MIME-Version: 1.0 Content-Location: file:///C:/4A89930C/2004Denverrodandpaul.htm Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii" 2004 Denver Annual Meeting (November 7–10, 2004)

20= 04 Denver Annual M= eeting (November 7–10, 2004)

Paper No. 243-23

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Presentation Time: 1:30 PM-5:30 PM

BAROMETRIC AND EARTH TIDE INDUCED WATER-LEVEL CHANGES IN A RIGID SANDSTONE AQUIFER, SOUTHWESTERN INDIANA

DOSS, Paul1, INKENBRANDT, Paul2, and BROWN, Robert2, (1) Geology and Physics, Univ of Southern Indiana, 8600 University Blvd, Evansville, IN 47712, pdoss@usi.edu, (2) Geology, Univ of Southern Indiana, 8600 University Blvd, Evansville, IN 47712

Water levels from a deep-shallow piezometer nest in the Inglefield sandstone depict a dynamic ground-water system. Water levels at both the 60 foot and 1= 10 foot depths fluctuate up to 0.5 feet in the matter of hours. Most of this fluctuation is driven by responses to atmosphe= ric pressure change. A remarkable inverse correlation exists between ground-w= ater levels and barometric pressure. Calculated barometric efficiency for this aquifer ranges from 0.85 to 0.94, indicating a rigid aquifer skeleton. Following successful quantification and removal of the barometric effects= on water-level data, the residual hydrographs suggested an additional, smalle= r amplitude periodicity was still present in the water-level records. These fluctuations were hypothesized to result from Earth-tide induced crustal deformation stress= es. Evaluation of barometric-corrected head data by a Fast Fourier Transform method identified periodicities of water-level changes at 12.01 and 12.4 hours. These periodicities correlate well with solar and lunar tide stres= sors, respectively. Other periods that were indicated by Fourier analysis (54 day and 2.5 hour) have not yet been interpreted and = may be artifacts of the evaluated period of record. Whereas barometric fluctuations of water levels are driven through the well-water column and= do not result from potential changes within the aquifer, Earth-tide induced fluctuations are the result of changes in aquifer potential. Further, the= se stress induced changes are suggestive of a confined system, yet simple stratigraphy suggests the aquifer is unconfined. Lithologic variability within the sandstone, specifically a finer-grained and mica-rich shallow zone, likely generates confined behavior. It is hoped that future wor= k can identify the source of the other observed periodicities and whether this aquifer responds to seismic stresses associated with the Wabash Valley Fa= ult System.

 

 

2004 De= nver Annual Meeting (November 7–10, 2004)
General Information for this Meeting

 

 

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Sess= ion No. 243
Hydrogeology (Posters) II
Colorado Convention Center: Exhibit Hall
1:30 PM-5:30 PM, Wednesday, November 10, 2004

Geological Society of America Abstracts with Programs, Vol. 36, No= . 5, p. 565

 

 

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