7-35 Sequence-stratigraphic architecture of the Claiborne aquifer, southwest Georgia: relevance for reservoir quality and extent

Session: Undergraduate Research, Part I (Posters)

Presenting Author:

Authors:

Abstract:

The Claiborne aquifer is an important source of groundwater in southwest Georgia, but it is lithologically heterogeneous, affecting fluid flow. Here, we examine its sequence-stratigraphic architecture and its potential influence on aquifer characteristics. Integrating geophysical well log data from EPD and EPA monitoring and production wells, this study correlates the subsurface units of the Claiborne group in a sequence-stratigraphic context. Plots for gamma, resistivity, and sonic logs were generated for 43 wells with custom software written in R. These form three clusters of updip production wells (covering respective areas of 30, 37, and 58 km²) and 1 north–south dip line (spanning 137 km). Data quality differs between production and monitoring wells; even for adjacent wells, respective gamma and resistivity values vary substantially, complicating efforts at correlation. The updip well clusters consistently contain 3–4 genetic sequences (i.e., with sequence boundaries defined by maximum flooding surfaces, following Galloway 1989). These sequences stack into a retrogradational sequence set that is laterally continuous across tens of kilometers and ranges from 55 feet thick in the northeast to 130 feet in the southwest. This retrogradational sequence set is also present on the drip line, where it includes up to five genetic sequences and thickens seaward. Coffey and Read (2004) report five depositional sequences from coeval strata on the Carolina coast, but these are progradationally stacked and have updip thicknesses of only 33–49 feet. The thickening of units from the Carolinas to west Georgia and the switch from progradational to retrogradational stacking suggest that subsidence rates were greater in Georgia than in the Carolinas. The sequence-stratigraphic architecture of the Claiborne reveals the presence of several shaly intervals, making the unit more lithologically heterogenous and containing more aquitards than previously thought. The prominence of these shaly tongues would be expected to increase downdip, owing to offshore fining. This may limit the quality and extent of the Claiborne aquifer to a narrow range and should be considered in future freshwater or CO₂ storage projects.

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.