Geology of Jasper Equivalent Aquifers
The Jasper Equivalent aquifer system is composed of the Miocene aged aquifers of the Baton Rouge area and St. Tammany, Tangipahoa, and Washington Parishes. These Miocene sediments outcrop in southwestern Mississippi. The sedimentary sequences that make up the aquifer system are subdivided into several aquifer units separated by confining beds. Northward within southeast Louisiana, fewer units are recognized because some younger units pinch out updip and some clay layers present to the south disappear. Where clay layers are discontinuous or disappear, aquifer units coalesce. The aquifers consist of fine to coarse sand and gravel, with grain size increasing and sorting decreasing with depth.
The deposits that constitute the individual aquifers are not readily differentiated at the surface and act as one hydraulic system that can be subdivided into several hydrologic zones in the subsurface. A zone or ridge of saline water occurs within the Miocene sediments beneath the Mississippi River alluvial valley. Recharge occurs primarily by the direct infiltration of rainfall in interstream, upland outcrop areas, and by the movement of water between aquifers. The hydraulic conductivity varies between 10-200 feet/day.
The maximum depths of occurrence of freshwater in the Jasper Equivalent range from 152.4 to 975.4 m (500 to 3,200 ft) below sea level. The range of thickness of the fresh water interval in the Jasper Equivalent is 487.7 to 716.3 m (1,600 to 2,350 ft). The depths of the Jasper Equivalent wells that were monitored in conjunction with the Baseline Monitoring Project range from 292.6 to 822. 9 m (960 to 2,700 ft).