The University of Southern Mississippi The Aquila Digital Community Master's Theses Spring 2018 Identifying Overwash Deposits in Arid Environments: Towards a Millennial-Scale Record of Cyclones and Makran Trench Tsunamis from Sur Lagoon, Oman Anne Griffis University of Southern Mississippi Follow this and additional works at: https://aquila.usm.edu/masters_theses Recommended Citation Griffis, Anne, "Identifying erOv wash Deposits in Arid Environments: Towards a Millennial-Scale Record of Cyclones and Makran Trench Tsunamis from Sur Lagoon, Oman" (2018). Master's Theses. 356. https://aquila.usm.edu/masters_theses/356 This Masters Thesis is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Master's Theses by an authorized administrator of The Aquila Digital Community. For more information, please contact [email protected]. Identifying Overwash Deposits in Arid Environments: Towards a Millennial-Scale Record of Cyclones and Makran Trench Tsunamis from Sur Lagoon, Oman by Anne Griffis A Thesis Submitted to the Graduate School, the College of Science and Technology and the Division of Marine Science at The University of Southern Mississippi in Partial Fulfillment of the Requirements for the Degree of Master of Science Approved by: Dr. Jessica E. Pilarczyk Dr. Davin Wallace Dr. Scott Milroy ____________________ ____________________ ____________________ Dr. Jessica E. Pilarczyk Dr. Jerry Wiggert Dr. Karen S. Coats Committee Chair Interim Division Chair Dean of the Graduate School May 2018 COPYRIGHT BY Anne Griffis 2018 Published by the Graduate School ABSTRACT Coastlines along the Arabian Sea are susceptible to marine inundation from Makran Subduction Zone (MSZ) earthquakes and tropical cyclones. Sediments deposited by these forms of inundation can expand the decadal instrumental record of events to include millennial timescales in regions without rich historical records (i.e., Oman). On November 28, 1945 a 8.1 Mw MSZ earthquake generated a tsunami that inundated coastlines of the Arabian sea with wave heights as high as 13m. The stratigraphic, sedimentological, foraminiferal, and geochemical signatures of deposit were examined from a small (12 km2), microtidal lagoon in Sur, Oman. The 1945 tsunami deposit contained distinctive taphonomic assemblages of foraminifera and bivalves. Below the 41cm thick 1945 shell-rich deposit at Sur Lagoon, seven additional anomalous sand (mean grain size of 3.73 1.66; very fine sand) layers, ranging in thickness from 7 to 32cm, were found preserved within fine-grained lagoonal sediment (mean grain size of 4.44 1.66; very coarse silt). The seven inferred overwash layers have features consistent with the 1945 tsunami deposit such as fining upward trends, marine foraminifera (e.g., Amphistegina spp., planktics) and increased concentrations of calcium and strontium. By contrast, the surrounding lagoon deposits contain finer grain sizes, intertidal and nearshore foraminifera (e.g., Ammonia tepida, miliolids), and increased concentrations of titanium and magnesium. Based on these data, the seven overwash layers found below the 1945 tsunami deposit have been attributed to marine inundation. Radiocarbon dating indicated an age of 3127 to 2515 cal yr BP for the deepest stratigraphic unit. ii ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Jessica Pilarczyk for her guidance and encouragement in helping shape this research but also helping me gain a foothold in the micropaleontology and geological communities. Dr. Pilarczyk has formed me into the student I am today and has provided me opportunities to present my research at international conferences. I would also like to thank my committee members, Dr. Scott Milroy and Dr. Davin Wallace for helping me think about my research in a different light. I would like to thank members of my lab group: Dr. Charlotte Brunner, Stephen Mitchell, and Thomas Kosciuch as well as Dr. Eduard Reinhardt, Dr. Gösta Hoffmann, Shawn Kovacs, Rachel Coen, and Dr. Stephan Howden for all their support and guidance in writing this thesis. iii DEDICATION This thesis is dedicated to my parents that have supported me for my whole life, and who I would be lost without. Thank you for allowing me to follow my dreams of becoming a real-life Clive Cussler character. I would also like to dedicate this thesis to Nicholas Langedyke who’s love and support has motivated me to keep going. iv TABLE OF CONTENTS ABSTRACT ................................................................................................................... ii ACKNOWLEDGMENTS ............................................................................................. iii DEDICATION .............................................................................................................. iv LIST OF TABLES ...................................................................................................... viii LIST OF ABBREVIATIONS ..........................................................................................x CHAPTER I – COASTAL HAZARDS ...........................................................................1 Introduction .................................................................................................................1 Makran Subduction Zone – a history of earthquakes and tsunamis ...............................7 1945 Makran Trench tsunami ......................................................................................9 Arabian Sea Cyclones – a short history ...................................................................... 10 Site Description ......................................................................................................... 14 CHAPTER II – METHODS .......................................................................................... 16 Core Collection and Stratigraphic Analysis ................................................................ 16 Grain Size Analysis ................................................................................................... 17 Foraminiferal Analysis............................................................................................... 18 Geochemical Analysis ............................................................................................... 19 Chronology ................................................................................................................ 20 CHAPTER III – RESULTS ........................................................................................... 22 Stratigraphy ............................................................................................................... 22 v Core 1 .................................................................................................................... 22 Core 3 .................................................................................................................... 24 Grain Size Analysis ................................................................................................... 24 Core 1 .................................................................................................................... 24 Core 3 .................................................................................................................... 31 Foraminiferal Analysis............................................................................................... 34 Geochemical Analysis ............................................................................................... 46 Core 1 .................................................................................................................... 47 Core 3 .................................................................................................................... 52 Chronology ................................................................................................................ 55 CHAPTER IV – DISCUSSION ..................................................................................... 57 Comparison of paleo-overwash deposits with the 1945 tsunami deposit ..................... 57 Elemental trends ........................................................................................................ 61 Distinguishing between storm versus tsunami deposition ........................................... 63 Historical context ....................................................................................................... 68 CHAPTER V – CONCLUSIONS .................................................................................. 69 APPENDIX A – Supplemental Data .............................................................................. 70 APPENDIX B – Foraminiferal Biodiversity ................................................................... 74 APPENDIX C – Taxonomic References ........................................................................ 75 APPENDIX D – MATLAB code for generating PSD graphs ......................................... 77 vi REFERENCES .............................................................................................................. 78 vii LIST OF TABLES Table 1 Table of historical and instrumentally recorded great earthquakes (Mw 6.5) generated from the Makran Subduction Zone. ..................................................................9 Table 2 Grain size statistics (averages with standard deviation) for lagoon and eight inferred overwash sections within Core 1. .....................................................................