59 Hydrogeology (Posters)

Wednesday, 23 March 2016
8:00 AM - 12:00 PM
Convention Hall

DO DIFFERENCES IN THE MINERALOGY OF GLACIAL TILLS IN WESTERN NEW YORK CONTROL THE OBSERVED VARIATIONS IN HYPER-LOCALIZED AQUEOUS GEOCHEMISTRY OF TILL-DERIVED WATER?

Paper number: 59-9
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Determining the contribution of solutes from weathering of glacial till requires the characterization of the mineralogy composing the till. The Hanley Biological Preserve in western New York is a diverse landscape of more than 40 man-made and natural ponds, forested ridges, and a creek that eroded through the local ground moraine. Aqueous geochemical research within ponds revealed significant changes in water chemistry (pH, HCO3-, Ca2+ and Mg2+ concentrations) across the preserve. To determine whether mineralogical variation of the underlying glacial till could factor into the hyper-localized changes in water chemistry, sediment samples were collected and analyzed using X-ray diffraction (XRD). A total of 22 samples were collected from topographically and hydrologically diverse sites including; forested ridges, stream cut-banks, and pond rims. XRD analysis focused on identification and determination of the relative proportion of Quartz, Dolomite, Calcite, Orthoclase, Plagioclase, and clay minerals. These minerals collectively account for almost all of the minerals in our samples and some can have a significant effect on water chemistry, such as Calcite and Dolomite. There are significant decreases in Calcite and Dolomite abundance from 14 to 8 weight percent with increased depth below the O-horizon. In contrast, Quartz comprised the highest percent composition in all 22 samples, and increased in abundance with depth. The percentage of clay minerals within the samples was highest in pond rims, but decreased at ridges, cultivated fields, and with depth below the surface at the Burroughs Creek exposure. Plagioclase and Orthoclase comprise less than two percent in all samples, with no distinct trends based on soil depth or environment. Calcite and Dolomite abundances were lowest in muds sampled from the ponds. Collectively, XRD analysis indicates that changes in water chemistry at the preserve could be related to the erosional and excavated depth of the ponds and creek. Overall, weathering of the till provides a different suite of cations than the local bedrock geology. If this mineralogical heterogeneity controls the solutes documented in the preserve, then early chemical evolution of lakes and ponds in western New York initially reflected a till- rather than bedrock-derived cation chemistry.

Geological Society of America Abstracts with Programs. Vol. 48, No. 1

doi: 10.1130/abs/2016NE-272885

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