofabrics, and discrete trace fossils are observed within and between component systems tracts, and reflect changes in substrate consistency, physical environmental energy, sedimentation rate, and bottom- and/or pore-water chemistry that are consistent with both the phase and magnitude of the associated eustatic cycles. These results demonstrate the potential of extended trace fossil studies in the context of sequence stratigraphy. In order to more fully assess this potential, detailed studies of strata representative of all of the twenty depositional sequences delineated in the Alabama Tertiary are proposed. The objectives of these analyses are: 1) to further assess the response of trace-fossil assemblages to predicted sea- level-mediated paleoenvironmental changes; and 2) to evaluate the ichnological variability that exists between and within systems tracts as a function of differences in depositional environment, lithofacies, and phase and magnitude of associated eustatic cycles. This research will 1) provide an independent test of sequence stratigraphic concepts and interpreted sea-level histories, 2) establish an improved set of ichnological criteria that can be incorporated into models useful for recognizing the eustacy signal, and 3) improve our overall understanding of trace fossils as paleoenvironmental indicators.
