North-Central Section–40th Annual Meeting (20

No= rth-Central Section–40th Annual Meeting (20–21 April 2006)
Paper No. 30-24	&nb= sp;

Presentation Time: 8:00 AM-12:00 PM
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THE STABLE ISOTOPIC SIGNATURE OF HURRICANE PRECIPITATION IN SOUTHWESTERN INDIANA AND ITS USE AS AN ENVIRONMEN= TAL TRACER
CURTIS-ROBINSON, Elizabeth and DOSS, Paul K., Geology and Physics, Univ= ersity of Southern Indiana, 8600 University Blvd, Evansville, IN 47712, pdoss@usi.edu The Evansville= , Indiana region typically receives a po= rtion of its annual precipitation from moisture originating in the Gulf of Mexico. However, during 2005, just four individual hurricanes (Arlene, Dennis, Katrina, and Rita) delivered an anomalously high proportion of local summer rainfall (24.2 cm of 43.4 cm = from June through September, 56%). Rain from these four hurricanes delivered approximately 23% of the local annual precipitation for 2005. We hypothes= ize that the precipitation from these storms will contain a distinctively hea= vier ^{18<= /sup>O/¹⁶O and= ²H (Deuterium) signature than “normal= 221; summer rainfall, and therefore might prove useful as an environmental tra= cer.} Isotopic analyses of eighteen water samples included three rain samples from two hurricanes (Katrina and Rita= ), four “typical” rainfall events, and two snow samples. Additionally nine bedrock ground water samples were collected from a deep – shallow piezometer nest in the Inglefield Sandstone located on th= e University of Southern Indiana campus. The Inglefield Sandstone Member is the lowest unit of the Pennsylvanian Patoka Formation, and is a thinly bedded, fine - medium grained, micaceous quartz arenite that forms a locally important domestic water supply. The deep – shallow piezometers are screened at depths of 33.5 m and 15 m, respectively. Stable isotopic ratios of precipitat= ion yielded a meteoric water line (δD =3D 6.4 δ¹⁸O + 6.8) specific to the Evansville, Indiana region. The δD ratios for typical rain range from –33 to ̵= 1;18 ‰, and δ¹⁸O ranges from = 211;6 to –4 ‰. Some sampled hurricane precipitation has a distincti= ve, heavier isotopic signature, with a range of δD from +11 to –31 ‰, and δ¹⁸O from + 0.4 to –4.4 ‰. Isotopic ratios of snow “anchor” the light extreme of sampled meteoric water with δD from –51 to –48 ‰, and δ¹⁸O at –9.3 ‰. Stable isotope ratios of both deep and shallow ground water generally fall on the local meteoric line, and cluster closely near a = 48;D =3D –37 to –36 ‰, and δ¹⁸O at –6 ‰. Deep ground water consistently displays slightly lighter ratios than shallow ground water. Given that 2005 hurricane rainfall appears to be isotopically and volumetrically distinct, it may assist in characterizing the local ground= water flow system, and recharge to, the Inglefield Sandstone aquifer. Sampling = and analyses for isotopic ratios is ongoing.
North-C= entral Section–40th Annual Meeting (20–21 April 2006) General Information for this Meeting
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Sess= ion No. 30--Booth# 24 Undergraduate Research Poster Session (Posters) Student Center, University of Akron: Ballrooms AB 8:00 AM-12:00 PM, Friday, 21 April 2006 Geological Society of America Abstracts with Programs, Vol. 38, No= . 4, p. 67
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THE STABLE ISOTOPIC SIGNATURE OF HURRICANE PRECIPITATION IN SOUTHWESTERN INDIANA AND ITS USE AS AN ENVIRONMEN= TAL TRACER