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Developing a 'Little Ice Age' Glacial Chronology in the Southern Peruvian Andes Using Lichenometry and Cosmogenic Beryllium-10 Surface Exposure Dating

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Developing a 'Little Ice Age' Glacial Chronology in the Southern Peruvian Andes Using Lichenometry and Cosmogenic Beryllium-10 Surface Exposure Dating University of New Hampshire University of New Hampshire Scholars' Repository Master's Theses and Capstones Student Scholarship Fall 2009 Developing a 'Little Ice Age' glacial chronology in the southern Peruvian Andes using lichenometry and cosmogenic beryllium-10 surface exposure dating Jean R. Taggart University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/thesis Recommended Citation Taggart, Jean R., "Developing a 'Little Ice Age' glacial chronology in the southern Peruvian Andes using lichenometry and cosmogenic beryllium-10 surface exposure dating" (2009). Master's Theses and Capstones. 498. https://scholars.unh.edu/thesis/498 This Thesis is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Master's Theses and Capstones by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. DEVELOPING A 'LITTLE ICE AGE' GLACIAL CHRONOLOGY IN THE SOUTHERN PERUVIAN ANDES USING LICHENOMETRY AND COSMOGENIC 10BE SURFACE EXPOSURE DATING BY JEAN R. TAGGART B.S., Beloit College 2006 THESIS Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Master of Science in Earth Sciences: Geology September, 2009 UMI Number: 1472084 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI UMI Microform 1472084 Copyright 2009 by ProQuest LLC All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 This thesis has been examined and approved. 0 Thesis Director, Joseph M. Licciardi Associate Professor of Earth Sciences V JulJaG.Bryce V Associate Professor of Geochemistry leredith A. Kell'Ay ^(J Assistant Professor of Earth Sciences Dartmouth College IpTUS" Date DEDICATION For M.J. iii ACKNOWLEDGEMENTS I would like to thank, first and foremost, my advisor Joe Licciardi who has enabled me to complete in this project. Thanks to Joe for allowing me to be involved in his endeavors in Peru, for help in the field with my component of the project, for teaching me the ropes in the lab, and for endless time, encouragement, advice, input, funding, and editing my grant proposals and thesis. I have learned a great deal from working with Joe on this project. I would also like to thank my committee members, Julie Bryce and Meredith Kelly, for their time invested in, patience with, and involvement in this project. Thanks for their input and collaboration. Thanks to everyone who provided assistance in the field, lab, and with various areas of this work: Anton Seimon, Barbara Mathe, Tom Lowell, Yves and Elena Chemin, Pablo, Dylan Rood, Bob Finkel, Vincent Jomelli, Delphine Grancher, Olga Solomina, and Antoine Rabatel. Thanks for the encouragement, advice, and support from Patrick, my parents, and my friends. Thanks also to my peers at UNH - including Florencia Prado, Mimi Szeto and Deb Goodwin - for their helpful language skills and technological expertise. This project would not have been possible without generous funding in the form of a Teaching Assistantship, research grant, and travel assistance from the UNH Department of Earth Sciences; a student research grant from the Geological Society of America, a Grant-in-Aid of Research from Sigma Xi, a Graduate TA Achievement award from UNH CEPS, and travel assistance from the UNH Graduate School. iv TABLE OF CONTENTS DEDICATION iii ACKNOWLEDGEMENTS iv LIST OF FIGURES viii LIST OF TABLES ix ABSTRACT x CHAPTER PAGE I INTRODUCTION 1 1.1 Project Overview 1 1.2 Study Location 4 1.3 Geologic Setting 6 1.4 Climate Setting 8 1.5 'Little Ice Age' Glacial History of the Peruvian Andes 11 II METHODS 14 2.1 Geomorphic Mapping 14 2.2 Moraine Dating Methods 14 2.2.1 Lichenometric Dating 15 2.2.2 Cosmogenic 10Be Surface Exposure Dating 20 2.3 ELA Reconstruction 25 2.3.1 Modern Mass Balance and ELA 27 v 2.3.2 Paleo-Glacier Reconstructions and ELA 29 2.3.3 ELA Depression and Paleoclimate Implications 31 III RESULTS 32 3.1 Geomorphic Relationships 32 3.2 Moraine Chronology 36 3.2.1 Lichenometry Results 3 6 3.2.2 10Be Surface Exposure Ages 39 3.3 ELA and Paleoclimate Results 43 IV DISCUSSION 48 4.1 Geomorphic Relationships 48 4.2 LIA Moraine Chronology 49 4.2.1 Lichenometric Age Relationships 49 4.2.2 10Be Age Considerations 52 4.2.3 Comparison of Lichenometric and 10Be Ages 54 4.2.4 Possible Differences in Glacier Response Time 54 4.3 Comparison with Tropical Andean Glacier Fluctuations 56 4.4 Comparison to Global LIA Chronologies 58 4.5 ELA Determinations and Paleoclimate Inferences 59 4.6 Comparison with Other Proxies 61 4.7 Possible Climate Drivers 66 V CONCLUSIONS 71 REFERENCES 73 APPENDICES 83 VI APPENDIX A: LICHEN MEASUREMENTS 84 APPENDIX B: SAMPLE SITES AND DESCRIPTIONS 92 APPENDIX C: GOOGLE EARTH ELEVATION CALIBRATION 98 APPENDIX D: GEOMORPHIC PHOTOGRAPHS 101 APPENDIX E: 10BE SAMPLE PREPARATION AND PRODUCTION RATE CALIBRATION 109 VII LIST OF FIGURES FIGURE PAGE 1. Peru location map 5 2. Geologic map of the Cuzco region 7 3. Meteorological Data from Cuzco, Peru 9 4. Published Cordillera Blanca Rhizocarpon sp. growth curves 18 5. Landsat TM images of the Cordillera Vilcabamba 28 6. Geomorphic map of field area 33 7. Histogram of lichen diameters 36 8. Reconstructed Rhizocarpon sp. growth curve 37 9. Lichenometric calendar and relative ages 38 10. 10r> 42 Be ages 11. ELAs and AELAs 45 12. Modern and paleo-glacier reconstructions 46 13. Percent of glacier surface area loss 47 14. Comparison of global LIA glacial records 57 15. Comparison with tropical ice core records 62 16. Comparison with climate change proxies 65 Al. Tucarhuay geomorphic photographs 101 A2. Rio Blanco geomorphic photographs 104 A3. Sisaypampa geomorphic photographs 106 LIST OF TABLES TABLE PAGE 1. Dates of the LIA culminations in Peru and northern Bolivia 12 2. Calibration points used in Cordillera Blanca lichen growth curves 21 3. Lichen data from the Cordillera Vilcabamba 38 4. 10Be results 40 5. Comparison of 10Be ages (alternative scaling schemes) 41 6. ELA estimates 44 7. Percent of glacier surface area loss 47 8. AAR and THAR values for tropical Andean glaciers 60 9. Modern ELAs and LIA ELA depressions in the tropical Andes 61 Al. Lichen measurements 84 A2. Calibration of Google Earth elevations 98 IX ABSTRACT DEVELOPING A 'LITTLE ICE AGE' GLACIAL CHRONOLOGY IN THE SOUTHERN PERUVIAN ANDES USING LICHENOMETRY AND COSMOGENIC ,0BE SURFACE EXPOSURE DATING by Jean R. Taggart University of New Hampshire, September, 2009 The timing and causes of tropical climate changes during the Holocene are important and unresolved issues in paleoclimatology. Glacier chronologies are crucial for discerning the role of the tropics in global climate change, but past glacier activity in this region remains poorly documented. In this study, mapping has identified two prominent glacier advances in three valleys in the Cordillera Vilcabamba (13°20'S). 10Be dating reveals that the most recent glacier culminations occurred during the late AD 1700's to early 1800's, which corresponds to the late 'Little Ice Age' period (LIA; AD 1350-1860). Lichenometric dating suggests near-coeval LIA moraine stabilization in all mapped valleys. The late LIA culmination in the Cordillera Vilcabamba is broadly correlative with glacier chronologies in Europe, North America, and northern Patagonia. However, the timing of events in southern Peru differs from culminations in Alaska and southern Patagonia and from patterns of glaciation in New Zealand. Reconstructed equilibrium line altitudes (ELAs) of glaciers in the Vilcabamba reveal an ELA rise of x -165-200 m since the LIA, suggesting that temperatures ~1.1-1.3°C cooler could have sustained glaciers at their LIA position. The difference between L;LAs of early Holocene and LIA glaciers is small relative to the ELA rise since the LIA, which highlights the magnitude of the LIA climate oscillation in the tropics. The favored climate hypothesis responsible for sustaining more advanced Vilcabamba glaciers includes a southward displacement of the Intertropical Convergence Zone during the LIA which may have enhanced moisture delivery. The new glacier chronologies developed here augment other high-resolution Holocene tropical records, thereby allowing a fuller understanding of inter-hemispheric climate processes and linkages. XI CHAPTER I INTRODUCTION 1.1 Project Overview Over 99% of all present-day tropical glaciers are located in the Andes, and more than 70% are in the Cordilleras of Peru (Kaser and Osmaston, 2002). Tropical glaciers are extremely sensitive to temperature, precipitation, humidity, and insolation variations and are among the most robust indicators of small oscillations in climate (Wagnon et al., 1999; Kaser and Osmaston, 2002). The Peruvian Andes contain extensive and well- preserved evidence of past glacier fluctuations, but the timing of recent glacial advances in the tropics and subtropics remains poorly documented. Chronologies of latest Holocene glacial culminations in the tropical Andes are limited by the scarcity of organic material required for radiocarbon dating of glacial deposits, and are constrained only to within broad limits (between ca. AD 1350 and 1720) from 14C ages and lichenometric dating (e.g., Mercer and Palacios, 1977; Mercer, 1984; Rodbell, 1992a; Seltzer, 1992; Rabatel et al, 2005; Jomelli et al., 2008; Rodbell et al., 2009).
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