Title page for ETD etd-07052012-181939


Type of Document Master's Thesis
Author Chamberlain, Elizabeth Laurel
Author's Email Address echamb1@tigers.lsu.edu
URN etd-07052012-181939
Title Depositional Environments of Upper Miocene through Pleistocene Siliciclastic Sediments, Baton Rouge Aquifer System, Southeastern Louisiana
Degree Master of Science (M.S.)
Department Geology & Geophysics
Advisory Committee
Advisor Name Title
Hanor, Jeffrey Committee Chair
Bentley, Sam Committee Member
Tsai, Frank Committee Member
Keywords
  • sea-level
  • aggradation
  • geomorphology
  • well log
  • fluvial
Date of Defense 2012-06-22
Availability unrestricted
Abstract
Saltwater encroachment northward into freshwater sands of the Baton Rouge aquifer system, southeast Louisiana, poses a serious environmental threat to the metropolitan water source. The aquifer consists of a 0.6 mile-thick succession of interbedded, unconsolidated south-dipping siliciclastic sandy units and confining mudstones dating from the Upper Miocene through the Pleistocene. The study area is crosscut by the Baton Rouge fault, a west-east trending listric fault that serves as a leaky barrier to saltwater intrusion from the south. A better understanding of the connectivity, morphology and depositional setting of this aquifer system and hydraulic properties of the Baton Rouge fault is necessary for developing strategies to halt or control saltwater intrusion.

This study provides an in-depth geologic evaluation of the depositional environments of these sediments. Seventy five well logs for boreholes located in East Baton Rouge, West Baton Rouge and Livingston parishes provided data for interpreting environments of deposition, correlating sand-rich and mudstone-rich zones, and identifying periods of low and high sediment aggradation. The correlation of units immediately south of the fault provided the basis for a separate study of the permeability architecture of the fault zone. It was concluded that sandy units of the Baton Rouge aquifer system were fluvially deposited and have complex geometries representing channel fill, floodplain, levee and crevasse splay facies. Aquifer sands are interpreted as zones of amalgamated sand bodies deposited during times of low aggradation associated with sea-level falling-stage and lowstand system tracts. The amalgamation created a high degree of connectivity which causes these zones to behave hydraulically like single units. Mudstone-rich sequences are interpreted as having been deposited during times of high aggradation associated with sea-level highstand. Roughly 10 cycles that correlate to USGS-designated aquifer sands were identified in lithology-depth curves. The number of sandy units is less than the 24 sea-level reversals documented in the northern Gulf of Mexico for the Upper Miocene through the Pleistocene. Fluvial systems are sensitive to changes in relative sea-level up to 400 miles inland but numerous and major unconformities in the study area have removed portions of the geologic record.

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