UNLV Retrospective Theses & Dissertations

1-1-2003

Late Quaternary glacial and periglacial environments, Snake Range, Nevada

John G Van Hoesen University of Nevada, Las Vegas

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Repository Citation Van Hoesen, John G, "Late Quaternary glacial and periglacial environments, Snake Range, Nevada" (2003). UNLV Retrospective Theses & Dissertations. 2558. http://dx.doi.org/10.25669/miuo-0qf5

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LATE QUATERNARY GLACIAL AND PERIGLACIAL ENVIRONMENTS,

SNAKE RANGE, NEVADA

by

John G. Van Hoesen

Bachelor of Science, Geology University of Albany 1998

Master of Science, Geoscience University of Nevada, Las Vegas 2000

A dissertation submitted in partial fulfillment of the requirements for the

Doctor of Philosophy Degree in Geoscience Department of Geoscience College of Sciences

Graduate College University of Nevada, Las Vegas December 2003

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Copyright 2004 by Van Hoesen, John G.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Dissertation Approval The Graduate College uNiyUNIVilHSIÎVüF NtVADA LAS.VltOAS University of Nevada, Las Vegas

October 2 ^20 03

The Dissertation prepared by

John G. Van Hoesen

Entitled

Late Quaternary Glacial and Perielacial Environments. Snake Range,

Nevada.

is approved in partial fulfillment of the requirements for the degree of

Doctor of Philosophy in Geoscience

Examination Committee Chair

Dean of the Graduate College

Examination Committee Member

Examination Committee Member \ ^ . NC l Graduate College Faculty Representative

PR/1017-52/1-00 11

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

Late Quaternary Glacial and Periglacial Environments, Snake Range, Nevada

by

John G. Van Hoesen

Dr. Richard L. Orndorff, Examining Committee Chair Assistant Professor of Geology Eastern Washington University

Limited research has been conducted on the paleoclimatic significance of glacial and

periglacial features in the Great Basin. Glacial features in the range were first recognized

and described by early explorers (Gilbert, 1875; Simpson; 1876 and Russell, 1884) and

subsequent authors have continued to substantiate and elaborate on earlier reports (Heald,

1956; Kramer, 1962; Currey, 1969; Peigat, 1980; Osborn and Bevis, 2001). Since this

early reconnaissance work, few studies have focused on the Late Quaternary evolution

and paleoclimatic implications of glacial and periglacial landforms in the Great Basin

(Wayne, 1983; Osborn, 1989; Bevis, 1995; and Osborn and Bevis, 2001). Wayne (1984)

describes relict rock glaciers, sorted circles, debris islands, solifluction lobes and sorted

stripes in the Ruby, Schell Creek, and Snake ranges. While Cuixey (1969) and Osborn

and Bevis, (2001) discuss the distribution of rock glaciers in numerous ranges throughout

the Great Basin, including the Snake Range, and the surrounding regions.

Ill

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This study presents new data on the glacial and periglacial Late Quaternary

conditions in the interior Great Basin based on studies carried out in the Snake Range,

located in east-central Nevada. I propose the Lehman rock glacier is an ice-cemented

landform that evolved via a recessional genesis, contrary to present glacial or periglacial

models that primarily propose constructional geneses for rock glaciers. Preliminary GPR

evidence suggests the Lehman rock glacier may retain interstitial lenses of ice; remnant

ice that has stagnated under modem climate conditions.

The spatial distribution of both glacial and periglacial landforms provides

paleoclimatic information derived using field evidence and computer modeling.

Neoglacial temperature depression estimates calculated using modem freezing and

thawing indices for relict rock glaciers, range from -0.25 °C to -1.00 °C while

temperature estimates calculated using the methodology described by Frauenfelder and

Kaab, (2000) and Frauenfelder et al., (2001) are 0.35 to 0.97 degrees lower than those

calculated using freezing and thawing indices. Full Glacial MAAT depression estimates

range from approximately -5.16°C to -6.61°C calculated using periglacial landforms, to

approximately -4.55°C to -5.77 °C, calculated from reconstmcted Angel Lake

equilibrium line altitudes (ELAs).

Finally, using scanning electron microscopy, it is possible to differentiate between a

glacial and non-glacial origin for pebbles and cobbles entrained in enigmatic sedimentary

deposits is a useful tool. Each depositional environment creates distinct micro-features

that can be identified and used to establish a glacial or non-glacial history.

IV

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

ABSTRACT...... Hi

LIST OF FIGURES...... vii

LIST OF TABLES...... x

ACKNOWLEDGEMENTS...... xii

CHAPTER 1 SIGNIFICANCE OF LATE QUATERNARY LANDFORMS IN THE INTERIOR GREAT BASIN OF THE SOUTHWESTERN UNITED STATES...... 1 References ...... 12

CHAPTER 2 THE PALEOCLIMATIC SIGNIFICANCE OF RELICT GLACIAL AND PERIGLACIAL LANDFORMS, SNAKE RANGE, NEVADA.. 19 Introduction ...... 20 Study A rea...... 22 Methods ...... 25 Results...... 29 Discussion ...... 53 Conclusions ...... 70 Acknowledgments ...... 72 References ...... 73

CHAPTER 3 GEOMORPHIC AND GPR EVIDENCE FOR THE POSSIBLE GENESIS OF A TONGUE SHAPED ROCK GLACIER, SOUTHERN SNAKE RANGE, NEVADA...... 80 Introduction ...... 81 Study A rea...... 83 Methods ...... 86 Results...... 88 Discussion ...... 101 Conclusions ...... 118 Future Work ...... 121 Acknowledgments ...... 121 References ...... 122

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4 PREDICTING THE SPATIAL DISTRIBUTION OF PERRENNIAL SNOW AND ICE IN THE SNAKE RANGE, NEVADA: IMPLICATIONS FOR INCREASED PRECIPITATION FROM PLUVIAL LAKE SYSTEMS?...... 130 Abstract...... 131 Introduction ...... 131 Study A rea...... 132 Methodology ...... 135 Results...... 141 Discussion and Conclusions ...... 157 Future Work ...... 163 Acknowledgments ...... 165 References ...... 166

CHAPTER 5 A COMPARATIVE SEM STUDY ON THE MICROMORPHOLOGY OF GLACIAL AND NON-GLACIAL CLASTS WITH VARYING AGE AND LITHOLOGY: EXAMPLES FROM THE ARCTIC AND SOUTHWESTERN UNITED STATES...... 171 Abstract ...... 172 Introduction ...... 172 Methods ...... 174 Sampling Sites ...... 175 Results...... 182 Discussion ...... 191 Conclusions ...... 195 Acknowledgments ...... 197 References ...... 198

CHAPTER 6 SUMMARY OF MAJOR RESULTS...... 204 References ...... 211

VITA...... 213

VI

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

CHAPTER 1 Figure 1.1 Extent of Great Basin Physiographic Province ...... 2 Figure 1.2 Correlation of regional glaciations in the Western United States...... 5 CHAPTER 2 Figure 2.1 Study area map ...... 23 Figure 2.2 Morphometric map of Lehman rock glacier ...... 33 Figure 2.3 Morphometric map of North Fork Baker rock glacier.... 35 Figure 2.4 Morphometric map of Teresa rock glacier ...... 37 Figure 2.5 Morphometric map of Jeff Davis rock glacier ...... 38 Figure 2.6 Morphometric map of Big Canyon rock glacier ...... 39 Figure 2.7 Rock glacier terminus elevation vs. MAAT ...... 41 Figure 2.8 Freezing and thawing indices for rock glaciers ...... 42 Figure 2.9 Modern and Neoglacial MAAT for rock glaciers ...... 45 Figure 2.10 Examples of solifluction lobes ...... 47 Figure 2.11 Examples of patterned ground ...... 49 Figure 2.12 Examples of cryoplanation terraces ...... 51 Figure 2.13 Examples of garlands 9nd protalus ramparts ...... 52 Figure 2.14 Regression of Snake Range temperature estimates ...... 55 Figure 2.15 Periglacial features vs. winter radiation values ...... 57 Figure 2.16 Periglacial features vs. summer radiation values ...... 58 Figure 2.17 Regression between winter and summer radiation values ...... 59 Figure 2.18 Surface plot of winter and summer radiation multivariate regression ...... 60 Figure 2.19 Geometry of Lehman Creek glacial lobe ...... 62 Figure 2.20 Comparison of AAR and THAR ELA estimates ...... 66 Figure 2.21 Comparison of BR and THAR ELA estimates ...... 67 Figure 2.22 Comparison of BR and AAR ELA estimates ...... 68

CHAPTER 3

Figure 3.1 Study area map ...... 84 Figure 3.2 Typical surface of Lehman rock glacier ...... 87 Figure 3.3 Location of GPR transects and RILAs ...... 89 Figure 3.4 Deep arcuate furrows on rock glacier ...... 92 Figure 3.5 Rose diagrams of talus block on rock glacier ...... 95 Figure 3.6 Typical GPR profiles collected from rock glacier ...... 98

VII

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 3.7 GPR profile from lower lobe of rock glacier ...... 100 Figure 3.8 GPR profile from middle lobe of rock glacier ...... 102 Figure 3.9 GPR profile from upper lobe of rock glacier ...... 103 Figure 3.10 Previously published models of rock glacier genesis... 105 Figure 3.11 Model of the Lehman rock glacier genesis under assuming a glacial origin ...... 106 Figure 3.12 Proposed evolution of Lehman rock glacier shown on aerial photos ...... 108 Figure 3.13 Lobate rock glacier in Teresa cirque ...... 110 Figure 3.14 Uniformity plots of orientation data ...... I l l Figure 3.15 Schematic illustration of the proposed evolution of the Lehman rock glacier ...... 112 Figure 3.16 Spatial relationship between Lehman rock glacier an surrounding topography ...... 119

CHAPTER 4

Figure 4.1 Study area m ap ...... 133 Figure 4.2 Spatial relationship between pluvial lakes and Great Basin mountain ranges ...... 136 Figure 4.3 Flowchart of the steps required to produce climate coefficients and grids ...... 140 Figure 4.4 Location of individual valleys and the spatial extent of each grid that is analyzed ...... 144 Figure 4.5 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow in Baker V alley...... 147 Figure 4.6 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow on Bald M ountain ...... 147 Figure 4.7 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow in Lehman V alley...... 150 Figure 4.8 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow on Lincoln Peak...... 152 Figure 4.9 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow on Mt Moriah ...... 153 Figure 4.10 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow in Snake Valley...... 155 Figure 4.11 Equilibration run time versus temperature perturbation and the predicted distribution of perennial snow in Williams Valley...... 156

VIll

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 4.12 Predicted distribution of perennial snow and ice in the Snake Range calculated using ELApse ...... 159

CHAPTER 5

Figure 5.1 Study area map ...... 176 Figure 5.2 Typical environments of analyzed samples ...... 179 Figure 5.3 Summary of micro-features observed on samples 184 Figure 5.4 SEM photos of micro-features on samples from the Spring Mountains and Devils Postpile National Monument.... 185 Figure 5.5 SEM photos of micro-features on samples from the Fish Lake Plateau and Snake Range ...... 188 Figure 5.6 SEM photos of micro-features on samples from the La Sal Mountains, Allan Hills, and Yosemite NP ...... 190 Figure 5.7 SEM photos of non-glacial micro-features on samples from the Spring Mountains, Klondike Gravel, Lake Bonneville Shoreline and North Fork Baker Creek ...... 192 Figure 5.8 Histogram of micro-features observed in glacial, non­ glacial and mixed environments ...... 194 Figure 5.9 Expected evolution of the preservation of microfeatures with respect to age and Ethology ...... 196

IX

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

CHAPTER 2 Table 2.1 Summary of lapse rates used to calculate MAAT ...... 26 Table 2.2 Summary of location and general characteristics of periglacial landforms ...... 31 Table 2.3 Neoglacial temperature estimates calculated from rock glaciers...... 44 Table 2.4 Full Glacial temperature estimates calculated from periglacial landforms ...... 54 Table 2.5 Comparison of possible error introduced by using a 30 meter digital elevation model ...... 56 Table 2.6 Summary of reconstructed Angel Lake and Lamoille glaciers in the Snake Range ...... 64 Table 2.7 Summary of ELA estimates and associated statistics ...... 65 Table 2.8 Summary of temperature depression calculated using ELA estimates calculated using the THAR, AAR and BR methods ...... 69 Table 2.9 Summary of previously calculated Full Glacial temperature depression estimates ...... 70

CHAPTER 3

Table 3.1 Summary of GPR profile characteristics ...... 90 Table 3.2 Fabric analysis circular statistics ...... 94

CHAPTER 4

Table 4.1 Climate station data used to calculated climate coefficients ...... 138 Table 4.2 Monthly climate coefficients ...... 139 Table 4.3 Summary of climate station characteristics ...... 137 Table 4.4 Summary of run time and predicted perennial snow and ice for Baker Valley, Bald Mountain, Lehman Valley, and Lincoln Peak ...... 142 Table 4.5 Summary of run time and predicted perennial snow and ice for Mt Moriah, Snake Valley, and Williams Canyon... 143 Table 4.6 Summary of predicted snow and ice in Baker Valley with a -5°C temperature change and incremental 1cm changes in precipitation...... 145

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 4.7 Summary of Lake Maxey and Spring characteristics... 157 Table 4.8 Summary of evaporation estimates from Lake Maxey and Spring ...... 158

CHAPTER 5

Table 5.1 Previously described micro-features from glacially affected quartz grains ...... 173 Table 5.2 Summary of sample sites ...... 177

XI

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

First and foremost I need to thank my father and stepmother for providing a safe and

stable environment, for not giving up on me during the “troublesome” years, for always

having faith in my abilities, and for always letting me learn things the hard way. I also

need to thank my high school biology teacher, Bonnie Durr, for her enthusiasm and

encouragement and for teaching me how to funnel my energy into science. Bill Kidd and

Win Means at the University of Albany were responsible for encouraging me to study

geology and challenging me every step of the way.

I would like to recognize those organizations who provided financial support for this

project including the: UNLV Graduate Student Association, UNLV Department of

Geoscience, UNLV Graduate College, Geological Society of America, American Alpine

Club, Arizona-Nevada Academy of Science, Colorado Scientific Society, Nevada

EPS cor, and Sigma Xi. My thanks to Ben Roberts, Kristina Heister, and Bryan Hamilton

at Great Basin National Park, Chad Hendrix, Cathy Snelson, Jim Watson, Joe Kula, and

Melissa Hicks for logistical support and company in the field. I also want to thank

Devil's Postpile National Monument and Yosemite National Park for their support and

cooperation.

My scientific interests and philosophy were enhanced and challenged over the past

few years by many insightful talks with Fred Bachhuber, Dave Weide, Michael Wells,

and Steve Rowland at UNLV, Lionel Jackson with the Geological Survey of Canada,

Steve Hicock at the University of Western Ontario and Doug Merkler with the Nevada

NRCS. In particular, I want to thank Fred Bachhuber for defining the word

professionalism and for his enthusiasm in teaching. You have set the bar that I will strive

XII

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to reach, and I hope that someday I have as powerful an impact on students as you had on

me. I don’t know how to fully express my gratitude to Rik Orndorff my PhD advisor.

Thank you for your respect, your enthusiasm and unparalleled support as both an advisor

and a friend. Your interest in and concern for undergraduate education is something I

admire and will carry over into my teaching pedagogy.

I also want to acknowledge the many friends and university staff who have helped me

along my academic journey and often helped me take time off for lunch, enjoy the

necessary “beverages” and engage in general mischief including (in no particular order or

relation to the aforementioned activities) Jim O’Donnell, Linda Robison, Clay Crow,

Maria Figueroa, Rebecca Boulton, Carole Hoefle, Dr. Paul Ferguson, Josh Hager,

Weiquan Dong, Nicole Nastanski, Jonathan Paver, Ruth Yates, Tracy Call, James

Watson, Jason Smith, Anna Draa, John Moss, Morrie Safford, Nick Wilson, Jamie

Harris, Tammy Diaz, Joe Kula, Melissa Hicks, Andy Jones, Nicole Nastanski, Eric

Nystrom, Danielle Villa, Shannon Renckens, Cheryl Radeloff, Sarah Lundberg, Robyn

Howley, Nick Hayman, Sarah Cloud, Nicole Ladue, Marc Smith, Jeff Anderson, Craig

Smith, Ed Muller, Bob Miller, and Jan and Larry Brock.

Finally, I need to thank Amy Brock for her unconditional love, her never ending

enthusiasm and support, for always being there and listening, but mostly just for putting

up with me. You made Las Vegas bearable - 1 could not have done this without you...

XllI

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1

SIGNIFICANCE OF LATE QUATERNARY LANDFORMS IN THE INTERIOR

GREAT BASIN OF THE SOUTHWESTERN UNITED STATES

The Great Basin is located in the Basin and Range physiographic province that drains

internally (e.g. - water that enters the Great Basin undergoes evaporation or groundwater

recharge and never reaches the ocean via fluvial drainages). Centered on the state of

Nevada, the Basin and Range Province is an extensive region (~ 200,000 mi^) of

alternating, north-south trending, faulted mountains and flat valley floors (Fig. 1.1). The

entire area experienced Cenozoic extension that caused the crust to deform and thin as it

was pulled apart, producing in extensive normal faulting. Numerous mountain ranges

were uplifted and valleys down-dropped along these roughly north-south-trending faults,

creating the characteristic horst and graben topography of the Basin and Range province.

The southern Snake Range is one such uplifted horst located in east central Nevada (Fig.

1.1). This range is composed of early Paleozoic quartzite, limestone, and shale intruded

by the Jurassic Snake Creek-Williams Canyon Pluton (Drewes, 1958; Whitebread, 1969;

Lee et al., 1970; Lee and Van Loenen, 1971; Lee et al., 1981; Lee and Christiansen,

1983 a, b; Lee et al., 1986; McGrew and Miller, 1995 and Miller, 1999). The dominant

Ethologies in the southern Snake Range are Cambrian aged Prospect Mountain quartzite

and Middle Cambrian Pole Canyon limestone and Pioche Shale.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125°00' 49°00!

Columbia Rivef

Idaho

Oregon Snake River

Green River

CaUfbmia a m & w f

Colorado River

Salton Sea 400Km I. Great Basin Hydrologie Province ■32°30' 108°00'

Figure 1.1: Line diagram illustrating the geographic extent of the Great Basin Physiographic Province in the Western United States.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3 Topographically high regions like the Snake Range are found throughout the Great

Basin and produce drastically different microclimates from the surrounding lower

elevation valleys. During the Late Quaternary climatic conditions in the Snake Range,

and other similar alpine environments throughout the Great Basin, facilitated the

development of many glacial and periglacial environments, which are no longer

supported under modem climate.

It has long been recognized that the Snake Range experienced glaciation during the

Pleistocene and Late Quaternary. Glacial features in the range were first recognized and

described by early explorers (Gilbert, 1875; Simpson; 1876 and Russell, 1884) and

subsequent authors have continued to substantiate and elaborate on earlier reports (Heald,

1956; Kramer, 1962; Currey, 1969; Peigat, 1980; Osborn and Bevis, 2001). Since this

early reconnaissance work, few studies have focused on the Late Quaternary evolution

and paleoclimatic implications of glacial and periglacial landforms in the Great Basin

(Wayne, 1983; Osborn, 1989; Bevis, 1995; and Osborn and Bevis, 2001). However, due

to the vast number of glacial deposits and ease of accessibility, the mountain ranges

along the margin of the Great Basin have been extensively studied (Ray, 1940;

Richmond, 1948; Moss, 1949; Richmond, 1965; Shroba, 1977; Burke and Birkeland,

1983; Birman, 1984; Dohrenwend, 1984; Mahaney, 1984; Mahaney et al., 1984;

Richmond, 1986; Richmond and Fullerton, 1986; Richmond, 1986; Zielinksi, 1987; and

Davis, 1988).

Blackwelder (1931) conducted the first preliminary investigation on glaciation in the

Great Basin and surrounding regions, describing glacial features from many mountain

ranges throughout the Sierra Nevada and the Great Basin. He recognized four distinct

glacial advances in the Sierra Nevada and established the terminology used today to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 describe alpine glacial stages. In stratigraphie order, from youngest through oldest, he

named these stages (1) Tioga, (2) Tahoe, (3) Sherwin and (4) McGee. He based his

interpretations on stratigraphie relatio nships between moraines in similar valleys, extent

of talus cone formation, cirque morphology, modification of the valley by axial streams,

weathering features, preservation of small-scale glacial features, and stream terrace

formation. Subsequent workers have since refined the glacial chronology of the Sierra

Nevada and established similar, tentatively correlative chronologies for the Lake

Lahonton Basin, Wind River Range, and Rocky Mountains (Fig. 1.2) (Birman, 1964;

Morrison and Frye, 1965; Mahaney, 1972; Miller and Birkeland, 1974; Mahaney, 1984;

Mahaney et al., 1984; Richmond, 1986; Richmond and Fullerton, 1986; and Richmond,

1986).

Following the guidelines established by Blackwelder, Sharpe (1938) initiated the first

detailed study of glacial features in the Great Basin. He described two discrete intervals

of glaciation in the Ruby Mountains - East Humbolt Range: (1) the Lamoille and (2)

Angel Lake advances. He correlated the Angel Lake advance with the Tioga stage and

the Lamoille advance with the Tahoe stage, suggesting that while they were indeed two

separate glaciations, they represented early and late Wisconsinan deposits. However,

Wayne (1984) states there is a marked discrepancy between surficial weathering features

of the two deposits, suggesting the Angel Lake advance is Wisconsinan in age while the

Lamoille advance is Ulinoian. Piegat (1980) conducted a preliminary investigation on

the interior ranges of the Great Basin. Using aerial photographs and limited fieldwork,

he defined a coarse glacial chronology for ranges in south central Nevada including the

Snake Range, the adjacent Shell Creek Range, and the Toiyabe Range (located in central

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q.

■D CD

C/) o' K 3 U o O Approximate 3 & Sierra Nevada Interior Great Basin Lake Lahontan Basin Wind River Range Rocky Mountains Years BP 8 ■D Matthes - Gannett Peak — — - Gannett Peak 0-500 o>d CQ' ou Late Neoglacial O U nnam ed ------Fallon - — — — — - Audubon 950-1,900 3i CD Recess Peak — Early Neoglacial — Early Neoglacial Early Neoglacial 2,700-4,500 "n c 3. 3 " Hilgard 12,000-14,000 CD

"OCD O « Q. c T io g a ------Angel Lake ------Sehoo - Toyeh — — - Temple Lake - — - 14,000-25,000 C ' C/) 1964 1931 1965 1974 and Mahaney, 1972

Figure 1.2: Approximate time stratigraphie correlation diagram between glacial deposits of the Great Basin and surrouding areas in the Western United States (modified from Piegat, 1980). 6 Nevada at approximately the same latitude as the Snake Range). The mapping completed

in this initial reconnaissance defined approximate boundaries between Lamoille, Angel

Lake and Neoglacial surficial deposits. One exception to the lack of data concerning

interior Great Basin glaciation is the Toiyabe Range (Ferguson and Cathcart, 1954;

Stewart and McKee, 1977; and Piegat, 1980). The glacial history of this range has been

formally investigated and the results suggest there were two discrete glacial advances

likely correlative with Tioga-Angel Lake and Tahoe-Lamoille units (Osborn, 1989).

However, the paleoclimatic significance of these deposits were not discussed, they were

only correlated with regional glacial events. Osborn and Bevis (2001) provide a detailed

description of the spatial distribution of Late Quaternary glaciation in ranges within the

Great Basin and a paper describing the paleoclimate of each range is in progress (pg.

137%k

Similarly, limited research has been conducted on the paleoclimatic significance of

periglacial features in the Great Basin. Wayne (1984) describes relict rock glaciers,

sorted circles, debris islands, solifluction lobes and sorted stripes in the Ruby, Schell

Creek, and Snake ranges. While Currey (1969) and Osborn and Bevis, (2001) discuss

the distribution of rock glaciers in numerous ranges throughout the Great Basin,

including the Snake Range, and the surrounding regions. However, considerable

research has been conducted on periglacial deposits located in the arid southwestern

United States (Smith, 1936; Richmond, 1962; Blagbrough and Breed, 1967; Blagbrough

and Farkas, 1968; Blagbrough and Breed, 1969; Galloway, 1970; Blagbrough, 1971;

Barsch and Updike, 1971; Péwé, 1975; Blagbrough and Breed, 1976; Péwé and Updike,

1976; Blagbrough,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 1984; Blagbrough, 1994; Nicholas, 1994; Nicholas and Butler, 1996; Wayne, 1984; and

Blagbrough, 1999).

Glacial and periglacial landforms present on mountains within and adjacent to the

Great Basin provide insight into the climatic conditions that prevailed throughout this

region during the Late Quaternary. Alpine glaciers and permafrost are sensitive

indicators of fluctuating temperature and precipitation (Péwé, 1969; Flint, 1971; Barsch,

1978; Brakenridge, 1978; Hagedom, 1984; Wayne, 1984; Zhang, 1988; Murray, 1990;

Jakob, 1992; Clark et al., 1994; French, 1996; Konrad et al, 1999; Dramis et al., 2001;

Davis, 2001; Frauenfelder et al, 2001). Therefore, by obtaining understanding how

certain climatic, geologic and topographic factors influence the formation and

preservation of relict glacial and periglacial landforms, we can use these features to

evaluate future climate changes and reconstruct Late Quaternary landscapes and

paleoclimatic conditions.

Such factors include (1) the mass of a mountain range, (2) the trend of a range, (3)

the proximity to and availability of moist air masses, (4) lithology, (5) slope, aspect and

curvature of the landscape, (6) latitude, and (7) elevation. The mass of a mountain range

above the zone of snow accumulation affects orographic precipitation and controls how

much snow will accumulate on the lee slope. The greater the mass of the range the

greater the chance for snow and thus an increased change that glaciers will develop

(Flint, 1971). The trend of the mountain range also affects orographic precipitation;

ranges that are perpendicular to moisture laden storm tracks, (i.e. - the Jetstream), create

a more significant barrier to this moisture. Ranges that are perpendicular to the Jetstream

also provide greater surface area for the accumulation of perennial snow and ice. One of

the most important factors is the availability and proximity of moisture-laden air masses.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Regardless of the temperature conditions, an increase in effective moisture supply is

required to develop substantial alpine glaciers in a region with such low humidity as the

Great Basin. This doesn’t necessarily imply precipitation significantly increased, just

that either the frequency or intensity of storm tracks increased as the Jetstream was

progressively depressed during the Last Glacial Maximum (LGM).

Lithology can influence curvature (i.e. - whether a surface is concave or convex)

and the development of niches and slot canyons that serve as accumulation zones.

Lithology can also influence the type and intensity of frost/heave sorting and thereby

influence the type and distribution of permafrost (Péwé, 1969; Evans, 1994; French,

1996; and Davis, 2000). Slope can influence zones of accumulation by controlling

whether perennial snow develops or whether it avalanches and accumulates at a much

lower elevation (possibly below the equilibrium line [ELA] altitude of a range) (Flint,

1971 and Sharp, 1938). Avalanching may also funnel snow into a “protected” area

where it survives the winter months and develops into perennial ice. Curvature also

influences whether snow accumulates or not. For example, the ridgeline of most

mountain crests is convex and therefore an unlikely zone of accumulation. However,

slopes and valleys below the ridgeline are often convex and provide suitable zones of

accumulation where nivation hollows and subsequently perennial ice can develop under

appropriate climate conditions. Slope also influences which types of periglacial features

develop (i.e. - solifluction lobes on dipping slopes versus patterned ground on flat level

surfaces). Aspect is also of considerable importance because it influences the potential

solar radiation the landscape receives throughout the year (Flint, 1971). North-northeast

facing slopes provide optimum localities for the development of alpine glaciers because

these slope on average, receive the least amount of solar radiation during any given year.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 The aspect of ranges in the Great Basin is also important because Sharp (1938, pg. 313)

identified a “wind shadow”. Although the west facing slopes of most ranges in the Great

Basin receive more precipitation, snow that does manage to accumulation on ridges is

blown into concave surfaces (niches, valley, hollows, etc) on the leeward side of the

range. Similar to aspect, latitude influences the effectiveness of solar radiation by

controlling solar duration (i.e. - length of day) and angle of incidence. Both glacial and

periglacial landforms are sensitive to changes in solar radiation (Blackwelder, 1931;

1934; Hint, 1971; Funk and Hoelzle, 1992; French, 1996; Benn and Evans, 1998;

Frauenfelder and Kaâb, 2000), which explains the decrease in frequency and extent of

glaciation from the poles to the equator (Flint, 1971). Finally, altitude directly

influences precipitation, solar radiation and depressed temperatures that facilitate the

development of perennial distribution of perennial snow and ice.

Specific factors that affect the development of permafrost and thus relict periglacial

features include: (1) frequency of freeze-thaw cycles, (2) depth of frost penetration, (3)

amount of thaw and percentage of water loss, (4) presence of water near the surface, (5)

depth of snow, and (6) vegetation cover (Péwé, 1969; Harris, 1981; Evans, 1994; French,

1996; and Davis, 2000). The frequency of freeze-thaw cycles and depth of frost

penetration influence the degree of sorting and development for some permafrost

features. The seasonal water loss associated with summer thaw can influence whether

sporadic or discontinuous permafrost develops. The presence of water at the surface can

influencesummer preservation of permafrost by either reflecting solar radiation (i.e. -

increased albedo) or if abundant water is present, by radiating absorbed solar energy into

the ground. The depth of snow cover (>50 cm) during the winter months has been

shown to significantly affect the development of permafrost (Harris, 1981 and French,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 1996) by insulating the ground and preventing the development of ground ice and thus

permafrost.

Finally, vegetation is the most complex variable because numerous interactions take

place between vegetation and the subsurface that are still poorly understood. Vegetation

also serves as an insulating barrier to solar radiation and the insulating effect is tree and

plant specific (Viereck, 1965 and French, 1996).

Understanding the conditions required for permafrost features to develop also

provides further insight into the genesis and preservation of periglacial landforms. In

addition, by understanding landform genesis we can begin to evaluate whether modern

features still retain interstitial and/or glacial ice. Rock glaciers in particular are potential

ancillary sources of water, something of particular interest in the southwestern United

States (Konrad et al., 1998; Burger et al., 1999; Degen hard t and Giardino, 2003;

Degendhardt et al., 2003; and Whalley and Azizi, 2003). Currey (1969), Piegat (1980)

and Osbom and Bevis (2001) describe the occurrence of numerous rock glaciers

throughout the Great Basin, including the Snake Range. These landforms are potentially

sequestering interstitial or glacial ice that may be released and utilized as global climate

continues to warm. Unfortunately, we still have a incomplete inventory of the relict rock

glaciers in the Great Basin and a poorer understanding of their ice content because of the

lack of research being conducted in the interior Great Basin on periglacial landforms.

However, with the current demand for water in the southwestern United States and the

projected mean global temperature warming of 1.5-5°C (Watson et al., 1990; Wilson and

Mitchell, 1987; Schlesinger and Zhao, 1989; Knox, 1991; and Mitchell et al., 1995)

these potential water reserves will certainly generate more interest.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 The goals of this project were to (1) provide a better understanding of the surficial

deposits associated with glacially derived landscapes in the Snake Range, (2) evaluate

the genesis and spatial distribution of glacial and periglacial deposits in the Snake Range,

(3) derive paleoclimatic estimates from these deposits using field evidence and computer

modeling, and (4) investigate the micro-characteristics of glacially derived clasts and

debris pertinent to alpine glacier studies. Chapter 2 describes the geomorphology and

paleoclimatic implications of glacial and periglacial deposits in the Snake Range and

evaluates the hypotheses that (1) solar radiation is an applicable tool for predicting the

distribution of permafrost and (2) the Snake Range records a paleoclimate signature

similar to adjacent ranges in Nevada and Utah (Bevis, 1995). Chapter 3 describes the

geomorphology of the Lehman rock glacier (LRG) in the southern Snake Range and

evaluates the hypothesis that (1) the LRG is composed of three distinct lobes and

evolved in response to the retreating Lehman Glacier. Chapter 4 presents results from

computer modeling that attempt to predict Late Quaternary temperature and precipitation

conditions in the Snake Range. My hypothesis was that using a snow and ice model, I

could predict temperature changes required to develop the moraines identified in the

field. Chapter 5 describes the micromorphology of glacially affected clasts and surfaces

from the southwestern United States and the Arctic. This study tested the hypothesis that

distinct micro-features develop on during transport or scouring by glaciers.

Each chapter addresses one or more paleoenvironmental conditions required to

initiate, develop, and support glacial and periglacial environments. The culminating

papers describe the genesis and distribution of landforms, suggest possible paleoclimate

scenarios, and suggest that glacial and periglacial processes were pervasive during the

LGM and the Late Quaternary.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12 References

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Birman, J.H., 1964, Glacial geology across the crest of the Sierra Nevada, California. Geological Society of America Special Paper, 75, p.80.

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Drewes, H., 1958, Structural geology of the southern Snake Range, Nevada. Geological Society of America Bulletin 69: 221-240.

Evans, D.J.A., 1994, Cold climate landforms. John Wiley and Sons, Inc., Chichester, England, 526 p.

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Frauenfelder, R., Haeberli, W., Hoelzle, M., and Maisch, M., 2001, Using relict rockglaciers in GIS based modelling to reconstruct Younger Dryas permafrost distribution patterns in the Err-Julier area, Swiss Alps. Norsk Geografisk Tidsskrift 5: 195-202.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 Frauenfelder, R. and Kaâb, A., 2000, Towards a paleoclimatic model of rock-glacier formation in the Swiss Alps. Annals of Glaciology 31; 281-286.

French, H., 1996, The Periglacial Environment. Longman Singapore Publisher Pte, Singapore, 341 p.

Funk, M. and Hoelzle, M., 1992, A model of potential direct solar radiation for investigating occurrences of mountain permafrost. Permafrost and Periglacial Processes 3: 139-142.

Galloway, R.W., 1970, The full-glacial climate in the southwestern United States. Annals of the Association of American Geographers 60: 245-256.

Gilbert, G.K., 1875, Geology: U.S. Geographical and Geological Surveys West of the lOO'*’ meridian (Wheeler) 3: 68 Ip.

Hagedom, J., 1984, Pleistocene periglacial landforms in the mountains of the southern Capelands of South Africa and their significance as paleoclimate indicators. Palaeoecology of Africa and of the Surrounding Islands and Antarctica 16: 405-410.

Harris, S.A., 1981, Climatic relationships of permafrost zones in areas of low winter snow cover. Arctic 34: 64-70.

Heald, W.F., 1956, An active glacier in Nevada. The American Alpine Journal 10: 64- 167.

Jakob, M., 1992, Active rock glaciers and the lower limit of discontinuous alpine permafrost, Khumu Himalaya, Nepal. Permafrost and Periglacial Processes 3: 253- 256.

Knox, J.B., 1991, Global climate change: impacts on California, an introduction and overview. ln\ Knox, J.B. and Scheming, A.F. (eds). Global Climate Change and California. Potential Impacts and Responses, University of California Press, l-25p.

Konrad, S.K., 1998, Possible outburst floods from debris covered glaciers in the Sierra Nevada, California. Geografiska Annaler. Series A: Physical Geography 80: 183-192.

Konrad, S.K., Humphrey, N.F., Steig, E.J., Clark, D.H., Potter, N. Jr, and Pfeffer, W.T., 1999, Rock glacier dynamics and paleoclimatic implications. Geology 27: 1131- 1134.

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Lee, D.E., Stem, T.W., Mays, R.W., and Van Loenen, R.E., 1968, Accessory zircon from granitioid rocks of the Mt Wheeler Mine area, Nevada. United States Geological Survey Professional Paper 600-D: 197-203.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 Lee, D.E., Marvin, R.F., Stem, T.W., and Peterman, Z.E., 1970, Modification of K-Ar ages by Tertiary thmsting in the Snake Range, White Pine County, Nevada. United States Geological Survey Professional Paper 700-D: 92-102.

Lee, D.E. and Van Loenen, R.E., 1971, Hybrid granitoid rocks of the southem Snake Range, Nevada. United States Geological Survey Professional Paper 68: 1-46.

Lee, D.E. and Christiansen, E.H., 1983a, The mineralogy of the Snake Creek-Williams Canyon pluton, southem Snake Range, Nevada. United States Geological Survey Open File Report 83-337,21p.

Lee, D.E. and Christiansen, E.H., 1983b, The granite problem in the southem Snake Range, Nevada. Contributions to Mineralogy and Petrology 83: 99-116.

Lee, D.E., Kistler, R.W., and Robinson, A.C., 1986, Muscovite phenocrystic two mica granites of northeastem Nevada are Late Cretaceous in age. ln\ Shorter Contributions to Isotope Research, Peterman, Z.E. and Schanabel, D.C., eds. United States Geological Survey Bulletin B1622: 31-39.

Mahaney, W.C., 1984, Superposed Neoglacial and late Pinedale (Wisconsinan) tills, Titcomb Basin, Wind River Mountains, westem. Wyoming. Palaeogeography, Palaeoclimatology, Palaeoecology 45: 149-163.

Mahaney, W.C., Halvorson, D.L., Piegat, J., and Sanmugadas, K, 1984, Evaluation of dating methods used to assign ages in the Wind River and Teton ranges, westem Wyoming. In: Quatemary Dating Methods, Mahaney, W.C. (eds), Elsevier Sci. Publ., Amsterdam, Netherlands, 355-374.

Mahaney, W.C., 1972, Audubon: New name for Colorado Front Range Neoglacial deposits formerly called “Arikaree”. Arctic and Alpine Research 4: 355-357.

McGrew, A.J. and Miller, E.L., 1995, Geologic map of Kious Springs and Garrison 7.5’ Quadrangles, White Pine County, Nevada and Millard County, Utah. United States Geological Survey Open File Report 95-10: 20p.

Miller, E.L., Dumitm, T., Brown, R.W., and Gans, P.B., 1999, Rapid Miocene slip on the Snake Range-Deep Creek Range fault system, east-central Nevada. Geological Society of America Bulletin 111: 886-905.

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Mitchell, J.F.B., Johns, T.C., Gregory, T.M., Tett, S., 1995, Climate responses to increasing levels of greenhouse gases and sulphate aerosols. Nature 376: 501-504.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16 Morrison, R.B. and Frye, J.C., 1965, Correlation of the middle and late Quaternary succession of the Lake Lahontan, Lake Bonneville, Rocky Mountain (Wasatch Range), Southem Great Plains and eastem Midwest areas. Nevada Bureau of Mines and Geology Report: 9: 34p.

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Nicholas, J.W., 1991, Rock glaciers and the Holocene paleoclimatic record of the La Sal Mountains, Utah. Unpublished Ph.D. dissertation, University of Georgia, Athens.

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Nicholas, J.W. and Butler, D R., 1996, Applications of relative age dating techniques on rock glaciers of the La Sal Mountains, Utah: An interpretation of Holocene paleoclimates. Geografiska Annaler 1%A: 1-18.

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Péwé, T.L., 1969, The Periglacial Environment. McGill-Queens University Press, Ottawa, Ontario, Canada, 487p.

Péwé, T.L., 1975, Quaternary geology of Alaska. United States Geological Survey Professional Paper 935, lA5p

Pewe, T.L., and Updike, R.G., 1976, San Francisco Peaks: A Guidebook to the Geology, Second edition, prepared for American Quatemary Association, 4th biennial meeting. Tempe, Arizona, October 7-11, 1976, San Francisco Field Trip: Flagstaff, Museum of Northem Arizona, 80 p.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17 Richmond, G.M., 1962, Quatemary stratigraphy of the La Sal Mountains, Utah. United States Geological Survey Professional Paper, 324.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18 Wayne, W.J., 1984, Glacial chronology of the Ruby Mountains - East Humbolt Range, Nevada. Quaternary Research 21; 286-303.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2

THE PALEOCLIMATIC SIGNIFICANCE OF RELICT GLACIAL AND

PERIGLACIAL LANDFORMS, SNAKE RANGE, NEVADA

This paper has been prepared for submission to Arctic and Alpine Research and is presented in the format of that journal. The complete citation will is:

Van Hoesen, J.G. and Orndorff, R.L., 2003, The paleoclimatic significance of relict glacial and periglacial landforms. Snake Range, Nevada. Arctic and Alpine Research (IN PREP)

19

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 Introduction

Previous researchers have described the existence and general characteristics of

glacial and periglacial landforms in the interior Great Basin (Blackwelder, 1931, 1934;

Sharp, 1938; Currey, 1969; Waite, 1974; Piegat, 1980; Wayne, 1983, 1984; Osbom,

1990; Osbom and Bevis, 2001). Osbom (1990) and Osbom and Bevis (2001) have

discussed the glacial history of the Snake Range. However, only preliminary studies

have focused on glacial and periglacial deposits in the Snake Range in east-central

Nevada (Heald, 1956; Kramer, 1962; Piegat, 1980; Wayne, 1983; Osbom, 1990; and

Osbom and Bevis, 2001). This study presents a detailed description and inventory of

relict rock glaciers and periglacial features in the Snake Range, and an interpretation of

their paleoclimatic significance.

The environmental thresholds of many periglacial features are discussed by Poser

(1994), Péwé (1973), Péwé (1969), Péwé (1983), and French (1996). Periglacial

landforms develop in regions characterized by continuous and discontinuous permafrost

(Péwé, 1969; Washbum, 1980; Harris, 1982; Evans, 1994; and French, 1996).

Continuous permafrost is perennially frozen ground that occurs in regions with a soil

temperature of at least 0°C for two consecutive years (Péwé, 1983 and Davis, 2000).

Discontinuous permafrost is also perennially frozen ground occurring near the 0°C

isotherm, however it is disrapted by talik, layers of unfrozen soil between the permafrost

table and the active layer (Péwé, 1983 and Davis, 2000). A number of periglacial

features identified in the southwestem United States are indicative of discontinuous

alpine permafrost (Smith, 1936; Richmond, 1962; Blagbrough and Breed, 1967;

Blagbrough and Farkas, 1968; Blagbrough and Breed, 1969; Galloway, 1970;

Blagbrough, 1971; Barsch and Updike, 1971; Péwé, 1975; Péwé and Updike, 1976;

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 Blagbrough, 1976; Wayne, 1984; Nicholas, 1994; and Nicholas and Butler, 1996).

Estimates for the lower limit of discontinuous alpine permafrost are variable and range

from -8.5°C in the Alps to 0.5°C on the Qinghai - Xizang Plateau, China (Haberli, 1978;

Harris, 1981 a, b, c; Wayne, 1983; Guodong, 1983; Frauenfelder and Kaâb, 2000; and

Frauenfelder et al., 2001). The high variability in temperature estimates is a function of

localized alpine microclimates governed by aspect, slope, solar insolation, albedo, and

snowcover (Harris, 1981 a, b, c; Barry, 1981; and Greenstein, 1983). Although many

periglacial features suggest the presence of discontinuous permafrost, rock glaciers have

the greatest potential for estimating the lower limit of discontinuous alpine permafrost

and therefore, the location of the 0°C isotherm (Pewe, 1969; Barsch, 1978; Jakob, 1992;

and Frauenfelder et al., 2001). The paleoclimatic significance of rock glaciers has only

been investigated in a few areas, even though they are intimately related to permafrost

and limited snowfall, implying that they have considerable potential for paleoclimatic

studies (Kerschner, 1978, 1980 and 1985; Buchenauer, 1990 and Humlum, 1998a, 1998b,

1999a, 1999b).

The use of rock glaciers in paleoclimate studies are limited because we require a

better understanding of the climate typical of rock glaciers, however as climate data

becomes more available from sites with active rock glaciers, these studies should

become more prevalent. However, the presence of periglacial landforms indicates that at

the very least, discontinuous alpine permafrost existed throughout the Snake Range

during the Neoglacial and the Last Glacial Maximum (LGM; Péwé, 1983). All of the

features identified in this study are inactive, indicating the 0°C isotherm was lowered

during the Neoglacial and LGM.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 22 Numerous methods have been employed to estimate temperatures for the

southwestem United States during the last Full Glacial (-20 ka). These studies suggest a

range of temperature depression from 2.8°C to 10°C (Broecker and Orr, 1958; Snyder

and Langbein, 1962; Brackenridge, 1978; Mifflin and Wheat, 1979; Dohrenwend, 1984;

Benson, 1986; Benson and Thompson, 1987; and Bevis, 1995). This study calculates

temperature depression estimates based on the elevation and distribution of relict

permafrost landforms and differences in modem mean annual air temperature (MAAT)

and calculated MAAT for Neoglacial and Full Glacial environments. These estimates

are compared with temperature depression estimates gamered from equilibrium line

altitudes (ELA) of reconstructed glaciers. ELAs are estimated using three techniques

and two sets of regional lapse rates to calculate minimum and maximum temperature

estimates.

Study Area

The Snake Range is located in east-central Nevada within the boundaries of the

Basin and Range physiographic province. The entire region experienced Cenozoic

extension resulting in extensive normal faulting. Along these roughly north-south-

trending faults, mountains were uplifted and valleys down-dropped, producing horst and

graben topography. The Snake Range is an uplifted horst bounded to the east by Snake

Valley and to the west by Spring Valley (Fig. 2.1). Topographically isolated regions

such as the Snake Range are found throughout the Basin and Range province and

produce drastically different micro-climates compared to the surrounding low lying

valleys. The climate is strongly influenced by both elevation and aspect.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23

LEGEND Mt Moriah (12,067 ft - 3999m) Bald Mountain (11,562 ft - 3,524m) Wheeler Peak (13,063 ft - 3,982 m) Jeff Davis Peak (12,771 ft - 3893 m) Baker Peak (12,209 ft - 3,748 m) Pyramid Peak (11,926 ft - 3893 m) Lincoln Peak (11,532 ft - 3999 m) Granite Peak (10,812 ft - 3999m) Permafrost Big Canyon rockglacier North Slope Jeff Davis rockglacier Teresa rockglacier North Fork Slope rockglacier & I Mt Moriah CT : Mt Moriah SL Bald Mt SL ; Wheeler Peak CT Wheeler Peak CT Teresa Cirque PR Jeff Davis Ridge SL ; North Fork Baker PR Baker Ridge CT, SP, G, & SL Johnson Pass PG, SL, CT : Lincoln Peak PG

Figure 2.1: Study area map depicting the location of landmarks and permafrost features. CT = cryoplanation terrace, SL = solifluction lobes, PR = protalus rampart, G = garlands, and PG = patterned ground.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 Average mean annual air temperatures within the Snake Range vary from -8°C to

30°C, and average annual precipitation from the valleys to the high peaks region varies

from less than 12 cm to greater than 50 cm (Houghton, 1969). The western Great Basin

is characterized by precipitation patterns that deliver a significant portion of mean annual

precipitation in the monsoon season during July and August (Houghton, 1969). Previous

studies have identified the “Great Basin High,” a thermally derived air mass that remains

stationary during much of the winter season and forces westerly storms north of 40°N

latitude (Houghton, 1969 and Mitchell, 1976). The Great Basin High is ephemeral and is

often depressed during the winter, providing a storm path to the southern portion of the

Great Basin. Much of the precipitation delivered to the interior regions of the Great

Basin occurs during these periods dominated by the “Pacific component” (Houghton,

1969). However, most of the precipitation received by the Snake Range occurs during

April to June and October to November when successive low-pressure cells dominate the

regional climate under the “Continental component” (Houghton, 1969).

The Snake Range is composed of early Paleozoic Prospect Mountain quartzite, Pole

Canyon limestone, and Pioche shale intruded by the Snake Creek-Williams Canyon

pluton that is Jurassic age (-160 Ma; Drewes, 1958; Whitebread, 1969; Lee et al., 1970;

Lee and Van Loenen, 1971; Lee et al., 1981; Lee and Christiansen, 1983 a, b; Lee et al.,

1986; Miller, 1995 and Miller, 1999). The Snake Range contains an excellent example

of a Basin and Range metamorphic core complex décollement. The décollement is

thought to have accommodated 12-15 km of rapid slip during the Miocene (17 Ma;

Lewis et al., 1999 and Miller et al., 1999), and an older episode of faulting is thought to

have occurred during the late Eocene - Oligocene (Miller et al., 1999).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25 Piegat (1980), Osbom (1990), and Osbom and Bevis (2001) summarize the glacial

geology in the Snake Range and correlated Late Wisconsin deposits with the Angel Lake

advance (AL) and Illinoian deposits with the Lamoille (LAM) advance. The AL and

LAM terminology was defined in the Ruby Mountains by Sharp (1938) and later applied

to the East Humbolt Range by Wayne (1984) and throughout the westem Great Basin by

Piegat (1980) and Osborn and Bevis (2001). Angel Lake and Lamoille moraines have

also been correlated with Blackwelder’s (1934) Tioga and Tahoe advances in the Sierra

Nevada. Sharpe (1938) and Wayne (1984) provide excellent descriptions of the

characteristics used to differentiate between Angel Lake and Lamoille glacial moraines.

Methods

We used aerial photography interpretation and field mapping during the spring and

summer of 2001 and 2002 to locate and identify glacial and periglacial landforms. We

obtained color aerial photographs (1:24,000 and 1:12,000 scale) from the United States

Department of Agriculture and black and white aerial photographs (1:48,000) from the

United States Geological Survey for the Snake Range. We mapped landforms on digital

orthophotos using a Geographic Information System (GIS) and later compared with

results from fieldwork. Rock glaciers are described and classified using the taxonomy of

Barsh (1996) and Corte (1987). We describe and measure the morphometric parameters

of each rock glacier using a GIS following guidelines described by Barsh, (1996).

We calculate paleotemperature estimates from periglacial landforms using

methodologies described by Harris (1981a, b, c and 1982), Greenstein, (1983)

Frauenfelder and Kâab (2000), Hoelzle (1996), and Frauenfelder et al. (2001).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 26 Using a 30-meter digital terrain model (DTM), modem climate data and Visual

Basic programming we calculate daily mean annual air temperatures (MAAT) for every

grid cell in the DTM and freezing and thawing indices for five rock glaciers in the Snake

Range. We also estimated MAAT using a thirty-year temperature record from the

Lehman Caves climate station and lapse rates defined by Greenstein (1983),

Dohrenwend (1984) and Wolfe (1992) (Table 2.1).

Source Altitude (m) Lapse Rate

Greenstein, 1983 > 2,600 5.0°C/Km Wolfe, 1992 2,400 - 2,600 3.7±0.2°C/Km 2,200 - 2, 400 2.6°C/Km 2,000 - 2,200 2.4±0.4°C/Km 1,800 - 2,000 2.5±0.8°C/Km 1,600-1,800 2.2±0.4°C/Km

Dohrenwend, 1984 > 2,000 5.4°C/Km < 2,000 7.6°C/Km

Table 2.1: Summary of lapse rates used to calculate modem and past MAAT for paleotemperature depression estimates.

The Lehman Caves climate station is located on the east side of the southern Snake

Range at 2073 meters above sea level (masl) and has a MAAT of 9.59°C. Lapse rates

were not corrected for the air drainage effect described by Barry (1981) and Harris (1982)

because of the lack of climate stations in the study area. Freezing and thawing indices

were calculated for each rock glacier using daily MAAT values and plotted versus the

lower limits of continuous, discontinuous, and sporadic permafrost calculated by Harris

(1981a, b, c). By assuming the terminus of each rock glacier represents the paleo-

distribution of the lower limit of discontinuous permafrost, paleotemperatures can be

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27 calculated for each rock glacier by depressing the modem lower limit of discontinuous

permafrost and measuring the temperature change.

Paleotemperatures are also calculated from rock glacier termini using a digital terrain

model, potential direct radiation values and MAAT following the methodology described

by Frauenfelder et al. (2001) and Frauenfelder and Kaâb (2000). Paleotemperatures were

estimated by calculating the current MAAT (Tp) at the terminus of each rock glacier

using modem climate data and lapse rates. Potential direct radiation values (lp(x,y,z))

were calculated for the winter and summer solstice using ArcView GIS and The Solar

Analyst Extension, a radiation model that utilizes a similar algorithm to Funk and

Hoelzle (1992). A hypothetical altitude (Hum) for each relict rock glacier is calculated

representing the elevation required for the rock glacier to be considered active using

Equation (1):

Hiim = alp(x,y,z)+è (1)

where a and b are constants calculated from BTS measurements in the Swiss Alps by

Hoelzle and Haeberli (1995) and Ip is modem potential direct solar radiation at the

terminus of each rock glacier. A hypothetical MAAT (Tum) was calculated using the

hypothetical altitude (Hum) as a proxy for temperature using Equation 2:

Tiim = (C-H|!m)6T (2) 6h

where C is the elevation of the regional 0° isotherm and ôT/ôh is the regional lapse rate.

These calculations provide MAAT under modem conditions and paleo-MAAT estimates

that can be used to calculate temperature change using Equation 3.

AT = Tp-T,im (3)

The difference (AT) between Tum and Tp represents the temperature depression from the

time each rock glacier developed and modem climate.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 The spatial distribution of periglacial features is also used to estimate MAAT

depression in the Snake Range during the Last Glacial Maximum (LGM). Using the

modem MAAT of 9-60°C and regional lapse rates (Greeenstein, 1983; Dohrenwend,

1984; andWolfe, 1992; Table 2.1), minimum and maximum estimates were calculated

for full glacial cooling in the Snake Range.

Paleotemperature estimates are calculated from modem and former equilibrium line

altitudes (ELA). ELA values are calculated using the spatial extent of Angel Lake and

Lamoille glaciers in the Snake Range following guidelines described by Meier and Post

(1962), Porter (1975), Dohrenwend (1984), Meierding (1982), Furbish and Andrews

(1984), Tomes et al. (1993), Benn and Gemmell (1997), and Benn and Evans (2001).

First order estimates of Angel Lake and Lamoille ELAs were calculated using the toe

to headwall altitude ratio (THAR; Charlesworth, 1957 and Richmond, 1965). The

highest probable extent of glacial ice and lowest altitude of each terminal moraine were

calculated for Angel Lake and Lamoille glacial lobes. THAR ratios of 0.35 and 0.40 are

assumed to most accurately represent paleo-ELAs because they produce the lowest root

mean square error (RMSE; Meierding, 1982). However, ELAs calculated using a THAR

ratio of 0.50 produce the most realistic values in the Snake Range when compared to the

spatial extent of glaciation.

ELAs were also calculated using the accumulation area ratio (AAR) method. This

methodology is more sensitive than the THAR technique because it assumes a fixed

proportion of the total glacier is located in the zone of accumulation (Meierding, 1982;

Locke, 1990; and Benn and Evans, 2001). This technique calculates former ELA values

by identifying the altitude on a glacier that corresponds to a specified accumulation area

(0.50,0.55, 0.45, 0.40, etc). This technique, using an AAR of 0.65, most accurately

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 (±100 m) represents the ELA of former glaciers based on RMSE error analyses

(Meierding, 1982 and Gillespie, 1991).

However, the AAR technique does not evaluate the hypsometry of former glaciers

and can produce erroneous ELA values. Therefore, ELAs were also calculated using the

balance ratio (BR) method developed by Furbish and Andrews (1984) and automated by

Benn and Gemmell (1997). The BR method incorporates the assumption that net

accumulation must exactly balance net ablation below the ELA using equation 4:

db*Ab = dc*Ac (4)

where db equals the average net annual ablation in the ablation zone, Ab is the area of the

ablation zone, dc is the average net annual accumulation in the accumulation zone and Ac

is the area of the accumulation zone (Furbish and Andrews, 1984). The ablation and

accumulation gradients are assumed to be linear so that db and dc are in equilibrium at

the area-weighted mean altitudes of the ablation area (Zb) and accumulation area (Zc). A

steady-state ELA is defined by the altitude that balances equation 5.

bnb/bnc = Zc*A«/Zb*Ab (5)

where b„b is the mass balance gradient in the ablation zone and bnc is the mass balance

gradient in the accumulation zone. Typically, small ablation zones with respect to

glacial area characterize glaciers exhibiting high balance ratios and glaciers with lower

balance ratios require larger ablation zones for equilibrium. BR values were calculated

using the spreadsheet model provided by Benn and Gemmell (1997).

First and second order local al and global polynomial surfaces are calculated for the

Snake Range using values calculated from each method using ArcGIS. Contouring these

surfaces produced ELA distribution maps for each technique and allowed for the

calculation of RMSE and correlation statistics (Table 2.2; Meierding, 1982).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30 Results

Permafrost Features

Relict permafrost features identified in the Snake Range include rock glaciers,

cryoplanation terraces, protalus ramparts, stone polygons, stone circles, solifluction lobes,

and garlands (Fig. 2.1). The location and characteristics of these landforms are

summarized in Table 2.2. The most common periglacial features in the Snake Range are

stone-banked solifluction lobes (8 sites), followed by stone polygons and circles (6 sites),

rock glaciers (5 sites), cryoplanation terraces (5 sites), garlands (3 sites), and pro talus

ramparts (3 sites). No preserved organic material has been discovered in any of the

features that would allow for radiocarbon dating. We assume these features developed

during the last glacial maximum, and during early deglaciation with the exception of

rock glaciers. Tephrachronology data indicates the presence of Mono Crater ash in the

lower two segments of the Lehman Cirque rock glaciers, indicating that these features

must be younger than 1200 years (Osbom, 1990).

Rock glaciers

The Snake Range contains 5 alpine rock glaciers located in Lehman Cirque, North

Fork Baker Cirque, Teresa Cirque, Big Canyon, and on the northwest slope of Jeff Davis

Cirque (Fig. 2.1). All five rock glaciers are located on or below steep cliffs composed of

Prospect Mountain Quartzite and are characterized by high rates of erosion and talus

production.

The Lehman rock glacier is approximately 900 m long. It is located in a northeast-

facing cirque composed entirely of Prospect Mountain Quartzite and is directly

connected

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■D O Q. C g Q.

■D CD Location* Feature Size** Lithology*** Elevation (m) Easting Northing C/) (/) WPR Cryoplanation Terrace 66931.027 (m^) PMQ 3700.00 732444.296616 4319011.785383 WPR Cryoplanation Terrace 113833.967 (m^) PMQ 3321.00 731822.419558 4320571.289497 TC Protalus Rampart 18699.634 (m^) PMQ 3198.00 732981.809625 4320024.241551 8 NFBC Protalus Rampart 2590.41 (m^) PMQ 3347.00 732682.148558 4317252.011221 "O NFBC Protalus Rampart 2811.144 (m^) PMQ 3369.00 732686.021670 4317128.655794 MMT Stone Polygons 4.0 - 5.2 (m) PCL 3358.00 742272.364413 4352205.759950 MMT Stone Circles 1.3- 1.8 (m) PCL 3362.00 742362.310218 4352034.045230

CD MMT Cryoplanation Terrace 1163607.638 (m^) PCL 3567.00 742771.154789 4352099.460361 MM Solifluction Lobes 2-8 (m) PCL 3506.00 741730.517797 4350897.234912 MM Solifluction Lobes 2-8 (m) PCL 3392.00 742135.777619 4351161.826035 3. 3" LP Stone Polygons 0.3 - 0.6 (m) PCL 3464.00 735152.164356 4306434.112533 CD LC Stone Circles 1.5-3.5 (m) PMQ 3332.00 733253.784717 4319105.464940 CD ■D JP Stone Circles 1 .5 -2 .0 (m) SCWP 3461.00 733757.705253 4314038.946599 O Q. JP Solifluction Lobes 1-5 (m) SCWP 3412.00 734016.570612 4314256.877950 C a JP Cryoplanation Terrace 30422.616 (m^) SCWP 3443.00 733938.779291 4314011.846650 O 3 JDR Garlands 1-4 (m) PMQ 3600.00 733231.150955 4317909.364737 "O JDR Garlands 1-4 (m) PMQ 3697.00 733591.674705 4318200.389933 o JDR Solifluction Lobes 3-7 (m) PMQ 3560.00 733546.066279 4317883.302779

CD JDR Solifluction Lobes 3-5 (m) PMQ 3708.00 734514.289339 4318597.373902 Q. JDR Solifluction Lobes 3-5 (m) PMQ 3576.00 735222.518026 4319058.826021 BM Solifluction Lobes 0.5-4 (m^) PMQ 3441.00 731649.174731 4321938.445402 BR Solifluction Lobes 2-4 (m) PMQ 3600.00 733076.965321 4316289.043636 ■D CD BR Garlands 2-3 (m) PMQ 3523.00 732743.461960 4315982.584760 BR Cryoplanation Terrace 43432.92 (m^) PMQ 3592.00 732637.939927 4315912.645739 (/) (/) * WPR = Wheeler Peak Ridge, TC = Teresa Cirque, NFBC = North Fork Baker Cirque, MMT = Mt Moriah Table, MM = Mt Moriah, LP = Lincoln Peak, LC = Lehman Cirque, JP = Johnson Pass, JDR = Jeff Davis Ridge, JDC = Jeff Davis Cirque, BM = Bald Mountain, and BR = Baker Ridge. ** Stone circles and polygon size measures the diameter and garlands and solifluction lobes measure length. *** PMQ = Prospect Mountain Quartzite, SCWP = Snake Creek-Williams Pluton, and PCL = Pole Canyon Limestone.

Table 2.2; Summary of general characteristsics and calculated temperature change at each site since the last Full Glacial. 32 to the source area (Fig. 2.2). The rock glacier is a complex, tongue-shaped feature

dominated by three distinct lobes composed of large (0.5 to 3.0 m) blocky quartzite

clasts with a minor component of fine-grained sediment. Deep, arcuate furrows separate

each lobe from one another. The upper lobe (LUL) of the rock glacier has a rooting

elevation of approximately 3667 masl, and the lower lobe (LLL) terminates at

approximately 3272 masl. The surface of the rock glacier exhibits well-developed

surface relief ranging from 2.0 to 3.0 m in the form of prominent furrows and ridges that

are oriented perpendicular to down-valley motion.

The upper lobe (LUL) is a convex landform approximately 434 meters long, 206

meters wide and exhibits well-developed arcuate furrows and ridges that range in

amplitude from 0.5 - 3.0 meters. The frontal and lateral margins of the lobe are

composed of light gray sediment and talus. They are steep (-34 - 36°), and capped by a

0.5 m thick sequence of dark blocky talus. The frontal margin lacks boulder aprons, and

sparse vegetation is found growing on the lowermost surface.

The middle lobe (LML) exhibits a moderately convex surface that is approximately

265 m long and 178 m wide. This lobe also exhibits moderately developed one-to-two-

meter deep arcuate furrows and ridges. The frontal margin is composed of fine-grained

sediment and talus overlain by a darker sequence of blocky talus that is approximately

one meter thick. The frontal slopes are steep (-32 - 36°), with small poorly developed

boulder aprons are present at the base of the steep frontal snout. This lobe contains

significantly more vegetation than the upper lobe. The lateral margins of the lobe are

difficult to distinguish because of talus input and subsequent coalescence of the rock

glacier and talus cones.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 33

~ 3652 m a.s

Lehman Glacier

Figure 2.2; Morphometric map o f the Lehman rockglacier. The inset photo of the Lehman rockglacier complex was taken approximately 500 meters downvalley on the Lehman-Bristlecone trail.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 The lower lobe (LLL) is a weakly convex landform approximately 195 m long and

100 m wide, lacking well developed surface furrows and ridges. The frontal margin is

dominantly fine-grained sediment and talus, overlain by a heavily weathered layer of

blocky talus. The frontal slopes are steep (-30 -33°). Numerous small bushes and

flowers exist on the slope, and well-developed boulder aprons and evidence for small

rockslides are present at the base of the steep frontal snout.

The North Fork Baker Creek rock glacier (NFBC) is a moderately convex tongue­

shaped landform approximately 673 m long, 88 m wide. It is located in an east-to-

northeast facing cirque composed of Prospect Mountain Quartzite, and it is directly

connected to the source area (Fig. 2.3). This is a complex landform composed of

multiple lobes that have evolved into the modem, tongue-shaped feature. Although

there are multiple lobes in this rock glacier complex, it is difficult to separate them into

distinct rock glaciers because of high rates of talus input from the surrounding cirque

walls. This rock glacier is located below a steep, north-facing ridge (approximately 50

to greater than 60 degrees) that provides significant shading during the summer months.

The surface of the rock glacier is dominated by blocky quartzite talus (0.5 -1 .5 m)

and is characterized by well-developed surface relief (0.5 - 2.5 m) in the form of

prominent arcuate shaped furrows and ridges. The rooting zone for the upper segment of

the rock glacier is located at approximately 3397 masl. The true rooting zone may be

located at a higher elevation, but this is not discernible in the field or from aerial photos

because of thick talus cover. The lowermost segment terminates at - 3261 masl. The

frontal and lateral margins of the rock glacier are steep (-32 - 34°), with reddish-gray

sediment overlain by a 0.5 m layer of dark, blocky talus. The margins of the rock glacier

exhibit moderately developed boulder aprons and contain sparse vegetation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35

• ■■■■■■■■ -■ ■' *V* ' m Protalus Ramparts^

Debns

-3369 ^ m.a.s.I

-3357 m.a.s J

ÇoinpIcxTongae Shaped Roc&gjlaaer

Aÿ:', * , .t'»

tfftSiSSW

’''T A -t

Figure 2.3: (a) Morphometric map of the North Fork Baker rockglacier located south of the Lehman rock glacier and (b) the location where the field photo was taken is designated with a star.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36 The Teresa rock glacier (TR) is a single, lobate-shaped convex upward landform

approximately 147 m long and 225 m wide. It is located in a small east-to-northeast

facing cirque composed of Prospect Mountain Quartzite, and it is detached from the

source area headwall (Fig. 2.4). Although this is a relatively small feature, the steep

frontal snout (-33 - 35°) and moderately developed furrows and ridges (1.0 - 1.5 m)

suggest that this is a rock glacier, and not a protalus rampart. The uppermost portion of

the rock glacier is located at approximately 3319 masl, and the lowermost portion is

located at approximately 3260 masl. Well-developed boulder aprons are present at the

base of the frontal snout, and evidence of small debris slides exists along the upper

portion of the snout. Numerous shrubs and grasses are growing on the frontal slope.

The North Slope Jeff Davis rock glacier (NSJD) is a single, weakly convex-upward,

tongue-shaped landform approximately 230 m long and 119 m wide. It is found on a

north-facing slope of Jeff Davis Peak that is composed of Prospect Mountain Quartzite

(Fig. 2.5). This landform is the only identified rock glacier in the Snake Range that is not

located in a cirque or below a steep-faced ridge. This rock glacier has a steep frontal

snout (-28 - 33°) and weakly developed furrows and ridges (0.5 - 1.0 m) suggesting that

is a rock glacier and not a protalus rampart. The uppermost portion of the rock glacier is

located at approximately 3402 masl and the lowermost portion is located at

approximately 3318 masl. Moderately developed boulder aprons are present at the base

of the frontal snout, and sparse vegetation is found growing on the frontal slope.

The Big Canyon rock glacier (BCR) is a single, weakly convex-upward, lobate-

shaped landform approximately 172 m long and 119 m wide. It is located below a west-

facing slope on Mt Moriah, which is composed of Prospect Mountain Quartzite (Fig.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37

Figure 2.4: (a) A morphometric map of Teresa rock glacier that is located to the north of Lehman rock glacier and (b) the red star on the aerial photograph is the approximate location where the photograph was taken

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38

Figure 2.5: (a) A morphometric map of the North Slope Jeff Davis rock glacier and (b) a photo taken from the Wheeler Peak Scenic Drive facing southwest.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39

v:

• f • S ^ . ^

»

r n m m

m i m m

Figure 2.6: (a) A morphometric map of the Big Canyon rock glacier located north of Mt. Moriah and (b) the red star indicates the approximate location where the field photo was taken.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) not included in the original manuscript are unavailable from the author or university. The manuscript was microfilmed as received.

40

This reproduction is the best copy available.

UMI’

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41

4200 Lehman Cirque - Upper Lobe o Lehman Cirque - Middle Lobe 4000 □ Lehman Cirque - Lower Lobe ♦ Teresa Cirque 3800 + Jeff Davis NW Slope

*■ North Fork Baker Cirque O Big Canyon Cirque I 3600 '3 CQ 3400 %

3200 A O s 3000

2800

The ellipse shows the prediction interval for a 2600 single new observation, given the parameter estimates for the bivariate distribution computed 2400 from the data, and the given n.

Regression Results : r^ = 0.9991; y = 3330.16349 - 198.77I969*x 2200 -4-3-2-10 1 2 3 MAAT Calculated From Climate Data

Figure 2.7: Rock glacier terminus elevation versus MAAT calculated from climate data.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42 2.6). The landform has a steep frontal snout (-28 - 33°) and weakly developed furrows

and ridges (0.5 - 1.0 m) suggesting that this is a rock glacier, and not a protalus rampart.

The uppermost portion of the rock glacier is located at approximately 3402 masl and the

lowermost portion is located at approximately 3318 masl. Moderately developed boulder

aprons are present at the base of the frontal snout, and sparse vegetation is found

growing on the frontal slope.

Paleoclimatic Significance of Snake Range Rock Glaciers

Rock glaciers have been used to estimate temperature change under the assumption

that they represent the lower limit of discontinuous permafrost (Barsch, 1978; Jakob,

1992; and Frauenfelder et al., 2001). Modem climate conditions were established to

quantify temperature change since the development of each rock glacier in the Snake

Range. The MAAT for the lower limit of each rock glacier is plotted against the

regional MAAT and elevation of the Snake Range in Figure 2.7. Freezing and thawing

indices calculated for each rock glacier are plotted against the freezing and thawing

indices for the limits of continuous, discontinuous, and sporadic permafrost (Fig. 2.8;

Harris, 1981a, b, c). Assuming rock glaciers represent the lower limit of discontinuous

permafrost, they should plot above the discontinuous permafrost isotherm. However,

under modem climate conditions every rock glacier falls below this isotherm, indicating

the region has cooled since they developed or the assumption that they represent the

lower most limit of discontinuous permafrost is invalid. The difference between modem

freezing and thawing indices and the lower limit of discontinuous permafrost for each

rock glacier should represent the temperature change between modem climate and the

climate under which each feature developed (Table 2.3). Temperature depression

estimates since the development of Neoglacial rock glaciers range from -0.25°C for the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42

Freeze - Thaw Indices For Snake Range, Nevada 2500

I 2000 & I Q U 1500 - I a 1000 - g T3 £ I 500 -

500 1000 1500 2000 2500 Thaw Index - Degree C Days Per Year

PERMAFROST LIMITS

- Sporadic 0.25 Isotherm

• Lehman Cirque - Upper Lobe Teresa Cirque Lehman Cirque - Middle Lobe 9 Jeff Davis NW Slope 9 Lehman Cirque - Lower Lobe ▼ Big Canyon - Mt Moriah A North Fork Baker Cirque

Figure 2.8: Freezing and thawing indices for 7 rockglaciers in Snake Range, Nevada, plotted with respect to the lower limits of the continuous, discontinous, and sporadic permafrost zones (After Harris, 1981,a, b, c and Greenstein, 1983)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 lower lobe of the Lehman rock glacier to -l.OC for the Big Canyon rock glacier, and the

estimates have a mean of -0.61°C.

GIS-based modeling was also used to calculate Neoglacial temperature change

estimates based on (a) the elevation of the lower limit of each rock glacier, (b) summer

and winter radiation values, and (c) modern MAAT following the methodology of

Frauenfelder and Kaab (2000) and Frauenfelder et al. (2001). Snake Range rock glaciers

are located in an altitudinal range of 3144 to 3336 masl with aspects ranging from 8° to

280° and they are subjected to a broad range of winter and summer solar radiation values.

Temperature depression estimates since the development of Neoglacial rock glaciers,

calculated using the relationship between modem potential direct solar radiation and

MAAT, range from -1.11°C for the North Fork Baker Cirque rock glacier to -1.61°C for

the Jeff Davis NW Slope rock glacier, with an estimated mean temperature change of

-1.42°C (Table 2.3). Modem MAAT (Tp), the hypothetical temperature (Tum) at the

Neoglacial rock glacier front, and the calculated difference (AT) for each rock glacier are

plotted in Figure 2.9. The distribution of temperature change in Figure 2.10 indicates a

similar relationship to that described above, with the ffeeze/thaw indices; the lowest

temperature depression occurs at the lower lobe of the Lehman rock glacier and the

greatest depression occurs at the Big Canyon rock glacier. This temperature gradient is

consistent with field observations because the lower lobe of the Lehman rock glacier is

presumed to be the youngest rock glacier in the Snake Range and is in close proximity to

the Lehman glacier and modern ELA, while the Big Canyon rock glacier faces directly

west and is approximately 192 m lower than lower lobe of the Lehman rock glacier.

The average temperature depression estimate of -0.61°C, calculated using freezing

and thawing indices, is lower than previously calculated Neoglacial temperature

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) Reference Location Elevation AT“C C/) Greenstein (1983) Wolfe (1992) Lehman - Upper Lobe 3335.84 -0.25 Lehman - Middle Lobe 3294.95 -0.40 CD -0.65 8 Lehman - Lower Lobe 3255.14 Jeff Davis NW Slope 3219.63 -0.50 North Fork Baker Cirque 3290.35 -0.75 Teresa Cirque 3234.40 -0.75 Big Canyon - Mt Moriah 3144.00 -1.00

Mean —> 3253.47335 -0.6142857 3. 3 " CD Location M AAT (Tp) (Ip) H,™ a b Turn C aT/crh AT°C ■DCD Frauenfelder and Kaab (2000) Lehman - Upper Lobe -0.0185698 21.5748 2719.14 95.83 651.63 1.2765 3327 0.0021 -1.295069 O Hoelzle and Haeberli (1995) Lehman - Middle Lobe 0.06730613 19.8612 2554.93 95.83 651.63 1.62135 3327 0.0021 -1.554043 Q. C Frauenfelder et al. (2001) Lehman - Lower Lobe 0.150897 19.0907 2481.09 95.83 651.63 1.776407 3327 0.0021 -1.62551 a Hoelzle (1996) Jeff Davis NW Slope 0.2254875 18.792 2452.47 95.83 651.63 1.836519 3327 0.0021 -1.611031 3o "O Funk and Hoelzle (1992) North Fork Baker Cirque 0.07695813 22.0284 2762.61 95.83 651.63 1.185216 3327 0.0021 -1.108258 o Teresa Cirque 0.19446277 19.8036 2549.41 95.83 651.63 1.632941 3327 0.0021 -1.438478 Big Canyon - Mt Moriah 0.3843 19.3752 2508.36 95.83 651.63 1.719154 3327 0.0021 -1.334854 Q.CD Mean 5T —> -1.423892

■D Table 2.3; Snake Range temperature estimates calculated from Neoglacial rock glaciers following, Greenstein(1983), Wolfe (1992), CD Hoelzle (1992), Hoelzle (1996), Frauenfelder and Kaab (2000), and Frauenfelder et al. (2001). C/) C/) 45

0.8 Modem MAAT Neoglacial MAAT 0.6 U 0.4 ^ 0.2

< - 0.2 ' S -0.4 - ^ -0.6 •

1 - 0.8 - I -1.0 -

,76028887 + 0.022465355 -1.4 0651

- 1.6

- 1.8 d) 0) cd x> g- I 00

Figure 2.9: Comparison of modern and Neoglacial MAAT calculated for the terminal elevation of Snake Range rock glaciers.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46 depression estimates in the Southwest (Wayne, 1984). Information about winter snow

cover is not available for the Snake Range, but these anomalously low temperature

estimates may be related to a winter snow cover of greater than 50 cm. Snowcover

greater than this critical thickness can produce erroneous results (Harris 1981, a, b, c).

The average temperature depression estimate of-1.42°C, calculated using MAAT and

potential direct solar radiation, is close to the range of previously calculated Neoglacial

cooling estimates of-1.5 ° - to 2°C (Wayne, 1984).

Other Peri glacial Features

The spatial distribution of patterned ground is often controlled by lithology, clast size,

precipitation, moisture conditions, and slope (Washburn, 1973; Troll, 1994; French,

1996; Davis, 2000; Benn and Evans, 2001). However, the size and elevation of relict

permafrost features can be used to estimate paleotemperature and extent of permafrost

during the full and late glacial conditions (Péwé, 1969; Washburn, 1980; Harris, 1981a;

Péwé, 1983; and Wayne, 1983).

The site with the most extensive preservation of stone-banked solifluction lobes is

the east to southeast facing slope of Jeff Davis Peak. The lobes on Jeff Davis Peak are

most easily identified in the late spring when snow remains in the hollows around and

between the lobes. These lobes range in length from 3 to 7 meters and occur on slopes

ranging from 21 to 33° degrees. Solifluction lobes are also present on the northern

slopes of Bald Mountain, Mt Moriah, Johnson Pass and Baker Ridge. These features

range in length from 0.5 to 8 m on slopes ranging from 27 - 36° (Fig. 2.10).

The most extensive area of sorted polygons and stone circles is located on “The

Table”, a relict upland surface on the eastern side of Mt Moriah. The large diameter of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47

Km##

t, f e ^ p4rw ^ 3

rfîs-'f > 'i- " m p

'-;"W Figure 2.10: (a) well developed solifluction lobes on a east to northeast facing slope on Jeff Davis Peak and (b) view of well developed solifluction lobes on Mt Moriah. The inset is an 1:12,000 aerial photo illustrating how extensive the lobes on Mt Moriah.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48 the polygons and circles on Mt. Moriah are comparable to patterned ground of

Wisconsin age in the Colorado Front Range (Pewe, 1983). Sorted polygons range in

diameter from 4.0 to 5.2 m, composed of tabular blocks about 0.3 to 1.0 m wide. Stone

circles range in diameter from 1.3 to 1.8 m. Other smaller stone polygons and circles

were found on Lincoln Peak, Johnson Pass, Baker Ridge, and on the lower lobe of the

Lehman rock glacier. These features range in size from 0.3 - 3.5 m and occur in an

elevation range of 3332 to 3664 masl. Patterned ground primarily occurs on

cryoplanation temaces and relatively flat surfaces in Prospect Mountain Quartzite.

Prospect Mountain Quartzite is the dominant lithology with the exception of stone

polygons that developed on Lincoln Peak in Pole Canyon Limestone and stone circles

that developed in Johnson Pass in Snake Creek-Williams Canyon granite (Fig. 2.11).

Most of these features are relatively small and it could be argued that they developed

because of less intense sorting. However, the larger polygons and circles developed in

competent, quartzite debris, and the smaller features developed in less competent

limestone and granite parent material. This suggests that the development of these

features may be a function of lithology rather than MAAT. Stone polygons and circles

developed adjacent to areas affected by glaciation with the exception of small stone

circles identified on the lower lobe of the Lehman rock glacier. This suggests some

areas developed permafrost features during the Neoglacial. However, other than the

sorted circles on the lower lobe of the Lehman rock glacier, it is impossible to

differentiate between Full Glacial and Neoglacial features without absolute ages.

Five cryoplanation terraces were identified in close proximity to patterned ground.

The terraces, which are located predominantly on northeast and northwest-facing slopes,

most likely developed in response to nivation and long periods of freeze-thaw sorting.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49

(A)

Figure 2.11: The various types of patterned ground observed on The Table and on Johnson Pass. (A) Sorted circles developed in quartzite on The Table (scale =1.5 m), (B) sorted circles developed in quartzite north of The Table (scale =1.5 m), and (C) non-sorted circle developed in granite on Johnson Pass (scale =1.3 m).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50 The largest terrace occurs on Mt Moriah as “The Table”, at approximately 3700 masl

that has an area of 1,163 m^. This terrace is located on the northeast slope of Mt Moriah

and has little topographic protection from incoming solar radiation. Two terraces are

located on the ridge between Bald Mountain and Wheeler Peak; one is located on the

ridge between North Fork Baker Cirque and Baker Cirque, and another is located

between Baker Cirque and Johnson Cirque in Johnson Pass (Fig. 2.12). They range in

size from approximately 43 m^ to 66,931 m^. The distribution of the terraces is

consistent with the idea that snow patches tend to accumulate away from prevailing

winds and direct sunlight. In the Great Basin, prevailing winds on the crest of the ranges

usually come from the west and southwest (Houghton, 1969).

Moderately developed garlands are rare in the Snake Range. This may not reflect a

lack of landform preservation, but rather that the slopes on which garlands typically

occur are steep and often inaccessible. So it is possible that other sites exhibit garlands

that were not identified (Fig. 2.13). Garlands were identified on a south-facing slope of

Jeff Davis Peak and on a south to southeast-facing slope on Baker Ridge. The three

sites with garlands are all on slopes ranging from 29° to 33° in an elevation range of 3500

to 3700 masl. Garlands range in size from 1.0 to 4.0 m long and approximately 8 to 15

m wide.

Three protalus ramparts occur in two locations; two are located at the head of North

Fork Baker Cirque and one is below a north-facing cliff in Teresa Cirque (Fig. 2.13).

The two identified in North Fork Baker Cirque are east to northeast-trending lobate

landforms, and the rampart in Teresa Cirque is a northwest-trending complex landform.

These features range in size from 3 to 4 meters high and 15 to 30 m long, and they lack

evidence of fine-grained sediment. The long axis of each landform is parallel to the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51

W^7

"W

4û4C-ij:steù»«:'.«5

Figure 2.12: (a) A view of two cryoplanation terraces on Wheeler Peak ridge (looking north to northeast) and (b) a view looking east of "The Table" on Mt Moriah in the Northern Snake Range, an extensive well developed cryoplanation terrace.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52

m

# 5 ^

Figure 2.13: (a) A view looking north to northwest of moderately developed garlands on a south-facing slope of Jeff Davis Peak and (b) a view looking east towards a protalus rampart and talus cone complex in Teresa Cirque.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53 source talus slope, and a well-developed nivation hollow separates each feature from the

talus slope.

Discussion

Paleoclimatic Significance of Snake Range Periglacial Features

The temperature thresholds for continuous and discontinuous permafrost are

discussed by Fenians (1965), Billings and Mooney (1968), Brown (1970), Brown and

Péwé (1973), Washburn (1979), and Wang and French (1994). Estimated MAATs for

discontinuous and permafrost range from -1°C to -13°C. We use the estimates provided

by Billings and Mooney (1965) because they report more significant figures (e.g. - 3.3°C

to -12.4°C). Temperature depression estimates since the development of Full Glacial

permafrost features were calculated using modem MAAT and regional lapse rates.

Temperature depression estimates using lapse rates from Dohrenwend (1984) range

from -5.02°C, calculated frorfi solifluction lobes located on a north-facing slope of Jeff

Davis Peak, to -7.76°C from a protalus rampart in North Fork Baker Creek. The

calculated temperature depression estimates have a mean value of -6.61°C (Table 2.4).

Temperature depression estimates using lapse rates from Greenstein (1983) and Wolfe

(1992) range from -3.88°C, calculated at a pro talus rampart in Teresa Cirque, to -6.43°C

from solifluction lobes on the north-facing slope of Jeff Davis Peak, with a mean value

of -5.32°C (Table 2.4). Temperatures calculated using both lapse rates are plotted

against one another in Figure 2.14 and have a correlation coefficient of 0.84. The

calculated mean values o f-6.61°C and -5.32°C for Full Glacial cooling are within the

range of previously calculated full glacial cooling estimates of Broecker and Orr (1958),

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD ATg*. C/) Location* Feature Elevation MAATd» MAAT,v»« AT\v** C/) BR Solifluction Lobes 3600 -2.01 -5.84 1.96 -5.89 BR Garlands 3523 -1.43 -6.42 2.34 -5.51 BR Cryoplanation Terrace 3592 -1.95 -5.9 2 -5.85 BR Stone Polygons 3664 -2.5 -5.35 1.64 -6.21 8 BR Solifluction Lobes 3441 -0.8 -7.05 2.75 -5.1 JDR Garlands 3600 -2.01 -5.84 1.96 -5.89 JDR Garlands 3697 -2.75 -5.1 1.47 -6.38 JDR Solifluction Lobes 3560 -1.71 -6.14 2.16 -5.69

CD JDR Solifluction Lobes 3708 -2.83 -5.02 1.42 -6.43 JDR Solifluction Lobes 3576 -1.83 -6.02 2.08 -5.77 JP Stone Circles 3461 -0.95 -6.9 2.65 -5.2 3. 3 " JP Solifluction Lobes 3412 -0.58 -7.27 2.9 -4.95 CD JP Cryoplanation Terrace 3443 -0.82 -7.03 2.74 -5.11 CD ■D LP Stone Polygons 3464 -0.98 -6.87 2.64 -5.21 O Q. MM Solifluction Lobes 3506 -1.3 -6.55 2.43 -5.42 C a MM Solifluction Lobes 3392 -0.43 -7.42 3 -4.85 3O MMT Stone Polygons 3358 -0.17 -7.68 3.17 -4.68 "O MMT Stone Circles 3362 -0.2 -7.65 3.15 -4.7 O MMT Cryoplanation Terrace 3367 -0.24 -7.61 3.12 -4.73 NFBC Protalus Rampart 3347 -0.09 -7.76 3.22 -4.63 CD Q. NFBC Protalus Rampart 3369 -0.25 -7.6 3.11 -4.74 TC Protalus Ramparts 3198 1.04 -6.81 3.97 -3.88 WPR Cryoplanation Terrace 3700 -2.77 -5.08 1.46 -6.39 ■D WPR Cryoplanation Terrace 3321 0.11 -7.74 3.35 -4.5 CD Mean —> -6.610417 -5.32125

C/) C/) * WPR = Wheeler Peak Ridge, TC = Teresa Cirque, NFBC = North Fork Baker Cirque, MMT = Mt Moriah Table, MM = Mt Moriah, LP = Lincoln Peak, JP = Johnson Pass, JDR - Jeff Davis Ridge, and BR = Baker Ridge. ** Lapse Rates (D) are derived from Dohrenwend (1984), (W) are derived from Greenstein (1983) and Wolfe (1992).

Table 2.4: Lapse rates and climate data used to calculate MAAT and temperature depression. Ln 55

- 3.6

W) r = 0.8410 -4.2 y = -9.79666097 - 0.676938656*.x

^ -4.4

-4.6

-5.2

-5.4

-5.6

- 6.2

-6.4

- 6.6 •8 -7.5 ■7 -6.5 6 -5.5 ■5 -4.5 Dohrenwend Temp Change

Figure 2.14: Regression of temperature estimates calculated using lapse rates from Dohrenwend (1984) versus temperature estimates calculated using lapse rates from Greenstein (1983) and Wolfe (1992).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 Brackenridge (1978), and Dohrenwend (1984). Temperature estimates here were

calculated using a 30-m DTM for the underlying calculations. Temperatures were

calculated for each periglacial feature, with 30 meters added and subtracted to the actual

elevation to assess the range of error introduced by the digital terrain model. A

comparison of the results using all three elevation ranges is provided in Table 2.5.

The spatial distribution of rock glaciers and smaller periglacial features are strongly

influenced by potential direct radiation (Funk and Hoelzle, 1992; Hoelzle, 1992; Hoelzle,

1996; and Frauenfelder et al., 2001). Potential direct radiation was calculated for the

Method Mean To Mean Tw AT d +30m AT q -30m ATw ATw -30m +30m Elev -6.6 rC -5.32°C - - - - Elev -H30 -6.40°C -5.48°C +0.26°C - -0.19°C Elev-30 -6.75°C -5.18°C - -0.09°C - +0.11°C

Table 2.5: Comparison of possible error introduced by using a 30-meter digital terrain model to estimate Full Glacial cooling. (Elev+30 = orginal DEM elevation plus 30 meters, Elev-30 = original DEM elevation minus 30 meters, and the AT +/- 30m values represent the estimated error in temperature estimates caused by possible errors in the elevation estimates).

lower limit of each rock glacier and for the mean elevation of each periglacial feature

identified in the Snake Range at the winter and summer solstices (Figs. 2.15 and 2.16).

Winter potential direct radiation values range from 0.0 to 8.07 MJm"^d“' and summer

radiation values range from 14.68 to 22.42 MJm"^d"\ Multiple regression analysis of

the solar insolation data implies that during the winter, potential direct solar radiation

decreases with increasing elevation and that during the summer, potential direct solar

radiation increases with increasing elevation (Fig. 2.17). This correlation is best

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57

I

I .S '5 a a k. a c g

Periglacial Features

Figure 2.15: Periglacial features versus winter radiation values illustrating the relatively low radiation values intercepted by rock glaciers.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58

Periglacial Features

Figure 2.16: Periglacial features versus summer radiation values.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) C/)

O) N) Summer Radiation vs Elevation Regression Results; F = 0.4363; y = 2664.61417 + 26.4648455*x ■D8 Winter Radiation vs Elevation Regression Results: f = 0.5596; y = 3281.79935 - 29.9117799*x g 3348.54470

3318.52350

3291.93460 3. I 3 " ^ 3267.06185 CD S ■DCD f g 3242.18910 O Q. © C 3218.59775 a 3O "O CL g 3193.72500 o 3168.85225 CD Q. n> 3145.26090

3118.67200 Elevation vs Summer Radiation ■D Elevation vs Winter Radiation CD I 3092.08310 C/) C/) I 3065.49420 I 4 6 8 10 12 14 16 Potential Direct Radiation (MJ

VOLA 60

3348.54 3308-66 & 3275-'2'^ § 3240-47 3201 .Oi 1 I 3173.51 3133-83 3105-31 3065-49

Figure 2.18: A surface plot of a multivariate regression between elevation and summer and winter radiation values.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61 illustrated as a 3D surface plot illustrating the summer and winter solstice radiation

values at any given elevation (Fig. 2.18). This relationship most likely reflects changes

in aspect and greater topographic interference at higher elevations in the range.

Equilibrium Line Altitude Reconstruction

Two episodes of glaciation have been identified and described in the interior Great

Basin. These are the Angel Lake and Lamoille advances, which correlate to Tioga and

Tahoe advances, respectively, based primarily on geomorphic characteristics and

stratigraphie position (Blackwelder, 1931; Blackwelder, 1934; Sharp, 1938; Wayne,

1984; Peigat, 1980; Osbom, 1990; and Osborn and Bevis, 2001). The spatial extents of

Angel Lake and Lamoille glaciers in the Snake Range were reconstructed using a

combination of field evidence and aerial photography mapping (Porter, 1975). A variety

of geomorphic features were used to delineate the extent of glaciation in each valley,

including terminal and lateral moraines, changes in valley morphology, trimlines, and

truncated spurs. Calculated values for the elevation of Angel Lake glacial ice in the

Snake Range have a mean of 3341 masl, and the mean of the lowest terminal extent of

Angel Lake glaciers is 2783 masl. The mean of the highest extent of Lamoille glacial ice

is 3349 masl, and the mean of the lowest extent of ice is 2478 masl. There is significant

uncertainty in the actual spatial extent of some Angel Lake glaciers and in the lower

limit of most Lamoille glaciers because many of the glaciers coalesced, making the

actual lowermost limit difficult to delineate (Fig. 2.19). The Lehman glacier developed

in the most protected and northerly facing cirque, and is assumed to have been more

robust than the Stella and Teresa systems. However, it most likely had a smaller

accumulation area and, unlike the Teresa and Stella lobes, it was confined to steep valley

walls. It is possible that the Teresa and Stella lobes could have been more extensive

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62

%

P

Ik %.

Figure 2.19: A diagram illustrating the geometry of the Lehman Creek glacial lobe. It is difficult to delineate the actual extent and influence of the Lehman, Teresa and Stella lobes that contributed to the overal geometry of the full valley lobe.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63 because they had a larger accumulation area and breached their respective cirque basins

at a higher elevation than did the Lehman lobe. The Lehman Creek glacial system most

certainly coalesced into a large valley glacier, however differentiating between the lobes

emanating from Stella, Teresa, and Lehman cirques is highly subjective. A summary of

the characteristics for each reconstructed Angel Lake and Lamoille glacier in the Snake

Range is provided in Table 2.6.

Absolute ages for each glaciation are lacking because of a number of factors: (1) the

moraines lack organic material suitable for radiocarbon dating, (2) the coarse resistant

Prospect Mountain Quartzite does not weather into material suitable for luminescence

dating, and (3) lateral and terminal moraines lack suitable boulders for cosmogenic

surface dating. Most Lamoille-age terminal moraines have been eroded, and those that

remain have been significantly dissected. Relative ages calculated from weathering

parameters were not possible because of the lack of well-developed patina on Prospect

Mountain Quartzite, with the exception of Snake Creek that is intruded by the Snake

Creek-Williams Canyon pluton.

Three techniques were used to reconstruct former ELAs in the Snake Range: the toe-

to-headwall altitude ratio method (THAR), the accumulation area ratio method (AAR),

and the balance ratio method (BR). Reconstructed AAR and BR ELAs for glaciers in

Lehman and Baker Creek are considered tentative because of sparse geomorphic

evidence to accurately delineate accumulation area zones. The mean ELAs calculated

using each technique and the statistics that were calculated from first and second order

trend interpolations are summarized in Table 2.7.

There is a high correlation between the three methods (THAR, AAR, BR) primarily

because each method uses the same 20-22 reconstructed glaciers, so they share similar

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C 8 Q.

■D CD

C/) Location Aspect Area (m^) Length (km) Area (m^) Length (km) 3o' Southern Snake Range Angel Lake Lamoille* Angel Lake Lamoille Angel Lake Lamoille O Johnson Cirque 094 1366516.281 2.690 5658556.754 19619.471 3389 3328 2831 2508 Shoshone Cirque 064 1511089.477 2.700 5658556.754 19619.471 3344 3344 2919 2508 8 Washington Cirque 089 425511.256 1.650 5658556.754 19619.471 3386 3309 2795 2500 "O N Fork Baker Creek 049 2452606.111 3.670 5608085.329 20524.802 3453 3362 2772 2491 Baker Cirque 065 1964349.264 3.200 5608085.329 20524.802 3351 3337 2772 2491 Bald Mountain N 002 312850.529 0.980 661206.042 5869.889 3199 3125 2926 2516 Bald Mountain E 041 827827.928 1.970 2444781.624 10647.009 3488 3238 2856 2298 CD Bald Mountain W 077 553435.760 1.450 755738.038 5451.302 3496 3261 2880 2733 Williams Canyon 327 822807.694 2.610 N/A N/A 3362 N/A 2620 N/A 3. Pyramid Peak N 006 N/A N/A N/A N/A 3390 N/A 2772 N/A 3 " CD Pyramid Peak E 041 995999.092 2.870 N/A N/A 3434 N/A 2865 N/A Pyramid Peak W 077 283698.126 2.070 N/A N/A 3339 N/A 2772 N/A ■DCD O Baker Creek Ridge 041 N/A N/A N/A N/A 3389 N/A 2772 N/A Q. C Stella Lake 064 3621805.651 2.76 5723071.627 17508.458 3287 3287 2783 2405 Oa Teresa Cirque 027 3621805.651 2.94 5723071.627 17508.458 3508 3508 2783 2405 3 Lehman Cirque 041 3621805.651 3.300 5723071.627 17508.458 3766 3654 2885 2405 ■D O Decathalon Canyon 176 330438.169 3.090 N/A N/A 3382 N/A 3137 N/A Lincoln Peak W 357 274495.011 1.32 N/A N/A 3299 N/A 2986 N/A

CD Lincoln Peak N 007 196453.867 1.520 N/AN/A 3148 N/A 2727 N/A Q. Lincoln Peak E 048 87897.303 0.780 N/A N/A 3167 N/A 2909 N/A Granite Peak 041 243278.439 1.330 N/A N/A 3144 N/A 2735 N/A

■D CD Northern Snake Range Big Canyon 316 1829843.923 4.120 N/A N/A 3536 N/A 2714 N/A C/) C/) Mt Moriah 1 048 655815.876 2.070 N/AN/A 3124 N/A 2477 N/A Mt Moriah 2 041 839371.807 2.860 N/A N/A 3162 N/A 2420 N/A Deadman Creek 092 675469.679 3.090 N/A N/A 3194 N/A 2479 N/A MEAN 1250689.661 2.501818182 4474798.319 15854.69009 3806.227273 3341.181818 3163.045455 2478.181818

Table 2.6: Summary of the characteristics of reconstructed Angel Lake and Lamoille glaciers. 2 CD ■ D O Q. C g Q.

■D CD Method Number Mean Local Polynomial Local Polynomial Global Polynomial Global Polynomial WC/) of Altitude First Order Surface Second Order Surface First Order Surface Second Order Surface 3o" 0 Cirques (m) RMSE (m) r: RM SE (m) r: RMSE (m) r^ RMSE (m) r: 3 THAR* 22 CD 8 0.50 3065.65 112.9 0.0084 159.2 0.9777 115.8 0.0017 161.9 0.9763 ■D THARl 11 (O'3" 0.50 2909.68 101.9 0.2655 80.6 0.9902 108.4 0.2235 83.34 0.9763 AAR 20 1 3 0.65 3034.59 125.9 0.7927 108.8 0.0781 136 0.595 112.1 0.0592 CD BR 20 "n 0.65 2895.98 147.9 0.2655 230.9 0.108 147.2 0.2235 243.7 0.1331 c 3. 3 " CD Comparison of ELA Calculation Methods ■DCD O Q. C Method n r r: P Oa 3 ■D AAR vs THAR 20 0.745 0.555 0.0002 O AAR vs BR 20 0.707 0.5 0.0005 THAR vs BR 20 0.868 0.754 7E-07 CD Q. * Global Polynomial Interpolation Parameters (81% Global and 19% Local)

■D Table 2.7: Summary of mean ELA's and summary statistics calculated using the THAR, AAR and BR methods. CD

(/)

o \ L /i 66

3400 n = 20 r' = 0.5545 r = 0.7447 p = 0.0002 y = 973.061312 + 0.672992787*% 3200

3100

3000

2900

2800

2700 2700 2800 2900 3000 3100 3200 3300 3400 ELA Calculated With THAR = 0.50 (m)

Figure 2.20: Comparison of ELAs calculated using the AAR and THAR methods.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67

3200

n = 20 i^ = 0.7540 o 3100 r= 0.8683 p = 0.0000007 y = 683.553966 + 0.722253355*x

3000

2900

2800

2700

2600 2700 2800 2900 3000 3100 3200 3300 3400 ELA Calculated With THAR = 0.65 (m)

Figure 2.21 : Comparison of ELAs calculated using the BR and THAR methods.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68

3200

n = 20 1= = 0.4998 3100 r = 0.7070 p = 0.0005 y = 921.36305 + 0.650702627*:

? 3000

2900

J 2800 CQ U 3 fd 2700

2600 2800 2900 3000 3100 32002700 3300 3400 ELA Calculated With AAR = 0.65 (m)

Figure 2.22: Comparison of ELAs calculated using the BR and AAR methods.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69 area to elevation characteristics (Figs. 2.20, 2.21, 2.22). The only major exception is the

Decathalon Canyon glacier, which has the highest calculated ELA in the Snake Range,

probably because this canyon faces directly south.

Paleoclimatic Significance of Estimated Equilibrium Line Altitudes

Equilibrium line altitudes calculated using different methods for twenty

reconstructed Angel Lake glaciers in the Snake Range exhibit a high correlation. The

mean ELA from each method was subtracted from the modern ELA of 3673 masl at the

Lehman Glacier on Wheeler Peak to calculate ELA depression since the last Full Glacial

and the temperature change associated with this depression. Temperature estimates were

calculated using lapse rates from Dohrenwend (1984) and Greenstein (1983) and Wolfe

(1992). The estimates using Dohrenwend's lapse rate of -0.76°C/km provides the most

realistic values and are assumed to most accurately reflect paleo-temperature (Table 2.8).

Location THAR al 0.50 AAR 0.65 BR 0.65 Mean 3065.68 3024.53 2909.98 Modem ELA 3673.00 3673.00 3673.00 ELA Depression 607.32 648.47 763.02 AT d -4.55 °C -4.86 T -5.72 °C ATw -3.04°C -3.24 °C -3.82 °C Angel Lake Mean Value AT d -5.05 °C A ngel Lake Mean Value ATw -3.36 °C

Table 2.8: Mean ELA values, estimated ELA depression since the last Full Glacial, and the calculated temperature change associated with this depression. The mean temperature change using each lapse rate (Dohrenwend, 1984 and Wolfe, 1992) is also provided.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70 The THAR method indicates an average ELA depression of 607 meters with a

temperature change of -4.55°C. The AAR method calculates an average ELA

depression of 573 meters with a temperature change of -4.29°C, and the BR method

suggests an ELA depression of 763 meters with a calculated temperature change of -

5.72°C. These values are consistent with previously calculated temperature depression

estimates for the last Full Glacial in the western Great Basin (Table 2.9).

Reference Basis for estimate Location A Tem p °C Broecker and Orr, 1958 Hydrologie budget Lake Lahonton, NV -5.0 Snyder and Langbein, 1962 Snow line lowering Lake Spring, NV -3.6 Brackenridge, 1978 Snow line lowering Southwest, USA -7.0 Mifflin and Wheat, 1979 Hydrologie budget Pluvial lakes in NV -2 8 Dohrenwend, 1984 Nivation landforms Westem GB -7.0 Benson, 1986 Pluvial lakes W estem GB -7.0 Benson and Thompson, 1987 Pluvial lakes W estem GB -7.0 t o -10 Bevis, 1995 ELA estimates W estem GB -4.0 to -8.0 Mean => -5.86

Table 2.9: Summary of previously calculated temperature depressions during the last Full Glacial in the wesem United States.

Conclusions

This study presents new information regarding the location and development of

permafrost in the high elevations of the Snake Range, Nevada. It is not surprising that

permafrost features are present at such high elevations in a mountain range with the only

modem glacier in the interior Great Basin and a very apparent history of late Pleistocene

glaciation. Many of the periglacial landforms identified in this study have been

described in mountain ranges throughout the southwest (Smith, 1936; Richmond, 1962;

Blagbrough and Breed, 1967; Blagbrough and Farkas, 1968; Blagbrough and Breed,

1969; Galloway, 1970; Blagbrough, 1971; Barsch and Updike, 1971; Péwé and Updike,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71 1976; Blagbrough and Breed, 1976; Wayne, 1984; Nicholas, 1994; and Nicholas and

Butler, 1996).

Neoglacial temperature depression estimates, calculated using modem freezing and

thawing indices for relict rock glaciers range from -0.25°C to -1.00°C. These estimates

are anomalously low and are thought to reflect a winter snow cover greater than 50 cm.

However, the temperature gradient illustrated by these estimates is identical to the

temperature gradient calculated using temperature estimates defined using MAAT and

potential direct solar radiation. The temperature estimates calculated using the

methodology described by Frauenfelder and Kaâb (2000) and Frauenfelder et al. (2001)

are 0.35° to 0.97°C lower than those calculated using freezing and thawing indices. The

calculated mean of -1.42°C for the higher estimates are more consistent with previously

published Neoglacial temperature estimates for the Great Basin (Wayne, 1984).

However, the MAAT calculated for each rock glacier terminus could not be corrected for

the effect of topographic shielding or local orographically-induced microclimates that

could significantly depress the MAAT.

Using temperature thresholds for continuous, discontinuous and sporadic permafrost,

as defined by Billings and Mooney (1968), the MAAT for relict permafrost features is

assumed to be approximately -7.8°C. Comparing modem and Full Glacial MAAT in the

Snake Range, calculated using regional lapse rates, results in an average depression of

the MAAT by approximately -5.16°C to -6.61°C. These estimates assume that winter

precipitation in the Great Basin during the last full glacial was not significantly greater

than present. This assumption is supported by previous paleoclimate studies in the

southwest (Galloway, 1970; Brackenridge, 1978; Spaulding et al., 1983; and Zielinski

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72 and McCoy, 1987). Not only do these estimates of full glacial MAAT compare

favorably with other estimates for this region (Table 2.9), they are also similar to the

MAAT depression of -4.55°C to -5.77°C calculated from reconstructed Angel Lake

ELAs.

Temperature estimates from both relict permafrost features and ELA depression are

consistent with previously published temperature gradients (Bevis, 1995). Bevis (1995)

calculated MAAT depressions of -8.0°C in the Ruby Mountains northwest of the Snake

Range, -5.0°C in the Deep Creek Mountains, to the northeast of the Snake Range, and -

4.0°C in the Tushar Mountains in south-central Utah. Estimates from landforms in the

Snake Range are consistent with the southeasterly depression of Full Glacial MAAT

estimates described by Bevis (1995). Periglacial deposits in the Snake Range are

inactive and appear to be relict features that most likely co-evolved with the onset of

alpine glaciation, although it is possible that some features were active during the

Holocene. Many of the landforms are similar in size and distribution as those previously

described in the Colorado Front Range of Wisconsin age (Pewe, 1983). The presence of

these features indicates that an extensive periglacial environment existed in the higher

elevations and protected niches of the Snake Range during the last Full Glacial and early

déglaciation.

Ackno wledgmen ts

We would like to thank the Arizona-Nevada Academy of Science, Colorado

Scientific Society, and The American Alpine Club, for financial support. The staff of

Great Basin National Park provided logistical support and T&D’s provided a place to

relax after a day of fieldwork. Thanks also to Chad Hendrix for his company in the field.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 References

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76

This reproduction is the best copy available.

UMI’

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Lee, D.E., Stem, T.W., Mays, R.W., and Van Loenen, R.E., 1968, Accessory zircon from granitioid rocks of the Mt Wheeler Mine area, Nevada. United States Geological Survey Professional Paper 600-D: 197-203.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3

GEOMORPHIC AND GPR EVIDENCE FOR THE POSSIBLE GENESIS OF A

TONGUE SHAPED ROCK GLACIER, SOUTHERN SNAKE RANGE, NEVADA

This paper has been prepared for submission to Permafrost and Periglacial Processes and is presented in the format of that journal. The complete citation will is:

Van Hoesen, J.G., Snelson, C., and Omdorff, R.L., 2003, Geomorphic and GPR evidence for the possible genesis of a tongue shaped rock glacier, southern Snake Range, Nevada. Permafrost and Periglacial Processes (IN PREP)

80

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81

Introduction

Rock glaciers have been recognized and studied as discrete geomorphic landforms

for over a century. While many questions concerning the conditions for their initial

development, evolution, and preservation have been investigated, the debate over a

glacial or periglacial origin is still controversial even though there is increasing evidence

these landforms evolve in both environments (Krainer and Mostler, 2000; Humlum,

2000; and Ishikawa et al., 2001).

The term rock glacier refers to a tongue or lobate shaped body of angular boulders

and fine material that contains either periglacial ice filling subsurface voids, (i.e.- ice

cemented), or buried glacial ice, (e.g.- ice cored), exhibiting ridges and furrows and has

a steep frontal snout at the angle of repose. Discussion by supporters of the “permafrost”

origin can be found in the following references (Wharhaftig and Cox, 1959; Barsh, 1987;

1988; 1992; and 1996; Berthling et al., 2000; Gui and Cheng, 1988; Gorbunov, 1983;

Haeberli and Schmid, 1988; Haeberli et al., 1988; 1992; 1998; Isaksen et al., 2000;

Ishikawa, et al., 2001; Jakob, 1992; 1994; King et al., 1987; Vonder Mühll and Haeberli,

1990; Vonder Mühll and Schmidt, 1993), while rock glaciers attributed to a “glacial

origin” are discussed by Benedict et al. (1986), Calkin et al. (1987), Clark et al. (1994

and 1996), Ellis and Calkin (1979), Embleton and King (1975), Evans (1993), Eyles

(1978), Gardner (1978), Haeberli (1989), Humlum (1982; 1988a; 1988b; and 1996),

Ishikawa, et al. (2001), Johnson and Laçasse (1988), Krainer and Mostler (2000),

Lliboutry (1953 and 1990), Martin and Whalley (1987), Outcalt and Benedict (1965),

Potter (1972), Whalley (1974 and 1992), Whalley and Martin (1992), Whalley et al.

(1994 and 1995) and White (1975). However, proponents of both origins generally

agree that active rock glaciers develop in alpine areas characterized by high rates of talus

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 2 production and local permafrost conditions (Corte, 1987). Thus, alpine environments

with high topographic relief are ideal locations because they provide the necessary talus

and local climatic conditions for the development of a rock glacier. Rock glaciers

typically exhibit two strati graphically and texturally distinct layers: an upper, active

layer (1 - 5 m thick) composed of blocky debris, and a lower layer (20 - 30 m thick)

composed of ice (either massive or interstitial) and talus derived debris. However, there

is still uncertainty regarding the specific mechanics responsible for the initiation and

genesis of rock glaciers (Humlum, 1998, 2000).

Considerable research has been conducted to address the long-standing debate

concerning whether rock glaciers should be classified as glacial or periglacial

geomorphic landforms. A first-order approach involves investigating the internal

composition of rock glaciers to identify whether they contain discontinuous lenses of

interstitial ice or a remnant core of glacial ice. Previous research on the internal ice

content and structure of rock glaciers has involved direct sampling of drill cores,

trenching or seismic reflection requiring explosives (White, 1971; Barsch et al., 1979;

Haeberli et al., 1988; Cui and Zhu, 1989; Vonder Mühll and Holub, 1992; Barsch, 1996;

Haeberli and Vonder Mühll, 1996; Elconin and La Chapelle, 1997; Fisch et al., 1997;

Konrad et al., 1999; Vonder Mühll et al., 2000; Musil et al., 2002; and Zurawek, 2002).

However, the study area is located in Great Basin National Park (GBNP), therefore any

attempt to investigate the internal characteristics of the rock glacier required a non-

intrusive and non-destructive technique. Previous research has illustrated the merits of

using ground-penetrating radar (GPR) to investigate the internal morphology of rock

glaciers and talus rich permafrost (Berthling et al., 2000; and Isaksen et al., 2000;

Degenhardt et al., 2000; Degenhardt et al., 2001a; 2001b; Hinkel et al., 2001; Volkel et

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83 al., 2001; S ass and Wollny, 2001; and Degenhardt e.t al., 2003). Therefore, we felt

confident using GPR as an alternative for the non-destructive evaluation of subsurface

structures in the Lehman rock glacier.

The goals of this study were to: (1) investigate the geomorphology of the Lehman

rock glacier, (2) improve our understanding of the processes controlling the development

of the Lehman rock glacier by investigating the internal structure using GPR, and (3) use

geomorphic and GPR data to evaluate our working hypothesis regarding the genesis of

the Lehman rock glacier. This study is not an attempt to resolve the debate over a glacial

versus periglacial origin for rock glaciers. Rather, we present results from a study of the

Lehman rock glacier in the southern Snake Range, Nevada and suggest an alternative

“recessional genesis” for some tongue-shaped rock glaciers in alpine regions.

Study Area

The southern Snake Range is located in east-central Nevada in the Basin and Range

physiographic province (Fig. 3.1). The Snake Range is an uplifted horst, bounded to the

east by Snake Valley and to the west by Spring Valley. Alpine environments throughout

the Basin and Range produce drastically different microclimates from the surrounding

lower elevation valleys. Meteorological measurements have been recorded at the

Lehman Cave weather station, located at an elevation of 2073 meters above sea level

(masl), in Great Basin National Park since 1961. The modem mean annual air

temperature (MAAT) recorded at the Lehman Cave weather station is 9.59°C; the coldest

month is January (-2.69°C) and the warmest month is July (22.75°C). Mean annual

precipitation at the Lehman Cave climate station is approximately 2.40 cm; the greatest

amount of precipitation falls in May (3.23 cm) and the least falls in July (1.63 cm).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84

NEVADA

?

Figure 3.1: Location map of the Southern Snake Range with a shaded relief map showing the spatial relationship of the Lehman rock glacier with the surrounding topography.

Reproduced witti permission of ttie copyrigfit owner. Furtfier reproduction profiibited witfiout permission. 85 Average mean annual temperatures for the entire park can range from -8°C to 30°C, and

average precipitation from the valleys to the high peaks region can vary from less than

12 cm to greater than 50 cm (Houghton et al., 1969).

Glaciated portions of the southern Snake Range are underlain by early Paleozoic

Prospect Mountain quartzite, Pole Canyon limestone, and Pioche shale intruded by the

Snake Creek-Williams Canyon pluton that is Jurassic in age (Drewes, 1958; Whitebread,

1969; Lee et al., 1970; Lee and Van Loenen, 1971; Lee et al., 1981; Lee and

Christiansen, 1983 a, b; Lee et al., 1986; Miller, 1995 and Miller, 1999). Glacial

features of the Snake Range were first recognized and described by early explorers

(Gilbert, 1875; Simpson; 1876; Russell, 1884; Blackwelder, 1931; and Flint, 1947), and

subsequent authors have continued to substantiate earlier reports and discuss the glacial

history and the Lehman rock glacier (Heald, 1956; Kramer, 1962; Curry, 1969; Piegat,

1980; Waite, 1974; Osborn, 1988; Osborn and Bevis, 2002). However, little research

has focused on the geomorphology, genesis, and significance of the Lehman rock glacier.

Preliminary reports have described the surface morphology and spatial extent of the

Lehman rock glacier (Kramer, 1962; Osborn, 1988; Osborn, 1990; Van Hoesen and

Omdorff, 2001; and Osborn and Bevis, 2002).

However, the internal structure of the rock glacier has never before been investigated,

and therefore it was uncertain whether it contained interstitial or massive ice. Without

understanding the internal structure and ice distribution within rock glaciers it is

impossible to thoroughly test how they develop and whether they are inactive or relict

landforms.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 Methods

We used aerial photographs and field measurements to identify and map the

geomorphology of the Lehman rock glacier. Color aerial photographs (1:24,000 and

1:12,000 scale) were obtained from the United States Department of Agriculture, and

black and white aerial photographs were obtained from the United States Geological

Survey (1:48,000). We identified and mapped surface features on aerial photos using a

geographic information system (GIS). During the summers of 2001 and 2002, these

features were later compared with field observations.

We describe and classify the rock glacier using the taxonomy of Barsh (1987) and

Corte (1987). The morphometric parameters of the rock glacier were calculated in a GIS

following the guidelines described by Barsh (1996). We also conducted a fabric analysis

(Wahrhaftig and Cox, 1959; Eskenasy, 1978; Giardino and Vitek, 1985; Perez, 1989;

Nicholas, 1994; and Thompson, 1999) of talus blocks (>0.5 m) located on three

prominent lobes of the Lehman rock glacier.

We used a Noggin Plus GPR system manufactured by Sensors and Software with

250 and 500 MHz antennas to collect GPR profiles from individual lobes of the Lehman

rock glacier over the period 19-23 August 2002. Conducting the survey at this time of

the year provided the best opportunity to use GPR because of increased access to the

rock glacier and low snow cover. The Noggin Plus instrument consists of a digital video

logger (DVL), two antennas, and a 12-volt battery. Selected GPR traces were processed

using WinEKKO v.1.0 Pro and Transform v.3.4 from Sensors and Software

(Mississauga, ON, Canada).

The GPR antennas were hand carried ~ 0.25 - 0.5 ra above the surface because large

blocks of quartzite talus cover the surface of the rock glacier lobes (Fig. 3.2).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 87

Figure 3.2: Typical surface of the Lehman Cirque rock glacier, composed of large blocks of quartzite.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The GPR unit was carried over a total of four transects; of the transects, three were

perpendicular to the flow of each lobe and the fourth was parallel to the long axis of the

upper lobe of the rock glacier (Fig. 3.3). Using the 500 MHz antenna we collected GPR

data for 4 depths: 38 m, 20 m, 10 m, and 5 m, using the 250 MHz antenna we collected

GPR data for 2 depths: 78 m and 45 m. Survey tape was used to mark 2.5 m intervals

along each transect. As the antenna passed over each 2.5-meter point, a fiduciary marker

was inserted into the radar profile. We were unable to obtain GPS coordinates for

topographic correction in the field because of steep topography in the upper portion of

the cirque. We attempted to extract GPS coordinates from a 30-meter USGS digital

elevation model (DEM) for the middle and upper lobes; however the resolution of the

DEM provided inadequate data for topographic correction. Table 3.1 summarizes the

location, antenna frequency, length, selected depth of penetration and the orientation of

each GPR profile.

Results

Geomorphologv

The Lehman Cirque rock glacier is approximately 900 m long, located in a steep

north-to-northeast facing cirque composed of Prospect Mountain Quartzite. The rock

glacier is in direct connection with the source area and it has an estimated rooting zone

elevation of 3667 masl (Fig. 3.3). The rock glacier is a complex feature containing three

distinct lobes mantled by large (0.5 to 3.0 m) quartzite boulders and composed of

poorly-sorted, fine-grained material. The surface of the rock glacier exhibits well-

developed relief (2.0 - 3.0 m) in the form of prominent furrows and ridges that are

oriented perpendicular to down-valley motion (Fig. 3.4). Most of the ridges have

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89

3652 masl

Lehman Glacier

Modem:RILA 3512 masl

f

gam»'

m

LEGEND o—o GPR traverse A Elevation markers -3272 Steep margin of rockglacier masl

Figure 3.3; United States Department of Agriculture aerial photograph (1:12,000) of the Lehman rock glacier showing the locatin of GPR transects and modem and former rock glacier initiation line altitudes (RILA).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) not included in the original manuscript are unavailable from the author or university. The manuscript was microfilmed as received.

90

This reproduction is the best copy available.

UMI'

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91 rounded crests, and the furrows are asymmetrical v-shaped features. Both the furrows

and ridges are composed of cobble-to-boulder-sized debris. The lateral margins of the

rock glacier are steep, and the upper surface of each lobe is generally convex with a

subtle southwest-to-northeast gradient.

Absolute ages are not available for the Lehman Cirque rock glacier for a number of

reasons: (1) organic material suitable for radiocarbon dating has not yet been recovered,

(2) the frost-riven nature of the quartzite boulders renders them unsuitable for

cosmogenic dating, and (3) low weathering rates of the quartzite debris does not provide

suitable material for luminescence dating. However, previous work suggests an age of

1200AD or younger for the Lehman Cirque rock glacier, based on the presence of Mono

Crater ash, and the upper lobe is thought to have formed during the Little Ice Age

(Osborn, 1990 and Osborn and Bevis, 2002).

The upper lobe is a convex landform approximately 434 m long and 206 m wide. It

exhibits well-developed arcuate furrows and ridges ranging in height from 1.5 - 3.0

meters. The frontal and lateral margins of the lobe are composed of light gray sediment

and talus. They are steep (34 - 36°), and capped by a 0.5 m thick sequence of dark brown

talus. The frontal margin of the lobe exhibits poorly developed boulder apron,s and

sparse vegetation is found growing on the surface. At the base of the terminus of this

lobe there is a well-developed, 3-4-meter-deep, arcuate trench that is oriented

perpendicular to the flow of the rock glacier (Fig. 3.4). Cobbles exposed in the trench

between the upper and middle lobe are dipping to the northeast 25 - 27 °.

The middle lobe is a moderately convex landform, approximately 265 m long and

178 m wide with moderately developed arcuate furrows and ridges that range in height

from 1

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Figure 4.4: Field photos of the Lehman Cirque rock glacier illustrating: (a) the morphology of a deep arcuate furrow at the terminus of the middle lobe, and (b) the location of other arcuate furrows and well-developed furrows and ridges on the upper lobe. VOFO 93 - 2 m. The frontal margin of this lobe is also composed of fine-grained sediment and

talus overlain by a darker sequence of blocky quartzite that is approximately 1 m thick.

The frontal slopes are steep (32 - 36°), vegetation is slightly more abundant than on the

upper lobe, and poorly developed boulder aprons are present at the base of the steep

frontal snout. The lateral margins of the lobe are difficult to distinguish because of the

presence of abundant talus and the subsequent coalescence of talus and rock glacier

margins. At the base of the frontal snout of this lobe there is also a well-developed, 2-3-

meter-deep, arcuate depression oriented perpendicular to the flow of the rock glacier.

Cobbles exposed in the trench between the middle and lower lobe, are dipping to the

northeast 20 - 23 °.

The lower lobe is a weakly convex landform. It is approximately 195 m long, 100 m

wide, and lacks well-developed surface furrows and ridges. The surface of the lower

lobe exhibits swell-and-swale topography, but it is poorly preserved. The frontal margin

is composed of fine-grained sediment overlain by weathered talus. The frontal slopes

are steep (30 - 33 °), well-developed talus aprons are present at the base of this lobe, and

the frontal snout is moderately vegetated.

The results of a statistical analysis of fabric data collected on talus blocks covering

the surface of the three rock glacier lobes are compared and summarized in Table 3.2.

The orientation and vector mean for talus blocks on each lobe are plotted on rose

diagrams shown in Figure 3.5. The vector mean ranges from 31° to 358°, the vector

resultant length ( R ) ranges from 0.92 to 0.97, and the von Mises distribution ( K ) ranges

from 6.39 to 18.99. The vector resultant length is a measure of dispersion and is

analogous to variance, except that values closer to 1.0 indicate that observations are

tightly bunched together (Mardia and Jupp, 1999; Fisher, 1993; and Davis, 1986). The

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C/) Location n R Mean von Mises Circular Circular Standard 95% Confidence F - Test t-Test Vector (p.) param eter (k ) 3o' Variance Standard Deviation E rror of Mean Interval (P) (P) O Upper Lobe 83 0.95 47.42° 9.63 0.05 18.99° 2.08° 43.34° ±51.51° <0.05 <0.05 Middle Lobe 72 0.92 358.02° 6.39 0.03 23.69° 2.79° 352.56° ±3.49° <0.05 <0.05 8 Lower Lobe 75 0.97 31.37° 18.14 0.08 13.65° 1.58° 28.28° ±34.46° <0.05 <0.05 v<■D

Table 3.2: Statistical variation between the geomorphically distinct Lehman rock glacier lobes.

CD F-Test null hypothesis is that the variances are equal t_test null hypothesis is that mean values are equal 3. 3 " CD ■DCD O Q. C Oa 3 "O O

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LRG Upper Lobe LRG Middle Lobe n=83 11=72 0°

270"23 90° 270°j

180° 180° LRG Lower Lobe n=75

^ / / / / 77Q O Z5 l'6 9 4 1

F i^re 3.5: Rose diagrams illustrating the orientation of talus block on the upper, middle and lower lobe of the Lehman Cirque rock glacier. Frequency bins were calculated at 10° intervals for the radius of each wedge. The mean vector and 99% confidence intervals are also provided. The statistics for each lobe are summarized in Table 3.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 von Mises distribution is equivalent to a normal distribution test and measures both a

mean direction (0) and a concentration parameter (k ). A s k increases, the probability of

observing a directional measurement very close to 0 increases (Mardia and Jupp, 1999;

Fisher, 1993; and Davis, 1986). Chi-Squared and F-Tests were calculated between each

of the lobes and have a probability level less than 0.05.

Ground Penetrating Radar

We utilize caution when describing and interpreting the GPR data gathered in this

study. We were unable to topographically correct the profiles, calculate a common

midpoint profile, or identify parabolic reflectors in any of the profiles. Without a

common midpoint profile we were unable to estimate the velocity of the medium or

perform semblance analysis to differentiate between air and ice in the upper section of

each profile. This is problematic because it prevents us from determining whether the

velocity of the reflectors represented the combination of the air wave reflection and

evanescent and direct wave, or just the air wave velocity (Degenhardt and Giardino,

2003 and Degenhardt et al., 2003). We assumed the velocity of the medium to be 0.11 m

ns~^ based on published values for temperate rock glaciers (Degenhardt et al., 2003).

This value was used for the depth conversion of each profile. We calculated the

theoretical vertical resolution for the 500 MHz and the 250 MHz antennas using the

equation À/4 = (V/F)/4 (Reynolds, 1997), where A, represents the wavelength in meters,

V represents the radio wave velocity of the medium (m ns“^), and F is the center

frequency of the antenna (MHz). The vertical resolution calculated for the 500 MHz

antenna is 0.09 m, and the 250 MHz antenna has a theoretical vertical resolution of 0.04

m. Therefore, each profile collected using the 250 and 500 MHz antennas provides

exceptional resolution for thin layers and smaller clasts, but lack the resolution to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97 identify medium to large sized clasts or layers. The wavelengths produced by higher

frequency antennas are too short to allow us to differentiate between the small, medium,

and large clasts. This study utilized higher frequency antennas than used in previous

studies; typical antenna frequencies range from 2 5 - 100 MHz.

Unfortunately, the Noggin Plus system does not yet have 25, 50, or 100 MHz antennas,

which could have provided data on deeper structures in the rock glacier and provided

profiles with better resolution of the larger debris fraction. Therefore, our descriptions

and interpretations of the GPR data are limited to the thinnest layers of the upper 2-15

meters of each lobe. Interpreting high-frequency radar data is often problematic because

the observed reflectors may represent primary and/or secondary events, background

noise, and attenuation caused by the presence of water or air.

Previous research has discussed the attenuation of high frequency signals caused

by high moisture content, sporadic ice content and a thick active layer (Lawson et al,

1998; Berthling et al., 2000; Hinkel et al., 2001; Sass and Wollny, 2001; and Degenhardt

and Giardino, 2003), however without the aid of common midpoint and semblance

analysis, we were unable to estimate average velocities for different materials

represented by the reflectors.

GPR profiles from each lobe reveal a similar network of parallel subsurface

reflectors (Fig. 3.6). Each lobe contains three identifiable and distinct layers. The

uppermost layer of each GPR depth profile represents the air layer between the Noggin

Plus unit and the surface of rock glacier. The second layer, ranging in thickness from 1 -

3 m, is interpreted to represent the active layer, or paleo-active layer, of each lobe and

contains reflectors of moderate amplitude that are horizontally discontinuous. The third

layer extends from the lower boundary of the active layer to depths ranging from -10 -

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WC/) 3o" O 13 25 Project 0: Line 4 8 22500 20000 17500 15000 12500 10000 7500 5000 2500 0 "O v< B (O' 3 .. . 1 - . i ‘ , i 13 ' " 1 ' i ' 3 CD 25 "n c 38 Project 1; Line 2 3- 3 " 25000 20000 15000 10000 5000 0 CD C CD 1 N , t(JH ■ ’ /■* / O 13 ' ' ' • Q. C 2f o 36 Project 5: Line 3 3 ■D 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 O 3 " D CT 1—H CD 1 .k-.I'.. ' , j! - '1 f-I- ^ O. 10 tI—*' . 20 3 " O 30 c Project 6: Line 3 T3 30000 25000 20000 15000 10000 5000

Position In Meters C/) c/) -25000 -12500 0 12500 25000

Figure 3.6: GPR profiles collected from the lower, middle and upper lobe. A, B and C were collected perpendicular to the flow of the rock glacier and D was collected parallel to flow. The y axis is measured in nanoseconds and the x axis is measured in meters. VOOO 99 15m and contains more sporadic, weak reflectors with lower amplitudes and more

lateral discontinuity.

Lower Lobe of the LRG

The upper 3.0 ns of the lower lobe profile represents the layer of air between the

Noggin and the surface of the rock glacier. Below the air layers is an approximately

13.0 ns thick layer containing laterally continuous reflectors that are primarily horizontal

and exhibit an ordered layering appearance. These reflectors exhibit the greatest

amplitude and contrast of any reflectors identified in the profile (Fig. 3.7). The third

layer observed in the radar profile is approximately 13 ns thick and contains weakly

dipping (up to -12°) reflectors that are less laterally continuous. Dipping reflectors are

more common near the beginning and end of the profile. Weak discontinuous reflectors

are observed down to a depth of 75 ns.

Middle Lobe of the LRG

The upper 4.0 ns of the middle lobe profile represents the layer of air between the

Noggin and the rock glacier. Below the air layer is an interval that is approximately 4.7

ns thick that contains reflectors that are horizontally and laterally continuous. These

reflectors exhibit the greatest amplitude and contrast of any of the reflectors observed in

this profile, similar to the lower lobe. The second layer in this profile is approximately

18.0 ns thick, consisting of moderately-to-steeply-dipping (up to -45°) reflectors that are

moderately angular. These reflectors are more discontinuous and truncated than those

observed in the lower lobe. Weak and discontinuous reflectors that can be identified to a

depth of 35.0 ns characterize the third layer in this profile.

Some reflectors in this profile appear to shallowly dip towards one another, overlain

by a region of high signal attenuation that lacks identifiable reflectors (Fig. 3.8). At least

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Figure 3.7: Representative portion of the radar profile collected from the lower lobe of the LRG. The bright red and blue horizontal layers represent the air layer between the Noggin and the ground surface. The layer below the air layer containing the reflectors that exhibit the greatest contrast, is thought to represent the paleo-active layer. Strong reflectors are observed down to a depth o f-40 ns and weak reflectors are present down to a depth o f-7 5ns. This is only a small segment of the entire GPR profile collected for the lower lobe. o o 101 four such structures were identified in this lobe and are randomly distributed throughout

the profile.

Upper Lobe of the LRG

The upper 4.5 ns of the upper lobe profile represents the air layer between the

Noggin unit and the surface of the rock glacier. Below the air layer is an interval that is

approximately 4.0 ns thick, consisting predominantly of laterally continuous and

horizontal reflectors. These reflectors are more angular in appearance than those

identified in the middle and lower lobe. The second layer in this profile is approximately

10 ns thick and contains moderately-to-steeply-dipping (up to -47°) reflectors that are

often chaotic in appearance. They are more chaotic near the edge of the profiles and

frequently terminate on other reflectors, creating a random pattern of onlap-offlap

structures. Weak, discontinuous reflectors that penetrate to a depth of 30.0 ns

characterize the third layer of this profile.

At least two structures in this profile exhibit reflectors with a geometry that is similar

to those identified in the middle lobe, with reflectors dipping towards one another

overlain by a sequence of strongly attenuated reflectors (Fig. 3.9).

Discussion

Previous research has described the movement of rock glaciers in alpine and

continental settings (Haeberli, 1985; Barsch, 1996; Whalley and Martin, 1992; and

Whalley and Azizi, 1994) and possible models for thier genesis (Potter, 1972; Wayne,

1981; Giardino, 1983; Johnson, 1984; Vick, 1987; Haeberli et al., 1998; Whalley and

Palmer, 1998; Burger et al., 1999; Konrad et al., 1999; Humlum, 2000; and Isaksen,

2000). Most models address the genesis of rock glaciers from the perspective of a

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Figure 3.8: Representative portion of the radar profile collected from the middle lobe of the LRG. The bright red and blue horizontal layers represent the air layer between the Noggin and the ground surface. The layer below the air layer containing the reflectors that exhibit the greatest contrast, is thought to represent the paleo-active layer. Strong reflectors are observed down to a depth of-35ns and weak reflectors are present down to a depth of-50ns. The structures identified with arrows are thought to represent thaw pits associated with attenuated reflectors (AR). This is only a small segment of the GPR profile collected from the middle lobe. ■o o Q. C g Q.

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Figure 3.9: Representative portion of the radar profile collected from the upper lobe of the LRG. The bright red and blue horizontal layers represent the air layer between the Noggin and the ground surface. The layer below the air layer containing the reflectors that exhibit the greatest contrast, is thought to represent the paleo-active layer. Strong reflectors are observed down to a depth of ~45ns and weak reflectors are present down to a depth of ~70ns. The structures identified with arrows are thought to represent thaw pits associated with attenuated reflectors (AR). This is only a small segment of the GPR profile collected from the upper lobe. LOo 104 glacial origin. With the exception of Giardino (1983), Johnson (1984), Haeberli et al.

(1998) and Isaksen (2000) who propose models of a periglacial origin. Models for the

development of ice-cored rock glaciers begin with the accumulation of rockfall debris

accumulating on low-angle slopes and at the base of glaciers, eventually developing into

a mantle of surface debris that insulates massive ice or snowbanks and initiates the

development of a rock glacier (Fig. 3.10). Each successive lobe of the rock glacier is

assumed to develop on the underlying debris mantle or existing lobe. This creates a

stratification of individual rock glacier lobes with different ages (Fig. 3.11).

Prior workers suggested that the Lehman Cirque rock glacier is composed of only

two distinct segments, an upper segment superimposed on a lower and more degraded

segment (Heald, 1956; Osborn, 1990; and Osborn and Bevis, 2002). Osborn (1990)

interpreted the Lehman Cirque rock glacier to be an ice-cored rock glacier, based on the

presence of glacial ice in the rooting zone that grades into the upper lobe of the rock

glacier. While it is possible that a transition zone exists at the rooting zone between a

debris-covered glacier and the upper lobe of the Lehman Cirque rock glacier, the

presence of a debris-covered glacier does not imply the rock glacier is ice cored (Barsch

and King, 1989; Jakob, 1992; and Barsch, 1996). Osborn (1990) also describes a steep

walled pit on the surface of the rock glacier that retains water during late summer and

which bears resemblance to the arcuate pits we describe at the terminus of each lobe. He

interprets this as a thaw pit, which he cites as further evidence to support the

interpretation of an ice-cored genesis. However, the presence of three arcuate pits with

such similar geometry and clasts dipping downvalley does not support the interpretation

that these are thaw pits. Clasts exposed in thaw pits' should dip towards the center of the

pit, not in the direction of downslope movement. Rather, we interpret these pits as

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105

Glacial Ice

Talus/Debris

: < v : > À < w

v>

(Î) High rates of ^ Decline in / debris and ice input ice input ij

Heavy ___ - Glacier debris cover jr '— Longitudinal ridges^^^^^/^ and furrows / Englacial debris yy Stretching and / transport Ridge of jff/ thinning clays \

Little Ice Age Lake

( 4) Decline in / ice input fj Slow movement of Glacier advances rock glacier blocks \ over the rock glacier

Slow creep //

^_v(^<._Isolated core Lakegy of ice

Figure 3.10: Previously published models for the development of the Galena Creek rock glacier, Wyoming and the Marinet rockglacier, France. A: Model published by Konrad et al. (1999). (1) debris begins accumulating (2) Ice overides existing talus while new talus accumulates on top of the ice, (3) glacier moves downslope transporting the debris layer, and (4) talus migrates over terminus while ice overides the debris. B: Model proposed by Whalley and Palmer (1998). (1) Advance of the glacier covered by a thin layer of debris, (2) input of talus provides thick debris cover that the glacier carries out of the cirque, (3) the glacier slows down in response to the rock glacier slowing down caused by decreased gradient and decreased ice content, and (4) debris at the terminal snout thickens and provides sufficient insulation to protect the lower ice core.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106

RG

' , \ ' ' ' s ' - L \'" 'S '- L\-~ ' ' '

>\> t\> '-\> f'XT' ;

Figure 3.11: Schematic diagram illustrating an idealized development of the Lehman rock glacier under the assumption that it developed from a glacial origin using the model proposed by Konrad et al. (1998). (a) The lower lobe of the rock glacier develops by overiding previously deposited debris created an ice cored lobe and (b) the middle lobe of the rock glacier developes in a similar fashion by overiding the upper surface of the previously exisiting lower lobe. The development of the upper lobe would follow a similar genesis as described for the middle and lower lobe. Applying this model to the Lehman rock glacier is inconsistent with the geomorphic evidence. This "layer cake" stratigraphy is not observed in the field and does not account for thepreferred orientation of each lobe or the arcuate pits described at the terminus of the upper and middle lobe.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107 representing the lowermost terminus of each progressively older lobe. We suggest that

individual lobes of the Lehman Cirque rock glacier formed by stacking up behind one

another in response to a retreating Lehman glacier during the Neoglacial, creating the

appearance of a cohesive tongue-shaped rock glacier (Fig. 3.12).

The limiting factor for the continued development and propagation of each lobe was

almost certainly the ice aggradation rate and not a debris supply because the rooting zone

is located below a steep headwall and the Lehman Cirque rock glacier is surrounded by

steep, well-jointed ridges (Osborn, 1990). Both the steep headwall and ridges

surrounding the Lehman Cirque rock glacier provide a more than adequate debris supply.

Geomorphic Evidence

The three distinct lobes of the Lehman Cirque rock glacier are visible both on aerial

photos and in the field. The upper lobe is generally accepted as the youngest segment of

the rock glacier, and the lower lobe is interpreted to be the oldest portion, based on

stratigraphy, degree of preservation, lichenometry studies, extent of surface relief, and

tephrachronology (Osbom, 1990 and Osbom and Bevis, 2002). The presence of three

distinct lobes suggests instability in the cirque glacier; if the glacier remained stable

throughout the late Pleistocene and Neoglacial, then the upper and middle lobes would

not have developed. The glacier must have retreated to provide room for each of the

lobes to develop (Fig. 3.12). We envision that a small lobate rock glacier developed in

Lehman Cirque as the glacier retreated, similar to that seen in Teresa Cirque (Fig. 3.13).

A slightly warmer climate would have increased the influx of debris into Lehman Cirque

and provided the necessary material to develop the middle and upper lobes during

subsequent cooler periods of the Neoglacial. Thus, alternating warm and cool periods

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Figure 3.12: Schematic diagram illustrating the hypothesized development of the Lehman rock glacier in response to the receding Lehman glacier (LG). (A) Initial development of the Lehman Glacier, (B) LG recedes and the lower lobe of the LRG develops (I), (C) LG continues to recede and the middle lobe of the LRG develops (II), and (D) the LG recedes to close to its modem location and the upper lobe of the LRG develops. Under modem conditions it appears that the upper lobe is inactive, although it displays evidence of recent activity. ______O C50 109 throughout the Neoglacial would have created ideal conditions for the development of

individual rock glacier lobes.

Fabric analysis of talus from each of the lobes indicates that all three lobes have

distinct longitudinal orientations. Pairwise Chi Squared tests suggest the sample

populations are significantly different (at the 0.05 level) and pairwise F-tests (also at the

0.05 level) indicate that this difference is derived from the difference between the vector

means of each lobe. Rayleigh uniformity plots provide further evidence supporting our

hypothesis that the lobes have a preferred orientation (Fig. 3.14). These plots illustrate

that the data from each lobe exhibit a departure from a uniform distribution and have a

statistically distinct preferred orientation.

One possible interpretation of these data is that each lobe began to develop and

flowed downslope from different locations in the cirque in response to changing local

topography as a function of headwall retreat or glacier geometry (Degenhardt et al.,

2003). However, if we accept the hypothesis that the Lehman Cirque rock glacier is

composed of three distinct lobes and is derived from a glacial origin, this implies that at

least three separate bodies of ice developed and were buried in Lehman Cirque,

subsequently evolving into the modem landform. Other than the development and rapid

burial of three bodies of ice, it is unclear how an ice-cored rock glacier could develop

multiple lobes stacked behind one another with different mean orientations. The

inference that three separate bodies of ice developed over a 1,200-year (Osbom, 1990)

period is unlikely. We suggest that the presence of Mono Crater ash in the lower lobe

does not necessarily indicate that this lobe formed no earlier than 1200 AD. It is quite

plausible, and more likely that Mono Crater ash fell on the surface of all three lobes of

the rock glacier. This ash could very easily infiltrate the porous, blocky talus that forms

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Figure 3.13: Small lobate rock glacier located north of Lehman rock glacier in Teresa Cirque. We suggest that the formation of multiple lobate rock glaciers, similar to this feature, could create the appearance of a tongue-shaped rock glacier. I l l

Upper Lobe 10-1 Middle Lobe

C/Î M

I 0.6- 0.6- ?T o g 0.4- 0.4- a

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Lower Lobe

O 0.4

0.2 0.4 0.6 0.8 1.0 Uniform Quantiles

Figure 3.14: Rayliegh uniformity plots illustrating a departure from a uniform distribution. The null hypothesis is that the data are uniform and therefore should plot along the reference line at a 45° angle. Any departure from this line indicates a departure from uniformity and therefore rejects the null hypothesis that the data do not have a preferred orientation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 the upper layer of the lobes, thereby becoming incorporated into the matrix of the lower

lobe. This suggests that the lower lobe was still active 1200 years BP, but it is likely that

it formed much earlier than this. Its maximum age is constrained by the presence of

5,000-year-old bristlecone pines on a moraine downvalley from the rock glacier (Osborn,

1990). This provides a time frame of 1200 years BP or younger for the upper segment

and 5000 years BP or younger for the lower segment, with evidence for downslope

activity occurring in the lower lobe approximately 1200 years BP.

We suggest that the variability in lobe orientation reflects a change in the geometry

of the Lehman glacier, induced by episodic degradation and possible re-advance in

response to a fluctuating Neoglacial climate (Clark and Gillespie, 1997; Dean, 1997;

Davis, 1998; Polyak et al., 2001; and Benson et al., 2003). The Lehman Glacier must

have retreated multiple times to provide space and sufficient debris for each lobe to

develop upslope from the previously developed lobe. We interpret the arcuate features

located at the terminus of the upper and middle lobes as evidence that each younger lobe

has not overridden the lower, older lobes. Talus and debris from each successively

younger lobe is exposed in these arcuate trenches, also suggesting that each older lobe

did not develop on the upper surface of a younger lobe. In plan view and in the field,

this creates the appearance of a single, cohesive, tongue-shaped rock glacier, when in

fact it is composed of multiple tongue or lobate rock glaciers (Fig. 3.15).

By accepting our hypothesis that three strati graphically distinct rock glacier lobes

developed in Lehman Cirque, we also have to accept that three rock glacier initiation line

altitudes (RILA) existed throughout the development of the existing landform (Humlum,

1998 and Humlum, 2000). Humlum (1988) defines the RILA as the altitude where rock

glaciers creep out from the overlying slope, identified by a break in slope or the upper

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113

Development of rock glacier I

Retreat of glacier followed by talus accumulation

Lobate rockelacier

Development of rock glacier II

Deep arcuate furrow Lobate rockelacier Lobate rockelacier « a

Figure 3.15: Possible evolution and genesis of the Lehman rockglacier. (a) devlopment of small tongue or lobate rock glacier, (b) map view of expected rock glacier morphology, (c) glacier retreats creating room for talus and disrupting the RILA, (d) map view of expected rock glacier and talus morphology (e) glacier re-advances and initiates the development of a rock glacier in downslope talus and (f) map view of "stacked" small tongue or lobate rock glacier exhibiting the appearance of a single tongue-shaped rock glacier.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 limit of debris-covered rock glaciers. The modern RILA can be identified on Figure

3.3 as the transition from the lower portion of the Lehman glacier and the rooting zone of

the Lehman Cirque rock glacier. The inferred former RILA for each lobe is also shown

in Figure 3.3. A similar environment with a more extensive Lehman Glacier is

envisioned for the middle and lower lobes, and the genesis of three well-developed lobes

suggests that the development of interstitial segregated ice lenses must have been

sufficient to induce downslope movement (Wayne, 1981; Whalley and Martin, 1992;

Whalley and Azizi, 1994; and Whalley and Palmer, 1998). However, because of the

lack of absolute ages, the temporal relationships between each lobe and the activity of

the Lehman Glacier are unclear.

It is possible that the lower lobe represents the Great Basin equivalent of a 4000

BP Neoglacial advance proposed by Davis (1998). Konrad et al. (1999) tentatively

correlated the development of the Galena rock glacier in the Absaroka Mountains of

Wyoming to this 4000 BP advance. This would suggest that the Lehman Glacier

advanced to an elevation of 3333 masl, the current elevation of the modem head of the

lower lobe of the Lehman Cirque rock glacier. The middle and upper lobes of the

Lehman Cirque rock glacier are certainly younger than the lower lobe, but it is

impossible to place absolute constraints on the timing of their development. Osborn

(1990) proposed a Little Ice Age origin for the upper lobe. We concur that this is likely,

based on the proximity to the modem Lehman glacier and geomorphic evidence

suggesting it has recently been active.

Evaluation of GPR Data

Representative radar profiles from each lobe are shown in Figure 3.8. We present

profiles that were collected using the 500 MHz antenna set to a depth of 5 m; because we

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 were unable to image the deepest reflectors, the combination of the highest frequency

and shallowest penetration provide the greatest detail. Both the horizontal and vertical

axes are expressed in meters. The maximum depth to which we record visible reflectors

is 16 m, 15 m and 14 m for the upper, middle and lower lobes respectively, based on an

assumed velocity of 0.11 m/ns. The upper (2-3 ns) horizontal layers at the top of each

profile represent the air layer between the GPR unit and the surface of the rock glacier.

Some of the inconsistency in depth of penetration between the radar profiles may be

attributed to the speed at which they were collected. Although every attempt was made

to maintain a constant speed when carrying the GPR over the surface of the rock glacier,

this was impossible due to the differences in terrain between the transects. Hinkel et al.

(2001) attributed inconsistencies between the amounts of subsurface penetration to the

speed at which the survey was collected. However, the lack of reflectors below variable

depths between different lobes using the same frequency antenna suggests inconsistent

attenuation along the lower boundary of each GPR profile probably caused by the

presence of water.

Radar profiles collected from the lower lobe exhibit more subdued and generally

more continuous and horizontally-oriented reflectors than those observed in the middle

and upper lobes. However, reflectors are less horizontal near the lateral margins of the

rock glacier. This indicates more shearing at the margins caused by increased friction as

predicted by model of glacier and rock glacier flow dynamics (Whalley and Martin,

1992 and Whalley and Azizi, 1994).

Profiles from the middle lobe exhibit reflectors that are slightly more discontinuous

and steeply dipping. Similar to the lower lobe, reflectors in the middle lobe are more

inclined near the margins of the rock glacier. The structures identified in the middle lobe

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116 (characterized by reflectors that dip towards one another and overlain by an area lacking

reflectors) are interpreted to represent thaw pits within the active layer of the rock glacier.

The area overlying the dipping reflectors is thought to represent voids containing water,

which would account for the lack of reflectors. These structures appear to occur

randomly through the profile.

Reflectors in the profile collected from the upper lobe of the rock glacier exhibit

sharp, relatively discontinuous and chaotic reflectors, in comparison to the reflectors

observed in the middle and lower lobes. Previous workers have identified angular

reflectors in rock glaciers and permafrost that are similar to those identified in this study

(Hinkel et al., 2001 and Degenhardt and Giardino, 2003). Degenhardt and Giardino

(2003) describe subsurface angular reflectors that correspond to furrows and ridges on

the surface of the Yankee Boy rock glacier in Colorado. Although the resolution of the

profiles in this study is less sensitive to thick layers, we suggest that the angular

reflectors identified in the upper lobe of the Lehman Cirque rock glacier are also

subsurface manifestations of the surface topography. The subsurface reflectors

identified in the middle and lower lobes are less angular and exhibit more lateral

continuity. This observation is consistent with the geomorphic expression of the surface

topography between each lobe; the upper lobe exhibits the best-preserved furrows and

ridges, while the middle and lower lobes exhibit moderate to weakly preserved furrows

and ridges.

We interpret the presence of chaotic reflectors in the active layer of the upper lobe as

evidence that it still contains lenses of segregated ice in the active layer (Moorman et al.,

1994 and Hinkel et al., 2001). Alternatively, it has been suggested that iiTegular layers

may indicate the development of less dense permafrost resulting in the deformation of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 the ice and sediment (Berthlin et al., 2000). This may be the case with the Lehman

Cirque rock glacier because it is located in a hot arid climate flanked to the east and west

by desiccated pluvial lakes that could provide sufficient salt to increase the unfrozen

water content (Berthling et al., 2000). The lack of common midpint and semblance

analysis make it impossible to evaluate whether the chaotic reflectors identified in the

profiles are solely a function of segregated ice or a warm environment with high salt

input, or a combination of both processes.

The layered structures identified from profiles collected perpendicular to the flow of

the upper lobe of the rock glacier were also identified on the profiles collected parallel to

the flow of the upper lobe. This suggests that they are spatially consistent in a three-

dimensional reference frame. The resolution of our data, and lack of geospatial

reference points, limits our ability to interpret the significance of the layering observed

in the Lehman Cirque rock glacier. However it is likely that they are similar to features

described by Isaksen et al. (2000), Berthling et al. (2001), and Degenhardt and Giardino

(2003). These studies attributed the presence of layered reflectors in rock glaciers to the

development of interstitial ice in response to alternating periods of snow accumulation

and sediment influx followed by rapid burial. The Lehman Cirque rock glacier is located

at the head of a steep, narrow, north-facing cirque, and it is composed of well-jointed

quartzite that is subject to active frost action and frequent rockfalls and dry grain flows.

During spring melt, sediment is transported into the cirque via steep gullies and bedrock

chutes (Fig. 3.16). The morphology of the cirque and the abundance of steep, narrow

chutes helps funnel debris and sediment onto the modem rooting zone of the rock glacier.

A similar scenario is envisioned during periods when the Lehman Glacier was more

extensive because the steep cirque walls were (and are) laterally continuous past the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 terminus of the lower lobe (Fig. 3.16). As previously mentioned, the limiting factor for

the development of the Lehman Cirque rock glacier was almost certainly the

development and preservation of snow/ice owing to the high rates of talus input into the

cirque. This process can be observed in the field during the summer months when

quartzite debris topples onto the upper slope of the Lehman glacier. Therefore, the

Lehman Cirque rock glacier is located in an ideal setting to develop alternating layers of

ice/snow and quartzite debris. During times of more extreme diurnal temperature flux,

we envision talus input is more frequent, which would contribute to the development of

layered structures in the rock glacier. Thus, we interpret the lateral continuity of the

layering, the consistency of the layered structures between the three lobes, and the

similarity to features described in the literature, as evidence that layers of ice and

sediment/debris developed through processes described by Berthling et al. (2000),

Isaksen et al. (2001) and Degenhardt and Giardino (2003).

Conclusions

Geomorphic and GPR data suggest that the Lehman Cirque rock glacier is composed

of at least three lobes, the development of which reflect the episodic nature of the

Lehman Glacier during the Neo glacial. However, these lobes are not superimposed on

one another in the traditional ‘layer cake’ stratigraphy predicted by proponents of a

glacial genesis for rock glaciers. We propose a recessional genesis model for the

Lehman Cirque rock glacier, in which each lobe developed at the terminus of the

Lehman Glacier as it progressively decayed to its modem position. This model is based

on (1) geomorphic evidence that suggests each lobe has a distinct and unique preferred

orientation, and (2) the presence of deep arcuate pits at the terminus of the upper and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) C/) Steep cirque walls LEGEND G: gully Qt: Quaternary talus LG; Lehman glacier 8 I, II, III: rock glacier lobes ■D TRG: Teresa rock glacier T: terminus of lower lobe

3. 3 " CD ■DCD O Q. C a m # 3O "O O TRGa

CD Q.

■D 'T& CD

C/) C/) 212.5 425 1 Millimeter = 6.5 Meters

Figure 3.16; USGS digital orthophoto quadrangle (DOQ) draped over a triangular integrated network (TIN) that illustrates the spatial relationships between the Lehman rock glacier and the surounding topography. 120 middle lobes. The presence of these pits suggests that the upper lobe of the Lehman

Cirque rock glacier has not overridden the middle lobe, and that the middle lobe has not

overridden the lower lobe. We also suggest the lower segment of the Lehman Cirque

rock glacier is older than 1200 years BP and may represent the initiation of a 4000-year

BP advance documented by Davis (1998). However, without absolute age constraints

this correlation is tentative.

We suggest that the chaotic reflectors and layered structure observed in the radar

profiles indicate that the upper lobe of the Lehman rock glacier retains interstitial ice and

supports a periglacial genesis. The middle lobe may also contain interstitial ice;

however the reflectors and layering are not as well preserved or developed. Both the

middle and upper lobe contain structures thought to represent thaw pits. The lack of

such features in the lower lobe suggests that either they never formed or, because the

lower lobe is much older, any thaw pits that developed have since filled in.

Furthermore, we suggest that GPR may be a useful tool for calibrating relative

age relationships between individual lobes on rock glaciers, based on consistency

between the angularity of subsurface reflectors and the degree of surface topography.

Future Work

A GPR survey using the Pulse Ekko system with lower frequency antennas will

provide more detail in the deeper section of the Lehman Cirque rock glacier. The Pulse

Ekko system is suggested rather than the Noggin Plus system because 25-100 MHz are

currently available for that system, and because CMP analysis can be readily obtained.

Laser surveying should be conducted to obtain precise topographic constraints for

topographic correction. Although the Lehman Cirque rock glacier is located in Great

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121 Basin National Park, a convincing case should be made to park officials to permit the

installation of bolts on prominent talus blocks for a long-term velocity measurement

study. The upper lobe is assumed to be inactive, however velocity measurements over a

5-10 year period would test this assumption. In the context of global warming, it is

imperative that we begin to monitor the activity of landforms, such as rock glaciers, that

are sensitive to climate change. Finally, a first order attempt should be made to quantify

the volume of the debris in each lobe and the annual debris input into the cirque during

the winter and summer months to evaluate the significance of the Lehman Cirque rock

glacier as a talus transport system throughout the Neoglacial.

Acknowledgments

We thank the Geological Society of America, Arizona-Nevada Academy of

Science, Colorado Scientific Society, UNLV Graduate Student Association, and The

American Alpine Club, for financial support. We also Great Basin National Park and

numerous UNLV graduate students for providing field support. We also thank Harry Jol

and John Degenhardt for their expertise and useful comments, and Brian Herridge from

3D Geophysics.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 122

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Musil, M., Maurer, H., Green, A.G., Horstmeyer, H., Nitsche, F.O., Vonder Miihll, D., Springman, S., 2002, Shallow seismic surveying of an alpine rock glacier. Geophysics 61: 1701-1710.

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Osbom, G. 1990. The Wheeler Peak Cirque and Glacier/Rock Glacier. Report for the Great Basin Natural History Association.

Osbom, G. and Bevis, K , 2001, Glaciation in the Great Basin of the Western United States. Quaternary Science Reviews 20: 1377-1410.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128 Polynak, V.J., Cokendolpher, J.C., Norton, R.A., and Asmerom, Y., 2001, Wetter and cooler late Holocene climate in the southwestern United States from mites preserved in stalagmites. Geology 29: 643-646.

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Sass, O. and Wollny, K., 2001, Investigations regarding alpine talus slopes using ground penetrating radar (GPR) in the Bavarian Alps, Germany. Earth Surface Processes and Landforms 26: 1071-1086.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129 Whalley, W.B. and Palmer, C.F., 1998, A glacial interpretation for the origin and formation of the Marinet rock glacier, Alpes Maritimes, France. Geografiska Annaler 80A: 221-236.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4

PREDICTING THE SPATIAL DISTRIBUTION OF PERRENNIAL SNOW AND

ICE IN THE SNAKE RANGE, NEVADA: IMPLICATIONS FOR INCREASED

PRECIPITATION FROM PLUVIAL LAKE SYSTEMS?

This paper has been prepared for submission to Earth Interactions Online Journal and is presented in the format of that journal. The complete citation will is:

Van Hoesen, J.G. and Orndorff, R.L., 2003, Predicting the spatial distribution of perennial snow and ice in the Snake Range, Nevada: Implications for increased precipitation from pluvial lake systems. Earth Interactions (IN PREP).

130

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 131 Abstract

We utilize Arc View GIS, a Snow and Ice Model (SIM), modern climate station data,

and digital elevation models (DEMs), to predict the modem and late Pleistocene

distribution of perennial snow and ice in the Snake Range, Nevada. The Snake Range

exhibits evidence of extensive glaciation during the last glacial maximum. By

calculating the distribution of perennial snow and ice under a variety of temperature and

precipitation boundary conditions and comparing model results to observed glacial

landforms, we attempted to predict likely Late Quaternary temperature and precipitation

conditions for the Snake Range. The results suggest that the combination of sparse

climate data and limitations of the SIM underpredict the expected distribution of both

perennial snow and ice when compared with previous estimates of perennial snow

distribution using ELApse and known Full Glacial limits that were delineated using

moraines.

The results from the SIM also suggest that the limiting factor on the initiation and

genesis of glaciers in the Snake Range is temperature and not precipitation; this finding

agrees with previous paleoclimate studies in the Great Basin. However, we suggest that

the presence of pluvial Lakes Spring and Maxey to the west of the Snake Range may

have provided a significant source of winter precipitation that is not reflected in the

floral and faunal record.

Introduction

The application of computer modeling to evaluate the late Quaternary paleoclimate

of the Great Basin is limited (Omdorff, 1994; Jones and Omdorff, 1999; Plummer et al.,

2000; Van Hoesen and Omdorff, 2001; Omdorff and Van Hoesen, 2001; and Negrini,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 132 2001). However, significant research has been conducted in areas surrounding the Great

Basin (Singer, 1985; Barry et al., 1990; Bartlein, 1998; and Plummer and Phillips, 2003).

This study evaluates the applicability of a Snow and Ice Model (SIM) developed by

Omdorff (1994) to 25 m raster data from the Snake Range, Nevada. We compare output

grids from SIM with previously calculated output grids from ELApse (Omdorff and

Jones, 1999 and Omdorff and Van Hoesen, 2001) and the expected distribution of

perennial ice based on known glacial limits delineated using lateral and terminal

moraines (Plate 1, in pocket'. Van Hoesen, 2003a).

Previous work suggests that lake-atmosphere feedback systems existed for Lakes

Lahonton and Bonneville during the late Quatemary (Hostetler et al., 1994). A number

of pluvial lakes existed to the west of the Snake Range, and a small arm of Lake

Bonneville developed to the east of the range. Through a first order, simplistic approach

we estimate the possible influence of pluvial lakes on the development of glaciers and

the implied correlation with global climate change during the Late Quatemary.

Study Area

The Snake Range is a north-south-trending range in east central Nevada, composed

of a northem and southern section and rising to 3981 meters above sea level (masl) at its

crest (Fig. 4.1). Glaciation was more extensive in the southern portion of the range

during the last Glacial Maximum. Glaciated valleys in the Snake Range are composed

of Paleozoic metasedimentary units, primarily Prospect Mountain Quartzite, Pioche

Shale, and Pole Canyon Limestone, that were intruded by the Jurassic Snake Creek-

Williams Canyon pluton (Drewes, 1958; Whitebread, 1969; Lee et al., 1970; Lee and

Van Loenen, 1971; Lee et al., 1981; Lee and Christiansen, 1983 a, b; Lee et al., 1986;

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 133

125°00' 49°00i-

Columbia Rivef

Idaho

Oregon Snake River

Green River

Nevada Great Salt Lake California \L ak e Tahoe

Colorado River

^-^Salton Sea Snake Range

400Km Great. Basin Hydrologie Province ■32°30' 108°00'

Figure 4.1: Line diagram illustrating the geographic extent of the Great Basin Physiographic Province in the Western United States and the location of the southern Snake Range.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 134 Miller, 1995 and Miller, 1999). A discussion on the glacial history of the Snake Range

is provided by Piegat (1980), Osborn (1990), Osborn and Bevis (2001), and Van Hoesen

and Omdorff (2003). The Lehman Cave weather station, located at 2073 masl, records a

modem MAAT of 9.59° C. The mean coldest month is January (-2.69 °C), and the

warmest month is July (22.75 °C). Mean annual precipitation is approximately 33.22 cm;

the greatest amount of precipitation falls in May (3.23 cm), and the least falls in July

(1.63 cm). Average mean annual temperatures for the entire range varies from -8°C to

30°C depending on elevation, and average precipitation from the valleys to the high

peaks region can vary from less than 12 cm to greater than 50 cm (Houghton et al., 1969).

During the Late Pleistocene the Snake Range experienced at least three separate

episodes of alpine glaciation. The terminology used to describe glacial advances in the

ranges of the Great Basin was developed in the Ruby Range; the younger is termed the

Angel Lake advance and the oldest advance is the Lamoille (Blackwelder, 1934). These

advances tentatively correlate to the Tahoe and Tioga glacial advances of the Siema

Nevada (Wayne, 1984; Osbom and Bevis, 2001). If these correlations are correct, then

an age of 19,000 to 20,000 years BP can be assigned to the Lamoille advance, and an age

of 14,000 to 12,000 years BP can be assigned to the Angel Lake advance.

The youngest glacial advance is thought to represent glacial activity during the

Neoglacial that tentatively correlates to the Matthes Stade of the Sierra Nevada and the

Gannett Peak Stade of the Rocky Mountains (Birman, 1964; Benedict, 1968; Piegat,

1980; and Osbom and Bevis, 2001). An approximate age on the Neoglacial advance is

5,000 to 8,000 years B.P. (Denton and Karlen, 1973; Porter and Denton, 1967; and

Madsen and Currey, 1979). The most extensive glaciation occurred in the central part of

range, primarily in the Wheeler Peak Quadrangle, However, scattered glaciers

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135 developed in the northem and southem sections of the range (Piegat, 1980; Osborn and

Bevis, 2001; and Van Hoesen, 2003a).

During the Late Pleistocene, pluvial Lakes Spring and Maxey developed in Spring

Valley to the west of the Snake Range, and one of the arms of pluvial Lake Bonneville

formed in Snake Valley to the east of the Snake Range (Snyder and Langbein, 1962;

Snyder et al., 1964; Mifflin and Wheat, 1979; Currey, 1982; and Reheis, 1999; and

Oviatt et al., 1992). Figure 4.2 shows the spatial distribution of pluvial lakes in relation

to ranges that experienced alpine glaciation during the Last Glacial Maximum (LGM).

Significant changes in the paleoecology occurred in the Snake Range, and throughout the

Great Basin, in response to the expansion of glacial and pluvial systems (Mead et al,

1982; Thompson and Mead, 1982; Mead, 1984; Mead and Mead, 1985; and Tummire,

1985).

Methodology

We use the Snow and Ice Model (SIM) and ELApse 3.0 developed by Omdorff

(1994) and Jones and Omdorff (1999) in combination with 25 m USGS digital elevation

models (DEMs) to predict the spatial distribution of perennial snow and ice under a Full

Glacial climate. DEMs are also used to calculate slope, aspect, solar insolation, and land

surface curvature. Our methodology incorporates shading effects and seasonal solar

insolation variability based on the sun's position at the summer and winter solstices. In

addition, we use slope and curvature surfaces to estimate stability and delineate areas

most suitable for snow and ice accumulation. Using the SIM, we estimate the spatial

distribution of perennial snow and ice for specified climate boundary conditions.

Modem climate data were obtained from the Westem Regional Climate Center to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136

Shell Cree

Monitor

Toquima CLIMATE STATIONS Range 1. Ely Yelland Field 2. Ruth 3. McGill 4. Great Basin National Park 5. Currant Highway Station Spnng 6. Lund M ou„.,„s 7. Geyser PLUVIAL LAKES A. Lake Meinzer (1768 m) I. Lake Diamond (1829 m) B. Lake Surprise (1567 m) I Lake Newark (1847 m) C. Lake Lahonton (1332 m) K. Lake Hubbs (1920 m) D. Lake Tahoe (1926 m) L. Lake Franklin (1850 m) E. Lake Dixie (1097 m) M. Lake Clover (1730 m) F. Lake Desatoya (1889 m) N. Lake Waring (4761 m) G. Lake Toiyabe (1702 m) O. Lake Spring (1759 m) H. Lake Railroad (1402 m) P. Lake Maxey (1762 m) 10 1 cm = 3 km Figure 4.2: Spatial distribution of pluvial lakes relative to mountain ranges that incurred glacial activity during the Last Glacial Maximum. Climate stations used to develop climate coefficients are indicated with black cirlces.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137 calculate modem monthly temperature maximum (Tmax), monthly temperature

minimum (Tmin), and monthly precipitation (Precip; Table 4.1). These data were used

to create climate coefficients using a multivariate regression bettveen elevation and

latitude of each station (Table 4.2). Climate data in the Great Basin are sparse, and

climate coefficients were calculated using the seven climate stations listed in Table 4.3.

Tmax and Precip grids were created using a C+ program written by Omdorff (1994).

The flowchart in Figure 4.3 summarizes the steps used to create these climate grids.

The climate coefficients were entered into ELApse and Tmax and Precip grids were

entered into the SIM so that modem temperature and precipitation can be perturbed to

reflect estimated Full Glacial climate.

Stations Station Elevation (m) Latitude Longitude Years ID Ely Yelland Field 2631 1905.9 39°17’00” 114°51’00” 104 Ruth 7175 2084.8 39°17’00” 114°59’00” 43 McGill 4950 1920.2 39°24’00” 114°46’00” 87 Great Basin NP 3340 2081.8 39°00’00” 114°13’00” 53 Currant Highway 2091 1903 38°48’00” 115°2r00” 15 Lund 4745 1697.7 38°51’00” 114°00’00” 44 Geyser 3101 1835.4 38°40’00” 114°38’00” 53

Table 4.3; Climate stations used to calculate modem climate coefficients and Tmax and Precip grids used with ELApse and the SIM.

The SIM calculates the spatial extent of perennial snow and ice within the domain of

the DEM and creates a raster grid that depicts the extent of predicted perennial snow and

ice. It has previously been shown that a similar model, ELApse, overestimates the extent

of snow and ice because it fails to incorporate the effects of topography and solar

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) C/) Variable Station January February March April May June July August September October November December

Tmax (”C) CD EYF 3.889 5.778 9.056 14.111 19.500 25.500 30.500 29.167 24.222 17.167 9.500 4.944 ■D8 R 3.222 5.111 8.167 12.500 17.889 23.778 28.778 27.722 22.889 16.722 8.556 3.944 M 3.833 5.778 9.278 14.111 19.556 25.389 30.333 29.167 24.444 17.611 9.833 5.056 (O' GBNP 4.833 6.444 9.333 14.000 19.278 25.278 29.722 28.444 23.667 16.667 9.167 5.278 CHS 3.222 5.944 9.000 12.667 19.944 24.667 30.111 28.000 23.611 19.500 9.222 3.389 L 6.167 8.667 12.111 16.500 21.722 27.278 31.500 30.444 26.222 20.000 11.722 7.167 G 4.500 7.222 10.167 16.000 20.833 27.278 31.444 30.167 25.944 19.444 11.833 5.944

3. 3" Tmin C O CD EYF -11.944 -9.389 -6.333 -2.944 1.000 4.667 8.889 8.278 3.056 -2.111 -7.333 -11.167 CD ■D R -14.333 -11.722 -7.833 -4.778 -0.444 3.556 7.278 6.611 1.056 -4.222 -9.278 -14.222 O Q. M -9.056 -6.667 -4.278 -0.611 3.667 8.333 12.889 11.833 6.667 1.056 -4.500 -8.056 C GBNP -7.278 -5.778 -3.722 -0.278 4.333 9.278 13.833 13.167 8.278 , 2.778 -3.444 -6.778 Oa 3 CHS -13.667 ■ -10.833 -8.333 -4.000 0.667 4.333 7.833 6.611 2.000 -1.833 -6.833 -12.778 "O L -9.722 -6.944 -4.667 -1.778 2.556 6.556 9.944 9.333 4.944 -0.278 -5.722 -9.278 O G -12.500 -8.778 -6.444 -3.000 1.222 4.944 9.056 8.000 3.667 -1.222 -7.000 -11.444

CD Q. Precip (cm) EYF 1.981 1.854 2.515 2.540 2.845 1.829 1.499 2.083 1.981 2.134 1.727 1.575 R 2.388 2.743 2.616 3.175 3.277 3.124 2.159 2.515 2.210 2.438 2.057 2.210 ■D M 1.600 1.575 1.803 2.337 2.667 2.108 1.702 2.032 1.829 ■ 1.981 1.372 1.422 CD GBNP 2.489 2.616 3.708 2.794 3.378 2.286 2.413 2.997 2.819 3.048 2.515 2.184 (/) CHS 2.464 2.235 2.007 2.261 2.235 3.073 1.778 1.930 2.108 2.464 1.473 2.819 (/) L 2.057 2.083 2.794 2.362 2.540 2.388 1.702 2.438 2.184 2.210 1.803 1.778 G 1.778 2.311 2.413 1.753 2.286 0.813 2.083 1.803 1.930 2.413 1.778 0.787

Table 4.1: Summary of mean monthly Tmax, Tmin, and Precip from climate station used to calculate climate coefficients and climate grids. (EYF = Ely Yelland Field, R = Ruth, M = McGill, GBNP = Great Basin National Park, CHS = Cun ant Highway Station, L = Lund, and G = Geyser). LO CO CD ■ D O Q. C g Q.

■D CD Variable January February March April May June July August September October November December C/) C/) Tmax 35.793512 76.090506 52.321 57.56148 84.6545 81.71286 62.7455 38.046458 62.54222187 123.89084 70.0545832 15.75752254 -0.615387 -1.518457 -0.7441 -0.72163 -1.31815 -1.11254 -0.5413 0.0868952 -0.61073232 -2.375202 -1.20009543 0.022534648 ■D8 -0.003925 -0.005415 -0.00713 -0.00788 -0.00697 -0.00661 -0.0059 -0.006476 -0.00743874 -0.006778 -0.00689446 -0.00601236 Tmin ë' -61.35736 -29.39483 -64.4549 -44.0119 -19.193 -30.2738 -47.688 -60.38427 -16.2538341 28.246922 3.70266647 -55.5654273 1.3716344 0.728909 1.643326 1.165123 0.58869 0.909219 1.40332 1.7096389 0.516060212 -0.768808 -0.23463403 1.284238177 -0.001775 -0.003987 -0.00294 -0.00206 -0.00101 0.000381 0.00149 0.0014379 0.000179729 0.000487 -0.00043999 -0.00266021 Precip 24.578384 38.136168 32.64498 -23.271 -17.6189 -15.9534 27.361 3.4402792 20.83651719 35.959291 20.0876181 15.05074997 3. 3 " -0.67136 -1.050089 -0.88715 0.572852 0.41629 0.380582 -0.7608 -0.110523 -0.56461884 -0.975913 -0.56921184 -0.45241102 CD 0.0019495 0.0026387 0.002367 0.001755 0.00214 0.001734 0.00221 0.0016324 0.001750473 0.0023585 0.00206031 0.002312696 ■DCD O Q. Table 4.2: Monthly climate coefficients produced using a multivariate regression between altitude and elevation at each climate statio C a 3O "O O

CD Q.

■D CD

C/) o' 3

U) VO 140

Climate Data Source (Westem Regional Climate Center) / Multivariate regression \ Monthly of Tmax and Precip versus] Climate Y latitude and elevation j Data

FORMAT Elevation, Latitude, Tmax_Jan, Tmax_Feb, etc. Elevation, Latitude, Tmin_Jan, Tmin_Feb, etc. Elevation, Latitude, Precip_Jan, Precip_Feb, etc

USGS N ED Data Average Latitude of Climate Stations Export ASCII \ Coefficients fromArcView J for Tmax and Precip

EQRMAT C = Tm(i) + [Tm(l)*l] + [Tm(e)*e] Visual Basic Climate \ I Grid Generator j Elevation Y (see code) J ASCII file

FORMAT ncols 260 nrows 146 xllcorner 731652.22513227 yllcorner 4314I96.I479973 cellsize 30.887464508638 NODATAvalue -9999

Tmax and FORMAT Precip Climate Tmax(tmaxl tmax?tmax3 etc.) Grids Preciplprecl, prec:^ prec3 etc.)

Figure 4.3: Flowchart illustrating the steps required to create Tmax and Precip grids for the SIM.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 141 insolation (Jones and Omdorff, 1999; Omdorff and Van Hoesen, 2001; and Van Hoesen

and Omdorff, 2001). Therefore, raster overlays of slope, curvature, and shading created

in Arc View to simulate alpine microclimates are used to refine the grids produced by the

SIM to provide a more realistic depiction of the spatial extent of perennial snow and ice.

Results

We used the SIM to estimate perennial snow and ice for various parts of the Snake

Range under modem conditions, and then we perturbed the modern climate by -2°, -3°,

-4°, -5°, -5.5°, -6° and -6.5°C. Each perturbation produces an output grid depicting the

distribution of perennial snow, perennial glaciers, a summary of results, and the volume

of snow and ice over time. Tables 4.4 and 4.5 provide a summary of the results for each

area of interest of the Snake Range (Fig. 4.4). Each portion of the Snake Range

investigated in this study, with the exception of Lincoln Peak, exhibits a similar trend

with increased equilibration time occurring at the boundary when perennial snow

transitions to perennial ice. A similar transition occurs when perennial snow first

develops on Bald Mountain, Lincoln Peak, and Williams Canyon where SIM doesn’t

predict modem perennial snow. However, the change in equilibration time between bare

ground and the first appearance of perennial snow is less drastic than the change

observed during the transition from perennial snow to ice.

We also used the SIM to estimate perennial snow and ice for Baker Valley by

perturbing the temperature by -5°C and increasing precipitation by 1,2, 3 and 4 cm to

evaluate the effects of changing temperature versus increased precipitation. We

compared the extent of perennial snow and ice produced with just a temperature change

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) Location AT (C°) Grid Extent (#cells) Snow Area (km^) Ice Area (km^) C/) Run Time (years) Perennial Snow (#cells) Glaciers (#cells)

Baker Modem 39 37,960 187 0 0.18 0 -2 88 37,960 1,408 0 1.35 0 CD -3 117 37,960 3,356 0 3.23 0 8 "D -4 23,076 37,960 6,427 50 6.18 0.05 -5 25,071 37,960 10,728 390 10.31 0.37 (O' -6 16,920 37,960 15,152 1585 14.56 1.52 -6.5 11,115 37,960 17,372 2705 16.69 2.6 Bald Modern 2 19,932 0 0 0 0 -2 2 19,932 0 0 0 0 3. -3 2 19,932 0 0 0 0 3" -4 66 19,932 301 0 0.29 0 CD -5 96 19,932 969 0 0.93 0 CD ■D -6 124 19,932 3,116 0 2.99 0 O Q. -6.5 40,429 19,932 6,012 43 5.78 0.04 C Lehman Modem 42 57,904 545 0 0.52 0 Oa 3 -2 98 57,904 2,305 0 2.22 0 "O -3 124 57,904 3,919 0 3.77 0 O -4 ■ 3026 57,904 6,295 49 6.05 0.05 -5 11,394 57,904 9,467 677 9.1 0.35 CD Q. -6 7,365 57,904 14,551 2147 13.98 2.06 -6.5 8,616 57,904 17,161 3029 ’ 16.49 2.91 Lincoln Modem 2 29,760 0 0 0 0 ■D -2 2 29,760 0 0 0 0 CD -3 2 29,760 345 0 0.33 0

(/) -4 74 29,760 1,057 0 1.02 0 (/) -5 108 29,760 3,742 0 3.6 0 -6 140 29,760 9,452 0 9.08 0 -6.5 155 29,760 13,213 0 12.7 0

Table 4.4: Perennial snow and ice output from the SIM under modern and perturbed climate for Baker and Lehman Valley, Bald Mt and Lincoln Peak. 4:^to CD ■ D O Q. C 8 Q.

■D CD

C/) Location AT (C°) Run Time (years) Grid Extent (#cells) Perennial Snow (#cells) Glaciers (#cells) Snow Area (km^) Ice Area (km^) C/)

Moriah Modem 2 49,163 233 0 0.22 0 -2 4 49,163 236 0 0.23 0 CD -3 69 49,163 679 0 0.65 0 8 ■D -4 101 49,163 1,659 0 1.59 0 -5 101 49,163 1,659 0 1.59 0 (O' -6 5,297 49,163 13,590 68 13.06 0.07 -6.5 397,732 49,163 20,635 1,349 18.57 1.21

Snake Modem 2 22,512 134 0 0.13 0 3. 3" -2 2 22,512 134 0 0.13 0 CD -3 53 22,512 237 0 0.23 0 CD ■D -4 84 22,512 1,021 0 0.98 0 O Q. -5 108 22,512 2,719 0 2.61 0 C a -6 148 22,512 5,110 0 2.99 0 3O -6.5 17,756 22,512 6,674 45 6.41 0.04 "O O Williams Modem 2 17,888 0 0 0 0 -2 2 17,888 0 0 0 0 CD Q. -3 42 17,888 92 0 0.09 0 -4 85 17,888 1,145 0 1.1 0 -5 108 17,888 2,670 0 2.57 0 ■D -6 147 17,888 4,631 0 4.45 0 CD -6.5 3,655 17,888 5,558 14 5.34 0.01

(/) (/) Table 4.5: Perennial snow and ice output from the SIM under modern and perturbed climate in Snake Valley, Williams Canyon, and on Mt Moriah. 144

: y , . ".: ■■

itmm:•'. L'j. 1 f . mmÊtMÊMà

Lehman :%Val'leÿ.::':^

mmi

Figure 4.4: Location of each area of interest with respect to the Snake Range crest.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q.

■D CD

C/) Location AP (cm) Run Time (years) Grid Extent (#cells) Perennial Snow (#cells) Glaciers (#ceils) Snow Area (km^) Ice Area (km^) C/)

Baker +1 10,249 37,960 13,913 959 13.37 0.92 +2 9,784 37,960 17,005 1,653 16.34 1.59 2,234 8 +3 134,471 37,960 26,432 22.62 2.54 ■D +4 146,832 37,960 31,839 2,961 26.21 3^ 7 +5 332,763 37,960 48,331 4,619 31.89 4.61 +6 389,336 37,960 52,821 4,376 33.33 5.13

Table 4.6: Summary of snow and ice predicted in Baker Valley with a -5°C temperature change and 1cm incremental changes in precipitation. 3. 3 " CD ■DCD O Q. C g. 3o "O o

CD Q.

■D CD

C/) C/) 146 of -6.5°C with the extent of perennial snow and ice created by changing temperature by

-5°C and +1, +2 and +3 cm of precipitation. The results are summarized in Table 4.6.

The SIM predicts perennial snow under modem conditions for a number of regions

in the Snake Range, however once the topographic controls (slope, curvature, and

shading) were applied, perennial snow is only predicted with a temperature change of

-5°C, and the spatial distribution of snow dramatically decreases. Perennial ice

throughout the Snake Range is only predicted on high alpine ridges and summits,

isolated to an elevation range of -3400-3900 masl. The perennial ice that was predicted

occurred only on steep slopes, convex ridges, or west-facing slopes. These are regions

that are not characterized as suitable for the development of small alpine glaciers. Once

the grids representing the optimum topographic conditions were applied, perennial ice

was not present in any of the investigated areas.

Baker Valiev

The SIM predicts the occurrence of perennial snow at the head of Baker Valley

under modem conditions. Perennial snow continues to develop without the co­

occurrence of ice until a temperature change of -4°. The area of perennial snow reaches

a maximum cover of 16.69 km^ at -6.5°C where perennial ice reach a maximum cover of

2.6 km^. There is an abmpt boundary in the equilibration run time, which drastically

increases from 117 years at -3°C to 23,076 years at -4°C (Fig. 4.5).

Although perennial snow is predicted under modern conditions in Baker Valley, once

the grids representing the optimum topographic controls are applied, perennial snow

isn’t predicted until a temperature change of -2°C (Fig. 4.5). However, a significant area

of perennial snow isn’t produced until a temperature change of -4°C.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147

Baker Valley: Equilibration Run Time versus Temperature Perturbation 26000 24000 Glacial ice begins to develop ------22000 20000 18000 i 16000 I 14000 12000 I 10000 8000 I 6000 4000 2000

0 T : : i i 1 -2 -3 -4 -5 -5 -6.5 Temperature Change (C“)

H

F

Modern -5“C MB0 -6 -2®C l i l l -4“C ] -6®C No Snow

Figure 4.5: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop in Baker Valley, (B) predicted evolution o f perennial snow in Baker Valley with temperature perturbations of -2, -3, -4, -5, -6 and -6.5®C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 Bald Mountain

The SIM doesn’t predict perennial snow on Bald Mountain until a temperature

change of -4°C with a total area of 0.29 km^. Perennial snow develops without the co­

occurrence of ice until -6.5°C when the area of perennial snow reaches a maximum of

5.78 km^ and perennial ice reaches a maximum cover of 0.04 km^. There is an abrupt

boundary in the equilibration run time, which drastically increases from 124 years at -

6°C to 40,429 years at -6.5°C (Fig. 4.6).

Perennial snow isn’t predicted until a temperature change of -4°C, however once the

grids representing the optimum topographic controls are applied, perennial snow isn’t

predicted until a temperature change of -5°C (Fig. 4.6).

Lehman Valiev

The SIM predicts the occurrence of perennial snow at the head of Lehman Valley

under modem conditions. Perennial snow continues to develop without the co­

occurrence of ice until a temperature change of -4°C. The area of perennial snow

reaches a maximum cover of 16.49 km^ and perennial ice reach a maximum cover of

2.91 km^ at -6.5°. There is an abrupt boundary in the equilibration run time, which

increases from 3,026 years at -4°C to 11,394 years at -5°C (Fig. 4.7). Equilibration run

time then decreases to 7,365 years at -6°C and then increases to 8,616 at -6.5°.

Although perennial snow is predicted under modern conditions in Lehman Valley,

once the grids representing the optimum topographic controls are applied, perennial

snow isn’t predicted until a temperature change of -2°C (Fig. 4.7). However, a

significant area of perennial snow isn’t produced until a temperature change of -3°C.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149

Bald Mountain: Equilibration Run Time versus Temperature Perturbation 45000

40000 Glacial i ee begins to develop-

35000

Z 25000

•c 20000

S 15000 I 10000

5000

0 •2 ■3 -4 ■5 •6 -6.5 Temperature Change (C®)

.3

Bald Mountain

% -4"C -6®C [ I I I No Snow M - 5 “C Wm -6.5"C

Figure 4.6: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop on Bald Mountain, (B) predicted evolution of perennial snow on Bald Mountain with temperature perturbations of -2, -3, -4, -5, -6 and -6.5°C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 150

Lehman Valley: Equilibration Run Time versus Temperature Perturbation 12000

10000

« 8000

^ 6000

ja 4000 Glacial ice begins to develop 2000

0 ■2 -3 -4 -5 -6 -6.5 Temperature Change (C)

Modem -3“C g -5% J -6.5®C -2“C -4“C -6®C S No Snow

Figure 4.7; (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop in Lehman Valley, (B) predicted evolution of perennial snow in LehmanValley with temperature perturbations of -2, -3, -4, -5, -6 and -6.5°C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 151 Lincoln Peak

The SIM doesn’t predict perennial snow on Lincoln Peak until a temperature change

of -3°C with a total area of 0.33 km^. Perennial snow develops without the co­

occurrence through a temperature change of -6.5°C when the area of perennial snow

reaches a maximum of 12.7 km^. No perennial ice is predicted for Lincoln Peak under

any climate regime using SIM. No abrupt boundaries occur in the equilibration run

times, which range from 2 years to 155 years (Fig. 4.8).

Perennial snow isn’t predicted until a temperature change of -3°C, however once the

grids representing the optimum topographic controls are applied, perennial snow isn’t

predicted until a temperature change of -4°C (Fig. 4.8). However, a significant area of

snow isn’t predicted until a temperature change of -5°C.

Mt Moriah

The SIM predicts the occurrence of perennial snow on Mt Moriah under modern

conditions. Perennial snow continues to develop without the co-occurrence of ice until a

temperature change of -6°C. The area of perennial snow reaches a maximum cover of

18.57 km^ and perennial ice reaches a maximum cover of 1.21 km^ at -6.5°C. There is

an abrupt boundary in the equilibration run time, which drastically increases from 101

years at -5°C to 5,297 years at -6°C and another from 5,297 years at -6.5°C to 397,732

years at -6.5°C (Fig. 4.9).

Although perennial snow is predicted under modern conditions on Mt Moriah, once

the grids representing the optimum topographic controls are applied, perennial snow

isn’t predicted until a temperature change of -4°C (Fig. 4.9). However, a significant area

of perennial isn’t produced until a temperature change of -5°C.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152

A Lincoln Peak; Equilibration Run Time versus Temperature Perturbation 180

160

140

o 80 Perennial snow begins to develop

0 ■2 •3 -4 •5 -6 -6.5 Temperature Change (C °)

Ti

K -4»C S. No Snow

Figure 4.8: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop on Lincoln Peak, (B) predicted evolution of perennial snow on Lincoln Peak with temperature perturbations of -2, -3, -4, -5, -6 and -6.5®C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153

A Mt Moriah: Equilibration Run Time versus Temperature Perturbation 500000

400000

a 300000

S 200000

cr

100000 Glacial tee begins ,to de'velop

0 0 •2 ■4 ■5■3 -6 -6.5 Temperature Change (C®)

Modem i # -3"C -5“C I Ü 1 -6-5“C Fix these colors! -2“C i 0 -4®C -6“C 1 No Snow

Figure 4.9: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop on Mt Moriah, (B) predicted evolution of perennial snow on Mt Moriah with temperature perturbations o f -2, -3, -4, -5, -6 and -6.5°C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 154 Snake Valiev

The SIM predicts the occurrence of perennial snow in Snake Valley under modem

conditions. Perennial snow continues to develop without the co-occurrence of ice until a

temperature change of -6.5°C. The area of perennial snow reaches a maximum cover of

6.41 km^ and perennial ice reaches a maximum cover of 0.04 km^ at -6.5°C. There is an

abrupt boundary in the equilibration run time, which drastically increases from 148 years

at -6°C to 17,756 years at -6.5°C (Fig. 4.10).

Although perennial snow is predicted under modern conditions in Lehman Valley,

once the grids representing the optimum topographic controls are applied, perennial

snow isn’t predicted until a temperature change of -4°C (Fig. 4.10). However, a

significant area of perennial isn’t produced until a temperature change of -5°C.

Williams Canyon

The SIM doesn’t predict perennial snow in Williams Canyon until a temperature

change of -3°C with a total area of 0.09 km^. Perennial snow develops without the co­

occurrence of ice until -6.5°C when the area of perennial snow reaches a maximum of

5.34 km^ and perennial ice reaches a maximum cover of 0.01 km^. There is an abrupt

boundary in the equilibration run time, which drastically increases from 147 years at -

6°C to 3,655 years at -6.5°C (Fig. 4.11).

Perennial snow isn’t predicted until a temperature change of -3°C, however once the

grids representing the optimum topographic controls are applied, perennial snow isn’t

predicted until a temperature change of -4°C (Fig. 4.11). However, a significant area of

snow isn’t predicted until a temperature change of -5°C.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155

Snake Valley: A Equilibration Run Time versus Temperature Perturbation 20000

18000 Glacial ice begins to

16000

14000

12000

H 10000

% 8000

5 6000 6 ® 4000

2000

0 ■2 •3 -4 ■5 -6 -6.5 Temperature Change (C°)

PH

Modern -3“C -6.5“C

-2®C a -4®C I I No Snow

Figure 4.10: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop in Snake Valley, (B) predicted evolution of perennial snow in Snake Valley with temperature perturbations of -2, -3, -4, -5, -6 and -6.5°C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156

Williams Canyon: Equilibration Run Time versus Temperature Perturbation 4000 Glacial ice begins to develop 3500

H2000

■K1500

11000

500

-500 0 -2 ■3 -4 •5 -6 -6.5 Temperature Change (C“)

Modern -3"C -5"C n -6 5®C -4®C - No Snow

Figure 4.11: (A) Illustration of the considerable jump in equillibration time once perennial ice begins to develop in Williams Canyon, (B) predicted evolution of perennial snow in Williams Canyon with temperature perturbations of -2, -3, -4, -5, -6 and -6.5°C using the SIM, and (C) predicted zones of actual accumulation derived using topographic controls.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157 Evaporation Estimates

The area of pluvial lakes Maxey and Spring were calculated using a 25 m DEM

based on the spatial extent of Late Quaternary pluvial lakes in the Great Basin (Rebels,

1999). There is little improvement over the methodology employed by Reheis (1999)

who calculated area based on contour lines extracted from a 250 m DEM. A summary of

the characteristics of Lakes Maxey and Spring is provided in Table 4.7.

Lake Areaa (m ) Areavn (na ) Perimeter Max Min Mean ______(m) Elev (m) Elev (m) Elev (m) Spring 617849191.16 617837120.00 220693.49 1946.00 1641.00 1718.00 Maxey 210872297.15 210866464.00 71775.06 17590.00 1752.00 1759.00

Table 4.7: Summary of spatial characteristics of Lakes Spring and Maxey, located to the west of the Snake Range. (AreaR = area calculated by Reheis, 1999 and AreaVH = area calculated in this study. Max Elev = maximum elevation of lake, Min Elevation = minimum elevation of lake, and Mean Elev = mean elevation of each lake).

Evaporation from each lake was estimated using Equation 1.0 from Mifflin and Wheat, (1979). Evap = 248- 1.46 (Elev/10) + 0.0036 (Elev/10) ^ (1.0)

Where Evap = evaporation (cm/yr) and Elev = elevation (m). The vector files produced

by Reheis, (1999) depicting the spatial extent of Late Pleistocene pluvial lakes were used

to extract elevation values for Lakes Maxey and Spring. Equation 1 was applied to the

estimated highest elevation of Lakes Maxey and Spring, producing the evaporation

estimates and comparisons shown in Table 4.8.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 158

Technique Evaporation (cm/year)

EVs, Lake Spring 116.8

EVmw Lake Spring 102.57 Lake Maxey 102.52

Table 4.8: Summary and comparison of evaporatioin estimates for Lakes Spring and Maxey based on previously published data and techniques described by Synder and Langbein, 1962 (EVsi) and Mifflin and Wheat, 1979 (EVmw).

Discussion and Conclusions

Geomorphic evidence indicates that late Quaternary glaciers were far more extensive

and developed at lower elevations than glaciers predicted using the SIM (Van Hoesen,

2003a; b). Thus, it appears the SIM underestimates the perennial distribution of

perennial ice and snow in the Snake Range. In addition, the spatial distribution of

perennial snow predicted by the SIM is significantly less than that predicted using

ELApse (Jones and Omdorff, 1999 and Omdorff and Van Hoesen, 2001). For example,

ELApse predicts perennial snow for every grid cell within the high peaks region of the

southern Snake Range with a temperature change of -6°C. Once topographic controls

are applied, this overestimate of perennial snow provides a more realistic representation.

The distribution of perennial snow predicted by ELApse is more consistent with the

expected accumulation zones of known glaciers in the investigated area (Fig. 4.12; Jones

and Omdorff, 1999 and Omdorff and Van Hoesen, 2001).

The discrepancies between the expected spatial distribution of perennial snow and

ice and the distribution predicted using the SIM are likely introduced by the paucity of

climate data and the methodology used to generate minimum temperature values (Tmin;

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 159

I 'jf KG#

» -/-

«5y;

AMW#f#à

Figure 4.12: Raster grids depicting the spatial distribution of perennial snow in the high peaks region of the southern Snake Range, NV. (A) distribution of snow under modem conditions, (B) distribution of snow with a -2°C temperature change, (C) distribution of snow with a -4°C temperature change, and (D) distribution of snow with a -6°C temperature change.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) not included in the original manuscript are unavailable from the author or university. The manuscript was microfilmed as received.

160

This reproduction is the best copy available.

UMI'

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 There is evidence suggesting that alpine glaciers in the Great Basin reached their

maximum extent at approximately-15-18 ka and started retreating by -13 ka (Elliott-

Fisk, 1987 and Dorn et al., 1990), Lake Bonneville in particular dropped 100 m at -14.5

ka in response to downcutting of the Zenda threshold (Oviatt et al., 1992). However,

many Great Basin pluvial lakes didn’t reach their maximum extent until approximately

14 ka. This suggests that glaciers started retreating prior to the maximum extent of

pluvial lakes in the Great Basin (Antevs, 1925; Lajoie, 1968; Scott et al., 1993; Wayne,

1984; and Bevis, 1995). This relationship is consistent with the hypothesis that

following the northward transition of the jet stream and storm tracks, in response to

reduced continental ice sheets, winter months became warmer, cloudier, and experienced

less precipitation (Antevs, 1948; Kutzbach and Guetter, 1986; Benson and Thompson,

1987; COHMAP Member, 1988; Allen and Anderson, 1993 and Kutzbach et al., 1993).

Decreased precipitation, decreased evaporation and increased temperature would

facilitate the decay of glaciers. This decay would be accompanied by increased fluvial

output and the subsequent growth of pluvial lakes to the east of the Schell Creek and

Snake Ranges in Spring and Snake Valley respectively.

However, it has been suggested that evaporation from pluvial lakes could provide an

ancillary source of moisture for the development of alpine glaciers in the Great Basin

(Hostetler et al., 1994; Bevis, 1995; Oviatt, 1996; 1997; Hostetler et al., 2000).

Estimated evaporation rates for Lakes Maxey and Spring are likely overestimates since

rates of evaporation rates are depressed in proportion to salinity, water color and depth,

and wind velocities (Harbeck, 1955; Langbein, 1961; Turk, 1970; and Smith and Perrott,

1983). Evaporation is also strongly controlled by fluctuating lake levels, humidity, air

and surface water temperature and variations in cloud cover (Benson, 1981; 1986).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 These parameters were not evaluated in this study so evaporation rates represent rough

estimates based solely on a regression between evaporation, surface area and elevation.

The results of climate perturbations in the Snake Range suggest the limiting factor on

the development of perennial snow and ice is temperature and not small changes in

precipitation. This inference is consistent with previous paleoclimate studies in the

Great Basin (Sears and Roosma, 1961; Wells, 1983; Thompson, 1992; Bevis, 1995; and

Hostetler and Clark, 1997). However, the presence of Lakes Spring and Maxey directly

west of the Snake Range could have provided a significant source of moisture (-120

cm/yr) facilitating the development of alpine glaciers. Much of this moisture would be

lost during evaporation, changes in wind direction, and interception by vegetation. If the

Snake Range intercepted just 5-10% of this moisture during the winter months, this

could potentially represent a 6-12 cm increase in precipitation. This rough estimate

doesn’t take into account the increase in precipitation of 20 cm and a reduction in

evaporation by 21.5 cm in order to develop and sustain Lake Spring suggested by Snyder

and Langbein (1962). It also doesn’t account for the possible input of moisture from a

number of pluvial lakes located to the west of the range (Fig. 4.2; Reheis, 1999).

Although, it is likely both Lake Spring and Maxey were partially covered by ice similar

to Lake Lahonton and Bonneville (Benson, 1981 and Hostetler et al., 1994). The

discrepancy between suggesting an increase in precipitation in the Snake Range derived

from pluvial lakes and previous paleoclimate and paleoecology studies that suggest the

region only experienced a small increase in precipitation, may result from the seasonality

of the precipitation. Increased precipitation may not be reflected in the flora or faunal

distribution in the Snake Range if it falls during the winter months and not during the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 early spring or growing season. During warmer months, much of the moisture derived

from pluvial lakes would be lost to the atmosphere rather than falling as precipitation.

Oviatt (1996, 1997), who suggests that changes in pluvial Lake Bonneville were

synchronous with Heinrich and Bond events, further enhanced the interrelationship

between pluvial lakes, the atmosphere, and alpine glaciers identified by Hostetler et al.

(1994). If the hypothesis that increased winter moisture derived from pluvial lake

systems facilitated the growth and preservation of alpine glaciers in the Great Basin is

valid, then it is plausible the decay of glaciers prior to the onset of lake degradation

created a lag in the response time of pluvial lakes to the northward migration of the

Jetstream during Heinrich and Bond events. Benson (1981) and Smith (1979) suggested

the meltwater derived from glacial ice in the Sierra Nevada were not sufficient to sustain

pluvial Lakes Lahonton and Searles. However, due to the smaller area of Lakes Spring

and Maxey, increased runoff and fluvial output could delay the collapse of pluvial lake

systems. Thus, in some cases the synchronicity of falling lake levels with Heinrich

Events may be reflecting a synchronicity with the final decay of alpine glaciers and the

loss of fluvial input.

Future Work

Numerous mountain ranges throughout the Great Basin experienced extensive

glaciation during the Last Glacial Maximum (LGM). Almost every glaciated range was

associated with a pluvial lake or lakes. The estimated potential winter evaporation and

precipitation relationship needs to be evaluated for each of these ranges to test for

consistency throughout the Great Basin. It is possible that glaciation in many of these

ranges developed under increased winter precipitation drawn from local pluvial lake

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 164 systems. However, a higher resolution estimate of lake evaporation based on mean

monthly air temperature, monthly means of air temperature, air humidity and solar

radiation should be calculated. This can be accomplished by using the Complementary

Relationship Lake Evaporation (CRLE) model that is widely used by electricity

companies in Brazil (Hostetler et al., 1990; dos Reis and Dias, 1998; and Leydecker and

Melack, 2000). CRLE provides estimates of monthly evaporation and the change of

stored enthalpy in lake waters and equilibrium temperature, a proxy for the actual water

surface temperature.

This study suggests the SIM drastically underestimates the spatial distribution of

perennial snow and ice, likely caused by the technique used to derive Tmin. However,

ELApse appears to be a more accurate tool for calculating perennial snow distribution.

Therefore, the next step would involve incorporating the plastic C+ subroutine from the

SIM (i.e. - the technique used to initiate the flow of ice from one grid cell to another)

into the ELApse code to better evaluate this technique on higher resolution digital

elevation models. Our goal is to create an extension for the program ArcGIS so users

can more readily access the integrated features of ELApse and the SIM.

To truly evaluate the interrelationship between falling lake levels and deglaciation in

the Snake Range, and throughout the Great Basin, a higher resolution absolute age

chronology must be established. Van Hoesen and Omdorff (2003) suggest age

constraints in the Snake Range will be difficult to obtain because of the lack of material

suitable for radiocarbon dating, cosmogenic surface exposure dating and luminescence

dating. However, the Schell Creek Range contains a similar glacial record as the Snake

Range and may provide opportunities to further constrain the glacial chronology in both

ranges. Similarly, the shorelines of Lakes Spring and Maxey have not been dated or

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 165 investigated for paleoclimatic indicators. Investigating the relationship between the

Schell Creek Range and Lake Spring and Maxey may provide insight into the

paleoclimate of the Snake Range and possibly illuminate the relationship between

pluvial lake systems and alpine glaciers.

Acknowledgements

We thank the Arizona-Nevada Academy of Science, American Alpine Club, Sigma

Xi and Colorado Scientific Society for financial support and Weiquan Dong at the

Univeristy of Nevada, Las Vegas for helpful discussions.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 166 References

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 168 Lajoie, K.P., 1969, Late Quaternary stratigraphy and geologic history of Mono Basin, eastern California. Unpublished Ph.D. dissertation. University of California, Berkeley, 217p.

Langbein, W.B., 1961, Salinity and hydrology of closed lakes. U. S. Geological Survey Professional Paper Report P0412, 20 p.

Mead, J.I., Thompson, R.S., and Van Devender, T.R, 1982, Late Wisconsinan and Holocene fauna from Smith Creek Canyon, Snake Range, Nevada. Transactions of the San Diego Society of Natural History 20: 1-26.

Mead, J.I. and Mead, M., 1985, A natural trap for Pleistocene animals in Snake Valley, Eastern Nevada. Current Research in the Pleistocene 2: 105-106.

Leydecker, A. and Melack, J.M., 2000, Estimating evaporation in seasonally snow- covered catchments in the Sierra Nevada, California. Journal of Hydrology 236: 121-138.

Negrini, R.M., 2001, The Quaternary climate record from pluvial lakes in the Great Basin; relationship to global climate change. Geological Society of America Abstracts with Programs 33: 81.

Omdorff, R.L., 1994, Development of a surface hydrologie model and its application to modem and Last Glacial conditions within the Great Basin. Ph.D. dissertation, Kent State University, 220p.

Omdorff, R.L. and Van Hoesen, J.G., 2001a, Using GIS to predict the spatial distribution of perennial snow under modem and Pleistocene conditions in the Snake Range, Nevada. 69* Annual Meeting of the Westem Snow Conference, Sun Valley, Idaho, 2001, pg. 119-123.

Omdorff, R.L. and Van Hoesen, J.G., 2001b, Microclimate controls on perennial snow in the Snake Range, Nevada: 45* Annual Meeting of the Arizona-Nevada Academy of Science, University of Nevada, Las Vegas.

Omdorff, R.L. and Van Hoesen, J.G., 2001, Using GIS to predict the spatial distribution of perennial snow under modem and Pleistocene conditions in the Snake Range, Nevada. 69th Annual Meeting of the Westem Snow Conference, Sun Valley, Idaho: 119-122.

Oviatt, C.G., Currey, D.R., and Sack, D., 1992, Radiocarbon chronology of Lake Bonneville, eastem Great Basin, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 99: 225-241.

Oviatt, C.G. and Thompson, R.S., 1996, Lake Bonneville water budget and the Laurentide ice sheet. Geological Society of America Abstract with Programs 28: 232.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 169 Oviatt, C.G., 1997, Lake Bonneville fluctuations and global climate change. Geology 25: 155-158.

Plummer, M.A., Philips, P.M., and Small, E.E., 2000, An inverse modeling approach to using both lacustrine and glacial records to better constrain paleoclimatic conditions. Geological Society of America Abstracts with Programs 32; 17.

Plummer, M.A. and Phillips, P.M., 2003, A 2-D numerical model of snow/ice energy balance and ice flow for paleoclimatic interpretation of glacial geomorphic features. Quaternary Science Reviews 22: 1389-1406.

Reheis, Marith, 1999, Extent of Pleistocene Lakes in the Western Great Basin.- USGS Miscellaneous Field Studies Map MF-2323, U.S. Geological Survey, Denver, CO.

Sears, P.B. and Roosma, A., 1961, A climatic sequence for two Nevada Caves. American Journal of Science 259: 669-678.

Sharp, R.P., 1938, Pleistocene glaciation in the Ruby-East Humbolt Range, northeastern Nevada. Journal of Geomorphology 1: 296-323.

Singer, M.P., 1985, A computer simulation model of the growth and desiccation of pluvial lakes in the southwestern United States. M.S. thesis, Kent State University, 436p.

Stewart, J.H. and McKee, E.H., 1977, Geology and mineral deposits of Lander County, NV. Part I: Geology. Nevada Bureau of Mines and Geology Bulletin 88: 106p.

Thompson, R.S., 1984, Late Pleistocene Holocene environments in the Great Basin. Unpublished Ph.D. dissertation. University of Arizona.

Thompson, R.S., 1992, Late Quaternary environments in Ruby Valley, Nevada. Quaternary Research 37: 1-15.

Thompson, R.S and Mead, J.I., 1982, Late Quaternary environments and biogeography in the Great Basin. Quaternary Research 17: 39-55.

Tummire, K., 1982, A preliminary analysis of fossil vertebrates from Owl Cave No.2, Nevada. Current Research in the Pleistocene 2: 109-110.

Turk, L.J., 1970, Evaporation of brine; a field study on the Bonneville Salt Flats, Utah. Water Resources Research 6: 1209-121.

Van Hoesen, J.G., Omdorff, R.L., and Saines, M., 2000, A preliminary assessment of an ice-contact deposit in the Spring Mountains, Nevada, Geological Society of America Abstracts with Programs.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 170 Van Hoesen, J.G. and Omdorff, R.L., 2001, Using GIS to predict the spatial distribution of perennial snow and ice under modem and Pleistocene conditions in the Spring Mountains, Nevada. Geological Society of America Abstracts with Programs 33: A67.

Van Hoesen, J.G. and Omdorff, R.L., 2003, The paleoclimatic significance of relict glacial and periglacial landforms. Snake Range, Nevada. This Volume, Chapter 2.

Van Hoesen, J.G., 2003, Surficial geology of glaciated canyons in Windy Peak an Wheeler Peak Quadrangles, Southem Snake Range, Nevada. This Volume: Plate I.

Wayne, W.J., 1984, Glacial chronology of the Ruby Mountains - East Humbolt Range, Nevada. Quaternary Research 21: 286-303.

Wells, P.V., 1983, Paleobiogeography of the montane islands in the Great Basin since the last glaciopluvial. Ecological Monographs 53: 341-382.

Whitebread, D.H. 1969. Geologic map of the Wheeler Peak and Garrison quadrangles, Nevada and Utah. United States Geologic Survey Misc. Survey Map 1-578.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 5

A COMPARATIVE SEM STUDY ON THE MICROMORPHOLOGY OF GLACIAL

AND NON-GLACIAL CLASTS WITH VARYING AGE AND LITHOLOGY:

EXAMPLES FROM THE ARCTIC AND SOUTHWESTERN UNITED STATES.

This paper has been prepared for submission to Paleoecology, Paleoclimatology, Paleogeography and is presented in the format of that journal. The complete citation will is:

Van Hoesen, J.G. and Omdorff, R.L., 2003, A comparative SEM study on the micromorphology of glacial and non-glacial clasts with varying age and Ethology: Examples from the Arctic and Southwestern United States. Paleoecology, Paleoclimatology, Paleogeography (IN PREP).

171

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172

Abstract

Preliminary research on striated clasts from a variety of depositional environments

suggests that scanning electron microscopy (SEM) of striated clasts of varying Ethology

in diamictons may prove useful in distinguishing a glacial origin. The evaluation of

SEM analysis of clasts from diamictons is an applicable technique to define a glacial

origin requires a better understanding of the micro-features on glacial and non-glacial

clasts. We describe the micromorphology of surface textures and characteristics for

samples of quartzite, granite, limestone, basalt, chert, pillow basalt, and quartz pebbles

collected from a variety of depositional environments. This study suggests that certain

micro-features are useful for differentiating glacial and non-glacial deposits based on the

micromorphology of entrained clasts.

Introduction

Limited data have been published on the analysis of micro-features and

characteristics of striated clasts thought to have a glacial origin (Wentworth, 1926;

Judson and Barks, 1961; Bjprlykke, 1974; Hicock and Dreimanis, 1989). Most research

concerning the micromorphology of tills has focused on individual quartz grains (Brown,

1973; Krinsley and Doomkamp, 1973; Folk, 1975; Mahaney et al., 1988; Mazzulo and

Ritter, 1991; Mahaney et al., 1991; Campbell and Thompson, 1991; Mahaney and Kalm,

1995; Mahaney, 1995; Mahaney et al., 1996; Mahaney and Kalm, 2000). Surface

textures of quartz grains have been used to determine local ice transport vectors, ice

thickness, and depositional environment. SEM results from these studies established that

sediment affected by glacial transport and deposition exhibits distinct microtextural

characteristics (Table 5.1). However, these characteristics are not isolated to

206

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173

Feature References Adhering particles Mahaney et al., 1986, 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Mazzullo and Ritter, 1991; Watts, 1985 Abrasion features Mazzullo and Ritter, 1991 Arc shaped steps Campbell and Thompson, 1991; Mahaney et al., 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995 Breakage blocks Campbell and Thompson, 1991 Chattermarks Campbell and Thompson, 1991; Folk, 1975 Conchoidal fractures Campbell and Thompson, 1991; Mahaney et al., 1988, 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Mazzullo and Ritter, 1991 Curved grooves Campbell and Thompson, 1991; Mahaney et al., 1988, 1996, 2001; Mahaney, 1995; Mahaney, 1990b Cresentic gouges Campbell and Thompson, 1991; Mahaney et al.,1988, 1996; Mahaney, 1995; Watts, 1985 Crushing features Mahaney, 1990a; Mahaney, 1990b; Mahaney et al., 1988 Deep troughs Mahaney et al., 1996, 2001; Mahaney and Kalm, 2000 Dissolution etching Campbell and Thompson, 1991; Mahaney et al., 1988,1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995 Edge rounding Campbell and Thompson, 1991; Mahaney et al., 2001; Mahaney and Kalm, 2000; Mahaney et al., 1996; Mahaney et al., 1991; Mahaney et al., 1988 Fracture faces Mahaney et al., 2001; Mahaney and Kalm, 2000; Mahaney et al., 1996 High relief Campbell and Thompson, 1991; Mahaney et al., 1988,1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Mahaney, 1990 Lattice shattering Mahaney et al., 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995 Linear steps Mahaney et al., 1996, 2001; Mahaney and Kalm, 2000 Low relief Campbell and Thompson, 1991; Mahaney et al., 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995 Medium relief Campbell and Thompson, 1991; Mahaney et al., 1988,1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995 Overprinted grains Mahaney et al., 1991, 1996, 2001; Mahaney and Kalm, 2000 Precipitation features Campbell and Thompson, 1991; Mahaney et al., 1988, 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Mazzullo and Ritter, 1991; Watts, 1985 Preweathered surfaces Mahaney et al., 1988, 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Watts, 1985 Sharp angular features Mahaney et al., 1988, 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Star-cracking Campbell and Thompson, 1991 Straight grooves Campbell and Thompson, 1991; Mahaney et al., 1988, 1996,2001; Mahaney and Kalm, 2000; Mahaney, 1995 Subparallel linear fractures Mahaney et al., 1991, 1996, 2001; Mahaney and Kalm, 2000; Mahaney, 1995; Mahaney, 1990b Subparallel crushing planes Mahaney, 1995; Mahaney et al., 1988 V-shaped percussion cracks Campbell and Thompson, 1991; Mahaney et al.,1991, 1996, 2001; Mahaney and Kalm, 2000; Krinsley and Doomkamp, 1973; Krinsley and Donahue, 1968

Table 5.1: Summary of previously described surface textures and features identified on auartz grains and bedrock using a scanning electron microscope.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 glacially derived quartz grains. While previous research has established the merits of

SEM analysis of quartz grains in glacial research, this study suggests that SEM analysis

of larger clasts in diamictons may also prove useful in defining a glacial origin. We

hypothesize that, clasts larger and commonly softer than quartz grains, exhibit some of

the same microtextural characteristics if the deposit from which they were collected has

a glacial origin.

The goals of this study are to (1) document the various micro-scale textures and

surface features exhibited by clasts of differing Ethologies from glacial environments, (2)

compare and contrast the observed textures and features with features identified on clasts

from non-glacial environments, and (3) establish whether SEM analysis of striated clasts

in diamictons is an applicable tool to infer a glacial origin.

Methods

Striated clasts ranging in size from 5.0 cm to 0.75 meters were collected from known

glacial, eolian, fluvial, and lacustrine environments throughout the southwestern United

States and Canada during 2000 to 2002. Till samples from Allan Hills, Antarctica were

also provided by Phil Holme. This study focused on the southwest and high latitude

regions because we reason that preservation of surface features will increase with

decreased physical and chemical weathering typical of these regions. Two sample sets

from glacial and non-glacial deposits were chosen for analysis: those that displayed

visible surface striations or markings and those that lacked visible surface features.

More samples were collected in glacially affected environments because one of the goals

of this study is to characterize the microfeatures related to glaciation. Samples collected

from

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) not included in the original manuscript are unavailable from the author or university. The manuscript was microfilmed as received.

175

This reproduction is the best copy available.

UMI*

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176

0 2500 5000 1 Millimeter = 71 Kilometers 1000 2000 3000 1 Millimeter = 31 Kilometers

1. Klondike Gravel, Yukon (KG) 6. Spring Moutains, NV (SM, SMF) 2. Yukon River, Yukon (YR) 7. Snake Range, NV (SC, NFB) 3. Allan Hills, Antarctica (AH) 8 . Fish Lake Plateau, UT (FL) 4. Yosemite National Park, CA (YS) 9. La Sal Mountains, UT (TUKU) 5. Devils Postpile National Monument, CA (DP) 10. Lake Bonneville Shoreline, UT (LB)

Figure 5.1: Location of study sites located in the Yukon, Antarctica and the southwestern United States.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■D O Q. C g Q. Name ID Latitude Longitude Lithology Relative Environment ■o Age CD Glacial YS 37° 50’ 39.7" 119° 27'31.3” Granite MP Bedrock WC/) o' 3 Yosemite NP, CA O DP 37° 37’ 32.6" 119° 05’ 02.3" Basalt MP Bedrock Devils Postpile NM, CA YR 64° 01’37.7" 139° 21’45.2” Chert ~1.5MA Till 8 Fort Selkirk, YT SM 36° 16’ 13.6" 115° 40’ 25.6" Limestone EP Till TD Spring Mountain's, NV SC 38° 15’ 53.8" 114° 15’51.8" Quartzite EP Moraine crest Snake Creek, NV AH-1 62° 48" 137° 20" Quartz Till Allan Hills, Antarctica AH-2 62° 48" 137° 20" Pillow Basalt Oligocene? Till

CD Fish Lake, UT FLO 38° 35’ 27.4" 111° 40’ 33.9" Trachyte EP Moraine crest 3. FL 38° 34’ 15.5" 111° 41’ 55.5" Trachyte LP Moraine crest 3 " CD La Sal Mountains, UT Tuku 38° 26’ 55.1" 109° 15’ 26.9 ” Trachyte LP Rock glacier lobe "OCD O Non-Glacial CQ. a O Bonneville Shoreline, UT LB 41” 3634" 113° 37’02” Quartzite MP Wave cut shoreline 3 "O Klondike Gravel, YT KG 64° 01’37.7" 139° 21’45.2" Chert LP Glacial outwash o North Fork Baker Creek, NV NFB 3 8°4 3 ’05” • 114° 2331" Quartzite H Fluvial

CD Q. Spring Mountain’s, NV SMFC 36° 27'20" 115° 67’04” Limestone H Fluvial

"O Table 5.2: Summary of sample sites, sample ID designation, geographic coordinates, lithology, relative age (EP = Early Pleistocene, CD MP = Middle Pleistocene, LP = Late Pleistocene, T = Tertiary, H = Holocene), and depositional environment.

C/) C/) 178 Mono Basin age deposits in the Sierra Nevada based on clast preservation and post-

depositional modification of the landform (Russell, 1889; Sharpe and Birman, 1963; and

Yount and L,aPointe, 1997). However, the lack of suitable organic material for

radiocarbon analysis precludes accurate age determination. Approximately 30 limestone

clasts were collected from the till and four limestone clasts were collected from fluvial

deposits upvalley from the deposit during the summer of 2000.

Southem Snake Range

The Snake Range is located in east central Nevada within the boundaries of the Basin

and Range physiographic province. It has long been recognized that the Snake Range

was glaciated during the Late Quaternary (Gilbert, 1875; Russell, 1884; Weldon, 1956;

Kramer, 1962; Whitebread, 1969; Osborn, 1990; Piegat, 1980; Osborn and Bevis, 2001).

Two discrete intervals of glaciation in the Snake Range are correlative with Lamoille and

Angel Lake advances (Sharpe, 1938; Wayne, 1983; Osborn and Bevis, 2001). The

Angel Lake advance is approximately correlative with the Tioga stage, and the Lamoille

advance with the Tahoe stage as described in the Sierra Nevada. The glaciated portions

of the Snake Range are primarily early Paleozoic Prospect Mountain Quartzite, Pioche

Shale, and Pole Canyon Limestone intruded by the Jurassic age Snake Creek - Williams

Canyon Pluton (Drewes, 1958; Whitebread, 1969; Lee et al., 1970; Lee and Van Loenen,

1971; Lee et al., 1981; Lee and Christiansen, 1983 a, b; Lee et al., 1986; Miller, 1995

and Miller, 1999). Two quartzite clasts were collected from the crest of a dissected

Lamoille moraine (Fig. 5.2b) in Snake Creek at approximately 2587 masl and two

quartzite clasts were collected from Holocene fluvial deposits in North Fork Baker Creek

at approximately 3038 masl during the summer of 2001.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 179

giilrïB

(C) Rockglacier

SïTjà

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Figure 5.2: Field photos illustrating typical environment of selected samples, (a) Big Falls Till in the Spring Mountains, NV , (b) Lamoille (Tahoe) age moraine in Southern Snake Range, (c) view of rock glacier on Mt Tukuhnikivatz from a lateral moraine, (d) polished surface o f granite in Yosemite NP, (e) Upper surface of polished basalt columns in Devils Postpile NM, (f) moderately consolidated diamicton along Yukon River, (g) upper surface o f Klondike Gravel SW of Dawson City, and (h) wave polished quartzite shoreline in NW Utah.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 180 La Sal Mountains. Utah

The La Sal Mountains are located in east - central Utah approximately 35 km east of

Moab, Utah. Evidence for Pleistocene glaciation includes characteristic U-shaped

valleys, moraines, and striated and polished bedrock (Richmond, 1962; Nicholas, 1994).

There is also evidence of Holocene glaciation in at least one locality in the range

(Nicholas, 1991; Nicholas and Butler, 1996). The range is composed of Late Cretaceous

to early Tertiary hypabyssal intrusions of trachyte and rhyolite porphyries overlain by a

thick Quaternary mantle (Hunt, 1958; Richmond, 1962; Ross, 1998). Two samples were

collected from a moraine dissected by Brumley Creek, a tributary to Pack Creek, on the

southwest flank of Mount Tukuhnikivatz (3805 masl; Fig. 5.2c).

Fish Lake Plateau. Utah

The Fish Lake Plateau is located southeast of Salt Lake City, Utah. The plateau is

composed of Tertiary volcanics, primarily red to purple trachyte and light gray sanidine

trachyte (Hardy and Muessig, 1952). Tertiary sedimentary rocks underlie the volcanic

successions and these in turn are thought to overlie the Green River formation (Hardy

and Muessig, 1952). Two episodes of glaciation are described as Wisconsin I and

Wisconsin II that more than likely represent the Tioga/Tahoe and/or Angel

Lake/Lamoille glacial stages. Samples were collected from a younger Wisconsin II

terminal moraine at the mouth of Pelican Canyon and an older Wisconsin I terminal

moraine north of Pelican Bay (also referred to as Widgeon Bay).

Yosemite National Park

Yosemite National Park is located in the west - central portion of the Sierra Nevada

batholith. The eastem section of Yosemite Valley is composed of granites intruded by

the Late Cretaceous Tuolumne Intmsive Suite (Bateman, 1992; Ratajeski et al., 2001).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 181 Matthes (1930) recognized the development and preservation of two ages of polished

surfaces indicative of older and younger glacial advances in Yosemite Valley. Four

samples of younger polished surfaces of Late Cretaceous granite were collected near

Tenaya Lake during summer 2001 (Fig. 5.2d).

Devils Postpile National Monument

Devils Postpile National Monument (DPNM) is located in southern California east of

Yosemite National Park and southwest of Mammoth Lakes. This flow is composed of

Pliocene columnar trachybasalt - trachyandesite whose upper surface was scoured and

polished during the last glaciation (Fig. 5.2e; Bailey, 1987 and Bailey and Hill, 1987).

Four samples of basalt were collected from the upper surface of the polished basalt flow

during the summer of 2001.

Yukon Territorv

A chert pebble was collected from a 1.5Ma year old (Ma) diamicton along the Yukon

River downstream from Fort Selkirk during summer 2001 (Fig. 5.2f; Jackson et al.,

2001). During the summer of 2002, six chert pebbles were collected from the upper unit

of the Klondike Gravel/Conglomerate southwest of Dawson City (Fig. 5.2g) and two

chert pebbles were collected from Pleistocene age glaciofluvial gravel at the head of

Dominion Creek (Froese, et al., 2000 and Froese, 1997).

Allan Hills. Antarctica

In the Allan Hills region, extensive peperites, hyaloclastites and irregular intrusive

masses are intermixed with tuffs and tuff-breccias of the Mawson Formation (Ballance et

al., 1971). These rocks, and correlatives 1500 - km along strike in the Transantarctic

Mountains, form regional pyroclastic deposits transitional between Beacon Supergroup

terrestrial sedimentation and Ferrar Supergroup flood basalt volcanism (Ballance et al..

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 182 1971; Denton and Hughes, 2002; and Atkins et al., 2002). Five quartz pebbles and two

pebbles of pillow basalt were extracted from a sample of the Sirius Group till, provided

by Phil Holme. The Sirius Group most likely developed during the Oligocene to

Miocene, although the age of this deposit has been controversial (Bruno et al., 1999;

Stroeven and Klehman, 1999; Holme, 2001; and Denton and Hughes, 2002).

Lake Bonneville Shoreline. Utah

Lake Bonneville occupied closed depressions in the eastern Great Basin and covered

approximately 20,000 square miles at its greatest extent. Lake Bonneville created three

major shorelines, the Provo, Bonneville, and Stansbury shorelines that can be identified

as terraces on many mountains throughout western Utah, eastern Nevada, and southern

Idaho (Oviatt et al., 1992). The Provo shoreline has an approximate age of 16,800 -

16,200 years BP, the Bonneville has an approximate ago of 18,000 - 16,800 years BP,

and the Stansbury shoreline has an approximate age of 24,400 - 23,200 years BP (Oviatt

et al., 1992). 4 samples of Quartzite of Clarks Basin were collected from a Bonneville -

age terrace in northeastern Utah at approximately 1553 masl (Fig. 5.2h).

Results

Previous studies have focused on scanning electron microscopy of quartz grains from

known glacial deposits or active glacial environments. These studies documented and

described distinctive micro-scale features that are characteristic of glacial environments.

The samples in this study exhibit many of these glacially derived features depending on

lithology, age, and source of the clast. Of particular interest is the presence of arc­

shaped and linear steps, and conchoidal and sub-parallel crushing features assumed to

develop through compression and grinding during glacial transport. Specific SEM-

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 183 observed micro - features for each lithology and depositional environment are

summarized in Figure 5.3.

Spring Mountains

Limestone clasts from the Big Falls till display both macro-scale features and micro­

scale features characteristic of a glacial origin. The surfaces of most clasts are strongly

polished and contain striations (1.0 - 4.0 mm wide), chatter marks (3.0 - 5.0 mm),

crescentic gouges (1.0 - 3.0 cm), and rare small - scale flute topography (1.0 - 3.0 cm

amplitudes) that are all visible to the unaided eye. Chatter marks occur individually on

the surface of the clasts, within the striations, and they commonly occur in small lenses

of micrite in the limestone. Scanning electron microscopy of fourteen striated limestone

clasts (with c - axes that varied from about 10 cm to 30 cm in length) reveals distinctive

micro-scale features attributed to the effects of glaciation including the following:

straight grooves (Fig. 5.4a), crescentic gouges, arc-shaped steps, curved grooves,

conchoidal and subparallel crushing features, and linear steps. Straight grooves range in

width from 2.0 - 10 jam, crescentic gouges range in size from 75 - 100 jam wide with

variable length, arc-shaped steps are 20 - 100 |am wide, and crushing features are 5.0 -

20 |am wide. None of the samples exhibit scouring features or v-shaped percussion

features, and very few contain features that appear to have been rounded since formation.

Many show evidence of dissolution etching, and some have weathered surfaces.

In contrast, limestone clasts sampled from fluvial deposits exhibit rounding, visible

scouring features and lack linear striations. SEM analyses indicate the presence of well

- developed v-shaped percussion features that are -100 - 175 pm wide at their apex,

prominent scouring features, and edge rounding (Figs. 5.7a - b).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■D O Q. C g Q.

■D CD

C/i C/i Micro Features Observed On Striated Samples

CD ■D8

(O'

AH-l- XIX X 1XI IX 1 XI i X X 1 1 AH-2- xjx V M ' xix xi Ix X 3"3. DP- IX X 1 1 IX XIX xfxl X IX XX CD FLO- X|X X I i i X XI X I ixix xix X X a ■DCD o FLY- IX X ixTxl XI xi IX IX X XI X O % Q. eg LB- X'jX X ix X x| ix X C u i^i a o NFB- IX XIII IX 1 XI r XI 1 XX o 3 SC- Xj XX jxjxjx Xi X xix X! ! _ ix X xi X V X| T3 XI X O 'cu SM- X ixTxlx XIX XIX X IX XI 1 XI IX X XI IX X XI X a SMF- XI X 1 1 ix |X X eg r 1 CD TUKU- XI X X 1 \ ]x xi XlX r ix 'xl IX X r X Q. CZ) KG- XI X X 1 1 1 |X iX X YR-xi'x X 1 1 1 'xi X xi 1: 1 xi ix 1 X i X X YS- XIX X 1 1 1 X XI X XI X XI !1 Î1 1 X X IX IX X X T3 CD

(/) (/)

Figure 5.3; Summary of observed microfeatures observed on striated samples from various depositional enviromnents and lithologies. Sample identification summary: AH = Allan Hills, DP = Devils Postpile, FL = Fish Lake, KG = Klondike Gravel, LB = Lake Bonneville, NFB = North Fork Baker, SC = Snake Creek, SM = Spring Mountains, SMF = Spring Mountains Fluvial, TUKU = La Sal Mountains, YR = Yukon River, and YS = Yosemite National Park. 2 185 Devils Postpile

The upper surface of the Devils Postpile basalt flow is strongly polished and striated

(Figs. 5.4g - h). Striations ranging in width from - 1 - 3 mm and crescentic gouges -1 -

1.5 cm wide are visible with the unaided eye. Under SEM magnification, these samples

exhibit sub - parallel linear fractures, straight grooves that are 1 - 2 pm wide, linear

steps that are 25 - 75 pm wide, deep troughs that are 5 - 15 pm wide, conchoidal

crushing features that are 10 - 90 pm wide, and arc-shaped steps -50 - 100 pm wide.

The glacial polish that is so obvious in the field is easily identified in the SEM as relict

polished, although this surface does exhibit evidence of dissolution etching.

Fish Lake

Two ages of sanidine trachyte were collected from the Fish Lake region representing

the older Early Pleistocene and younger Late Pleistocene glacial advances. The surface

of the older sample is more weathered and lacks visible striations, while the younger

sample is well weathered but retains visible striations ranging in width from 1 - 4 mm

(Fig. 5.5a - b). Viewed with the SEM, the older sample exhibits arcuate grooves that

range in width from 75 - 125 pm, arc-shaped steps ranging in width from 50 - 80 pm,

and crushing features. Relict polish occurs as pre - weathered surfaces that are

weathered and eroded. Arcuate grooves and arc-shaped steps are weakly preserved in

some instances but difficult to recognize. The younger sample exhibits arcuate grooves

that range in size from 50 - 100 pm wide, arc-shaped steps ranging from 30 - 70 pm

wide, sub - parallel crushing planes that are 10-20 pm wide, fracture faces, relict

polish, and crushing features (Figs. 5.5c - d).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 186 ixsm

, . ■ - " %. '/ ^ylB3#E

, C0kuC yX'.wa ie«-a00e r 2 .

w

m m L Æ i

SMCSh SMC4b

KM I B i M Figure 5.4: SEM photomicrographs of representative glacial features from Spring Mountain and Devil's Postpile samples, (a) Polished limestone surface showing numerous deep troughs (arrows) and arcuate grooves/striations (ag), (b) deep arcuate groove surrounded by surface with some evidence of dissolution etching, (c) lunate fracture containing conchoidal crushing features (cef), (d) close-up of crushing features, (e) subparallel crushing features (f) crushing features (erf) and breakage blocks (bb), (g) relict polished surface on basalt, (h) close-up of polished basalt showing numerous arcuate grooves

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 187 Snake Range

Two quartzite samples collected from the crest of a Lamoille age moraine exhibit

well-preserved striations -2 -4 mm wide, visible with the unaided eye. Under

magnification, these samples contain numerous well - preserved features, including sub

- parallel crushing features that are 10 - 20 pm wide, conchoidal fractures 2 - 5 pm

wide, sub - parallel linear fractures, straight grooves that are 5 - 10 pm wide, linear

steps that are 5 -3 0 pm wide, fracture faces, curved grooves that are 20 - 30 pm wide,

arc-shaped steps that are 10 - 20 wide, chattermarks, and star cracking (Figs. 5.5e - h).

In contrast, two quartzite samples collected from a fluvial deposit are sub - rounded to

rounded and are heavily scoured. Viewed under the SEM, they exhibit well - developed,

v-shaped percussion features that are -150 - 180 pm wide at their apex, moderately

developed scouring features, and minor edge rounding.

La Sal Mountains

Trachyte clasts collected from the surface of a Late Pleistocene moraine exhibit well-

developed striations. These samples display crushing features 15 - 30 pm wide, curved

grooves that are 10-20 pm wide, and arc-shaped steps that are 15 - 40 pm wide (Figs.

5.6 a - b). They also show evidence of mechanically upturned plates, dissolution etching,

and relict polish preserved as pre - weathered surfaces.

Allan Hills. Antarctica

Two lithologies were identified in the Allan Hills till sample. Five quartz pebbles

ranging in size from 1 - 3 cm and two pebbles of pillow basalt ranging in size from 0.5

to 1.0 cm were analyzed. The quartz pebbles were well rounded and finely polished, and

the pillow basalt was sub-rounded and heavily weathered. The quartz pebbles exhibit a

combination of glacial and non-glacial characteristics including v-shaped percussion and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 8 8

FLOli

Figure 5.5: SEM photomicrographs illustrating typical features and textures on Fish Lake (old and young) and Snake Creek samples, (a) relict polished surface (pws) with deep arcuate grooves, (b) close-up of deep arcuate groove containing crushing features, (c) quartz crystal showing fracture faces (fi) and subparallel crushing features (spof), and (d) anotiier quartz crystal exhibiting fracture faces, subparallel crushing features and conchoidal crushing features (ccf), (e) sub-parallel conchoidal fractures, conchoidal fractures and crushing features, (1) close-up of conchoidal fractures and crushing features (g) conchoidal fractures and subparallel crushing features, and (h) fracture faces with sub-parallel conchoidal fractures and conchoidal crushing features.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 189 scouring features and arc-shaped steps. V-shaped percussion and scouring features are

the most common, but well-developed arc-shaped steps and rare lunate fractures are also

present (Figs. 5.6c - d). The v-shaped percussion features range in size from* 10 tO 100

pm, arc-shaped steps range in size from 50 to 100 pm, and lunate fractures are 80 - 125

pm wide. The pillow basalt pebbles lack diagnostic micro-features that could be used to

identify an erosional origin. They are strongly weathered and exhibit high relief and

abundant abrasion features.

Yosemite National Park

Samples were collected from strongly polished surfaces exhibiting small (-0.5 - 1.0

mm) striations visible with the unaided eye. Samples are moderately weathered and

have high mineral relief. SEM analysis reveals the presence of 2 - 5 pm wide, sub­

parallel linear crushing features, straight grooves that are 2 - 8 pm wide, curved grooves

that are 50-150 pm wide, arc-shaped steps that are 30 - 60 pm wide, deep troughs that

are 25 - 75 pm wide, breakage blocks and fracture faces (Figs. 5.6e - f). The polished

surfaces visible in the field are well preserved at the micron scale as pre-weathered relict

surfaces with little evidence of dissolution etching. These samples are characterized by

high relief and sharp angular features with no evidence of v-shaped percussion cracks or

scouring features.

Yukon Terri torv

A chert sample collected from a -1.5 Ma diamicton along the Yukon River is well

polished and well rounded and exhibits small (0.5 - 1 mm wide) visible striations and

chatter marks. SEM analysis of the clast shows the presence of straight grooves that are

5 - 15 pm wide, deep troughs that are 10 - 15 pm wide, arc-shaped steps that are 10 - 20

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 190

m

lukulk

jQHrYS^£.^

####

| h H

Sskv;'* '\'^^&6e: zeeW i- : .j u k - vr

Figure 5.6: SEM photomicrographs o f representative glacial features on clasts from the La Sal Mountains, Antarctica, Yosemite NP, and Yukon River, (a) Surface of polished quartz pebble showing numerous v-shaped percussion features (arrows) and rare arcuate gouges (ag), (b) close-up o f v-shaped percussion feature (vpf), (c) close-up o f lunate fracture (If) surrounded by smaller v-shaped percussion features (arrows), (d) surface of Alan Hills pillow basalt showing no evidence of preserving micro-features, (e) quartz crystal exhibiting deep arcuate groove on a relict polished surface (pws), (f) close-up o f arcuate groove and relict polish, (g) sub-parallel straight grooves, (h) sub-parallel linear grooves and arcuate lunate fracture or gouge.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 191 p,m wide, rare v-shaped percussion features, evidence of dissolution etching, and some

scouring features (Figs. 5.6g - h).

Chert samples from the Klondike Gravel are well polished and round to sub -

rounded. Small striations and abrasion features are visible in the field using a hand lens.

SEM analyses indicate the presence of well-developed, v-shaped percussion features that

are -25 - 100 |iim wide at their widest point, prominent scouring features, and edge

rounding (Figs. 5.7c - d).

Lake Bonneville Shoreline

Samples from a Bonneville-age, wave-cut terrace are well polished and show visible

signs of scouring and abrasion. Striations, chattermarks, and crescentic gouges are not

visible in the field with a hand lens. These samples exhibit v-shaped percussion features

that are -25 - 75 p,m wide, arcuate grooves that are - 5 - 20 |im wide, scouring features,

and relict polish preserved as pre-weathered surfaces (Figs. 5.7e - f).

Discussion

Mahaney and Andres (1996) identified conchoidal and linear fractures on quartz

grains from fluvial and eolian environments. They noted the depth and preferred

orientation of fractures and striations on grains affected by glacial processes. The

consistency of the preferred orientation, and the well-developed morphology of such

features suggest they are diagnostic of a glacial origin and are not derived from eolian or

fluvial processes. The development of some microfeatures has also been attributed to

dissolution etching in weak hydrochloric acid, and the affects of river ice (Wentworth,

1928 and Dunn, 1933). The morphology of these striations and polish, and abundance of

clasts from the same environment exhibiting similar characteristics suggest they are not

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192

m

SMFC3

I

LBl-4

Figure 5.7: SEM photomicrographs of representative non-glacial features on fluvial and lacustrine sarnies from the Spring Mountains, Klondike Gravel, and Lake Bonneville shoreline, (a) Surface of limestone showing numerous v-shaped percussion features, (b) close-up of scouring features and relict surface, (c) numerous v-shaped percussion features and rare arcuate gouges, (d) close-up of v-shaped percusssion feature outlined in 7c, (e) surface o f shoreline exhiWting scouring features, arcuate gouges but predominantly v-shaped percussion features, and (f) shoreline exhibiting numerous v-shaped percussion features.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 dissolution features. It is also unlikely they reflect an environment that could sustain

river ice since almost all of these samples are collected from arid regions or alpine

localities. However, in this study we differentiate between three groups of samples, (1)

those that were only affected by glacial activity, (2) those only affected by non-glacial

processes, and (3) samples that were transported or modified by both glacial and non­

glacial processes. Each group of samples exhibits distinct microfeatures indicative of the

specific environment from which they were derived (Fig. 5.8).

Microfeatures are most readily preserved in samples with a homogeneous

mineralogy. Samples of polymineralic granite, trachyte, and pillow basalt display the

most evidence for post - depositional weathering and weakly preserved microfeatures

compared to more homogeneous samples of chert, quartzite and limestone. Samples

from the Snake Range

and Spring Mountains (SC and SM) exhibit the best - preserved features but are thought

to be older than many of the other samples. It is likely the Snake Creek samples retain

their features because quartzite is so resistant to erosion and weathering, although the

Spring Mountain samples are anomalously pristine given their presumed age. Limestone

is highly susceptible to dissolution etching and weathering, so the excellent preservation

of microfeatures on samples from the Big Falls till is thought to reflect their burial

through mass wasting events and subsequent isolation from most physical and chemical

weathering processes (Orndorff and Van Hoesen, in press). However, the older and

younger Fish Lake samples illustrate the expected effects of weathering on the

preservation of microfeatures through time. Features observed on the older Fish Lake

(FLO) samples are not only more subdued and less well preserved than the younger Fish

Lake (FLY) samples, but many of the characteristic features attributed to glacial action

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 194

Frequency of observed micofreatures for glacial, non-glacial and samples affected by both environments.

Primarily Glacial Non-glacial (3) i«M^I Both (3)

6 -

Primarily Mixed Non-Glacial I Environments 0 4 O «

1 I I T 1—T C/]C/]W(/5C/]CAMC0 ( / ) C/3 g:# (U CD f s S 8% C rS P. g ë II f l i l l MS « 5).'I II II II DO C ■s I 1} e--3 C M tilliaII 11 , f g W g) II F i ô , cd H P P3 O o u 0) O < ! î 5 oII D- § Q CJ s ■ s g- 1(j _ c 1OQr >

Figure 5.8: Frequency of observed microfeatures differentited by glacial, non-glacial or mixed formational environments.

Reproduced witti permission of ttie copyrigfit owner. Furtfier reproduction profiibited witfiout permission. 194 are lacking. The preservation of these features is directly affected by the amount of time

spent on the surface of a landform or contained in a glacial/non-glacial deposit. Samples

from Devils Postpile, Yosemite Valley, Snake Creek, Fish Lake, and La Sal Mountains

were collected at sites with direct exposure to the elements. Increased surface area and

exposure to physical and chemical weathering processes most certainly causes a higher

rate of microfeature degradation than typically observed on quartz grains. The

likelihood of preservation for microfeatures as a function of relative age and lithology is

illustrated in Fig. 5.9.

V-shaped percussion features were identified only on clasts affected by glaciofluvial

activity (Krinsley and Doornkamp, 1973) with the exception of AH - 1 and WR.

Previous studies have documented the prevalence of v-shaped percussion features on

quartz grains from tills deposited by alpine glaciers compared to continental glaciers

(Mahaney et al., 1988 and Mahaney, 1995). These samples (AH - 1 and WR) were

collected from tills deposited by continental glaciers and were likely influenced by either

fluvial or glaciofluvial processes prior to incorporation into glacial ice. The lack of v-

shaped percussion features on samples collected from bedrock surfaces is consistent with

our expectations; however the absence of such features on samples from alpine moraines

and rock glaciers suggests a short transport distance. Field relationships suggest the

source for these samples is primarily frost-riven talus from local cirques (e.g. samples

from a lateral moraine crest, terminus of a rock glacier breaching a cirque bedrock sill).

We infer that talus is transported into the cirque basin through mass wasting and rockfall

events and that transport downvalley is primarily achieved through glacial advance

rather than fluvial or glaciofluvial processes, so the lack of v-shaped percussion features

is not surprising.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 195 Many of the microfeatures (arc-shaped steps, crescentic gouges, deep grooves, etc.)

described in this study are thought to develop during transport by glaciers greater than

500 m thick in response to glacial abrasion and high basal shear stress (Mahaney et al.,

1988; 1991; and Mahaney, 1990b). This relationship is not reflected in this study

because many of the samples are less competent than quartz grains and therefore should

require less basal shear stress to produce similar features. They may also be produced in

alpine environments that exhibit steep gradients and coarser material entrained in glacial

ice that can affect the average shear stress at the base of the glacier (Benn and Evans,

1998). We suggest the most important factor is the competence and homogeneity of

bedrock and the material being transported by the glacier. The homogeneity of samples

is not thought to affect the frequency of occurrence of microfeatures as much as the

preservation of these features.

Conclusions

This study indicates that distinct microfeatures are present on striated clasts with a

glacial origin and that they can be used to differentiate between diamictons of a glacial

versus non-glacial origin (Fig. 5.8). Arc-shaped steps, chattermarks, curved grooves,

deep troughs, fracture faces, linear steps, relict polish, subparallel linear fractures, and

subparallel crushing planes dominate samples from the seven glacial environments.

These features were primarily observed on samples with a known glacial origin. The

characteristic microfeatures for the samples with a non-glacial origin are breakage blocks,

scouring features, and percussion features. The samples that were affected by both

glacial and non-glacial processes exhibit a combination of these microfeatures including

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■D O Q. C 8 Q.

■D CD

C/) C/)

CD 8 % Q uartzite y "O 2 3 (O' sw CQ C hert 2 u Lim estone

3"3. G ranite CD s y ' 0 CD ■D Trachyte O Q. C 1 a Basalt 3O E "O Pk O T3

■D CD

(/) (/) Decreasing Age and Increasing Competence of Samples

Figure 5.9; Schematic diagram illustrating the most likely relationship between the preservation of micofeatures in relation to lithology and age of the samples. With increasing age and decreasing lithologie competence microfeatures should be less common, however the samples in this study with the best preserved microfeatures are assumed to be older than many of the other samples. VO ON 197 arc-shaped steps, chattermarks, and v-shaped percussion features. As with previous

studies addressing the micromorphology of quartz grains, we conclude that the presence

of arc-shaped steps, chattermarks, deep grooves and arcuate and conchoidal crushing

features are diagnostic indicators of a glacial origin, and v-shaped percussion marks and

scouring features are characteristic of fluvial and glaciofluvial environments. Further

study on additional depositional environments and lithologies is necessary to evaluate

the consistency of microfeatures. Furthermore, additional work can also be done on the

correlation between specific features documented on striated clasts and the estimated ice

thickness.

Acknowledgments

We thank the Arizona - Nevada Academy of Science, Colorado Scientific Society,

Sigma Xi Scientific Society, and The American Alpine Club, for financial support. We

appreciate the cooperation of Great Basin National Park, Yosemite National Park, and

Devils Postpile National Monument. We also thank Vic Levson with the Victoria

University, British Columbia Geological Survey Branch and Phil Holme at the Antarctic

Research Centre in Wellington, New Zeland, for supplying samples. We graciously

thank Steve Hicock at the University of Western Ontario and Lionel Jackson with the

Geological Survey of Canada, Vancouver Office for their useful comments and

suggestions.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 198

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Yount, J. and LaPointe, D.D., 1997, Glaciation, faulting, and volcanism in the southern Lake Tahoe Basin. In: Dillet, B., Ames, L., Gaskin, L., and Kortemeier, W., (eds). Where the Sierra Nevada Meets The Basin and Range. Field Trip Guidebook for The National Association of Geoscience Teachers, Far Western Section, 1997 Fall Field Conference, 34 - 56.

Wayne, W.J., 1984, Glacial chronology of the Ruby Mountains - East Humbolt Range, Nevada. Quaternary Research 21: 286 - 303.

Whitebread, D.H., 1969, Geologic map of the Wheeler Peak and Garrison quadrangles, Nevada and Utah: United States Geologic Survey Misc. Survey Map, I - 578.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 6

SUMMARY OF MAJOR RESULTS

The papers presented in this dissertation attempt to evaluate the Late Quaternary

environment(s) of the Snake Range, east central Nevada. Geomorphic evidence

indicates the range supported both glacial and periglacial climate regimes; more than

likely, although a tentative hypothesis, they evolved concurrently and may have

supported one another through positive feedback mechanisms. Previous workers have

described much of the glacial geology in the Snake Range, however an absolute age

chronology is lacking. Plate 1 presents the efforts of a surficial mapping project in the

Wheeler Peak and Windy Peak quadrangles and provides a clearer representation of the

glacial geology with respect to Quaternary and Holocene deposits. The spatial

distribution of both glacial and periglacial landforms provides paleoclimatic information

derived using field evidence and computer modeling. Although the modeling predicts

less snow and ice than required to form the observed glacial moraines, the evolution and

distribution of snow and ice under perturbed climate is consistent with modem alpine

environments. Analyses of these data suggest, similar to previous authors (Sears and

Roosma, 1961; Thompson and Mead, 1982; Wells, 1983; Dohrenwend, 1984; Thompson,

1992; Bevis, 1995; and Hostetler and Clark, 1997), that temperature played a more

significant role in the development and growth glaciers in the Snake Range. However,

204

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 205 there may be a relationship between winter moisture input from pluvial lakes and

glaciation that has yet to be fully evaluated in the interior Great Basin.

Periglacial Landforms

Without a higher resolution inventory of periglacial features and a better

understanding of their spatial relationships to documented glacial deposits, our

understanding of Late Quaternary conditions throughout the interior Great Basin will be

limited. This study presents new data documenting the distribution of relict periglacial

features and provides evidence suggesting the Snake Range supported discontinuous

permafrost during the LGM and/or Late Quaternary.

The presence of rock glaciers, solifluction lobes, garlands, sorted and unsorted

polygons and circles and cryoplanation terraces in both the northern and southern Snake

Range suggests snow cover was thin enough to allow discontinuous permafrost to

develop. Barsch (1978) and Jakob (1992) state that rock glaciers define the lower limit

of discontinuous permafrost. Therefore, the presence of five rock glaciers in the Snake

Range suggests discontinuous permafrost was present in the Snake Range during the

Late Quaternary. The distribution of permafrost in the range is consistent with this

inference since patterned ground is only found at elevations higher than each rock glacier.

However, without absolute age constraints, it is impossible to tell whether they

developed coeval with the maximum extent of glaciation or whether they developed

during deglaciation as temperatures increased and snow cover decreased. The fact that

almost all patterned ground is found on flat lying surfaces, are moderately to well

developed features, and that glaciers developed in cirques directly east of all four major

cryoplanation terraces, suggests they could have developed during the LGM with

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 206 sufficient westerly winds blowing snow out of the saddles into adjacent cirques. This

scenario could create a positive feedback in which permafrost develops as snow cover is

thinned, glaciers develop as snow is blown into niches and hollows on the eastern flank

of the range, and as glaciers develop they create local microclimate that help support

relatively small patches of permafrost (with the exception of The Table). Therefore, it is

quite likely that relict patterned ground observed in the Snake Range is considerably

older than the rock glaciers.

Without digging trenches, finding exposed subsurface features like the stream cut on

Mt Moriah, or using ground penetrating radar (GPR), it is difficult to address the specific

evolution of most periglacial features. At best, I can infer that most features developed

as ground ice accumulated in response to cooling temperatures, through freeze-thaw

action, and under the influence of gravity; such as in the case of solifluction lobes and

garlands. Similarly it is unclear whether stone polygons and circles and cryoplanation

terraces identified in the range developed solely under the action of freeze-thaw or if

solifluction, gelideflation, slope, and debris supply played an important role as suggested

by Boch and Krasnov (1994), Troll (1994), and Francou et al. (2001). However,

lithology and slope are certainly important factors influencing the development of certain

landforms because solifluction lobes and garlands are only found on slopes steeper than

-25° and sorted polygons and circles are most strongly developed in Prospect Mountain

Quartzite (PMQ). Although the platy nature of PMQ is more conducive to over

steepening and downslope flow than sub-angular limestone or rounded granite, the

observed lithologie control may also be related to the fact that the highest portion of the

range are almost entirely composed of PMQ. Unfortunately, the geneses of many

periglacial features are still contentious and poorly understood, including rock glaciers.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 207 Proposed Genesis of Lehman Rock Glacier

The proposed genesis for the Lehman rock glacier (LRG) is not an attempt to settle

the debate over the glacial versus periglacial origin of rock glaciers discussed in Chapter

2. Rather, I suggest a new genesis for tongue shaped rock glaciers through the

coalescence of smaller lobate rock glaciers that developed in response to the retreating

Lehman Glacier. The geomorphology and GPR findings suggest the LRG is composed

of three distinct individual lobes and that it is likely the upper, and possibly the middle

lobe, retain lenses of relict periglacial ice. Therefore, I suggest the LRG is an ice

Cemented rock glacier that developed through the action of periglacial processes. I am

not suggesting that all tongue shaped rock glaciers develop through this process, but only

offer an alternative periglacial model of growth. The presence of interstitial ice is

significant because it suggests other rock glaciers in the range as well as throughout the

Great Basin may still contain remnant ice (although not necessarily interstitial) that

could be valuable sources of water in a region so desperate for water resources.

However, the lack of absolute ages, surface velocity measurements and detailed

descriptions of the internal structure of the rock glacier prevent a more thorough

interpretation of the genesis and may possible inhibit future finite element modeling that

could provide further insight into its development. Although, as I suggested in Chapter 2,

an estimated age of 1200 AD to 5000 BP is a plausible assumption. The presence of the

LRG and other rock glaciers is also useful for evaluating paleotemperature conditions

during the Neoglacial.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 208 Paleoclimatic Implications of Glacial and Periglacial Landforms

Osborn and Bevis (2001) provide a detailed description of glacial features throughout

the Great Basin, including the Snake Range, but little detail regarding the paleoclimatic

conditions in the range during the Late Quaternary is provided by the current literature.

Therefore, Chapter 1 evaluates the paleoclimatic significance of glacial and periglacial

deposits in the Snake Range using techniques described by Harris (1980, 1981a, b);

Meierding, (1982); Greenstein (1983); Locke, (1990); Benn and Evans, (1998);

Frauenfelder and Kaab (2000); Hoelzle (1996); and Frauenfelder et al. (2001).

Neoglacial temperature depression estimates calculated using modem freezing and

thawing indices for relict rock glaciers, range from -0.25 °C to -1.00 °C while

temperature estimates calculated using the methodology described by Frauenfelder and

Kaab, (2000) and Frauenfelder et al., (2001) are 0.35 to 0.97 degrees lower than those

calculated using freezing and thawing indices. The calculated mean of -1.42 °C for the

higher estimates are more consistent with previously published Neoglacial temperature

estimates for the Great Basin (Wayne, 1984). This suggests that rock glaciers are indeed

sensitive indicators of climate change. Therefore, with the proposed global temperature

increase of 1.5 to 5°C (Watson et al., 1990; Wilson and Mitchell, 1987; Schlesinger and

Zhao, 1989; Knox, 1991; and Mitchell et al., 1995), active rock glaciers throughout the

world should be carefully monitored for ice content and potential water loss to evaluate

how quickly they respond to climate change.

By comparing modem and Full Glacial MAAT in the Snake Range, calculated using

regional lapse rates, I suggest the Snake Range experienced an average MAAT

depression of approximately -5.16°C to -6.61°C. Not only do these estimates of full

glacial MAAT lowering compares favorably with other estimates for this region

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 209 (Chapter 1; Table 5.9), they are also similar to the MAAT depression of-4.55°C to -

5.77 °C that I calculated from reconstructed Angel Lake equilibrium line altitudes

(ELAs). Temperature estimates from both relict permafrost features and ELA

depression are also consistent with previously published temperature gradients (Bevis,

1995). Bevis, (1995) calculated MAAT depressions of -8.0°C in the Ruby Mountains

northwest of the Snake Range, -5.0°C in the Deep Creek Mountains, located to the

northeast of the Snake Range, and -4.0°C in the Tushar Mountains in south-central Utah.

Possible Application of SEM for Environmental Reconstruction

One component of this study identified microfeatures on quartzite clasts from the

Snake Range are similar to features observed on quartz grains that are distinctly glacial

in origin (Van Hoesen and Omdorff, 2003). The results of this study suggest it may be

possible to use striated clasts and surfaces to reconstruct ice thickness and debris

transport mechanisms similar to Mahaney et al. (1988) and Mahaney (1990 and 1991).

However, I did not attempt to evaluate these parameters because only 3 samples of

quartzite were collected from the Snake Range. More collections and further study is

required on the factors influencing the formation these microfeatures. Previous work has

only investigated quartz grains; therefore it is unclear how microfeatures on less

competent lithology will vary with ice thickness and transport histories. So although I

did not use microfeatures to reconstruct Late Quaternary environmental conditions, it

presents new data that suggests it may be possible with further investigation.

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210

This reproduction is the best copy available.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 211 References

Barsch, D., 1978, Rock glaciers as indicators of discontinuous alpine permafrost. An example from the Swiss Alps. ln\ Proceedings, Third International Conference on Permafrost, National Research Council, Ottawa, 349-352.

Benn, D.I. and Evans, D.J.A., 1998, Glaciers and Glaciation. Edward Arnold, London, England, 760p.

Bevis, K.A., 1995, Reconstruction of Late Pleistocene paleoclimatic characteristics in the Great Basin and adjacent areas. Ph.D. dissertation, Oregon State University, 278 p.

Boch, S.G. and Krasnov, I.I., 1994, On altiplanation terraces and ancient surfaces of leveling in the Urals and associated problems. ln\ Cold Climate Landforms, Evans, D.J.A., (ed), John Wiley and Sons, Chichester, England, 177-186.

Dohrenwend, J.C., 1984, Nivation landforms in the western Great Basin and their paleoclimatic significance. Quaternary Research 22: 275-288.

Francou, B., Le Méhauté, N., and Jomelli, V., 2001, Factors controlling spacing distances of sorted stripes in a low-latitude, alpine environment (Corillera Real, 160S, Bolivia). Permafrost and Periglacial Processes.l2\ 367-377.

Frauenfelder, R., Haeberli, W., Hoelzle, M., and Maisch, M., 2001, Using relict rockglaciers in GIS based modelling to reconstruct Younger Dryas permafrost distribution patterns in the Err-Julier area, Swiss Alps. Norsk Geografisk Tidsskrift 55: 195-202.

Frauenfelder, R. and Kaab, A., 2000, Towards a paleoclimatic model of rock-glacier formation in the Swiss Alps. Annals of Glaciology 31: 281-286.

Greenstein, L.A., 1983, An investigation of midlatitude alpine permafrost on Niwot Ridge, Colorado Rocky Mountains, USA. hr. International Conference on Permafrost, Proceedings, Pewe, T.L. and Brown, J., (eds)., 4, pp.380-383.

Harris, S.A., 1979, Ice caves and permafrost zones in southwest Alberta. Erdkunde 33: 61-70.

Harris, S.A., 1981a, Distribution of active glaciers and rock glaciers compared to the distribution of permafrost landforms, based on freezing and thawing indices. Canadian Journal of Earth Sciences 18: 376-381.

Harris, S.A., 1981b, Climatic relationships of permafrost zones in areas of low winter snow cover. Arctic 34: 64-70.

Hoelzle, M., 1996, Mapping and modeling of mountain permafrost distribution in the Alps. Norsk Geografisk Tidsskrift SO: 11-15.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 212 Hostetler, S.W. and Clark, P.U., 1997, Climatic controls of western US glaciers at the last glacial maximum. Quaternary Science Reviews 16: 505-511.

Jakob, M., 1992, Active rock glaciers and the lower limit of discontinuous alpine permafrost, Khumu Himalaya, Nepal. Permafrost and Periglacial Processes 3: 253- 256.

Knox, J.B., 1991, Global climate change: impacts on California, an introduction and overview. Iri: Knox, J.B. and Scheuring, A.F. (eds). Global Climate Change and California. Potential Impacts and Responses, University of California Press, l-25p.

Locke, W.W., 1990, Late Pleistocene glaciers and the climate of western Montana, U.S.A Arctic and Alpine Research 22: 1-13.

Mahaney, W.C., 1990, Macrofabrics and quartz microstructures confirm glacial origin of Sunnybrook drift in the Lake Ontario basin. Geology 1%: 145-148.

Mahaney, W.C., Vortisch, W., and Julig, P., 1988, Relative differences between glacially crushed quartz transported by mountain and continental ice - some examples from North America and East Africa. American Journal of Science 288: 810-826.

Mahaney, W.C., Vaikmae, R. and Vares, K., 1991, Scanning electron microscopy of quartz grains in supraglacial debris, Adishy Glacier, Caucasus Mountains, USSR. Boreas 20: 395-404.

Meierding, T.C., 1982, Late Pleistocene glacial equilibrium-line altitudes in the Colorado Front Range: A comparison of methods. Quaternary Research 18: 289- 310.

Mitchell, J.F.B., Johns, T.C., Gregory, T.M., Tett, S., 1995, Climate responses to increasing levels of greenhouse gases and sulphate aerosols. Nature 376: 501-504.

Schlesinger, M.E. and Zhao, Z.C., 1989, Seasonal climate changes induced by doubled CO2, as simulate by the OSU atmospheric GCM mixed layer ocean model. Journal o f Climate 2: 459-495.

Sears, P.B. and Roosma, A., 1961, A climatic sequence for two Nevada Caves. American Journal of Science 259: 669-678.

Thompson, R.S., 1992, Late Quaternary environments in Ruby Valley, Nevada. Quaternary Research 37: 1-15.

Thompson, R.S and Mead, J.I., 1982, Late Quaternary environments and biogeography in the Great Basin. Quaternary Research 17: 39-55.

Troll, C., 1994, The subnival or periglacial cycle of denudation. In: Cold Climate Landforms, Evans, D.J.A., (ed), John Wiley and Sons, Chichester, England, 23-44.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 213 Van Hoesen, J.G. and Orndorff, R.L., 2003, A Comparative SEM Study the micromorphology of glacial and non-glacial clasts with varying age and lithology. This Volume, Chapter 5.

Watson, R.T., Rodhe, H., Oescheger, H., and Siegenthaler, U., 1990, Greenhouse gases and aerosols. In: Houghton, J.T., Jenkins, G.I., and Ephraums, J.J. (eds). Climate Change: The IPCC Scientific Assessment. Cambridge University Press, l-40p.

Wayne, W.J., 1983, Paleoclimatic inferences from relict cryogenic features in alpine regions: in- Permafrost: Fourth International Conference Proceedings, (ed) Pewe, T.L., National Academy Press, Washington DC, p.1378-1383.

Wells, P.V., 1983, Paleobiogeography of the montane islands in the Great Basin since the last glaciopluvial. Ecological Monographs 53: 341-382.

Wilson, C.A. and Mitchell, J.F.B., 1987, A doubled COo climate sensitivity experiment with a global climate model inducing a simple ocean. Journal of Geophysical Research92: 13315-13343.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA

Graduate College University of Nevada, Las Vegas

John Van Hoesen

Local Address; 1551 Lorilyn Ave Apt#l Las Vegas, NV 89119

Home Address: P.O. Box 26 East Berne, NY 12059

Degrees:

Bachelor of Science, Geology, 1993 State University of New York, Albany

Masters of Science, Geoscience, 2000 University of Nevada, Las Vegas

Special Honors and Awards:

-Barrick Fellowship, University of Nevada, Las Vegas (2002-2003) -Outstanding Student Research Award, Geological Society of America Research Grant (2002) -Second Place Best Student Presentation - Utah Geological Assc. Meeting, (2001) -UNLV Graduate Research GREAT Assistantship (1999 and 2001) -Best Masters Thesis - College of Science, UNLV (2001) -Best Student Paper - Geological Society of America Cordilleran meeting (2000) -Honorable Mention, Geological Society of America Quaternary Geology and geomorphology Division: Howard Mackin Award (1999).

Publications:

Omdorff, R.L., Van Hoesen, J.G., and Saines, M., in press, Implications of New evidence for Late Quaternary Glaciation in the Spring Mountains, Southern Nevada. Journal of the Arizona-Nevada Academy of Science.

214

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 215 Buck, BJ. And Van Hoesen, J.G., in press, Assessing the applicability of isotopic analysis of pedogenic gypsum as a paleoclimate indicator: Jornada and Tularosa basins, southern New Mexico. Journal of Arid Environments.

Van Hoesen, John G. and Omdorff, Richard L., 2003, Using GIS To Evaluate An Enigmatic Diamicton In The Spring Mountains, Southem Nevada. Professional Geographer 55:206-215.

Van Hoesen, John G., 2002, Geologic Tour of Red Rock National Conservation Area, in: Geology of the Southem Nevada Region, National Association of Geology Teachers Far Westem Section, Spring Field Conference, Las Vegas, NV, pg. 86-95.

Buck, Brenda J., and Van Hoesen, John G., 2002, Snowball Morphology and SEM Analysis of Pedogenic Gypsum, southem New Mexico, Joumal of Arid Environments: 51: 469-487.

Omdorff, Richard L. and Van Hoesen, John G., 2001, Using GIS to predict the spatial distribution of perennial snow under modem and Pleistocene conditions in the Snake Range, Nevada. 69"^ Annual Meeting of the Westem Snow Conference, Sun Valley, Idaho, 2001, pg. 119-123.

Van Hoesen, John G., Buck, Brenda J., Merkler, Douglas, J., and McMillan, Nancy, 2001, An investigation of salt micromorphology and chemistry. Las Vegas Wash, Nevada: Proceedings of the 36"^ Annual Symposium on Engineering Geology and Geotechnical Engineering. Luke, Jacobson, and Werle (eds). University of Nevada, Las Vegas, March 28-30, pg. 729-737.

Phillips, P.J., Wall, G.R., and Van Hoesen, J., 1999, Metolachlor and it’s Metabolites in Tile Drain and Stream Runoff in the Canajohairie Creek Watershed, Environmental Science and Technology 33: 3531-3537.

Dissertation Title: Late Quaternary Glacial and Periglacial Environments, Snake Range, Nevada.

Thesis Examining Committee: Chairperson, Dr. Richard L Orndorff, Ph.D Committee Member, Dr. Frederick W. Bachhuber, Ph.D Committee Member, Dr. Stephen M. Rowland, Ph.D Graduate Faculty Representative, Dr. Helen Neill, Ph.D

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Oversize maps and charts are microfilmed in sections in the following manner:

LEFT TO RIGHT, TOP TO BOTTOM, WITH SMALL OVERLAPS

This reproduction is the best copy available.

UMI

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2700 I J Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PLATE I: Surficial Geology of Glaci Wheeler Peak Quadrangles, So -4 3 2 2 0 0 0 John G. Van H

DESCRIPTION OF

Holocene Hac Holocene avalanche chutes:steep gullies containing frost riven debris that lies Q stratlgraphically on Quaternary talus, glacial till and unconsolidated, poorly sorted un-differentiated alluvium. The debris is clast supported and consists of angular to subangular dark brown pebbles and boulders of Prospect Mountain Quartzite (PMQ). Surface clasts are predominantly fresh and unweathered, indicative of recent activity.

Holocene rock glaciers:deposits of unsorted, angular frost shattered boulders and cobbles. These deposits ocurr as both tongue and lobate-shaped morphologies, composed of quartzite debris that can be differentiated into an upper and lower layer. -4 3 2 0 0 0 0 The upper layer is clast supported and consists of angular to subangular, reddish brown cobbles and boulders of PMQ. The lower layer is primarily matrix supported and consists of orange to brown, angular to subangular sand and cobbles. Rock glaciers are differentiated from protalus ramparts by the presence of furrows and ridges and the surface morphology of the terminus (Barsh, 1996).

Holocene protalus ramparts:deposits of unsorted, angular frost shattered boulders and cobbles of PMQ. The upper surface of these features Is subdued and typically orange to dark brown.

Quaternary

Quaternary talus (younger): deposits of angular to sub-angular quartzite debris derived from frost riving and rapid gravity transport on steep slopes and cirque headwalls, gullies and avalanche chutes. They typically form cones or aprons that lie at or near the angle of repose along valley walls and often transition into the margins of rock glaciers. Surface clasts are light grey to brown and lie stratigrahicaly above older Q tl , >4318000 ! : deposits. Qtl Quaternary talus (older): deposits of angular to sub-angular quartzite debris derived from frost riving and rapid gravity transport on steep slopes and cirque headwalls, gullies and avalanche chutes. They typically form cones or aprons that lie at or near the angle of repose along valley walls and often transition into the margins of rock glaciers. Surface clasts exhibit more patina, are dark brown and lie stratigrahicaly below younger Qt2 deposits.

-4 3 1 6 0 0 0

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. y of Glaciated Canyons in Windy Peak and ngles, Southern Snake Range, Nevada. n G. Van Hoesen, 2003

DESCRIPTION OF MAP UNITS

bris that lies Quaternary glacial till (Angel Lake);poorly sorted, poorly stratified deposits containing poorly sorted angular to subangular pebbles, cobbles and boulders of PMQ, Pioche Shale (PS), ists of angular Pole Canyon Limestone (POL), and Snake Creek-Wllllams Canyon pluton (SCWP). tain Quartzite The surface morphology is hummocky and is covered with sporadic cobbles and Indicative of boulders of weakly weathered PMQ and moderately weathered cobbles and boulders of SCWP. Quartzite and granite clasts are weakly faceted and exhibit rare striations.

)ulders and Quaternary glacial till (Lamoille): poorly-sorted, poorly-stratified deposits containing jrphologies, Qgl angular to subangular pebbles, cobbles and boulders of PMQ, and Snake Creek and lower layer, Williams Canyon Pluton (SCWP). The surface morphology Is weakly hummocky and jiar, reddish much more subdued than Qga deposits. A weakly developed soil mantles the surface trix supported of these deposits and surface cobbles and boulders of PMQ and SCWP are )bles. Rock moderately to strongly weathered. This unit is correlated to Lamoille deposits decribed urrows and by Sharpe, 1938 rather than Pre-Angel Lake (Osborn and Bevis, 2002).

Quaternary glacial tarn or kettle:glacially-derived lakes that formed through direct glacial ed boulders and scouring or melting. The floor of kettle lakes are mantled with cobbles and boulders of 1 typically reddish orange PMQ and SCWP:

Q h t Quaternary hummocky talus:deposits of angular to sub-angular cobbles and boulders of PMQ derived from frost riving and rapid gravity transport on steep slopes and cirque headwalls, gullies and avalanche chutes. They have a hummocky, furrowed surface morphology and were likely affected by periglacial activity (permafrost?) and occur e debris derived from downslope from rock glacier deposits and at the base of steep slopes. Surface clasts adwalls, gullies are light grey to brown. it or near the angle ock glaciers, Quaternary frost-riven debris: extensive deposits of frost-rlver] PMQ that mantles numerous der Qt1 slopes and tables above treeline. Quartzite debris is angular and light grey to brown with evidence for periglacial activity (cryoturbation, cryoplanation, solifluction, patterend ground and garlands). ebris derived from Mesozoic/Paleozoic adwalls, gullies \t or near the angle ock glaciers, Bedrock (undivided); Undifferentiated bedrock consisting of Prospect Mountain Quartzite, caly below younger Pioche Shale, Pole Canyon Limestone and Snake Creek-Wllllams Canyon Pluton (Drewes, 1958; Whitebread, 1969; Lee and Van Loenen, 1971 and Lee and Christiansen, 1983).

LEGEND

Glacial meltwater channel abandoned-

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. L 4 3 1 6 0 0 0

üaaa Figure 1; Tongue-shaped rock glacier (Hrg) complex 'Figure 2: Characteristic Qti talus aprons o\|| located below Wheeler Peak. Note Qti and2 coalescingQt Note the lobate rock glacier in the foregrouj' along the lateral margins of the rock glacier. reddish brown debris.

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Figure 3; Characteristic Angel Lake till (Qga) located belowFigure 4; Characteristic Lamoille till (Qgl)Id Teresa Cirque. Note the angularity of the clasts, lack-ofLehman soil Creek. Note the more subangularj and reddish brown coloring. soil and light grey to brown coloring.

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Figure 5: Characteristic hummocky till (Qht) located in Figure 6: Characteristic frost-riven mantle Ij Lehman Cirque. Note the furrows and ridges of the rocksouthern face of Bald Mountain. glacier in the foreground.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^-4 ,

Glacial meltwater channel- abandoned

(AL) Crest line of moraines (L) oooooooooooooo

Striations - arrow shows direction of movement and the dot indicates the point of observation

Glacial flow direction

Sites of interest - correspond to figures Stic Qti talus aprons overlying Qta- 1-6. Arrow points in direction the photo (D- : glacier in the foreground exposing was taken..

Cirque headwall

Summit of selected peaks

REFERENCES

Barsch, p., 1996, Rock glaciers: indicators for the present and former geoecoiogy in high mountain environments. Springer, Berlin, 331 p.

wsÿi'aS‘5? aaiîsfi Drewes, H., 1958, Structural geology of the southern Snake Range, Nevada. Geological Society of America Bulletin 69: 221-240.

Lee, D.E. and Van Loenen, R.E., 1971, Hybrid granitoid rocks of the southern Snake Range, Nevada. United States Geological Survey Professional Paper 68:1-46. Stic Lamoille till (Qgl) located along te the more subangular edges, a weak Lee, D.E. and Christiansen, E.H., 1983b, The granite problem in the I brown coloring. southern Snake Range, Nevada. Contributions to Mineralogy and ' Petrology 83: 99-116.

Osborn, G. and Bevis, K., 2001, Glaciation in the Great Basin of the Western United States. Quaternary Science Reviews 20: 1377-1410.

Sharpe, R.P., 1938, Pleistocene glaciation in the Ruby-East Humbolt Range, northeastern Nevada. Journal of Geomorphology1: 296-323.

Whitebread, D.H. 1969. Geologic map of the Wheeler Peak and Garrison quadrangles, Nevada and Utah. United States Geologic Survey Misc. Survey Map 1-578. Qf

S i l Acknowledments; The cooperation of the staff at Great Basin National ■ Park, field support of Chad Hendrix and technical adivice from Robert Ï • •L, T^sîSSîS’, Chaney at the Nevada Bureau of Mines is greatly appreciated.

Stic frost-riven mantle located on the Maplnfo: The GIS layers were originally digitized in ArcView GIS 3.2 d Mountain. using USGS digital raster graphics and digital orthophoto quads and imported into Adobe Illustrator 10.0 using Mapubiisher 5.0.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Precip _var DEM Corr _da{a

Parameters INPUT’ SNOW_ ACCüM

PLASTIC SNOW_ ABLAl'

SNOW

SORT_ ELEV SNOW_ ABLAl' ;

Prccip Tniax Grids Grids ^ I READ_DAm SNOW_ ABLAT

Flowchart Key V ,\ Contingency ^

input Grids Porslacicrs >.

Snow lee Snowpaek I c+ I V Volume Subrouiinc |

/X S.^ y ' . / Output \ IcomcU |>r, Icepack Rainfall \ G n d s ^ -

Flow Direction Plate 2: Flowchart depicting the order of operations and the required data when running the Snow and Ice Model.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission