Identifier

etd-04192012-100213

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

A major environmental and economic problem confronting the Baton Rouge area, southeastern Louisiana, is the progressive salinization of the Baton Rouge aquifer system, an important source of fresh municipal and industrial groundwater. The Baton Rouge fault marks a boundary between fresh groundwaters to the north and predominately brackish waters to the south. Determining the permeability architecture of the fault is an essential component of modeling groundwater flow and saline contamination north of the fault. Understanding the sources and pathways of the saline waters that are migrating into the freshwater sands north of the fault is thus essential in helping to establish fault permeability. This study has confirmed that plumes of saline water extend vertically upward above the top of salt at the St. Gabriel field south of Baton Rouge, a suspected source of saline water. The plumes may have been produced by the episodic expulsion of waters from overpressured sediments at depth. Spatial variations in formation water salinity support the conclusion that there has been lateral migration of shallow saline waters northward from the St. Gabriel field toward the Baton Rouge fault. There is a shallow plume of saline water which has migrated to the northwest in the lower part of the Mississippi River Alluvial Aquifer, and a more diffuse brackish zone below this where there has been mixing of saline waters from St. Gabriel with fresh meteoric waters from the Baton Rouge aquifer sands to the north. There are also well-defined tongues of fresh water that have moved laterally across the fault to the south. The results of the present research support the conclusion that there has been extensive lateral migration of waters across the Baton Rouge fault in the past rather than vertical migration up the fault. Although the presumed anisotropy in permeability of the fault zone should favor flow vertically up the fault over flow perpendicular to the fault, the large density contrast between the fresh and brackish waters above a depth of 3,000 feet with the highly saline waters below may inhibit this.

Date

2012

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Hanor, Jeffrey

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