Browsing by Author "Ustipak, Kelsi"

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    Integration of Water Tracing and Structural Geology for the Delineation of Springsheds
    (Minnesota Ground Water Association, 2012-10) Ustipak, Kelsi; Green, Jeffery A.; Alexander, E. Calvin, Jr.
    Fountain, Fillmore Co., Minnesota, a small town self-identifed as “The Sinkhole Capitol of the U.S.A.,” is located on a large sinkhole plain in the Upper Ordovician Galena Group. Recent mapping of the structural setting in the Fountain area provides new constraints for the interpretations of flow paths in springsheds defined by three decades of dye traces (Runkel, 2012, private communication). The strata of the Galena Group are deformed into a low-angle, assymetric syncline that is plunging northwest. The Fountain East dye traces, initiated in May 2012, were designed to further refine springshed boundaries on the northern edge of the sinkhole plain and to delineate source areas for cold-water springs that feed Minnesota designated trout streams in the area, particularly Rice Creek. Two major springsheds were previously mapped in the Fountain East area: the Fountain Springshed, which drains northwest and forms the headwaters for Rice Creek; and the Mahoney Springshed that drains southeast to form the headwaters for Mahoney Creek. The newest tracing efforts begin to document a new springshed to the northeast of Fountain feeding Klomp’s Spring and ultimately Rice Creek. The integration of dye trace data, structural contours, and ArcGIS imagery contextualizes the regional subsurface flow and further provides evidence for the delineation of the Fountain, Mahoney and Klomp Springsheds. Knowledge of the structural setting of the Fountain East trace area is a significant step in answering broader questions regarding the hydrogeologic behavior of the Galena Group karst system and its role in the productivity of designated trout streams.
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    Twentieth century varve formation in urban Twin Lake, Golden Valley, MN: Evidence for deposition of multiple laminae per year
    (Geological Society of America, 2011-10-11) Ustipak, Kelsi; Myrbo, Amy
    Lakes in urban settings are subject to a suite of environmental perturbations from the surrounding cityscape, such as increased flux of nutrients, input of road salts, and erosion of shoreline from housing and recreation. High-resolution lamination studies of a small, deep lake in central Minnesota suggest that the lake experiences unusually high sedimentation rates as a result of urbanization in the basin. Twin Lake is located in Golden Valley, Minnesota, five miles from downtown Minneapolis. It is a small, deep lake with a surface area of 8.5 hectares and a maximum depth of 16.6 meters. Twin Lake is relatively isolated from urban development due to its steeply sloped shoreline and remains sheltered from wind-driven mixing by its steep banks and tree cover on the hills surrounding the lake; the lake is bordered on the east by Wirth Park with luxury housing developments on the northern and western shores. In order to understand the impact of twentieth century urban sprawl and construction on the sediment lithology, a freeze core was collected for high-resolution color analysis, thin section preparation, and smear slide analysis. Lamina counting and lead-210 dating provide contrasting age models for Twin Lake, suggesting multiple laminae are deposited annually, with up to 1 cm per year of sediment deposition. Mass accumulation rates reach 0.4 g/cm2 yr (over 10 times the background rate) during the late 1970s and early 1980s, when historical water quality monitoring data indicate poor conditions. Such extraordinary sedimentation rates are due to high rates of authigenic calcite precipitation, diatom deposition, and wash-in of terrigenous material from the steep banks surrounding the lake. Diverse diatom assemblages and diagenetic iron phosphate minerals in the sediment indicate high levels of nutrient flux to the lake and support the hypothesis that Twin Lake has experienced unusually high sedimentation rates in the past 100 years.