Browsing by Subject "geomorphology"

Now showing 1 - 4 of 4
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    Guidebook 16. Field Trip Guidebook for Quaternary and Cretaceous Geology of West-Central Minnesota and Adjoining South Dakota
    (Minnesota Geological Survey, 1987) Balaban, N.H., Editor
    CONTENTS GEOMORPHOLOGY AND PLEISTOCENE GLACIAL GEOLOGY OF CENTRAL MINNESOTA, Barry Goldstein CRETACEOUS ROCKS ON THE EASTERN MARGIN OF THE WESTERN INTERIOR SEAWAY: A FIELD GUIDE FOR WESTERN MINNESOTA AND EASTERN SOUTH DAKOTA, George W. Shurr, Jay P. Gilbertson, Richard H. Hammond, Dale R. Setterholm, and Peter M. Whelan
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    Guidebook 22. Field Trip Guidebook Landforms, Stratigraphy, and Lithologic Characteristics of Glacial Deposits in Central Minnesota
    (Minnesota Geological Survey, 2006) Knaeble, A.R.
    This guidebook was prepared for the 50th Midwest Friends of the Pleistocene Field Conference, sponsored by the Minnesota Geological Survey and held at St. John's University on June 4-6, 2004. The purpose of this guidebook is to provide conference participants with an up-to-date general summary of the glacial geology of central Minnesota and a comprehensive reference list of previous research completed in the area. There are a number of reasons why we were motivated to host the Friends of the Pleistocene in central Minnesota. First, over the last 10 years the Minnesota Geological Survey has completed numerous mapping projects in the central Minnesota area (Steams, Pope, and Crow Wing County atlases; the Otter Tail regional hydrogeological assessment; and the USGS Statemap St. Cloud, Baxter, Brainerd, and Gull Lake quadrangle maps), and is in the process of completing mapping projects in Todd, Traverse, and Grant Counties. The large volume of data (samples and descriptions from outcrops and drill holes) collected from these projects has allowed us to evaluate the work done by previous researchers and contribute new insights and interpretations. Second, in 1954 Herb Wright, AI Schneider, and Harold Ameman led the 5th Midwest Friends of the Pleistocene field trip in central Minnesota. We will revisit the area, on this 50th anniversary of that trip, to examine how interpretations have changed and evolved. The guidebook will use a simple, direct approach to summarize the region's glacial geology, similar to that used in 1954. It is our intention to pay tribute to the accomplishments of Herb and AI during the field trip and banquet. We will also acknowledge other researchers who, over the last 50 years, have made contributions to the glacial geology of central Minnesota. Third, we would like to discuss how mapping techniques and technology have changed in the last 50 years. We will examine which techniques have been most effective in understanding the complex stratigraphy of central Minnesota. Finally, field exposures were selected to stimulate interest and discussion about the following glacial topics: erosion, transport, and deposition of source-area materials; processes involved in drumlin formation; the relationship between ice dynamics and glacial landforms; processes important in the formation of the St. Croix moraine; and the challenges of interpreting thick, complex drift stratigraphy. These stops highlight geomorphic features, stratigraphic relationships, and specific unit characteristics (lithology, color, etc.) in an attempt to provide an overview of the glacial geology of this region.
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    Phosphorus-sediment interactions and their implications for watershed scale phosphorus dynamics in the Le Sueur River Basin
    (2018-08) Baker, Anna
    Phosphorus is a leading pollutant of global surface waters, and sediment is a known driver of phosphorus loading to downstream receiving waters. This master’s thesis investigates sources and dynamics of phosphorus in the Le Sueur River basin in southern Minnesota, a highly agricultural watershed whose glacial history has rendered it vulnerable to massive erosion, and which contributes disproportionately to downstream sediment and phosphorus loading. We develop a mass balance for sediment-derived phosphorus, incorporating sediment-total and dissolved phosphorus into a robust sediment budget describing sources and sinks of sediment to this system. This budget explores the extent to which agricultural top soil and upland ditch-banks, and eroding near channel features such as bluffs, stream banks, and ravines, can be implicated for phosphorus loading to this basin. Further, we explore the extent to which in-stream processing alters the fate, bioavailability, and persistence of phosphorus in this system via the incorporation of sorption experimental data into this budget. Our results show that fine (silt and clay sized) source sediment can only account for at most 24% of the total phosphorus exported from the Le Sueur River. These results suggest that sediment and phosphorus sources are largely decoupled, and that if we managed 100% of fine sediment erosion we would only reduce phosphorus loading by 24% or less. Sorption tests were used to examine the role of fine sediment as a source or sink for phosphorus. Results of these tests demonstrate that agricultural sediments donate phosphorus, while near channel sediments bind phosphorus from the water column. Incorporation of these results into our budget indicates that 2-24% of total phosphorus may be in particulate form as a result of in-stream equilibrium processes between sediment and dissolved orthophosphate in the water column. Sorption of dissolved phosphorus by sediment may depress dissolved phosphorus load by as much as 31%. These results point to the importance of understanding dissolved phosphorus source and dynamics, and to the management of both sediment and dissolved phosphorus source being critical to addressing excess phosphorus in this basin.
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    A Study Of Particle Entrainment In Two Common Particle-Fluid Flows In Nature: Bedload Transport In Rivers And Debris Flows In Upland Regions
    (2020-05) Ghasemi, Amirreza
    This work performed for the research describes in this dissertation concerns particle entrainment in two common particle-fluid flows in nature: 1) bedload transport in rivers, and 2) debris flows in steep upland regions. The bedload transport work addressed here concerns height-dependent entrainment from a bed of a channelized flow. Towards this, we perform distinct element method (DEM) simulations to study the roles of particle size and fluid flow on the transport rate, bed surface variations, and depth-dependent particle entrainment. We do so in the context of a theoretical probabilistic formulation derived to better capture spatial variation in sediment exchange between bed material load and alluvial deposits (Parker et al. (2000)). Our findings allow us to provide a link between the longitudinal bedload transport rate with vertical bed surface statistics and provide closure for a theoretical model designed to model transport and bed-surface exchange in the presence of bed variabilities. The debris flow erosion work here focuses on the effect of grain size distribution of a debris flow on the rate of entrainment of bed material. Towards this, we perform several experiments in a laboratory flume where we measure the relative roles of inclination angle, bed composition, and average flow composition on average and instantaneous erosion dynamics. Most significantly, we find that the infiltration of fine particles into a coarse bed can markedly increase the rate of erosion. Further, the infiltration rate is maximized for intermediate concentrations of small particles in the flow. We show this is due to the interplay of two simultaneous mechanisms: (1) segregation dynamics known as kinetic sieving in the shear flow when there is sufficient agitation of the coarse particles to allow the small particles to sink into the bed and (2) correlated interparticle forces which create sufficient agitation only with an adequately high concentration of coarse particles. In this presentation, we demonstrate how a better understanding of these two processes can contribute to a better understanding of the "sediment cycle" in earth-surface dynamics.