ABSTRACT: An Integrated Lithostratigraphic, Biostratigraphic, and Sequence Stratigraphic Approach to Paleogeographic Reconstruction: Examples from the Upper Eocene and Lower Oligocene of Alabama and Mississippi

TEW, BERRY H., and ERNEST A. MANCINI, Geological Survey of Alabama, Tuscaloosa, AL

Paleogeographic reconstruction involves determining the spatial and temporal relationships of strata that can represent diverse ancient environments of deposition. The production of a paleogeographic map at a given temporal horizon generally requires that a time datum be drawn between spatially separated stratigraphic intervals that often have different lithofacies which represent the same time interval. This

method of reconstruction is often hampered by the fact that chronostratigraphic resolution provided by the most often used tool (biostratigraphy) is commonly inadequate when used in paleogeographic reconstruction across lithologically diverse strata that represent different environments of deposition at a specific temporal horizon. Unconformity-bounded depositional sequences determined from sequence stratigraphic analysis can be used as a basis for paleogeographic reconstruction. Major surfaces associated with depositional sequences present a physical stratigraphic framework that provides relative chronostratigraphic datums which may be used to construct paleogeographic maps. Surfaces associated with a depositional sequence that have chronostratigraphic significance include upper and ower sequence bounding unconformities, transgressive surface, and surface of maximum sediment starvation/maximum transgression. These bracketing surfaces are used as constraints to interpret relative time lines at various points within the sequence. Interpreted time correlative points are then used in conjunction with lithostratigraphic and biostratigraphic relationships to produce paleogeographic maps illustrating the regional distribution of paleoenvironments and rock types at various time horizons within relative sea level cycles.

AAPG Search and Discovery Article #91014©1992 AAPG GCAGS and GC-SEPM Meeting, Jackson, Mississippi, October 21-23, 1992 (2009)