Late Holocene Glacial Advances in the Klamath Mountains
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CALIFORNIA STATE UNIVERSITY, NORTHRIDGE LATE HOLOCENE GLACIAL ADVANCES IN THE KLAMATH MOUNTAINS, NORTHERN CALIFORNIA, DETERMINED FROM 10BE COSMOGENIC EXPOSURE DATING AND DENDROCHRONOLOGY A thesis submitted in partial fulfillment of the requirements For the degree of Master of Science in Geology By Joshua T. Graham December, 2013 The thesis of Joshua T. Graham is approved: _________________________________________ __________________ Dr. Julie Laity Date _________________________________________ __________________ Dr. James Hayes Date _________________________________________ __________________ Dr. John Yule Date _________________________________________ __________________ Dr. Richard Heermance, Chair Date California State University, Northridge ii Acknowledgements The completion of my thesis would not have been possible without the assistance and support of many people along the way. First and foremost, I thank my advisor, Dr. Richard Heermance, for his extraordinary guidance, knowledge and fortitude throughout the coarse of my studies at CSUN. His passion for geology and enthusiasm about research has been an endless source of motivation for me over the last two and a half years. I also want to extend great appreciation to my committee members, Dr. Julie Laity, Dr. James Hayes and Dr. Doug Yule for their tireless efforts to bring my thesis to the highest level of scientific integrity possible. I am very appreciative of the faculty, staff and students in the Department of Geological Sciences at CSUN for the invaluable support and encouragement. I would also like to acknowledge my family and friends for their support during my graduate studies. Particularly, my friends and fellow classmates Ryan Witkosky and Jose Cardona, who spent two weeks camping in the Trinity Alps to help me complete my field work in the summer of 2012. I also thank Marylyn Hanna and the Geological Society of America for their financial contributions, which made my field and lab work possible. iii Table of Contents Signature Page……………………………..………...………..…………………………..ii Acknowledgements…………………..………..……..…………………………………..iii List of Figures…….………………..…………..……..…………………………………..vi List of Tables…….………………………..……..………………..…………………….viii Abstract……………………………..……………………………..………………….…..ix Chapter 1: Introduction……………………………………………..…………………..…1 Chapter 2: Study Area……………….……………………………..……………………...4 Chapter 3: Background……………………………………………..…………….…….…5 3.1 Glacier Response to Climate………..…………………….………….......……5 3.2 Holocene Climate Variability…..……………………..……..………………..6 3.3 Previous Studies……………..………………………………………….....…..9 3.3.1 LIA in the Northern Hemisphere……...…………........................…...9 3.3.2 LIA in Western North America …...……..……….......................….10 Chapter 4: Methods….………………………...………………..……….…………….....13 4.1 Mapping………………………………...……………………………………13 4.2 Relative Dating …………………………………....………………..…….....13 4.3 10Be Cosmogenic Dating ……………………………………..………….…..15 4.3.1 Sample Collection…………….………………………………….….15 4.3.2 Laboratory Methods…………………..……..…………………..…..15 4.3.3 Determining Ages from 10Be /9Be ratios………………………..…..16 4.4 Dendrochronology/Dendroglaciology…………………..…….……..….…...17 4.4.1 Sample Collection……………………………...……...………...…..18 4.4.2 Determining a Minimum Moraine Age…………………...……...…19 4.4.3 Laboratory Methods…………………………..……………...……...20 4.4.3.1 Constructing a skeleton chronology…………….…………20 4.4.3.2 Statistical Analysis Using COFECHA……..…...…..…….21 4.5 Determining Equilibrium Line Altitudes (ELA’s)…………........……….….22 4.5.1 Equilibrium Line Altitude (ELA)………………..………….…...….22 4.5.2 Accumulation Area Ratio (AAR)………………………..……....….23 4.6 Climate Change Estimates…………………..……………………………….24 Chapter 5: Results……………………………………....…………..………………...….27 5.1 Mapping…………………………………………..………………………….27 5.2 Establishing Relative Moraine Ages………………………..……………..…27 5.3 10Be ages……………………………………………………………..………29 5.4 Dendrochronology…………………….………….……………………...…..29 5.5 Equilibrium Line Altitudes……………………..…...……………………….30 5.6 Climate Change Estimates………………………………..………………….31 iv Chapter 6: Discussion……………………………………………………..……………..31 6.1 Ages of Moraines and Striated Bedrock………………..………………...….31 6.1.1 10Be ages……………………………………………..…………..…..31 6.1.2 Dendrochronology……………..…………………………………….35 6.2 Glacier Dynamics and Growth……..…………………………………….….36 6.2.1 Glacier Response to Climate.………………..……………………....36 6.2.2 Equilibrium Line Altitude Fluctuations……..……………………….37 6.3 Climate Record and Glacier Implications………...……………….................…..38 6.3.1 Climate Signal from Dendrochronology……………..………………38 6.3.2 Climate Chronology……………………………………..………...…41 6.3.3 Climate Change Estimates……………………..…………………….43 6.3.4 Timing of Moraine Deposition………………..…………...…….…..46 6.3.4.1 M-1……………………………..………….………………46 6.3.4.2 M-2………………………..………………….……………48 6.4 Regional Significance…………………………………………………................51 6.4.1 Regional Perspective……………...………….……….………...……51 6.4.2 Correlation with Regional Cycles………..…………………….….…54 Conclusion…………………………………………...…………..………………………55 References…………………………………………...……………...………………..…..58 Appendix A. Figures…………………………………………………..……..….…….…66 Appendix B. Tables…………………………………………………....……...………..113 Appendix C. Accelerator Mass Spectrometer Data…………………..…………..….…119 Appendix D. COFECHA Output Data……………………………..…………...………123 v List of Figures Figure 1. Location map of the Grizzly Valley in the Klamath Mountains 66 Figure 2. DEM of Grizzly Valley cirque 68 Figure 3. Glacial maxima chronology 69 Figure 4. M-1 and M-2 moraine crests 71 Figure 5. Sample site location map 72 Figure 6. Tree species for dendrochronology 74 Figure 7. Pith correction schematic 75 Figure 8. Moraine age from dendrochronology 76 Figure 9. Skeleton plot diagram 77 Figure 10. ELA climate conditions and envelope 78 Figure 11. Location map of temperature stations 79 Figure 12. Location map of precipitation stations 80 Figure 13. M-1 and M-2 crest comparison 81 Figure 14. M-2 profile 83 Figure 15. M-1 soil development 85 Figure 16. Moraine surface soil/clast diagrams 86 Figure 17. 10Be cosmogenic ages 89 Figure 18. Grizzly Valley cirque cosmogenic sample map and ages 90 Figure 19. Tree ages with ecesis interval 92 Figure 20. Graphs of the M-1 standardized tree-ring chronologies 93 Figure 21. Tree-ring width correlations 95 Figure 22. DEM of cirque with ELAs 97 vi Figure 23. Climate estimates at ELAs 99 Figure 24. Location map of proximal tree-ring studies 101 Figure 25. Temperature records 102 Figure 26. Regional subdivisions for dendrochronology 104 Figure 27. Precipitation records in NW North America 105 Figure 28. Precipitation records of study region 107 Figure 29. Precipitation lapse rate 108 Figure 30. Temperature lapse rate 109 Figure 31. Tree-ring widths and ENSO record 110 Figure 32. Reconstructions of the Grizzly Valley glacier 111 vii List of Tables Table 1. Documented ecesis intervals in North America 113 Table 2. Summary of boulder and moraine characteristics 114 Table 3. Summary of M-1 soil descriptions 115 Table 4. Temperature and winter precipitation changes at calculated ELA’s 116 Table 5. COFECHA statistical analysis values 117 Table 6. Descriptions of precipitation data weather stations 118 viii ABSTRACT LATE HOLOCENE GLACIAL ADVANCES IN THE KLAMATH MOUNTAINS, NORTHERN CALIFORNIA, DETERMINED FROM 10BE COSMOGENIC EXPOSURE DATING AND DENDROCHRONOLOGY By Joshua Tate Graham Master of Science in Geology The well!preserved moraines in the cirque at the head of Grizzly Creek, Klamath Mountains, California, provide the most complete record of late!Holocene glacier fluctuations yet documented in this region. Two separate moraine complexes lie below the modern glacier, within the cirque, only one of which supports substantial tree growth. 10Be cosmogenic ages of scoured bedrock surfaces and moraine boulders, as well as tree!ring ages indicate the approximate timing of glacial maxima in the Grizzly Valley cirque. The combination of the detailed climate record, provided by tree!ring widths, and the estimated moraine ages, determined from dendrochronology and cosmogenic dating, allows for an accurate reconstruction of the Grizzly Valley Glacier fluctuations over the last 1,000 years. Nine new cosmogenic exposure ages, combined with dendrochronology, constrain the timing of glacier maxima to ~690, ~150 and ~130 years before present (ybp). Around 690 ybp, the equilibrium!line altitude (ELA) was depressed ~160 meters relative to the ELA of the modern glacier. Using local temperature and precipitation lapse rates and the elevation of the contemporary glacier, we found that in comparison with modern climate conditions, the mean summer temperature during the ~690 ybp glacier ix maximum was ~0.9°C less and winter precipitation was ~95 cm in snow water equivalent (SWE) greater. During the ~150 and ~130 ybp glacier maxima, the ELA was ~67 meters lower than the modern ELA. The mean summer temperature corresponding to this glacier maximum was ~0.4°C cooler and winter precipitation was ~44 cm greater in comparison with modern climate. The climate regime over the last 1,000 years in the Klamath Mountain region seems to be cool and exceptionally wet. The ~690 ybp glacier maximum in the Klamath Mountains is not apparent in the Sierra Nevada or Cascade Ranges. Also, glaciers in the Sierra Nevada and Cascade Ranges retreated from their most recent LIA maxima ~20-30 years before the glaciers of the equivalent advance in the Klamath Mountains. The climate in the Klamath Mountains likely varies from the Sierra Nevada and Cascade ranges due to the proximity