ALLUVIAL FANS IN THE MCMURDO DRY VALLEYS: A PROXY FOR MELTING ALONG TERRESTRIAL MARGINS OF THE EAST ANTARCTIC ICE SHEET A Thesis Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Felix Jacob Zamora In Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Major Program: Environmental and Conservation Science June 2013 Fargo, North Dakota North Dakota State University Graduate School Title Alluvial fans in the McMurdo Dry Valleys: A proxy for melting along terrestrial margins of the East Antarctic Ice Sheet By Felix Jacob Zamora The Supervisory Committee certifies that this disquisition complies with North Dakota State University’s regulations and meets the accepted standards for the degree of MASTER OF SCIENCE SUPERVISORY COMMITTEE: Dr. Adam Lewis Chair Dr. Kenneth Lepper Dr. Stephanie Day Dr. Jack Norland Approved: th June 30 , 2013 Dr. Craig Stockwell Date Department Chair ABSTRACT Surface melting along Antarctic ice sheet margins is the most poorly understood input in models of future sea level rise. Alluvial fans in the McMurdo Dry Valleys originate from meltwater produced from high-elevation glaciers and snowbanks along these margins but many show no evidence for recent melting. These fans could serve as a record of past melting along terrestrial ice sheet margins, which would help quantify inputs to sea-level rise. To describe how melting has taken place in the past, five representative fans were examined. Fans are composed of thin, planar-bedded gravelly sands deposited by sheetflooding. Geospatial analsysis suggests the distance of the meltwater source from the Ross Sea is the predominant control on fan activity, and that aggradation results when regional climatic gradients shift inland. Geomorphic observations suggest centuries to millennia pass between periods of aggradation. OSL dating indicates that fans are no older than Holocene in age. iii ACKNOWLEDGEMENTS I would like to acknowledge several people for their assistance in my graduate school endeavors. Most importantly, I would like to thank my advisor, Dr. Adam Lewis. His knowledge and guidance provided me the means to become a successful student. Next, I would like to thank my committee members, Dr. Kenneth Lepper, Dr. Stephanie Day, and Dr. Jack Norland for their guidance throughout this process. Also, I would like to thank Ashley Steffen, Marcie Occhi, Dr. Jane Willenbring, Deidra Lies, and Marianne Okal for their assistance with fieldwork and laboratory work. Lastly, I would like to thank my family for their encouragement and teaching me the importance of a good work ethic. iv DEDICATION This work is dedicated to my grandfather, Felix Joseph Zamora, who exemplifies what is achievable with hard work and persistence. v TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................................... iv DEDICATION .................................................................................................................................v LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ..................................................................................................................... viii LIST OF APPENDIX TABLES ......................................................................................................x LIST OF APPENDIX FIGURES................................................................................................... xi CHAPTER 1. INTRODUCTION ....................................................................................................1 CHAPTER 2. DEPOSITIONAL SETTING ..................................................................................17 CHAPTER 3. GEOSPATIAL ANALYSIS ...................................................................................39 CHAPTER 4. TIMING OF FAN DEPOSITION ..........................................................................52 CHAPTER 5. CONCLUSIONS ....................................................................................................71 REFERENCES ..............................................................................................................................74 APPENDIX A. EXCAVATION LOCATIONS ............................................................................82 APPENDIX B. EXCAVATION DIAGRAMS .............................................................................87 APPENDIX C. GRAIN SIZE ANALYSIS .................................................................................102 APPENDIX D. RESULTS OF PALEOHYDRAULIC RECONSTRUCTION ..........................110 APPENDIX E. GEOGRAPHIC ATTRIBUTES OF FANS USED IN GEOSPATIAL ANALYSIS ..................................................................................................................................112 vi LIST OF TABLES Table Page 3.1. Results of linear regression analysis of fan area and geographic attributes ......................47 3.2. Highest correlated results of multiple linear regression analysis.......................................49 4.1. Concentration of dosimetrically relevant elements From INAA .......................................66 4.2. Results of OSL analysis .....................................................................................................66 4.3. Ages of the most recent alluvial fan deposits on the sampled fans ...................................67 4.4. Ages of recent deposits on the Jason Fan ..........................................................................67 4.5. Summary of age constraints based on stratigraphic and geomorphic observations and OSL dating of the youngest deposits .....................................................70 vii LIST OF FIGURES Figure Page 1.1. Aeolus Fan ...........................................................................................................................3 1.2. Sponsors Central Fan ...........................................................................................................4 1.3. Satellite image of the McMurdo Dry Valleys, Antarctica ...................................................7 1.4. High-elevation alpine glaciers along the Asgard Range ......................................................8 1.5. Jason Fan ............................................................................................................................12 1.6. Northern Bull Pass Fan ......................................................................................................14 1.7. Southern Bull Pass Fan ......................................................................................................15 1.8. Upper Wright Fan ..............................................................................................................16 2.1. Image of pit FZE-11-01 .....................................................................................................23 2.2. Sand-gravel couplets of Jason Fan alluvium .....................................................................24 2.3. Image of pit FZE-11-02 .....................................................................................................25 2.4. Stacked melt-packages along the northern margins of the Aeolus Fan .............................26 2.5. Channels at the head of the Aeolus Fan .............................................................................27 2.6. Planar-bedded sand at the head of the Aeolus Fan ............................................................28 2.7. Set of three stacked melt-packages at the head of the Aeolus Fan ....................................29 2.8. Image of pit FZE-11-48 .....................................................................................................31 2.9. Image of pit FZE-11-30 .....................................................................................................31 2.10. Image of pit FZE-11-58 .....................................................................................................33 2.11. Image of pit FZE-11-62 .....................................................................................................34 3.1. ELA position as illustrated by the source glacier of the Mt. Harker Fan ..........................47 3.2. Comparison of distance from the Ross Sea and fan area ...................................................49 4.1. Domed polygons on the Jason Fan ....................................................................................58 viii 4.2. Differing polygonal ground maturity on the Southern Bull Pass Fan ...............................58 4.3. Relict sand wedge cross-cutting alluvium on the Aeolus Fan ...........................................59 4.4. Image showing evidence of minor flow within polygon troughs ......................................60 4.5. Image of a large sand wedge underlying till pavements on the Jason Fan ........................61 4.6. Image of OSL sampled sand wedge on Jason Fan .............................................................68 ix LIST OF APPENDIX TABLES Table Page C.1. Cumulative percentage values of grain size distribution of sediment samples .............................................................................................................................102