Abstract: Paleoenvironments and Hydrogeology of the Eutaw Aquifer in Montgomery, Alabama

WOOD, H. Alexander R., III, DAVID T. KING, Jr., and LEE MING-KUO, Auburn University, Auburn, AL

Paleoenvironments of the Late Cretaceous Eutaw Formation in central Alabama are all paralic and inner shelfal. Linear shoreline sand bodies consist of barrier-island and associated tidal-pass deposits of two minor late Santonian sea-level high stands. Intercalated lagoonal and shallow-shelfal deposits comprise silty, calcareous clays and clayey marls. Eutaw paleoenvironmental facies are packaged in two thin stratigraphic sequences comprising a lower and upper sequence 40 m and 20 m thick, respectively.

Hydrogeology of the Eutaw aquifer is dictated by its paleoenvironmental history, postdepositional erosion, modem recharge area and shallow-subsurface hydrologic conditions. Eutaw aquifer zones are fed by an unconfined, modem-soil aquifer zone and Quaternary alluvial and terrace deposits lying unconformably on the Eutaw Formation. Eutaw sandy paralic facies are aquifer zones, and intercalated fine-grained facies act as aquicludes. Thus, Eutaw aquifer zones have much greater lateral than vertical hydraulic conductivity and transmissivity.

The Eutaw is the main source of groundwater for Montgomery, Alabama. The rapid municipal and industrial growth in this area is beginning to have impacts on water supply as a result of high pumping rates from the aquifer. Two- and three-dimensional flow and contaminant modeling address problems including local water-level drawdown, change in flow directions, and degradation of water quality. Assessment of these aquifer characteristics and detailed groundwater modeling is utilized to make future predictions concerning the water supply of the Eutaw in Montgomery.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas