Hydrologic Differences Arising from Source Material Differences Between Southwestern Louisiana Aquifers and Their Age Equivalents in Southeastern Louisiana

Douglas Carlson and Riley Milner
Louisiana Geological Survey, Louisiana State University, Baton Rouge, LA

There are three major aquifers in southwest Louisiana: Chicot, Evangeline and Jasper Aquifers. To the east of the Mississippi River there are three major aquifers in southeastern Louisiana which are age equivalent, Chicot Equivalent, Evangeline Equivalent and Jasper Equivalent. However, these two sets of aquifers have different sources of materials and have different depositional styles. The latter are either continuous or episodic. This difference of sources will yield two sets of aquifers that have different geologic and hydrogeologic properties.

The deposition of sands and silts for southwestern aquifers was in general continuous while the deposition for southeastern aquifers was more episodic. These differences of sources will yield differences in the grain size distribution between southwestern and southeastern aquifers. For these six aquifers a number properties of grain size distribution will be determined for about 5000 sieved samples, each aquifer has over 400 tests. In general, median, standard deviation, skewness and kurtosis will be considered. These differences of grain size distribution properties will in turn influence the hydraulic characteristics of southeastern aquifers to be different from southwestern aquifers. The hydraulic properties that will be considered are porosity, and hydraulic conductivity. About 1200 values of porosity were determined from analysis of geophysical logs and water quality data. Hydraulic conductivities were determined from about 1200 specific capacity tests analyzed for each of the six aquifers; each aquifer has over 100 tests.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004