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Aeolian Sediments of the Mcmurdo Dry Valleys, Antarctica a Thesis Presented in Partial Fulfillment of the Requirements for the D

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Aeolian Sediments of the Mcmurdo Dry Valleys, Antarctica a Thesis Presented in Partial Fulfillment of the Requirements for the D Aeolian Sediments of the McMurdo Dry Valleys, Antarctica A Thesis Presented in Partial Fulfillment of the Requirements for The Degree Master of Science in the Graduate School of The Ohio State University By Kelly Marie Deuerling, B.S. Graduate Program in Geological Sciences The Ohio State University 2010 Master‘s Examination Committee: Dr. W. Berry Lyons, Advisor Dr. Michael Barton Dr. Garry D. McKenzie Copyright by Kelly Marie Deuerling 2010 ABSTRACT The role of dust has become a topic of increasing interest in the interface between climate and geological/ecological sciences. Dust emitted from major sources, the majority of which are desert regions in the Northern Hemisphere, is transported via suspension in global wind systems and incorporated into the biogeochemical cycles of the ecosystems where it is ultimately deposited. While emissions within the McMurdo Dry Valleys (MDV) region of Antarctica are small compared to other source regions, the redistribution of new, reactive material by wind may be important to sustaining life in the ecosystem. The interaction of the dry, warm foehn winds and the cool, moist coastal breezes ―recycles‖ soil particles throughout the landscape. The bulk of sediment movement occurs during foehn events in the winter that redistribute material throughout the MDV. To understand the source and transfer of this material samples were collected early in the austral summer (November 2008) prior to the initiation of extensive ice melt from glacial and lake surfaces, aeolian landforms, and elevated sediment traps. These were preserved and processed for grain size distribution and major element composition at the sand and silt particle sizes. Major elemental oxide analysis indicated that the silt and sand size particles are of different composition: SiO2 values for silt range from 50 to 59% by weight and for sand range from 59 to 74%. When compared to the elemental oxide composition four rock types present in the MDV, the composition of the silt indicates a ii mixing influenced mostly by the igneous rock types (Ferrar Dolerite and McMurdo Volcanic basanite) and sand a mixing influenced largely by the sedimentary rocks (Beacon Sandstone and the metasedimentary Basement Complex). This could imply a local source of the aeolian material that is corroborated by low CIA values at both particle sizes (44-57%) indicating low degrees of chemical weathering. In addition, comparison of 87Sr/86Sr and 143Nd/144Nd to values published for the major MDV rock types and ice core dust to values analyzed in 3 silt size glacier sample and one bulk glacier sample also indicates a local source of sediments and that it is not likely to be transferred inland. During the melt season, the aeolian material is actively solubilized where it interacts with water, releasing solutes and vital bioavailable nutrients throughout the aquatic system. Differences in the chemistry of supra- and proglacial streams as well as lake surface waters may be derived from the deposition and dissolution of these aeolian sediments. To simulate these conditions, a two-step leaching method using deionized water to represent glacial melt in field conditions was employed and leachates analyzed for major ion and nutrient constituents. Leachates represent a small degree (<0.7%) of dissolution of major elements, and are solubilized to a greater extent from samples closer to the coast or with increased silt content. The composition of the leachates reflects the dissolution of the major salts found in the MDV. Leach 1 (cold water) indicates that Na- and Cl-bearing salt phases are dissolved to a greater extent than seen in Leach 2 (freeze- thaw). Conversely, Leach 2 compositions indicate that carbonate mineral dissolution and Mg-bearing silicate weathering are proceeding to a greater extent than in Leach 1. iii Inorganic N:P ratios follow the same patterns of nutrient limitations based on the Redfield Ratio found by Priscu (1995) in the terminal lakes of the Taylor Valley: N- limited in the Fryxell and Hoare basins (east) and P-limited in the Bonney basin (west). This is also consistent with the age of the tills in the area, as found by Gudding (2003). The concentration of soluble Fe in the leachates is about the same as soluble inorganic P, and thus is not a limiting nutrient in the leachates. Comparison of total dissolved N and P to their inorganic counterparts reveals increased organic nutrients in the glacier and lake leachates that may indicate the influence of biota. Nutrient fluxes based on known sediment fluxes from elevated sediment traps deployed throughout the MDV and the composition of these leachates range from 0.34-330 g a-1 for N, 0.02-8.3 g a-1 for P, and 0.03-8.6 g a-1 for Fe. These are at least two orders of magnitude less than calculated loads from streams to the lakes in the Taylor Valley and, thus, should be considered underestimations or minima. This work provides the first investigation into the composition and source of aeolian transported materials in the MDV, as well of what is potentially solubilized from it during the austral summer melt season. In addition, it will contribute to the understanding of the interplay between aeolian and aquatic processes in the MDV and further the understanding of this unique ecosystem. iv For my parents. v ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Berry Lyons, for his guidance and support throughout the course of my two years at OSU. You have provided me with many opportunities to learn and grow as a scientist and encouraged me to take advantage of opportunities as they avail themselves. You sent me to the Ice twice, which is more than a person could hope for, and an opportunity for which I am forever grateful. Thank you to Kathy Welch for the miles, conversations, unit conversions, and IC analyses. To Sue Welch, thank you for the nutrient analyses and rundowns, fun times, and re-introduction to swimming. Steve Goldsmith taught me everything there is to know about the XRF and helped me get started. All three of you have been a great support system. Thank you to Hassan Basagic, Dr. Liz Bagshaw, and Dr. Martyn Tranter for letting me tag along to collect samples of the glaciers. To Rae Spain and Sandra Liu – thanks for putting up with my FNG-y ways. Sandra, I will always remember our attempt on the Matterhorn. To Deb, JD, and Terra: thanks for the support and being great friends; Rich for the love, laughs, and support; my family for always being my biggest fans. And finally, Annette Trierweiler: your puns, conversation, and support have meant the world to me. vi VITA November 4, 1985 Born – Tallahassee, Florida May 2008 B.S. Geology, University of Florida September 2008-2009 University Fellow, The Ohio State University September 2009-2010 National Science Foundation Graduate Research Fellow, The Ohio State University October-December 2010 Graduate Research Associate, The Ohio State University FIELD OF STUDY Major Field: Geological Sciences Environmental Geochemistry vii TABLE OF CONTENTS Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................ vi Vita .................................................................................................................................... vii Field of Study .................................................................................................................... vii List of Figures ..................................................................................................................... x List of Tables ................................................................................................................... xiii Dust in the Global Scale ..................................................................................................... 1 Geochemistry of Aeolian Sediments of the McMurdo Dry Valleys, Antarctica ................ 9 Introduction ..................................................................................................................... 9 Field Area Description .................................................................................................. 15 Methods ........................................................................................................................ 23 Results ........................................................................................................................... 29 Discussion ..................................................................................................................... 34 Conclusions ................................................................................................................... 47 Experimental Leaching of Aeolian Sediments, McMurdo Dry Valleys, Antarctica ........ 69 Introduction ................................................................................................................... 69 Methods ........................................................................................................................ 75 Results ........................................................................................................................... 78 Discussion ..................................................................................................................... 82 Conclusions ..................................................................................................................
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