Late Holocene Glacial History of Manatee Valley,

Upper Lillooet Provincial Park,

Southern Coast Mountains, British Columbia

By

Lindsey Koehler

B.Sc., University of Puget Sound, 2004

A Thesis Submitted in Partial Fulfillment

of the Requirements for the Degree of

Masters of Science

in the Department of Geography

 Lindsey Koehler, 2009

University of Victoria

All rights reserved. This thesis may not be reproduced in whole or in part, by photocopy

or other means, without the permission of the author. ii

Supervisory Committee

Late Holocene Dendroglaciologic History of Manatee Valley,

Upper Lillooet Provincial Park,

Southern Coast Mountains, British Columbia

by

Lindsey Koehler

B.Sc., University of Puget Sound, 2004

Supervisory Committee

Dr. Dan Smith (Department of Geography)

Supervisor

Dr. Jim Gardner (Department of Geography)

Departmental Member

Dr. Richard Hebda (School of Environmental Studies)

Departmental Member iii

Abstract

Supervisory Committee Dr. Dan Smith (Department of Geography) Supervisor Dr. Jim Gardner (Department of Geography) Departmental Member Dr. Richard Hebda (School of Environmental Studies) Departmental Member

This investigation uses dendrochronologic and radiometric techniques to infer the timing of glacier advance for four ice lobes that are drained by Manatee Creek in a remote valley located in the southern Coast Mountains, British Columbia.

Dendroglaciologic evidence exposed by retreating glaciers provides evidence for increasing complexity in the Holocene glacial record, particularly for mid-late Holocene events. Since Holocene ice fronts periodically extended below treeline in the region, previous glacier advances overrode and buried forests beneath till deposits. The dendroglaciologic evidence presented here corroborates the record of glacier advances described for other southern British Columbia Coast Mountain glaciers and details ice front position at ca. 4270 14C yr BP, 3430 14C BP and 2350 14C yr BP. Well-preserved sequences of lateral, nested moraines were mapped and profiled to delineate the boundaries of Manatee and Oluk glaciers. Relative dates provided by lichenometry and dendrochronology were used as limiting dates for the deposition of 5-6 moraines during the late 14th, early 16th, early 18th, 19th, and early-20th Century. Reconstructions of

Holocene glacial history offer insight into the regional, climatic regime and add to the discussion about pervasive, millennial-scale cycles. iv

Table of Contents

Supervisory Committee...... ii Abstract...... iii Table of Contents...... iv List of Figures...... vi List of Tables...... vii Acknowledgments...... ix Chapter 1: Introduction...... 1 Research Background...... 1 Research Objectives...... 2 Thesis Overview...... 3 Works Cited...... 4 Chapter 2: Review of Dendroglaciologic and Lichenometric Research in Pacific North America...... 5 Introduction...... 5 Review of Methods...... 5 Dendroglaciology...... 5 Lichenometry...... 9 Holocene Glacial Activity in the B.C. Coast Mountains...... 11 Early-Holocene Advances ...... 12 “Garibaldi Phase”...... 13 “4200 yrs. BP Event”...... 13 “Tiedemann Advance”...... 14 “Unattributed Advance”...... 14 First Millennium Advances (FMA)...... 15 Little Ice Age ...... 16 Holocene Glacial Activity in PNA...... 19 Canadian Rocky Mountains...... 19 Alaska...... 20 Summary...... 21 Works Cited...... 22 Chapter 3: Late-Holocene glacial activity of Manatee Valley, southern Coast Mountains, British Columbia...... 32 Introduction...... 32 Research Background...... 33 Study Area...... 37 Methods...... 40 Dendroglaciology...... 41 Lichenometry...... 43 Results...... 44 Dendroglaciologic Evidence...... 45 Moraine Dating...... 56 Synthesis and Interpretation...... 64 v

Conclusion...... 68 Works Cited...... 70 Chapter Four: Discussion...... 78 Introduction...... 78 4200 14C yrs BP Event...... 79 Tiedemann Advance...... 82 First Millennium Advances AD...... 85 Little Ice Age ...... 85 Conclusion...... 87 Works Cited...... 89 Chapter Five: Summary...... 95 Limitations and Suggestions for Future Work...... 96 Works Cited...... 99 Appendix A: Manatee Valley Master Tree-Ring Chronology...... 100 Figure A.1. (continued) Subalpine fir master tree-ring chronology (residual and ARSTAN version...... 103 Works Cited...... 104 Appendix B: Subalpine Fir Subfossil Tree-Ring Chronology...... 105 vi

List of Figures

Figure 3.1. Map of the Manatee valley study area, located in the southern Coast Mountains of B.C. The forefields and lateral moraines of four of the glaciers that drain via Manatee Creek were investigated for this study: Orca (unofficial), Beluga (unofficial), Manatee, and Oluk glaciers. Features and sampling locations have been superimposed on the 1970 Canada topographic series 92J/12 map...... 39

Figure 3.2. Orca Glacier released several pieces of detrital wood into the headwaters of Manatee Creek in (Site 1). The outermost rings of two subfossil trees were radiocarbon dated at 3500±60 14C yr BP (MC06-27) and 4270±60 14C yr BP (MC06-03). The foreground shows the western lateral moraines formed by the confluent ice front of Orca and Beluga glaciers during the late-LIA (Site 5)...... 48

Figure 3.3. A buried subalpine tree located along the proximal slope of the eastern lateral moraine of Manatee Glacier. This sample (MC06-07) was killed in 3430±60 14C yr BP, when ice almost thickened to late-LIA proportions...... 50

Figure 3.4a. Subfossil subalpine fir stump (MC06-23) found rooted in a paleosol within the Orca/Beluga glacier forefield (Site 3). A sample of perimeter wood had a radiocarbon age of 2350 ±70 14C years BP...... 52

Figure 3.4b. A glacially-sheared subalpine fir tree (MC07-22) found in a near-growth position below Manatee Glacier (Site 4). The sample cross-dated with the radiocarbon controlled floating subalpine fir chronology constructed from samples collected at Site 3...... 53

Figure 3.5a. The construction of the late-LIA moraine buried this subalpine fir tree (MC06-04) along the western marginal of Orca/Beluga glacier in 1738 AD (Site 5)...54

Figure 3.5b. Standing snag (MC06-06) located adjacent to the distal slope of the western lateral moraine of Orca/Beluga glacier (Site 5). The tree died in 1736 AD following the deposition of the moraine...... 55

Figure 3.6. Rhizocarpon geographicum growth curve for the Mt. Waddington area revised with control points from this study and additional data from Larocque and Smith (2004)...... 58

Figure 3.7. Topographic cross-sections of the lateral moraines surveyed on the northern and southern margins of Manatee Glacier and the southern boundary of Oluk Glacier (see Figure 3.1 for transect locations). The moraines are numbered so that M1 is always in the most distal. Numbers from different transects are not necessarily time synchronous...... 61 vii

Figure 3.8. This figure compares the growth trends of the living Abies lasiocarpa chronology collected in Manatee Valley to lateral moraine dates that were determined with lichenometry along the margins of Manatee and Oluk glacier (see Figure 3.1 for exact location). The thick black line represents a 10-year moving average. Plotted on the right-hand axis is the number of series in the master chronology. Each grey rectangle spans 25-year intervals that are centered on a lichenometric dates for each moraine...... 68

Figure 4.1. Relief map of British Columbia including the location of previous studies that investigate environmental changes in the alpine during the Holocene: Eastern Pacific Ranges(Lillooet, Bridge, Manatee glaciers); Central Coast Mountains (Tiedemann glacier, Mt. Waddington area); Garibaldi Provincial Park (Garibaldi, Fitzsimmons, and Spearhead ranges); Insular Ranges (Strathcona Provincial Park); Heal Lake; Boundary Ranges (Todd Valley, Tide Lake, Jacobsen glacier)...... 80

Figure A.1 (continued) Subalpine fir master tree-ring chronology (residual and ARSTAN version...... 103

Figure A.1. Subalpine fir master tree-ring chronology (raw and standardized versions). 102

Figure B.1. Subalpine fir floating chronology (raw and standardized versions)...... 105

Figure B.1. Subalpine fir floating chronology (residual and ARSTAN versions)...... 106 viii

List of Tables

Table 3.1. Rates of linear recession of Manatee Valley glaciers over the 20th Century, as calculated from historical photographs...... 40

Table 3.2. Control sites used to determine tree and lichen ecesis intervals within the Manatee Glacier forefield...... 46

Table 3.3. Chronology statistics for the two subalpine fir collections from Manatee Valley. The first collection is the master dating series, while the second is a floating chronology of subfossilized wood recovered at Sites 3 and 4...... 47

Table 3.4. Summary of radiocarbon dated, dendroglaciologic evidence recovered in Manatee Valley...... 56

Table 3.5. Lichenometric dates derived for lateral moraine stabilization at Manatee Glacier and Oluk Glacier. Transect locations and orientations are displayed in Figure 3.1. Minimum dates for moraine stabilization incorporate systematic errors associated with the Rhizocarpon geographicum growth curve from the central Coast Mountains (Larocque and Smith, 2004\; Smith and Desloges, 2000)...... 62

Table 4.1. Summary table of Holocene glacier advances in the B.C. Coast Mountains...81 ix

Acknowledgments

I would like to express my gratitude to a number of people who helped me complete this thesis. Dan, thank you so much for the opportunity to explore the mountains of B.C. and for bringing together such an amazing group of girls. I truly could not have asked for a more fun and supportive supervisor. Thanks to everyone who helped me in the field. Kelly and Michi, thanks for teaching me not to (always) follow Dan.

Bethany and Leslie, your perseverance through 8 days of rain and crumbling moraines in

2007 was more than I ever could have expected. Thanks to Aquila, Lisa, Trisha, Sarah, and Kate for endless laughter in the lab and having, the occasional, valuable discussion about dendrochronology. I will miss you all very much!

There are, of course, several other individuals who offered their continued support. Mom and Dad, thanks for your encouragement and financial support. Mike and

Lisa, you have undeniably played important roles throughout this experience. Thank you for believing in me and making home, home.

1

Chapter 1: Introduction

Documentation of glacier extent and volume changes over the last half century in

Pacific North America demonstrates that most have experienced significant frontal retreat and downwasting (Scheifer et al., 2007; VanLooy and Forster, 2008). Some of the most rapid changes in western Canada have occurred in the southern cordillera where a 12.5% decrease in ice-cover has occurred since 1985 (Bolch et al., 2008). Researchers have often used instrumental mass balance records from southern British Columbia (B.C.) to describe the attendant glacier mass balance linkages with climate on interannual

(Letréguilly, 1988; Bitz and Battisti, 1999), decadal, and multi-decadal time-scales

(Hodge et al., 1998; Kovanen, 2003). Assessing the response of glaciers to climate prior to the mid-20th Century, however, necessitates reconstruction of centennial to millennial length proxy records (Bradley and Jones, 1993).

Research Background

Decreasing glacier cover since the beginning of the 20th Century has been described as hemispheric in scale, probably relating to increased global air temperatures

(Oerlemans, 2005). Given the regional nature of the glacier-climate relationship, it is reasonable to assume that the distribution of moraines within glaciated valleys provides a long-term perspective of alpine environmental conditions during the late-Holocene. The prevalence of intact moraine sequences in Pacific North America overcomes the poor spatial and temporal coverage of documented records to provide relatively detailed glacier histories by applying tephrochronologic, dendrochronologic, and lichenometric 2 dating techniques (Grove, 1988).

Retreating glaciers in the Coast Mountains regularly expose the remains of forests buried by past advances (Mathews, 1951). These subfossil remains have successfully been interpreted using dendroglaciology to detail ice front fluctuations spanning the

Holocene interval (Ryder and Thomson, 1986; Luckman, 2000; Menounos et al., in press). The purpose of this thesis is to describe the prehistoric behaviour of glaciers located in a remote headwater area of the southern Coast Mountains and gain insight into low frequency climate variability in the North Pacific. The intent was to use complimentary dendroglaciological and lichenometric methodologies to present a chronology of late-Holocene glacier activity.

Research Objectives

Given the research needs of the region, the primary objectives of this research were to:

1. Reconstruct glacial fluctuations at Manatee Valley in the Coast Mountains of

southern B.C. over the Holocene by: a) applying dendroglaciologic and radiometric

techniques to determine the extent and timing of former glacier advances; and b)

employing lichenometric techniques to date the stabilization of lateral moraine

complexes.

2. Compare the findings of these investigations with existing glaciological and

paleoenvironmental records from other locations in B.C., Alberta, Alaska, and

Washington State (WA) in order to identify common intervals of glacier advance and

any elucidate spatial relationships. 3

Thesis Overview

This thesis is organized into five chapters. Following this introduction, Chapter

Two provides historical context for glaciologic research in western Canada and reviews current dendroglaciological investigations, particularly those undertaken in the Coast

Mountains. A brief review of dendroglaciology and lichenometry are also included in this chapter to provide a background for interpreting reconstructions of glacier activity.

Chapter Three describes the main findings of this research, and was prepared as a manuscript for submission to a peer-reviewed professional journal. Chapter Four provides an expanded discussion of the results and compares the findings with those of previous studies in the Canadian Cordillera, WA, and Alaska. Chapter Five, summarizes the main conclusions of the research, discusses some of the limitations, and offers suggestions for future dendroglaciological research in B.C. Supplementary data is included in the Appendices. 4

Works Cited

Bitz, C.M., and Battisti, D.S., 1999. Interannual to decadal variability in climate and the glacier mass balance in Washington, western Canada, and Alaska. Journal of Climate, 12: 3187-3196. Bradly, R.S., and Jones, P.D. 1993. 'Little Ice Age' summer temperature variations: their nature and relevance to recent global warming trends. The Holocene, 3: 367-376. Bolch, T., Menounos, B., and Wheate, R. 2008. Remotely-sensed Western Canadian Glacier Inventory 1985-2005 and regional glacier recession rates. Geophysical Research Abstracts, 10: EGU2008-A-10403. Grove, J.M. 1988. The Little Ice Age. Methuen, London, UK. Hodge, S.M., Trabant, D.C., Krimmel, R.M., Heinrichs, T.A., March, R.S., and Joseberger, E.G. 1998. Climate variations and changes in mass of three glaciers in western North America. Journal of Climate, 11: 2161-2178. Kovanen, D.J. 2003. Decadal variability in climate and glacier fluctuations on Mt Baker, Washington, USA. Geografiska Annaler, 85A: 43-55. Letréguilly, A. 1988. Relation between the mass balance of western Canadian mountain glaciers and meteorological data. Journal of Glaciology, 34: 11-18. Luckman, B.H., 2000. Little Ice Age in the Canadian Rockies. Geomorphology, 32: 357-384. Mathews, W.H. 1951. Historic and prehistoric fluctuations of alpine glaciers in the Mount Garibaldi map-area, southwestern British Columbia. Journal of Geology, 59: 357-380. Menounos, B., Osborn, G., Clague, J., and Luckman, B. In press. Latest Pleistocene and Holocene glacier fluctuations in western Canada, Quaternary Science Reviews, 30. Oerlemans, J. 2005. Extracting a climate signal from 169 glacier records. Science, 308: 675-677. Ryder, J.M., and Thomson, B. 1986. Neoglaciation in the southern Coast Mountains of British Columbia: Chronology prior to the late Neoglacial maximum. Canadian Journal of Earth Sciences, 23: 273-287. Schiefer, E., Menounos, B., and Wheate, R. 2007. Recent volume loss of British Columbian glaciers, Canada. Geophysical Research Letters, 34: L16503. VanLooy, J., and Forster, R. 2008. Glacial changes of five southwest British Columbia icefields, Canada, mid-1980s to 1999. Journal of Glaciology, 54: 469-478. 5

Chapter 2: Review of Dendroglaciologic and Lichenometric Research in Pacific North America

Introduction

Since the retreat of the Late Wisconsin Cordilleran Ice-Sheet in Pacific North

America (PNA) from its maximum extent after 15,000 cal. yr BP (Blaise et al., 1990), alpine basins in this region have experienced several glacial advance intervals, most notably during the late-Holocene Little Ice Age (LIA) interval. Grove (1988) reviews the

LIA as a concept global in scale, although the supporting data are heavily biased towards

European glaciers. Documentation of down valley ice extent for North American glaciers is typically limited to the 20th Century. Fortunately, the ongoing discovery of datable organics within the forefields of glaciers in PNA is offering the opportunity to construct relatively detailed Holocene glacial histories. Geobotanical methods, such as dendrochronology and lichenometry, have commonly been used to characterize the

Holocene behaviour of alpine glaciers in the region (Grove, 1988). The key concepts and assumptions of these methodologies are reviewed in this chapter. The chapter also provides an historical framework for Holocene glacial research in the Canadian

Cordillera and a review of the current state of knowledge.

Review of Methods

Dendroglaciology

Dendroglaciology refers to the application of dendrochronologic methods to 6 reconstruct past glacier activity (Smith and Lewis, 2007). This approach to event dating rests foremost on the assumption that trees in the higher latitudes form early-wood and late-wood cells in tree-rings annually; and, second that tree ring-widths vary in response to limiting factors (ie. temperature and/or precipitation climate) to create distinctive time series (Fritts, 1976). Complete reviews of dendroglaciology methodologies and applications are available in Schweingruber (1988) and Luckman (1988). This review considers only those concepts necessary to guide the interpretation of the glacier history reconstructions that follow.

Dendroglaciology allows for the dating of glacier activity by:

1. Determining minimum ages for glacial landforms with annual ring counts of the

oldest tree inhabiting deglaciated terrain, referred to herein as the geobotanical

approach (Lawrence, 1946; Heusser, 1956).

2. Establishing the calendar year of glacial advance into ice-marginal forests, through

the selection of trees exhibiting callous tissue, corrasion scars, or reaction wood,

which demonstrate abnormal cell development in response to encroaching glaciers

(Alesto, 1971; Schroder, 1980; Luckman, 1988; Wiles et al., 1996).

3. Resolving the year of death of glacially overridden trees by cross-dating, a process

that involves comparing ring-width patterns, between living and glacially reworked

trees (Schweingruber, 1988; Luckman, 1995).

4. Applying radiometric dating to the perimeter wood of subfossilized samples, when

ring-widths fail to cross-date with a master chronology, or when the preservation of

wood is poor (Wood and Smith, 2004).

5. Relating the ring-width patterns of ice marginal trees to: a) moraine building 7

episodes (LaMarche and Fritts, 1971; Scuderi, 1987; Wiles et al., 1996); b)

instrumental mass balance records (Lewis and Smith, 2004a; Watson and Luckman,

2004); and/or, c) climate records (Villalba, et al., 1990; Larocque and Smith, 2005).

Although dendroglaciology benefits from simplicity and low cost, several limitations are worth noting. The success of dendroglaciological research depends upon an abundant supply of wood and the subsequent preservation within actively eroding proglacial environments (Luckman, 1988). Dendroglaciologic interpretations are also restricted in their temporal range. For example, the success of cross-dating depends upon the longevity of local trees, which often fail to exceed 300-400 years in many subalpine locations (Schweingruber, 1988). Nonetheless, millennial length chronologies have been compiled for a few glaciated valleys in PNA (Scuderi, 1987; Barclay et al., 1999, 2009).

Limitations to dendroglaciological dating arise because: a) intercepting the pith when coring a tree is rare, especially for large diameter trees (Villalba and Veblen, 1997); b) extracting cores from the root ball is challenging (McCarthy et al., 1991; Wincester and Harrison, 2000); c) tree-ring series sometimes contain missing and/or false ring boundaries, resulting in incorrect age determinations; and most importantly, d) opportunities for determining locally relevant ecesis intervals, the time it takes for seedlings to establish, are often limited by the lack of reliable control surfaces and/or inconsistent colonization rates due to microclimatic effects (Sigafoos and Hendricks,

1969; Villalba et al., 1990; McCarthy and Luckman, 1993; Koch, 2009).

Over the past century, glaciologic studies from the Canadian Cordillera have contributed greatly to research efforts concerned with providing detailed reconstructions of late-Holocene glacier activity (Clague and Slaymaker, 2000). Glaciers in this region 8 have regularly interacted with subalpine forests, and late-Holocene glacial sediments are well-preserved. Lawrence (1946) was the first to apply tree-ring dating techniques to date glacial landforms in the Olympic Mountains, Washington State (WA). Following his application, dendrochronological research methodologies were applied in the Garibaldi

Range, B.C. (Mathews, 1951; Brink, 1959), and in the Canadian Rocky Mountains

(Heusser, 1956; Bray and Struik, 1963; Luckman and Osborn, 1979). In both regions, extensive LIA advances obliterated most pre-existing moraine sequences, therefore precluding insight into the magnitude of pre-LIA events.

Dendroglaciology provides a number of opportunities for dating glacier events

(Luckman, 2000; Smith and Lewis, 2007). Overridden forests provide information about the timing of onset, culmination, and duration of glacial events. Subfossilized wood samples recovered from a glacier forefield that lack a direct association with glacial sediments, are helpful in providing limiting dates for advancing ice snouts. Glacially- sheared in-situ stumps provide direct evidence of an advance and demarcate the position of a former glacier margin (Luckman, 1995; Wood and Smith, 2004). The timing of maximum ice cover, or culmination, can be estimated by dating trees that are found growing on recently deglaciated surfaces or on stabilized moraine complexes (Luckman,

1988). In addition, many lateral moraine sites in the Canadian Cordillera display stacked tills and woody detritus interbedded with paleosols. When combined with radiometric dating, the stratigraphic records exposed in these moraines, have been interpreted to extend the temporal range of dendroglaciology to span millennia (Osborn et al., 2001;

Reyes and Clague, 2004; Jackson et al., 2008). 9

Lichenometry

Lichenometry is a relative dating methodology that is employed to estimate minimum dates for the surface stabilization of moraines (Andrews and Weber, 1969;

Innes, 1985). Beschel (1950, 1961) pioneered lichenometric dating, and was the first to investigate the relationship between thallus age and diameter on moraine surfaces.

Although lichenometry applies best to moraine sequences dating to the last 500 cal. years

(Innes, 1985), surfaces up to 900 years old have been dated by extrapolating growth-rates with radiometrically-dated control surfaces (Larocque and Smith, 2004). Detailed reviews of lichenometry are available from several authors (Jochimsen, 1973; Innes,

1985; 1988). The key assumptions are:

1. Thallus expands radially at a constant rate.

2. Thallus size, measured in terms of maximum diameter, is directly related to the

surface age of a deposit (Beschel, 1961).

3. The age of the reference surface is known to the calendar year.

4. Individual thalli can be identified at least to the subspecies level (Benedict, 1988).

5. The methods for data collection and the character of sampling sites, selected for

lichenometric work are comparable between reference surfaces and surfaces with

unknown age.

The first assumption is often the most difficult to substantiate because of uncertainties about the life history of lichen species in relation to climatic effects.

Although Porter (1981) and others have quantified the relationship between lichen growth and macro-scale climate, microclimatic effects can also contribute to anomalous 10 growth (Jochimsen, 1973). The microclimatic factors shown to influence thallus growth rates include: moisture availability, the substrate aspect, duration of snow-cover, and fertilization from alpine inhabitants (Porter, 1981; Smith et al., 1995; Lewis and Smith,

2004b). Microclimate, however, has a less pronounced effect on the age assigned by lichenometry to a substrate when the search area is increased (Innes, 1988).

A key assumption of lichenometry is that thalli display a predictable rate of growth with time. The most commonly adopted growth-rate curve is that of a second- order polynomial that presumes slow rates of thallus expansion during a phase of initial establishment, later acceleration during the “great period”, and finally decreasing rates of growth during the “senescent” phase (Beschel, 1961; Andrews and Webber, 1969; Porter,

1981; Innes, 1988). Although the range of age-growth relationships adopted for lichenometric work suggest this may not always be the case (Armstrong, 2005), only limited research has focused on establishing lichen growth rates by direct observation

(McCarthy, 2003; Armstrong, 2005; Bradwell and Armstrong, 2007).

Another major limitation of lichenometric studies has been a lack of consistency among the sampling methods used to establish age-size relationships (Innes, 1985). Two distinct sampling protocols have been reviewed by Innes (1988) and Karlén and Black

(2002). The traditional method proposed by Beschel (1950, 1961) requires the development of a relationship between thallus expansion on surfaces of unknown age and substrates of known age. This indirect method, although benefiting from simplicity, does not allow for the assignment of confidence intervals based upon normal population structures. The size-frequency and percent-cover approach, on the other hand, does allow for statistically defined estimates of uncertainty (Locke et al., 1979; McCarroll, 1994). 11

Unfortunately this technique is time-consuming and requires a substantial number of samples.

Lichenometric growth curves have been developed for Rhizocarpon geographicum (L.) DC for several locations in the mountains of western North America.

In the Coast Mountains, the growth curve established by Smith and Desloges (2000) near

Bella Coola was modified with additional data provided by Larocque and Smith (2004) from the nearby Mt. Waddington Range. Independent growth curves have been developed for the Insular Ranges on Vancouver Island (Lewis and Smith, 2004b) and for the Cascade Range, WA (O'Neal and Schoenenberger, 2003). The latter growth curve is notable for the rapid rate of expansion shown by lichens growing on Mounts Baker,

Hood, and Rainier. All of these curves have been assessed for their ability to date moraine sequences in the southern Coast Mountains (Allen and Smith, 2007; Koch et al.,

2007a).

Holocene Glacial Activity in the B.C. Coast Mountains

Following the disintegration of the Cordilleran Ice-Sheet, valley glaciers in coastal B.C. rapidly decayed to present day extents by ca. 9500 14C yrs BP (Fulton, 1971;

Clague, 1981; Friele and Clague, 2002), which broadly corresponds with the arbitrary definition set forth by Hopkins (1975) for the beginning of the Holocene Epoch.

Intact lacustrine sediments contain paleobotanical evidence that characterizes the early-Holocene as having relatively warm and dry conditions compared to those present today. Defined as the “Hypsithermal” by Deevey and Flint (1957) for eastern North

America, this term has restricted utility in the coastal ranges of B.C. because of its time- 12 trangressive character (Mathewes, 1985). Hebda (1995) sought to resolve some of these conflicting interpretations from B.C. paleoecological records by subdividing the early-

Holocene into a warmer and drier “xerothermic” and a warm, moist “mesothermic” interval. Following this interval, glaciers in the region began advancing, presumably in response to the deteriorating climatic conditions, marking the onset of the “Neoglacial” in the southern Canadian Cordillera by 5000 14C yrs BP (Porter and Denton, 1967;

Denton and Karlén, 1973a). Compositional changes in vegetation assemblages surrounding high elevation lakes in B.C. mountains, however do not show adjustments until 4400-3700 14C yrs BP (Hebda, 1995; Spooner, 2002; Heinrichs et al., 2004). In this review dates are represented in 14C yrs BP for most episodes of Holocene glaciation.

Wood ages assigned to the LIA, and those that have been securely cross-dated with master chronologies, are herein reported in calendar years AD.

Early-Holocene Advances

Preservation of early-Holocene deposits is rare in glaciated basins, requiring researchers to obtain paleoenvironmental records from down valley sedimentary sinks.

With the prevalence of warm and dry climatic conditions evident from lacustrine and marine records (Mathewes, 1985; Pellatt et al., 2000; Palmer et al., 2002; Spooner et al.,

2002), the expansion of alpine glaciers was, presumably, not climatically facilitated in the early-Holocene (Davis and Osborn, 1987; Clague and Mathewes, 1989). Nonetheless, detrital wood found within glacier forefields in the southern Coast Mountains has been interpreted in concert with lacustrine records to suggest a short-lived glacial advance at

7770- 7380 14C yrs BP, coeval with the 8200-year cold event defined from Greenland ice 13 cores (Reasoner et al., 2001; Menounos et al., 2004). Thomas et al. (2000) offer evidence for tephra-constrained till units that demonstrate a considerable depression in glacial limits at this time on Mt. Baker. This finding agrees with the ages assigned to charcoal- bearing moraines located on Glacier Peak (Begét, 1981) and Mt. Rainier (Heine, 1998) in the Cascade Mountains. This event is also possibly synchronous with till units deposited before the deposition of Mazama ash at sites located in the Canadian Rocky Mountains

(Luckman and Osborn, 1979).

“Garibaldi Phase”

In-situ glacially deposited wood recovered from sites in Garibaldi Provincial Park dating to 6000-5300 14C yrs BP provides the first indication of a mid-Holocene glacier advance (Stuiver et al., 1960; Lowdon and Blake, 1968, 1975). Ryder and Thomson

(1986) identified this interval as the “Garibaldi Phase”, and not an “advance”, as the sites lacked an association with corresponding down valley till deposits.

“4200 yrs. BP Event”

Dendroglaciologic evidence from the southern B.C. and Alberta has been reinterpreted along with recent radiocarbon evidence and paleolimnological records to identify at least two glacier advances between 4200-3500 14C yrs BP (Menounos et al., in press). The onset of this glacial interval is indicated from interpretations of the origin of detrital wood recovered from the forefields of Sphinx, Helm, (Koch et al., 2007a),

Spearhead (Osborn et al., 2007), and Goddard glaciers (Menounos et al., 2008). The earliest phase of this advance at ca. 4200 14C yrs BP is indicated within lake sediment 14 records. It is suggested that this period of ice expansion was restricted and did not see glaciers advance to positions near those attained in the late-Holocene. Correlative support for the regional significance of this event comes from evidence recovered at glaciers located in the Interior Ranges of B.C. and the Canadian Rocky Mountains (Menounos et al., in press). During a readvance at ca. 3800 14C yrs BP, several glacier termini reached down valley positions close to those reached in the LIA in southern B.C.(Menounos et al., 2008; in press). High elevation lake sedimentation rates during this interval correspond in rate and magnitude to those associated with LIA glacial activity

(Menounos et al., 2008).

“Tiedemann Advance”

The most widely recognized late-Holocene period of pre-LIA glacier expansion is the Tiedemann Advance. This episode of glacier advance was originally proposed to have occurred between 3300 to 1900 14C yrs BP (Ryder and Thomson, 1986). Recent investigations have since confirmed the regional nature of this event in the B.C. Coast

Mountains (Clague and Mathews, 1992; Clague and Mathewes, 1996; Reyes and Clague,

2004; Laxton, 2005; Allen and Smith, 2007; Koch et al., 2007b; Osborn et al., 2007;

Jackson et al., 2008). The “Tiedemann Advance” is considered to be coeval with the

“Peyto Advance” of the Canadian Rocky Mountains (Luckman and Osborn, 1979;

Osborn and Karlstrom, 1989; Wood and Smith, 2004).

“Unattributed Advance”

Several authors offer alternative interpretations for ice augmentation from 2300 to 15

1900 14C yrs BP time. In-situ ice-associated wood radiometrically dated to 1900 14C yrs

BP has been obtained from the lateral flanks of Todd Valley in the northern Coast

Mountains (Laxton, 2005; Jackson et al., 2008). Detrital wood from the southern Coast

Mountains dating to this period has been retrieved from sites in the Bridge River valley

(Allen and Smith, 2007) and from within the Lillooet Glacier lateral moraine (Reyes and

Clague, 2004). Although no evidence has been discovered regarding the extent of ice around 2300 14C yrs BP, the close association with underlying paleosols at all of these sites indicates that environmental conditions ameliorated long enough to allow for tree establishment on Tiedemann-age deposits.

First Millennium Advances (FMA)

Reyes et al. (2006) provide an extensive review of the available evidence for multiple episodes of ice extension during the First Millennium AD in PNA. Radiocarbon dated organics from numerous glacier forefields suggest ice began advancing from

1900-1750 14C yrs BP (200 to 300 AD), and reached its maximum extent ca. 1600-1250

14C yrs BP (400 to 700 AD) (Reyes et al., 2006). In the eastern Pacific Ranges, this event was identified as the “Bridge Advance” based on glacially-sheared in-situ stumps collected by Allen and Smith (2003) at the type location below Bridge Glacier. Since this initial discovery correlative glacier advances have been described from the Lillooet

Glacier forefield (Reyes and Clague, 2004), at sites located in Garibaldi Provincial Park

(Koch et al., 2007b), at sites located in the Northern Boundary Ranges (Laxton, 2005;

Jackson and Smith, 2008), and in Alaska (Calkin et al., 2001; Wiles et al., 2008). The remains of a forest overrun by the Tebenkof Glacier, in Alaska's Kenai Mountains, were 16 cross-dated into a millennial length chronology to show that the glacier was advancing down valley between 710's to 720's AD (Barclay et al., 2009). Although direct evidence for moraine construction during the First Millennium is generally lacking, Denton and

Karlén (1973b) have presented lichenometric dates on moraines from the St. Elias

Mountains that correlate with the FMA.

Little Ice Age

Most fresh-looking till and moraine deposits found within the Canadian

Cordillera are attributed to LIA glacier advances (Luckman, 2000). Although the most extensive LIA moraines in the southern Coast Mountains were constructed by the early

18th Century in the southern Coast Mountains, moraines from earlier LIA advances have been preserved in some locations.

Research into LIA glacier behaviour has been completed in the southern Coast

Mountains (Pacific Ranges: Ryder and Thomson (1986); Mt. Waddington Range:

Larocque and Smith (2003); Vancouver Island Insular Mountains: Lewis and Smith

(2004a, 2004b); Eastern Pacific Range: Reyes and Clague (2004) and Allen and Smith

(2007); Garibaldi Range: Koch et al. (2007a); and in the northern Coast Mountains

(Desloges and Ryder, 1990; Clague and Mathews, 1992; Clague and Mathewes, 1996;

Laxton, 2005; Lewis and Smith, 2005; Jackson et al., 2008). Corollary information on

LIA glacier activity is available from the Canadian Rocky Mountains (Luckman, 2000) and Alaska (Wiles et al., 1999a, 199b), and is only briefly reviewed here.

The earliest evidence for the onset of LIA glaciation dates to the 11th and 13th

Centuries in the Coast Mountains. Evidence recovered in Garibaldi Provincial Park by 17

Koch et al. (2007a) indicates that Warren Glacier overran a valley-bottom forest in 1050

AD, reaching its maximum down valley extension by the 12th Century. This finding agrees with radiocarbon dates presented by Ryder and Thomson (1986) from Klinaklini

Glacier to the north, where organics were buried by a glacial advance in the 11th or early

12th Centuries. Davis et al. (2007) examined the remains of a forest found in lateral moraines at Coleman Glacier on Mt. Baker in the Cascade Range that indicate they were buried by an advance in 1000-1210 AD (ca. 940 14C yr BP).

Sundry locations within the Pacific Coast Ranges indicate moraine construction during the 13th Century. Geobotanical dating techniques provide minimum dates for the till surfaces within Garibaldi Provincial Park (Koch et al., 2007a; Koch, 2009) and at

Bridge Glacier, where a late-13th Century date was assigned with lichenometry to the outermost terminal moraine (Allen and Smith, 2007). Early-LIA glacier activity may have culminated earlier in the central Coast Mountains where Desloges and Ryder (1990) and Larocque and Smith (2003) estimate moraines were emplaced by the early 1200's

AD. Contemporary glacial activity has also been documented further in the northern

Coast Mountains, where Lewis and Smith (2005) and Jackson et al. (2008) report early- mid 13th Century advances took place.

Lichenometric dates point to a subsequent advance throughout southwestern B.C. that ended in the early to mid 14th Century (Larocque and Smith, 2003; Lewis and Smith,

2004b; Allen and Smith, 2007; Koch et al., 2007a). Corresponding dates have also been suggested from geobotanical evidence located on the slopes of Mt. Rainier by Burbank

(1981), following concurrent discoveries at Cowlitz Glacier (Crandall and Miller, 1964) and in the Dome Peak area (Miller, 1969). 18

Several glaciated valleys in western B.C. contain evidence of a 15th Century advance. Wood collected from the lateral margins of Lillooet Glacier supports moraine construction at this time (Reyes and Clague, 2004). Further to the north, organic layers buried beneath a fen down valley of Berendon and Frank Mackie glaciers correspond with a 15th Century advance (Clague and Mathews, 1992; Clague and Mathewes, 1996).

In the Mt. Waddington area Larocque and Smith (2003) found evidence for advances from 1506 to 1524 AD and from 1562 to 1575 AD. Synchronous events were also recorded in the northern Cascade Mountains from moraines situated on Dome Peak

(Miller, 1969), Mt. Baker (Heikinnen, 1984; Davis et al., 2007), and Mt. Rainier

(Sigafoos and Hendricks, 1972; Burbank, 1981). Following these advances, Larocque and Smith (2003) propose two moraine-building events, one from 1597-1621 AD, and a second from 1657 to1660 AD. Corresponding moraine-building events recorded within fen sediments in the northern Coast Mountains (Clague and Mathews, 1992; Clague and

Mathewes, 1996) and from Mt. Baker (Easterbrook and Burke, 1971; Fuller, 1980) offer additional evidence for an early 17th Century glacier front oscillation.

The majority of LIA moraines from the southern Coast Mountains date to the 18th

Century. Glaciers advancing down valley at this time carved still visible trimlines through subalpine forests. Allen and Smith (2007) and Koch et al. (2007a) report on an advance in the early decades of the 1700's AD, which slightly post-dates a corresponding advance reported in Tweedsmuir Provincial Park (Smith and Desloges, 2000). At sites in the northern Coast Mountain, there is evidence to suggest that this event culminated slightly later in 1760 AD (Jackson et al., 2008). Contemporaneous glacier advances are described by moraines the Gulf of Alaska (Wiles et al., 1999a) and in the Cascade 19

Mountains (Burbank, 1981; Heikkinen, 1984).

Moraines deposited after the 18th Century record less extensive readvances and are characteristically located up-valley from terminal LIA deposits. Larocque and Smith

(2003) report on two episodes of moraine construction in central B.C. from 1821-1837

AD and 1871-1900 AD. Two moraines dating to the 1900's AD are reported from Bridge

Glacier (Allen and Smith, 2007), and in the Mt. Waddington area moraine construction is also reported between 1915-1928 AD and 1942-1946 AD (Larocque and Smith, 2003).

On Vancouver Island, Lewis and Smith (2004b) propose moraine emplacement in the

1930's AD.

Holocene Glacial Activity in PNA

Canadian Rocky Mountains

In the Canadian Rocky Mountains the earliest indication of glacier activity in the last millennium dates to the 12th -13th Centuries. Luckman (1993, 1995, 1996) reports on a sustained advance from 1142-1350 AD at Robson and Peyto glaciers. Depressed summer air temperatures in the 1690's AD, and an interval of increased precipitation from 1660-1690 AD, may have prompted early 1700's AD moraine construction

(Luckman, 2000). During the 18th Century extensive advances are recorded at South

Cirque Glacier (Bednarski, 1979), Yoho Glacier (Bray and Struik, 1963), Angel Glacier

(Luckman, 1977); as well as in Maligne Ice Field (Kearney, 1981), the Premier Range

(Watson, 1986), at Mt. Robson (Heusser, 1956; Luckman, 1995), Peter Lougheed and Elk

Lakes Provincial Park (Smith et al., 1995), at Dome Glacier, (Luckman, 1998), at 20

Manitoba Glacier (Robinson, 1998) and at Stutfield Glacier (Osborn et al., 2001).

Regionally, glaciers in the Canadian Rocky Mountains built their outermost moraines in the mid-1800's AD (Luckman, 2000). Dendroclimatic reconstructions suggest that this advance occurred in response to decreased summer air temperatures during preceding decades (Luckman, 2000). Several moraines record readvances in the latter half of the century, from 1840-1900 AD, at Mt. Robson (Luckman, 1995) during an interval of increased regional precipitation (Luckman, 2000).

Alaska

Evidence of LIA glacier activity in Alaska indicates that glaciers began to advance down valley between 1100 and 1200 AD in the Wrangell Mountains (Wiles et al., 2002) and in the Kenai Mountains (Wiles and Calkin, 1994). Indications of glacial activity during the 13th Century are found in the Gulf of Alaska (Wiles et al., 1999a), western Prince William Sound (Wiles et al., 1999b), Wrangell Mountains (Wiles et al.,

2002), Kenai Mountains (Wiles and Calkin, 1994), and Brooks Range (Evison et al.,

1996). Mid-LIA extensions during the 15th Century are indicated earlier in the century by

Calkin et al. (2001), at a time when the Kenai Mountains were experiencing increased precipitation and decreased summer air temperatures (Wiles and Calkin, 1994). Denton and Karlén (1977) and Evison et al. (1996) present evidence for the down valley movement of glaciers in Alaska in the 1400's AD. Subsequent advances were also noted during the 16th Century (Denton and Karlén, 1977; Evison et al., 1996). The Kenai and the Wrangell Mountains experienced and increased ice-cover in the mid-1600's AD

(Wiles and Calkin, 1994; Wiles et al., 1999a; Wiles et al., 2002) and the St. Elias 21

Mountains (Reyes et al., 2006).

Summary

Ongoing glaciological research in the glaciated basins of coastal B.C. has revealed an increasingly complex story of glacier activity over the last 10,000 years

(Menounos et al., in press). With persistent sampling effort and increased exposure of subfossilized wood, regionally synchronous events such as the “Tiedemann Advance” and the LIA are suggestive of sustained intervals of wet and cool climatic conditions in the late-Holocene (Walker and Pellat, 2003). Other glacial events, however, have no counterpart in climatic history. Notable in this regard are records of glacier expansion in the early-Holocene (Reasoner et al., 2001) and during the FMA (Reyes et al., 2006), when lake sediments record warmer temperatures than present. Dendroclimatic reconstructions from this region interpreted within the context of the present record of glaciation, suggest that regionally the LIA glacial interval coincides with the coldest decades of the past centuries and a notable period of moraine construction in both the

Coast Mountains (Larocque and Smith, 2003) and the Canadian Rocky Mountains

(Luckman, 2000).

The detailed history offered from Coast Mountain glaciological research for the

LIA, perhaps, may serve as an analog to glacier activity during the entire Holocene. In agreement with the original proposal by Mathes (1939), it seems that the Holocene is best described as a time of numerous “little ice ages”. This research aims to test this hypothesis of increasing complexity in the Holocene glacial record. 22

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Smith, D.J. and Desloges, J.R. 2000: Little Ice Age history of Tzeetsaytsul Glacier, Tweedsmuir Provincial Park, British Columbia. Géographie physique et Quaternaire, 54: 135-141.

Smith, D. and Lewis, D. 2007. Dendroglaciology. In: Elias, S.A. (Ed). Encyclopedia of Quaternary Science. Elsevier Scientific, 2: 986-994.

Smith, D.J., McCarthy, D.P., and Colenutt, M.E. 1995. Little Ice Age glacial activity in Peter Lougheed and Elk Lakes provincial parks, Canadian Rocky Mountains. Canadian Journal of Earth Sciences, 32: 579-589.

Spooner, I.S. Mazzucchi, D. Osborn, G., Gilbert, R., and Larocque, S.J. 2002. A multi- proxy Holocene record of environmental change from the sediments of Skinny Lake, Iskut region, northern B.C., Canada. Journal of Paleolimnology, 28: 419-431.

Stuiver, M. Deevey, E.S., and Granlenski, L.J. 1960. Yale natural radiocarbon 30 measurements V. American Journal of Science, Radiocarbon Supplement, 2: 49-61.

Thomas, P.A., Easterbrook, D.J., and Clark, P.U. 2000. Early Holocene glaciation on Mount Baker, Washington State, USA. Quaternary Science Reviews 19: 1043-1046.

Villalba, R., Leiva, J.C., Rubulls, S., Suarez, J. and Lenzano, L. 1990. Climate, Tree-Ring and Glacial Fluctuations in the Rio Frias Valle, Rio Negro, Argentina. Arctic and Alpine Research, 22: 215-232.

Walker, I.R., and Pellatt, M.G. 2003. Climate change in coastal British Columbia- A paleoenvironmental perspective. Canadian Water Resources Journal, 28: 531-566.

Watson, W., and Luckman, B.H., 2004. Tree-ring-based mass-balance estimates for the past 300 years at Peyto Glacier, Alberta, Canada. Quaternary Research, 62: 9-18.

Wiles, G.C., and Calkin, P.E. 1994. Late Holocene, high-resolution glacial chronologies and climate, Kenai Mountains, Alaska. Geological Society of America Bulletin, 106: 281-303.

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Wiles, G.C., Post, A., Muller, E.H. And Molnia, B.F. 1999a. Dendrochronoloy and Late Holocene History of Bering Piedmont Glacier, Alaska. Quaternary Research, 52: 185-195.

Wiles, G.C., Barclay, D.J., and Calkin, P.E. 1999b. Tree-ring-dated ‘Little Ice Age’ histories of maritime glaciers from western Prince William Sound, Alaska. The Holocene, 9: 163-173.

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Chapter 3: Late-Holocene glacial activity of Manatee Valley,

southern Coast Mountains, British Columbia

Introduction

Southwestern British Columbia (B.C.) has experienced significant volumetric losses in glacial ice over the last century (Schiefer et al., 2007; Vanlooy and Forster,

2008), creating a striking visual contrast between the extensive distribution of late-

Holocene till and the presently retracted ice fronts (Mathews, 1951; Ryder and Thomson,

1986). Since the beginning of mass balance observations in the mid-1960's, the dynamics of several B.C. glaciers have been related to annual climate variations, mainly summer air temperatures and winter precipitation totals (Letréguilly, 1988). The brevity of these records, however, prevents a reliable characterization of alpine glacierization on longer time scales.

Over the past decade, dendroglaciological research from coastal B.C. mountains has contributed greatly to the discussion about the variability of alpine environmental conditions throughout the past 10,000 ka cal. years BP (Walker and Pellatt, 2003;

Menounos et al., in press). Several studies demonstrate the ability of dendroglaciology to extend glaciologic records of the Coast Mountain glaciers through the Holocene, by providing accurate age determinations for glacial deposits (Ryder and Thomson, 1986;

Smith and Desloges, 2000; Larocque and Smith, 2003; Lewis and Smith, 2004; Allen and

Smith, 2007; Koch et al., 2007a, 2007b; Jackson et al., 2008).

This chapter presents the results of dendroglaciologic and lichenometric 33 investigations at four glacier forefields in the Manatee Valley area of the southern B.C.

Coast Mountains. Reconnaissance investigations in 2006 led to the discovery of buried subfossil stumps and forest detritus within the glacier forefields. A second trip in 2007 provided an opportunity to search for additional wood samples and to detail the age of

Little Ice Age (LIA) moraines in this region. In this chapter I present and compare the results of my research to other paleoenvironmental records from B.C. mountains.

Research Background

Dendroglaciology describes the application of tree-ring dating principles to assign ages to glacial sediments and landforms. Lawrence (1946) pioneered early efforts and used the total number of annual rings within first-colonizing trees as a minimum estimate of surface age. Within the Canadian Rocky Mountains, historical records and accessibility encouraged the refinement of dendroglaciology to develop LIA glacial histories (Heusser, 1956; Smith et al., 1995; Luckman, 2000). By comparison, dendroglaciological applications were employed only rarely until recently in the Coast

Mountains (Mathews, 1951; Ryder and Thomson, 1986; Smith and Laroque, 1996).

Within the last decade, however, extensive ice front retreat and focused attention on exposed dendroglaciological evidence has allowed for the development of detailed records of glacier behaviour throughout the Holocene (Larocque and Smith, 2003; Lewis and Smith, 2004; Reyes et al., 2006; Allen and Smith, 2007; Koch et al., 2007a, 2007b;

Jackson et al., 2008).

The renewal of alpine glaciation around 6000 14C years BP following early-

Holocene warming, was defined by Porter and Denton (1967) as the “Neoglacial”. 34

Although the Neoglacial was assumed to represent the initial expansion of glaciers in the

Holocene (Ryder and Thomson, 1986), recent research has revealed ice fronts did advance during the early-Holocene (prior to 6000 14C years BP) in the southern and northern Coast Mountains (Laxton et al., 2003; Smith et al., 2005; Koch et al., 2007b), in the Canadian Rocky Mountains (Luckman, 1988), and in the North Cascade Range of

Washington State (WA) (Béget, 1981; Heine, 1998; Thomas et al., 2000). Because environmental reconstructions argue for the dominance of warm and dry conditions during this interval (Clague and Mathews, 1989; Hebda, 1995; Walker and Pellat, 2003),

Reasoner et al. (2001) and Menounos et al. (2004) suggest this advance was short-lived.

The onset of regional glacial conditions in the Holocene corresponds to the

6000-5300 14C yrs BP interval. Coined the “Garibaldi Phase” by Ryder and Thomson

(1986), the original interpretation of glacier expansion during this period was based upon radiocarbon evidence from sites located within Garibaldi Provincial Park (Stuiver et al.,

1960; Lowdon and Blake, 1968, 1975). In their conservative interpretation, the term

“phase” was preferred over “Advance” because the magnitude of the event was unknown. Recent discoveries from the northern (Smith, 2003; Smith et al., 2006) and southern Coast Mountains provide convincing evidence for a distinct interval of ice front expansion 6400-5100 14C yrs BP (Koch et al., 2007b). Paleobotanical reconstructions of

Holocene climate suggest a shift to wetter and cooler conditions occurred at 5000 14C yrs

BP (Spooner et al., 2002; Walker and Pellatt, 2003).

Based on reinterpretations of forests buried by glaciers in Garibaldi Provincial

Park, recent data collected at Tiedemann Glacier, and the evaluation of sedimentation records of alpine lakes in southern B.C., Menounos et al. (2008) proposed a distinct 35 glacial advance at ca. 3800 14C years BP (4200 cal years BP). The '4.2 Advance' likely saw glaciers extend down valley for only a short duration (Menounos et al., 2008).

Menounos et al. (in press) report evidence for a minimum of two ice front advances during the interval between 4200 and 3500 14C years BP. These advances coincide with the end of an interval of warm and moist “mesothermal” climate, and the development of

“modern” conditions (Hebda, 1995).

The widely cited Tiedemann Advance in the Coast Mountains was originally intended to describe a series of pre-LIA glacier fluctuations that took place between 3300 and 1900 14C yrs BP (Fulton, 1971; Ryder and Thomson, 1986). Perimeter dates from in- situ, glacially-killed, trees identifies a regional glacier advance centered at ca. 3000 14C yrs BP (Ryder and Thomson, 1986; Desloges and Ryder, 1990; Clague and Mathews,

1992, Clague and Mathewes, 1996; Reyes and Clague, 2004; Haspel et al., 2005; Lewis and Smith, 2005; Allen and Smith, 2007; Koch et al., 2007a, Osborn et al., 2007; Jackson et al., 2008). Concurrent intervals of glacier expansion occurred in the Cascade Range of

WA (Crandell and Miller, 1964, 1974; Burbank, 1981; Fuller et al., 1983), in Alaska

(Calkin et al., 2001; Barclay et al., in press), and in the Canadian Rocky Mountains from

3300 to 2800 14C yrs BP (Osborn, 1986; Osborn and Karlstrom, 1989; Osborn et al.,

2001; Wood and Smith, 2004).

In their description of the Tiedemann Advance, Ryder and Thomson (1986) define a subsequent pulse of activity ca. 2300 14C yrs BP. Recent interpretations of subfossil wood recovered from within buried sediments at Lillooet Glacier (Reyes and Clague,

2004), in the Todd Valley (Jackson et al., 2008) and at Bridge Glacier (Allen and Smith,

2007), however, suggest that the ca. 2300 14C years BP event represents a distinct 36 readvance. An advance at 2500 14C yrs BP reported by Luckman et al. (1993) at Peyto

Glacier in the Canadian Rocky Mountains may describe a subsequent ice front extension similar to those reported from the Coast Mountains.

During the First Millennium AD glaciers throughout the coastal cordillera of

Pacific North America were advancing down valley from 1700 to 1400 14C years BP.

Known locally as the 'Bridge Advance', Allen and Smith (2003) were the first to describe this advance in the Pacific Ranges. Now regionally recognized as the First Millennium

Advance (FMA; Reyes et al., 2006), corresponding evidence for a period of glacier expansions has been reported from many Coast Mountain drainages (Reyes and Clague,

2004; Allen and Smith, 2007; Koch et al., 2007a; Jackson et al., 2008) and in Alaska

(Calkin et al., 2001; Wiles et al., 2008; Barclay et al., 2009).

The onset of LIA glacier expansion dates to the 11th Century in southern B.C.

(Koch et al., 2007b), with a period of moraine construction reported to have occurred in the late 12th to mid 13th centuries (Smith and Desloges, 2000; Larocque and Smith, 2003;

Allen and Smith, 2007). This early period of LIA expansion was followed by an interval of ice front retreat of unknown duration, followed by a significant episode of expansion and moraine construction in the early 1700's AD. Many Coast Mountain glaciers maintained extended down valley positions until early in the last century (Larocque and

Smith, 2003; Lewis and Smith, 2004). Detailed histories of LIA glacier activity have been developed at several southern Coast Mountains sites based on dendrochronological and lichenometric dates for end moraine complexes in Strathcona Provincial Park, on

Vancouver Island (Smith and Laroque, 1996; Lewis and Smith, 2004), in the Mt.

Waddington area (Larocque and Smith, 2003), in Garibaldi Provincial Park (Koch et al., 37

2007b), and at Bridge Glacier (Allen and Smith, 2007).

Study Area

The Manatee Valley study area is located within the eastern Pacific Ranges, a belt of heavily glaciated mountains separated from the Cascade Range to the south by the

Fraser River, and the Kitimat Ranges to the north. The valley is drained by Manatee

Creek, a northward flowing tributary of the Lillooet River that flows into Silt Lake, about

70 km to the northwest of the town of Whistler, B.C. (Lat 50º 37' N, Long 123º 41' W)

(Figure 3.1).

Bedrock in the study area is composed primarily of granodiorite with local outcroppings of metasedimentary and volcanic rocks belonging to the Gambier Group

(Monger and Journeay, 1994). Drainage networks carved during the Tertiary were broadened by a succession of Pleistocene glaciers (Tribe, 2002, 2003). During the Late

Wisconsinan an ice sheet covered the area, reaching its maximum extent by

15,000-14,000 14C yrs. B.P. (Clague et al., 1988). By 10,000 14C yrs. B.P., following downwasting and stagnation, glacier cover in the region was likely similar to that of today (Clague and James, 2002). Evidence for Quaternary volcanism is present east of

Manatee Creek, where a volcanic ash blanketed the slopes of Polychrome Ridge along with other upland areas of the Lillooet River Valley (Read, 1990). Deposited following an eruption of Plinth Peak ca. 2350 14C yrs. B.P., the ash potentially provides a useful stratigraphic horizon (Reyes and Clague, 2004).

The hydroclimatic regime of the study site is influenced by orographic lifting of weather systems originating in the Pacific Ocean that regularly deliver moisture laden air 38 masses. During the winter months, snowfall totals at the nearest climate station (Whistler,

B.C.; Lat 50° 7.800' N, Long 122° 57.000' W; 657.80 m asl) average 411 cm per year

(Environment Canada, 2008). Over the past 25 years, winter precipitation totals show slight increases. Summer air temperatures average 13.5 °C at Whistler (Environment

Canada, 2008) and reflect the moderating influence of ocean winds driven by the Pacific

High. Summer air temperatures have been rising over the past 25 years in the region

(Environment Canada, 2008).

The study area lies exclusively within the Engelmann Spruce Subalpine Fir

(ESSF) and Alpine Tundra (AT) biogeoclimatic zones (Klinka et al., 1991), where persistently wet and cool winters limit tree growth. Tree cover is restricted locally to elevations below ca. 1737 m asl Subalpine parklands on the valley walls above the glaciers in the study area are characterized by subalpine fir (Abies lasiocarpa) tree islands as well as scattered mountain hemlock (Tsuga mertensiana) and whitebark pine

(Pinus albicaulis) stems. Valley slopes and valley bottoms have only recently been exposed by glacier downwasting and retreat. The most common colonizers include River

Beauty (Epilobium latifolium), young subalpine fir and whitebark pine seedlings, and at lower elevations alder thickets (Alnus crispa).

Five glaciers occupy headwater areas of Manatee Creek: Beluga (unofficial name), Dolphin, Manatee, Oluk (unofficial name), and Orca (unofficial name) glaciers

(Figure 3.1). These glaciers extend from a maximum altitude of 2475 m asl to ice front positions in 2006 at ca. 1625 m asl. Like glaciers throughout the region (Vanlooy and

Forster, 2008), glaciers in Manatee Valley have retreated over the last century from their down valley LIA positions at rates averaging from 5 to 35 m/yr (Table 3.1). 39 ), Manatee, and and Manatee, ), (unofficial Beluga Beluga , ) (unofficial Map of the Manatee valley study area, located in the southern Coast Mountains of B.C. The forefields and lateral moraines of of moraines lateral and forefields The B.C. of Mountains Coast southern the in located area, study valley Manatee the of Map

four of the glaciers that drain via Manatee Creek were investigated for this study: Orca study: this for 3.1. investigated map. Figure were 92J/12 Creek Manatee series via topographic drain 1970 Canada the that on glaciers superimposed the been of have four locations sampling and Features glaciers. Oluk 40

Strandlines on the valley walls below Manatee Glacier indicate the location of a drained proglacial lake in the lower portion of the valley.

Table 3.1. Rates of icefront retreat of Manatee Valley glaciers over the 20th Century, as calculated from historical photographs.

Glacier Name Recession Rate Recession Rate Average Rate 1948a-1970b AD 1970-2006 AD 1948-2006 AD (m/yr) (m/yr) (m/yr) Orca* 34.6 38.7 36.7 Beluga* 32.5 17.4 25.0 Manatee 19.1 10.5 14.8 Oluk* 20.5 4.7 12.6

* unofficial name a BC aerial photograph series: BC686:7, BC686:8 b 92J/12 Canada topographic series (Dept. of Energy, Mines, and Resources. Ice front position based upon aerial photographs from 1970.

Methods

During reconnaissance surveys in 2006 detrital wood fragments were observed washing from the meltwater outlet of Orca Glacier, glacially-sheared stumps were located within the Beluga/Orca forefield, and dead trees were discovered within the debris composing the outermost Beluga Glacier lateral moraine. In 2007 a deep late-lying snow-pack restricted surveys to the Manatee and Oluk glacier forefields and moraines.

A chronology of ice margin fluctuations within the study site was developed by employing dendroglaciological sampling techniques and radiocarbon analysis to date detrital and in-situ wood samples. Lichenometric analysis of prominent lateral moraine complexes was used to indicate the relative age of surface stabilization and to develop a 41 chronology of LIA glacier activity.

Dendroglaciology

Dendroglaciology integrates information stored in tree rings to establish the timing of glacial events (Luckman, 1998; Smith and Lewis, 2007). Unlike most

Quaternary dating tools, dendrochronology offers the opportunity to annually resolve glacier events (Luckman, 1988, 1998; Shweingruber, 1988). In dendroglaciologic applications tree-rings are: used either to chronicle moraine construction by identifying the oldest tree growing on a deposit and using the total number of annual rings as a minimum estimate of age for the underlying surface (Lawrence, 1946; Heusser, 1956); or, are used to cross-date glacially-buried wood samples to living tree-ring chronologies to identify the year they were killed (Luckman, 1985; Smith and Lewis, 2007). Where cross-dating fails, radiocarbon dating of perimeter wood samples provides a relative kill date (Wood and Smith, 2004; Allen and Smith 2007).

To locate subfossil wood samples in the study area all glacier forefields and the proximal slopes of all lateral moraine faces were systematically surveyed. Specific attention was given to exploring the lee-side of bedrock knolls where low-pressure pockets would have existed under glacial ice. Observations regarding the provenance of the in-situ material was noted before samples were sectioned with a chainsaw and secured with duct tape for transport.

To characterize ice margin fluctuations in the study area all trimline boundaries and lateral moraine deposits were mapped and surveyed. Trimlines were examined to identify individual trees that might have been directly impacted by glacier ice, resulting 42 in either death or the suppression of cambial growth (Schroder, 1980; Wiles et al., 1996).

At selected nested lateral moraine sites survey transects were established and morphological profiles mapped with a tape measure and abney level (Figure 3.1).

Moraine crests were numbered so that the M1 moraine was always in the most distal position.

Where trees were found growing on moraine crests, representative tree-ring samples were collected to provide a date for surface stabilization (Larocque and Smith,

2003). In the case of mature trees, cores extending to the root ball were removed with an increment borer. Where seedlings and saplings were assumed to be the oldest cohort, representative examples of the largest individuals were destructively sampled to accurately determine the number of annual rings. Local ecesis intervals were established from control surfaces identified from historical aerial photographs (Sigafoos and

Hendricks, 1969; McCarthy and Luckman, 1993).

A living tree-ring chronology was collected in Manatee Valley for use as a reference for cross-dating glacially-killed individuals. Mature subalpine fir trees were sampled with an increment borer, with two 0.5 mm diameter cores extracted at right angles to each other at breast-height. To extend the tree-ring record, increment cores were also collected from standing snags located within the surrounding subalpine forest. All increment cores were stored in plastic straws and transported to the University of Victoria

Tree Ring Laboratory for surface preparation and analysis.

Both the increment cores and subfossil 'cookie' samples were polished, measured, and cross-dated according to standard dendrochronological protocols (Stokes and Smiley,

1968; Fritts, 1976; Schweingruber, 1988). A flatbed scanner was used to obtain digital 43 images of the samples and the annual ring-width increments measured to the nearest

0.001 mm with a WinDendroTM tree-ring measuring system (v. 2006b) (Guay et al.,

1992). The tree-ring chronology samples were subsequently cross-dated and statistically verified (50 year segments lagged by 25 years with a critical correlation level [99%] of

0.32) using the International Tree Ring Data Bank software program COFECHA

(Holmes, 1999; Grissino-Mayer, 2001). Standardized ring-width indice files were constructed by fitting the tree-ring series to a negative exponential curve using the software program ARSTAN (Cook and Holmes, 1999).

The fragility of the subfossil wood samples and the prevalence of growth disruptions in the samples required a modified analytical procedure. Using WinDendroTM ring-widths were measured along at least two radial paths selected to avoid sections of abnormal growth. The ring-width series from each path were subsequently internally cross-dated to identify missing rings. Attempts were first made to cross-date individual series to the living tree-ring chronology. Where cross-dating failed, site-specific floating chronologies were constructed and relative dates were assigned with radiocarbon dating

(Wood and Smith, 2004). Perimeter wood samples from representative cookies were submitted to Beta Analytical Inc. (Miami, Florida, USA) for standard radiometric analysis. The assigned radiocarbon ages were calibrated using the INTCAL 04 database to express dates in cal yrs BP (Reimer et al., 2004).

Lichenometry

Lichenometry assigns minimum dates to glacial landforms by assuming a constant relationship between the size of lichen thallus and age of the substrate (Beschel, 44

1973; Innes, 1985). Although the technique benefits from its simplicity and low cost, the uncertainty in growth trends introduced by microclimatic factors can significantly affect age estimates (Jochimsen, 1973; Innes, 1985). Three Rhizocarpon geographicum growth curves have been developed for lichenometric analysis in this region: one for Vancouver

Island (Lewis and Smith, 2004), one for the Bella Coola/Mt. Waddington area (Smith and

Desloges, 2000; Larocque and Smith, 2003), and another for the Cascade Range (Porter,

1981; O'Neal and Schoenenberger, 2003).

Lichenometry has previously been used to provide relative ages for LIA moraine sequences in several glaciated southern Coast Mountain basins (Larocque and Smith,

2003; Lewis and Smith, 2004; Allen and Smith, 2007; Koch et al., 2007b). In this application, lichenometric measurements were completed at moraine crest interception points found along linear transects (Figure 3.1). To avoid the inclusion of anomalous thalli, the search area was restricted to undisturbed plots paralleling the crests for ca. 30 m, on either side of the transect intercept. The maximum (a-axis) and minimum diameter

(b-axis) of near circular thalli were measured with digital calipers to the nearest 0.1 mm.

In order to determine which Rhizocarpon growth curve best suited the study area, lichen measurements were also taken on control surfaces that had exposure dates known to the calendar year from historic aerial photographs and/or dendroglaciologic dates.

Results

Distinct LIA forest trim-lines and nested lateral moraine sequences illustrate the ice level within the valley. A prominent feature is the proximal slope of the east-facing lateral moraine of Manatee Glacier that exposes a vertical section composed of a 150 m 45 thick unit of till. The moraine reaches a maximum elevation of 2100 m asl and is dissected by steep gullies that terminate on the valley floor to form debris cones. Despite careful scrutiny, individual units were not distinguished within the till mass.

An eroded terminal moraine complex at ca. 1300 m asl marks the confluent extension of Orca, Beluga, and Manatee glaciers down Manatee Creek. The terminus of

Oluk Glacier historically spilled into Manatee Creek valley, but has now retreated to a bedrock bench at ca. 1900 m asl. Thickets of alder blanket these terminal moraines and precluded exhaustive surveys of the terminal moraine complex.

Abundant dendroglaciologic and lichenometric evidence was collected at several glacier forefield sites that represent late-Holocene glacier occupations in the study area

(Figure 3.1). Dates for LIA events are reported in calendar years AD, whereas the radiocarbon age of dendroglaciologic material is reported in 14C years BP with an associated error range.

Dendroglaciologic Evidence

Scrutiny of recently deglaciated valley bottoms and surveys of lateral moraine margins yielded both living and/or subfossil tree-ring evidence of ice margin fluctuations.

Aerial photographs and maps of the study site were examined to identify historical ice front positions of Manatee Glacier in 1948 and 1970 (Table 3.1). The age of all the seedlings found at these locations was determined by counting the number of annual branch whorls and/or the number of annual rings (Table 3.2). Based upon this limited survey, a seeding ecesis interval of 19 years was assumed for this area (Table 3.2). 46

Table 3.2. Control sites used to determine tree and lichen ecesis intervals within the Manatee Glacier forefield.

Date Aerial Ice Front Position Surface Age of Tree A-axis Lichen Photo- Age oldest ecesis of largest ecesis graph Abies lichen No. seedling (yrs) (yrs) (yrs) (mm) (yrs) 1738* N/A Lat:50° 36.882' N 268 125 143 55.3 -85 Long:123° 41.595' W Altitude: 1616 m asl 1948 BC686: Lat: 50° 37.098' N 59 39 20 26.3 -5 7 Long: 123° 42.162' W BC686: Altitude: 1515 m asl 8 1970 NTS Lat: 50° 37. 098' N 37 20 17 22.4 -11 92J/12* Long: 123° 42. 394' W * Altitude: 1521 m asl Mean 60 Mean -34

* Dendroglaciologic date obtained at Site 5. ** 92J/12 Canada topographic series (Dept. of Energy, Mines, and Resources). Ice front position based upon aerial photographs from 1970.

A master tree ring chronology was constructed from living and dead subalpine fir trees found on a north-facing slope between Beluga and Manatee glaciers (Figure 3.1).

Twenty living trees were used to build a reference chronology extending from 1573 to

2007 AD. Cores from 6 of 10 standing snags sampled cross-dated with the living tree- ring chronology. One of the cross-dated snag cores contained 557 annual rings and extended the master chronology to 1299 AD. In total, the combined chronology extends over 709 years, displays an interseries correlation of 0.547; and has a mean sensitivity of

0.214 (Table 3.3). 47

Table 3.3. Chronology statistics for the two subalpine fir collections from Manatee Valley. The first collection is the master dating series, while the second is a floating chronology of subfossilized wood recovered at Sites 3 and 4.

Chronology Elevation No. of No. of Interseries Total length Mean Type series trees Correlation Sensitivity m asl (ft) years Master 1628 49 32 0.547 709 0.214 (5340) Floating 1514 15 15 0.389 398 0.250 (4967)

Site 1

In 2006, the western snout of Orca Glacier terminated on a gentle slope of ground moraine at 1676 m asl (5500 ft asl) (Figure 3.2). Detrital subalpine fir wood fragments were collected within a channel located immediately downstream of a subglacial meltwater portal. Included within the detritus was a small portion of stem with 120 annual rings (MC06-27; Table 3.4). A bulk radiocarbon age for the outermost 24 rings yielded an age of 3500±60 14C years BP (Table 3.4). A second bole fragment (diameter

<30 cm) with 146 annual rings was found partially buried in alluvial sediments ca. 590 m down valley from the western snout of Orca Glacier (MC06-03; Table 3.4). The outermost 32 tree-rings date to 4270±60 14C years BP (Table 3.4).

Site 2

A layer of woody debris was located within a till deposit on a bedrock shelf along the southern boundary of Manatee Glacier (Figure 3.3). Positioned 8 vertical metres below the flank of the most proximal lateral moraine at 1606 m asl (5270 ft asl), the remnants of four small krummholz trees and a few branches were found pressed into an underlying paleosol (Figure 3.3). The perimeter rings of a sample (MC06-07) with 146 48

Figure 3.2. Orca Glacier released several pieces of detrital wood into the headwaters of Manatee Creek in (Site 1). The outermost rings of two subfossil trees were radiocarbon dated at 3500±60 14C yr BP (MC06-27) and 4270±60 14C yr BP (MC06-03). The foreground shows the western lateral moraines formed by the confluent ice front of Orca and Beluga glaciers during the late-LIA (Site 5). 49 annual rings were radiocarbon dated to 3430±60 14C years BP (Table 3.4).

Site 3

A large collection of in-situ glacially-sheared subalpine fir stumps and large detrital boles was located on the lee side of a prominent bedrock knoll below the confluent Orca/Beluga lobe (Figure 3.4). Historical aerial photographs indicate the site was exposed by retreating ice in ca. 1948.

Samples from 8 stumps rooted in a well-developed paleosol layer were recovered over a 100 m2 area (Figure 3.4a). All the samples were oriented down valley and most appeared to have been broken ca. 1 m above the ground surface. The samples contained from 94 to 302 annual rings, and were cross-dated to produce a floating chronology

(Table 3.3). Although no bark was present and some perimeter wood had rotted away, cross-dating indicates all the trees were killed within a 50 year period. A sample of perimeter wood from one of the cross-dated stumps (MC06-23) was radiocarbon dated to

2350±70 14C years BP (Table 3.4).

Site 4

Sixteen bole fragments were found partially exposed within a veneer of till along the lower proximal slopes of a north-facing lateral moraine 900 m down valley of

Manatee Glacier (Figure 3.1). Aerial photographs indicated this area became free of ice in ca. 1948, at which time the ice front of Manatee Glacier extended to the bedrock bench at the northeastern end of the adjacent proglacial lake (Figure 3.1).

The boles were found positioned on the surface of a discontinuous paleosol that extended over a 100 m distance along the western shore of the lake. They were oriented parallel to the valley axis (Figure 3.4b). Although bark was not found on the boles, there 50

Figure 3.3. A buried subalpine fir bole fragment located along the proximal slope of the eastern lateral moraine of Manatee Glacier. This tree (MC06-07) was killed in 3430±60 14C yr BP, when the glacier had thickened to late-LIA proportions. 51 was little evidence of surface mastication. This observation suggest the boles were not transported a great distance before being buried by a cover of till. Examination of the samples from site 4 indicates that they represent the remnants of a mature subalpine forest that was growing on the sides of the steeply sloping valley. Counts of the number of annual of growth rings indicate the trees ranged in age up to 200 years.

Thirteen of the tree-ring samples from site 4 cross-date into the floating subalpine fir chronology constructed at site 3. Cross-dating indicates that the trees at site 4 were killed ca. 123 years later than those at site 3. Given this relationship, it is assumed that

Manatee Glacier was advancing down valley into a mature forest cover and reached this point in ca. 2473 ±70 14C years BP (Table 3.4).

Site 5

The remains of 3 large subalpine fir trees were located along the west lateral moraine margin of the confluent Orca/Beluga Glacier at 1644 m asl (Figure 3.5). Two of the trees (MC06-04 and MC06-05) were incorporated within the distal debris of the outermost moraine (Figure 3.5a). A solitary standing snag was located adjacent to the outermost moraine at the site (Figure 3.5b). A sample of perimeter wood from the latter sample had a radiocarbon age of 290±70 14C years BP (Table 3.4).

Ring-width measurements from the three trunks cross-date into the master tree- ring chronology constructed from the dead and living trees found within the adjacent subalpine forest. The two trees incorporated within the lateral moraine were killed in ca.

1733 and 1736 AD (Table 3.4). The standing snag died a short-time later in 1738 AD

(Table 3.4). 52

Figure 3.4a. Subfossil subalpine fir stump (MC06-23) found rooted in a paleosol within the Orca/Beluga glacier forefield (Site 3). A sample of perimeter wood had a radiocarbon age of 2350 ±70 14C years BP. 53

Figure 3.4b. A glacially-sheared subalpine fir tree (MC07-22) found in a near-growth position below Manatee Glacier (Site 4). The sample cross-dated with the radiocarbon controlled floating subalpine fir chronology constructed from samples collected at Site 3. 54

Figure 3.5a. The construction of the late-LIA moraine buried this subalpine fir tree (MC06-04) along the western marginal of Orca/Beluga glacier in 1733 AD (Site 5). 55

Figure 3.5b. Standing snag (MC06-06) located adjacent to the distal slope of the western lateral moraine of Orca/Beluga glacier (Site 5). The tree died in 1738 AD following the deposition of the moraine. 56

Table 3.4. Summary of radiocarbon dated, dendroglaciologic evidence recovered in Manatee Valley.

14C age Lab Beta Age No. of Site Description 2 σ ID ID rings no. Calibration submitted

(yr BP) (cal. (Cal. years yrs) BP) 4270± MC06 227635 146 32 1 Wood projecting from 4960-4800 60 -03 glacial drift 4760-4700 approximately 590 m 4670-4650 down valley from the 2006 frontal position of Orca Glacier. 3500± MC06 230434 120 27 1 Detrital wood sample 3920-3630 60 -27 washed out from glacial stream draining Orca Glacier 3430± MC06 230433 164 27 2 Branches found lying 3840-3560 60 -07 on paleosol just below right lateral moraines of Manatee Glacier 2350±7 MC06 227637 302 37 3 Rooted stump in 2700-2640 0 -23 paleosol exposed in 2610-2590 glaciofluvial outwash 2540-2300 sediments below left 2240-2170 lateral of Orca/Beluga Glacier. 290±70 MC06 227636 239 17 5 Subalpine fir tree buried 500-270 -04 by the west-lateral 210-140 moraine of Orca/Beluga 20-0 glacier.

a Radiocarbon Laboratory: Beta Analytical Inc., Miami, FL. b Radiocarbon dates were converted to cal years BP using IntCal04 (Reimer et al., 2004).

Moraine Dating

Reconnaissance traverses within the study area revealed the presence of R. 57 geographicum thalli and/or tree seedlings on the crests of most lateral moraine surfaces.

In order to date these surfaces, it was first necessary to establish the local age-growth trends and ecesis intervals.

Lichen Growth-Curve and Ecesis

Three dated control points were established to determine which of the existent lichen growth curves best approximated the lichen growth trends at this site. Two of the points consisted of exposed bedrock surfaces and boulders located within the forefields of Manatee and Oluk glaciers. Historical aerial photographs indicate the sites were exposed in ca. 1948 and 1970. Measurements of the a- and b-axis of >20 thalli at each site were used to estimate the age-size of the first lichen colonizer site and to provide ecesis interval estimates that average -8 along valley floors (Table 3.2). A third control point was established on the surface of the outermost lateral moraine at site 5, where collaborating dendrochronologic and radiocarbon evidence indicate moraine emplacement killed trees growing on the distal slope by 1738 AD. Identification of the largest lichen thallus, with a diameter of 55.3 mm, found at site 5 provides a tree-ring dated 268-year control point (Table 3.2).

Comparison of the age-growth characteristics of lichen found at the three dated control sites suggests that R. geographicum thalli in the study area most closely match those documented by Larocque and Smith (2004) for the central Coast Mountains. This finding is similar to that of Allen and Smith (2007) at nearby Bridge Glacier, providing additional support for the regional applicability of this growth curve. Lichen growth on the M1 moraine at site 5 exceeds the growth rate predicted by the central line of the

Larocque and Smith (2004) curve from the Mt. Waddington area, and therefore required 58 59 local calibration for growth in Manatee Valley. This study contributes to the further development for a regional southern Coast Mountain growth curve by providing the oldest, calendar year control point in the region. Minimum dates for moraine construction derived from lichenometry are reported in years AD in the text. Error ranges associated with each date are included in Table 3.5 according to the 95% confidence level. The uncertainty increases on older moraine surfaces.

Tree Ecesis

Subalpine fir seedlings located at the three dated (1948 and 1970) sites in

Manatee and Oluk valley were used to establish the local tree ecesis interval. The oldest seedlings (38 and 20 years) indicate that an average ecesis of 19 years should be assumed

(Table 3.2). A total of 17 trees were surveyed on the 1948 surface, and 9 from the bedrock area exposed in 1970. The youngest individuals had 15 and 8 annual rings for the 1948 and 1970 control surfaces in Manatee Valley, respectively.

An independent estimate of ecesis on the 1733-1738 AD moraine surface at site 5 provides a cautionary note. The oldest trees found growing on this surface were cored to the rootball and returned maximum ages of 125 years. Although this finding could be interpreted to suggest an ecesis in excess of 100 years for these surfaces, based upon the valley-bottom seedling establishment histories from Manatee and Oluk valleys it seems certain that the cohort of trees presently found growing on the moraine did not germinate when the moraine stabilized. Whether it was the lingering presence of the nearby glacier, the persistence of late-lying snowpacks or variable seed crops that precluded seedling establishment until recently is uncertain (Sigafoos and Hendricks, 1969). 60

Relative Moraine Dates

Transect A-a'

Transect A-a' extends across a nested sequence of lateral moraines at ca. 1640 m asl on a northwest trending slope above Manatee Glacier (Figure 3.1). In total, six distinct moraine crests cross the transect (Figure 3.7).

The most distal crest (M1) consisted of a discontinuous line of large boulders located within the adjacent subalpine fir parkland. Distinguishable over a 70 m length, from 10 to 12 small fir and mountain hemlock trees were established on the subdued crest of M1. Coalesced R. geographicum thalli blanket most boulders, making it difficult to distinguish each individual thallus. The largest near circular individual measured 78.6 mm in diameter and indicates a minimum moraine stabilization date of 1417 AD (Table

3.5). Large boulders with diameters ranging from 0.3-0.5 m form the sharp crests of M2 and M3 (Figure 3.7). The largest lichen found on these moraines indicate that they were deposited in ca. 1823 AD and 1832 AD, respectively (Table 3.5). The more proximal crests of M4 and M5 demarcate moraine positions occupied in the late 19th and early 20th centuries, where lichens reached ages of 125 and 97 years old, respectively. The most recently deposited moraine records an interval of ice expansion that ended after ca. 1950

AD (Table 3.5).

Transect B-b'

Four sharp-crested and laterally contiguous moraines were nestled behind a bedrock knoll on the southeast-facing valley wall of Manatee Valley (Figure 3.1). In the vicinity of B-b' the moraine crests are largely devoid of vegetation, with only a sparse cover of small willows (Salix sp.) in sandy areas. The largest thallus found on the most 61

Figure 3.7. Topographic cross-sections of the lateral moraines surveyed on the northern and southern margins of Manatee Glacier and the southern boundary of Oluk Glacier (see Figure 3.1 for transect locations). The moraines are numbered so that M1 is always in the most distal. Labels from different transects are not necessarily time synchronous. 62

Table 3.5. Lichenometric dates derived for lateral moraine stabilization at Manatee Glacier and Oluk Glacier. Transect locations and orientations are displayed in Figure 3.1. Minimum dates for moraine stabilization incorporate systematic errors associated with the Rhizocarpon geographicum growth curve modified for the study area.

Location Elevation Maximum Age Minimum 95 % Thallus Moraine CI Dates (m asl ) (mm) (years) (year A.D.) (year A.D.) Transect A-a' M1 1640 78.6 590 1417 1348-1506 M2 1625 41.8 184 1823 1784-1867 M3 1620 41.0 175 1832 1793-1875 M4 1616 36.0 125 1882 1847-1920 M5 1615 32.5 97 1910 1908-1912 M6 1615 25.2 57 1950 1948-1952 Transect B-b' M1 1805 50.1 276 1731 1685-1786 M2 1807 36.8 132 1875 1839-1913 M3 1808 34.8 115 1892 1859-1929 M4 1803 33.9 107 1900 1898-1902 Transect C-c' M1 1605 56.7 349 1658 1607-1721 M2 1597 52.5 302 1705 1657-1762 M3 1592 51.9 296 1711 1664-1768 M4 1589 40.5 170 1837 1799-1880 M5 1585 36.8 132 1875 1839-1913 Transect D-d' M1 1735 66.8 460 1547 1488-1622 M2 1737 66.3 455 1552 1494-1627 M3 1734 46.8 239 1768 1725-1818 M4 1724 36.0 125 1882 1847-1920 M5 1722 33.0 101 1906 1904-1908 distal moraine crest (M1) was 50.1 mm in diameter and dated glacier expansion that ended prior to the early 18th Century (Table 3.5).

M2 and M3 were traced 400 m down valley, where they were dissected by a meltwater stream draining across the proximal face of the lateral moraines (Figure 3.1). A 63

36.8 mm thallus found on the crest of M2 indicates moraine stabilization occurred in ca.

1875 AD (Table 3.5). M3 and M4 record succeeding intervals of ice expansion that terminated by lichenometric determination in ca. 1892 AD and ca. 1900 AD, respectively

(Table 3.5).

Transect C-c'

Transect C-c' is located in Manatee Valley, ca. 0.5 km down valley from the position of Transect B-b' (Figure 3.1). The five lateral moraine crests intersected by the transect extend down valley over a bedrock ridge before being lost to sight within an alder-filled depression.

The outermost moraine crest (M1) is colonized by a mature forest composed of century-old subalpine fir trees, moss, lichen, and shrubbery in the forest under-story. A lichen thallus measuring 56.7 mm located on a boulder positioned on the crest of M1 indicates the moraine stabilized following downwasting of Manatee Glacier in ca. 1658

AD (Table 3.5).

Young trees (< 68 years in age), willows, grasses, and mosses cover the surface of both M2 and M3. The two moraine crests merge together at several points and appear to have been deposited within a short time of each other (ca. 1705 AD and ca. 1711 AD, respectively; Table 3.5). Lichens on boulders on the crest M4 and M5 indicate their deposition occurred between ca. 1837 AD to ca. 1875 AD.

Transect D-d

Transect D-d' crosses a prominent lateral moraine complex along the southern perimeter of the Oluk Glacier forefield (Figure 3.1). Distal sediments and boulders cascade down a steep slope into the mature subalpine forest located above Manatee 64

Glacier.

Five distinct moraine crests were distinguished on the surface of the moraine complex. R. geographicum thalli on the two most distal moraines indicate they were constructed in a short span of time between ca. 1547 AD to ca. 1552 AD (Table 3.5). M3 was deposited sometime before ca. 1768 AD when the crest stabilized. M4 and M5 record periods of glacier expansion that ended by ca. 1882 AD and ca.1906 AD, respectively (Table 3.5).

Synthesis and Interpretation

Dendroglaciologic and lichenometric evidence from the study area indicates that at least four distinct intervals of glacial expansion occurred during the late-Holocene, in about 4200 14C yr BP, 3500 14C yr BP, and 2300 14C yr BP, and during LIA standstills.

● 4200 14 C yr BP year event : In a recent publication Menounos et al. (in press)

present evidence in support of two intervals of glacier expansion in the southern

Coast Mountains centered at 4.2 ka cal. years BP. The detrital wood dating to

4200 14C yr BP discovered washed out from beneath Orca Glacier at Site 1 offers

some support for a glacier advance at this time. Given the close correspondence

between the kill dates of this trees and trees killed at Sphinx Glacier in Garibaldi

Provincial Park at 4080±40 14C yrs BP (Koch et al., 2007a), it may be that Orca

Glacier and other glaciers in the study site advanced to positions some 500 m

down valley from their present-day snouts although no evidence for this

hypothesis was recovered during these investigations. 65

● “Early Tiedemann” Advance (3500 14 C yrs BP) : Detrital and in-situ wood exposed

by the retreat of Orca and Manatee glaciers suggests a distinct interval of ice

expansion was underway in the study site by this time. Although the detrital wood

sample dating to 3500 14C yrs BP found washing from beneath Orca Glacier offers

some support for this interpretation, the treeline forest buried in 3430±60 14C yrs

BP along the eastern margins of Manatee Glacier indicate that glaciers in the area

had thickened to near LIA depths by the mid-Holocene. This discovery in

Manatee Valley supports the interpretation of a glacier advance, following a

regional climate shift that brought a period of increased precipitation and

decreasing air temperatures from 4400 14C yrs BP and 3700 14C yrs BP (Hebda,

1995; Heinrichs et al., 2004).

 Late Tiedemann (2350-1900 14 C yrs BP) : A growing body of evidence from

coastal North American mountains provides evidence for a distinct glacier event

between 2300 and 1900 14C yr BP. Dendroglaciological evidence collected during

these investigations within the forefields of both Manatee Glacier and the

confluent Orca/Beluga glacier documents a sustained interval of glacier advance

was underway in 2340±70 14C yrs BP into mature valley-bottom forests. The

valley-bottom position of these forests in Manatee Valley would have required

both substantial ice retreat and downwasting following the “Early Tiedemann

Advance” at 3430±60 14C yrs BP. Given that the trees are 200 years in age and

were found on the surface of a well-developed paleosols, a lengthy interval of 66

exposure must have occurred between 3430±60 to 2370±70 14C yrs BP in

Manatee Valley.

Evidence for the regional character of the “Manatee Advance” is recorded

nearby at Lillooet and Bridge glaciers. At Lillooet Glacier Reyes and Clague

(2004) described till in a stacked lateral moraine sequence with a limiting date

that is equal to, or younger than 2500 14C yrs BP. At Bridge Glacier Allen and

Smith (2007) recovered roots and detrital logs that record a glacier advance in

1930±70 14C yrs BP. In Garibaldi Provincial Park Koch et al. (2007a) report on

evidence for a period of glacial expansion between ca. 2300 to 2000 14C yrs BP.

Jackson et al. (2008) found the remains of a forest buried by an advancing glacier

in 2300±60 14C yrs BP.

 Little Ice Age : Lichenometric investigations of lateral moraines in the study area

illustrate distinct intervals of LIA glacier expansion. A single moraine fragment at

Transect A-a' was assigned a early-15th Century stabilization date. The subdued

topographic character, extensive lichen cover, and location of this bouldery ridge

within the established forest suggests, however, that it could be significantly older

and have been deposited by a pre-LIA event. Moraines of similar age have been

identified at nearby Bridge Glacier (Allen and Smith, 2007), at Colonel Foster

Glacier (Lewis and Smith, 2004), and in Garibaldi Provincial Park (Koch et al.,

2007b). Interestingly, the ring-widths of trees in Manatee Valley master

chronology display minimum values around 1400 AD consistent with cold

summer air temperatures expected in an early-LIA glacier advance (Figure 3.8). 67

Lichens measured on the lateral moraines at Oluk Glacier suggest a period of moraine construction in the mid 1500's AD. Annual ring-width measurements from local subalpine fir trees show and increasing growth trend during the early decades of the 16th Century, following relatively decreased values ca. 1500 AD

(Figure 3.8). Terminal moraines of corresponding age were recorded at Bridge

Glacier (Allen and Smith, 2007).

The discovery of buried and glacially-killed trees with perimeter dates between 1733 and 1738 AD confirms that glaciers in the study site attained their maximum depths and extents in the 18th Century. This discovery agrees with similar findings at many sites in the southern Coast Mountains (Smith and

Desloges, 2000; Larocque and Smith, 2003; Lewis and Smith, 2004; Allen and

Smith, 2007; Koch et al., 2007b). Radial expansion of subalpine trees above the eastern limit of Manatee Glacier progressively decreased to near minimum values ca. 1700 AD following a peak in 1550 AD (Figure 3.8). Dendroglaciological mass balance reconstructions from the Mt. Waddington Range indicate a slightly later peak in the 1750's AD (Larocque and Smith, 2005). The steep decline in ring- width values shown in the Manatee chronology appear to closely agree with evidence that shows the coldest intervals of the last 500 years in North America were in between ~1570 and ~1730 AD (Bradley and Jones, 1993).

Less extensive ice front oscillations during the 19th Century are recorded by at least 3 additional moraines at Manatee Glacier. Synchronous events have been noted at a number of locations throughout southwestern B.C. (Lewis and Smith,

2004; Allen and Smith, 2007; Menounos et al., in press), and presumably 68

Figure 3.8. This figure compares the growth trends of the living Abies lasiocarpa chronology collected in Manatee Valley to lateral moraine dates that were determined with lichenometry along the margins of Manatee and Oluk glacier (see Figure 3.1 for exact location). The thick black line represents a 10-year moving average. Plotted on the right-hand axis is the number of series in the master chronology. Each grey rectangle spans 25-year intervals that are centered on a lichenometric dates for each moraine. correspond to a shot-lived readvance of glacier snouts.

Conclusion

Dendroglaciologic and lichenometric surveys of glacier forefields within the study area indicate that the four glaciers draining Manatee Valley responded similarly to changing environmental conditions from the mid-Holocene to present, particularly during late-Holocene events. Ice front positions were documented for advances in ca. 4200 14C yrs BP; ca. 3500 14C yrs BP; and 2350-1900 14C yrs BP, while the most extensive ice 69 front positions were reached in the last millennium. The retreat of ice from the maximum positions occupied during the late 17th to early 18th century reveals that present-day glacial limits are unprecedented in the last 4000 cal. years. 70

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Chapter Four: Discussion

Introduction

This thesis chronicles ice extent on a millennial scale for mid-late Holocene events, and on a centennial scale for Little Ice Age events. Although fragmentary, dendroglaciologic evidence from Manatee Valley demonstrates adjustments in ice geometry that are synchronous with regional accounts. The objective of this chapter is to examine tree-ring evidence from Manatee Valley, in light of the glacial histories and paleoenvironmental records that have been derived from other locations of western

Canada and Washington State (WA). Continuous records based on pollen and spore assemblages generally correspond with the conclusions from this study and show a cooling trend over western British Columbia (B.C.) beginning a couple of centuries before 4200 14C yrs BP, when ice fronts in Manatee Valley reached 2006 occupations

(Hebda, 1995). Continued cooling was accompanied by increased precipitation entering the latter half of the Holocene driving glaciers in this study area to reach near maximum limits by ca. 3500 14C yrs BP (Hebda, 1995). Climatic anomalies matching the Garibaldi, and First Millennium Advances, however have not been represented in paleobotanical data, and interestingly are also not represented in the Manatee Valley glacial chronology either. A recent review of Holocene glacial records from western Canada, argues for at least 6 glacial intervals since the disintegration of the Cordilleran ice-sheet (Menounos et al., in press). The findings of this research compliment the conclusions of previous studies, and also substantiate the claim for complex glacier behaviour throughout the late-Holocene. 79

4200 14C yrs BP Event

Dendroglaciologic evidence from Manatee Valley supports the regional interpretation for a moderate expansion of ice ca. 3800 14C yrs BP (Menounos et al.,

2008, in press). Although the majority of reported evidence for an advance ca. 4200 14C yrs BP arises from the B.C. Coast Mountains, glacially-killed wood samples with similar radiocarbon ages have also been reported from glacier forefields in the Interior Ranges of

B.C. (Castle Glacier, 4210±80 14C yrs BP; Menounos et al., 2008), Canadian Rocky

Mountains (Boundary Glacier, 4050±70 14C yrs BP; Gardner and Jones, 1985; Wood and

Smith 2004), and Cascade Ranges of WA (South Cascade Glacier, ca. 4367 14C yrs BP and ca. 4142 14C yrs BP; Miller, 1969).

The occurrence of detrital wood at Orca Glacier corresponds to the glacially reworked trees located in the Sphinx Glacier forefield (Garibaldi Provincial Park; Figure

4.1) dating to 4280±80 14C yrs BP (Koch et al., 2007a). Subfossil wood of similar age has emerged from below the snouts of other retreating glaciers in the southern Coast

Mountains over the past decade (Table 4.1). A stump exposed in 2003 by the downwasting of Helm Glacier dates to 4080±40 14C yrs BP (Koch et al., 2007a), and overlaps in age with wood released from Goddard Glacier (4120±60 14C yrs BP;

Menounos et al., 2008). Although a growing body of radiocarbon dated detrital samples provide circumstantial evidence for ice augmentation around 4200 14C yrs BP, dendrochronologic investigations have so far failed to identify the maximum down valley extent of this event.

Corresponding paleoenvironmental reconstructions for alpine areas of southern 80

Figure 4.1. Relief map of British Columbia including the location of previous studies that investigate environmental changes in the alpine during the Holocene: Eastern Pacific Ranges(Lillooet, Bridge, Manatee glaciers); Central Coast Mountains (Tiedemann glacier, Mt. Waddington area); Garibaldi Provincial Park (Garibaldi, Fitzsimmons, and Spearhead ranges); Insular Ranges (Strathcona Provincial Park); Heal Lake; Boundary Ranges (Todd Valley, Tide Lake, Jacobsen glacier). 81

Table 4.1. Summary table of Holocene glacier advances in the B.C. Coast Mountains. Location Reference Early Garibaldi '4.2 'Early' 'Late' FMA Little Ice Holocene Event' Tiedemann Tiedemann Age events (9600-660 (6000-500 (4200-35 (3500-3000 (2300-1900 (1700- (1100-190 014C yrs 0 14C yrs 00 14C 14C yrs BP) 14C yrs BP) 1400 0 AD) BP) BP) yrs BP) 14C yrs BP) Manatee This study Valley x x x x Allen and Bridge Smith, Glacier x x x x 2007 Garibaldi Koch et Ranges al., 2007a x x x x x x Spear head and Osborn et Fitzsimm al., 2007 x x x ons ranges Reyes and Lillooet Clague, Glacier x x x x 2004 Green and Menounos Joffre et al., 2004 x lakes Goddard Menounos glacier et al., 2008 x x Tiede- Ryder and mann Thomson,1 x x Glacier 986 Desloges Jacobsen and Ryder, Glacier x x 1990 Tiedema Menounos nn et al., in x x x x x glacier press Todd Jackson et Valley al., 2008 x x x x Tide Clague and Lake Mathews, x x 1992 82

B.C. show a transition to cooler conditions ca. 5000 14C yrs BP (Palmer et al., 2002), accompanied by a decrease in treeline, and reached present altitudes by ca. 2474 14C yrs

BP (Evans, 1997). Although the source of the detrital wood washing out of Orca Glacier remains unknown, the position of this glacier at the hydrological divide argues for an elevated treeline relative to today for at least 150 cal. years (the age of MC06-03) before forests were overridden by ice.

Evidence for a major shift in climatic regime at this time is widespread across western North America. Synchronous glacier advances have been hypothesized in the

American Cordillera as well, although there is somewhat less dating control in this region

(Davis, 1988). In Colorado's Front Range the 'Triple Lakes' moraines were assigned dates ranging in between 4500 and 2900 14C yrs BP, interpreted to represent 4 distinct glacial advances (Benedict, 1985). The relative abundance and size of archaeological sites dating to the mid-late Holocene suggests that a dramatic cultural transition occurred ca. 4300

14C yrs BP, probably in response to changing climatic conditions (Moss et al., 2007). In coastal B.C. technological advances in woodworking were encouraged by the increasing abundance of large western red cedars (Thuja plicata) in the region around this time

(Hebda and Mathewes, 1984).

Tiedemann Advance

The most widely represented pre-LIA glacial event in the B.C. Coast Mountains is the Tiedemann Advance from 3300-1900 14C yrs BP. First described by Ryder and

Thomson (1986) from buried trees in moraines at Tiedemann Glacier, corresponding events have been recorded at sites in the southern (Desloges and Ryder, 1990; Reyes and 83

Clague, 2004; Allen and Smith, 2007; Koch et al., 2007a; Osborn et al., 2007), and northern B.C. Coast Mountains (Clague and Mathews, 1992; Haspel et al, 2005; Lewis and Smith, 2005; Jackson et al., 2008). Coeval records of a Tiedemann-aged glacier advances have been reported from the Canadian Rocky Mountains (Luckman et al., 1993;

Osborn et al., 2001; Wood and Smith, 2004; Menounos et al., in press) and WA (Crandell and Miller, 1964).

Paleoenvironmental proxies suggest that shifting climatic regimes may have led to a two phase Tiedemann advance. Identified here as the “Early Tiedemann” and “Late

Tiedemann” advances, this interval of glacier expansion was likely precipitated by shift to wetter and cooler conditions around 3500 14C yrs BP that led to establishment (Pellatt et al., 2000) and closure of Engelmann spruce-subalpine forest (Heinrichs et al., 2004) in the southern Coast Mountains. Accompanying these changes in forest character a decreasing trend in fire frequency also occurred in the region (Hallett et al., 2003). At

Moraine Bog, just outside late-Holocene limits at Tiedemann Glacier, recognition of distinct pollen zones before 2600 14C yrs BP, from 2500 to 2300 14C yrs BP, and after

1900 14C yrs BP (Arsenault et al., 2003) suggest the intervention of shifting climate regimes that led to a period of glacial expansion, retreat, and readvance between 3300 to

1900 14C yrs BP.

a) 3500 14C yrs BP event (“Early Tiedemann”)

There is a growing body of evidence from this region to suggest that glaciers were advancing down valley at 3500 14C yrs BP to reach “Early Tiedemann” positions close to those reached during the LIA. Menounos et al. (2008) have compiled dendroglaciologic dates from glaciers in southern B.C. and Alberta that suggest a slightly earlier onset for 84 ice build-up regionally, however the event may be a series of closely spaced advances, analogous to the LIA.

Abrupt changes in paleobotanical records just before the Tiedemann Advance indicate the 3850 14C yrs BP date as a notable event in climate history as conditions in western B.C. transitioned from the “mesothermic” to the cooler late-Holocene climate

(Hebda, 1995). An exceptional tree-ring record from Heal Lake, on southern Vancouver

Island, demonstrates abrupt reductions in ring-widths at this time, suggestive of a climatic anomaly (Zhang and Hebda, 2005) that is consistent with the onset of mid-

Holocene glacial advances.

b) 2350-1900 14C yrs BP event (“Late Tiedemann”)

The discovery of in-situ glacially-sheared stumps in the forefields of both

Manatee Glacier and the confluent Beluga/Orca glaciers dating to ca. 2350 14C yrs BP confirms the synchronous response of ice lobes in the study area. Mature forests evidently covered the glacier forefields of Manatee valley prior to their burial by this advance. The ages of trees below Orca/Beluga glaciers exceeded 300 cal. years, in some cases, and lived at the same time as trees that were killed 100 cal. years later. The longevity of this chronology, and in-situ setting of this wood, implies that ice fronts retracted to at least the 1948 positions before readvancing by ca. 2350 14C yrs BP.

Corresponding in age to the most extensive moraines at Tiedemann Glacier dated to 2300 14 yr BP by Ryder and Thomson (1986), there is now sufficient regional evidence to support recognition of a distinct episode of glacier expansion at this time (Reyes and

Clague, 2004; Laxton, 2005; Jackson et al., 2008). Fragmentary dendroglaciologic and radiocarbon evidence for advancing glaciers at this time is also available from several 85 glacier forefields in the Canadian Rocky Mountains (Luckman et al, 1993; Osborn et al.,

2001; Luckman, 2006).

First Millennium Advances AD

Over the past decade, dendroglaciologic evidence from the Coast Mountains has pointed to a regional advance of valley-glaciers during the first millennium (Reyes et al.,

2006). Since the initial discovery of glacially killed trees below Bridge Glacier by Allen and Smith (2003), radiocarbon dates have been replicated in a number of other valleys in

B.C., the Yukon Territory, and Alaska (Reyes et al., 2006). Synchronous events, dating to

1800 14C yrs BP, have also been yielded from three glaciated valleys of Mt. Baker (Fuller et al., 1983; Davis, 1988).

Little Ice Age

Lichenometric surveys of the lateral moraine complexes of Manatee and Oluk glaciers chronicle at least 6 episodes of moraine emplacement, during the early-15th, mid-16th, early-18th , mid-late-19th, and early 20th centuries. Due to variable forest cover on moraines on the somewhat drier slopes of the Lillooet Valley, lichenometry has proved to be an indispensable dating tool for detailing ice expansions over the last millennium.

Since early LIA deposits have usually been disturbed by advances in the last few centuries, the onset of glacial activity is represented by glacially sheared trees dating to the 11-12th centuries (Ryder and Thomson, 1986; Desloges and Ryder, 1990; Larocque and Smith, 2003; Davis et al., 2007; Koch et al., 2007b). Moraines had formed by the early 1300's AD in the Cascade Range (Crandell and Miller, 1964; Miller, 1969; 86

Burbank, 1981), and by the late-14th Century in the B.C. Coast Mountains (Larocque and

Smith, 2003; Lewis and Smith, 2004a; Allen and Smith, 2007; Koch et al., 2007b).

Lichen growth on the two most distal lateral crests above Oluk Glacier, indicate moraine stabilization during the 16th Century. This interpretation parallels moraine dates from several other sites in coastal B.C. (Larocque and Smith, 2003; Allen and Smith,

2007), the Canadian Rocky Mountains (Luckman and Osborn, 1979; Smith et al., 1995), the Cascades (Miller, 1969; Sigafoos and Hendricks, 1972; Fuller, 1980; Burbank, 1981;

Davis et al., 2007), and Alaska (Denton and Karlén, 1977; Evison et al., 1996).

Numerous moraine stabilization dates in southwestern B.C. indicate that regionally, most glaciers built substantive moraines in the early 1700's AD. This conclusion is supported by investigations in the Coast Mountains (Smith and Desloges,

2000; Larocque and Smith, 2003; Reyes and Clague, 2004; Allen and Smith, 2007; Koch et al., 2007b), Canadian Rocky Mountains (Heusser, 1956; Luckman, 1995; Smith et al.,

1995; Luckman, 1998, Luckman, 2000; Osborn et al., 2001), and in Alaska (Wiles et al.,

1999; Wiles et al., 2002). Regionally the 1750's AD were years with positive mass balance conditions (Larocque and Smith, 2005).

A detailed record of 19th Century advances is available within many glaciated valleys in PNA (Heusser, 1957; Luckman, 1995; Luckman, 2000; Smith and Desloges,

2000; Calkin et al., 2001; Osborn et al., 2001; Wiles et al., 2002; Larocque and Smith,

2003; Lewis and Smith, 2004a; Allen and Smith, 2007; Koch et al., 2007b). Proximal moraine crests deposited along the lateral boundaries of both Manatee and Oluk glaciers during the late-19th to early-20th centuries confirm a similar glaciologic response in the study area. 87

The exceptional preservation of till sequences in the Coast Mountains illustrates a complex history of ice-level fluctuations during the late-Holocene, and perhaps, serves as an analog to better understand the glacier behaviour throughout past millennia. Relating

LIA glacial histories to climatic reconstructions, however, remains complicated

(Mathews and Briffa, 2005). Comparisons are obscured by the inherent uncertainties of lichenometric and dendrochronologic techniques, and because of the various responses of individual glaciers to fluctuating climatic inputs (Hodge et al., 1998). Nonetheless, recent research from the southern Canadian Cordillera has demonstrated a potential for reconstruction of glacier mass balance conditions using tree-rings (Lewis and Smith,

2004b; Watson and Luckman, 2004; Larocque and Smith, 2005). Unfortunately, the

Abies lasiocarpa samples collected for this research could not be significantly correlated with regional mass balance records. Larocque and Smith (2005) and Allen (2006) also found that the ring-widths from A. lasiocarpa trees were a relatively poor predictor of glacial mass balance, compared to other species.

Conclusion

Dendroglaciology offers direct evidence for environmental change in the alpine and serves as a calibration point for more continuous records, such as lacustrine sediment cores and dendroclimatic reconstructions. Long-term trends are difficult to detect in dendroclimatic reconstructions since they complicate the signal of the interannual variation, so moraine dates are important for verifying hindcasted climatic conditions.

Detailed analysis of the interactions between glaciers and climate indicates there is a significant relationship to winter precipitation totals and summer air temperatures. 88

Presumably these factors were also dominant during mid-Holocene as well. Mass balance regimes have also demonstrated significant relationships with atmospheric circulation patterns such as the El Nino Southern Oscillation and the Pacific Decadal Oscillation

(Kovanen, 2003; Larocque and Smith, 2005).

The distribution of dendroglaciologic material in the valleys of southwestern BC

(Ryder and Thomson, 1986; Larocque and Smith, 2003; Lewis and Smith, 2004; Reyes and Clague, 2004; Reyes et al., 2006; Allen and Smith, 2007; Koch et al., 2007a, 2007b;

Osborn et al, 2007; Menounos et al., 2008; Menounos et al., in press), interpreted in concert with these results, implies that ice fronts were reaching advanced positions around 4200, 3500, 3000, 2300, 1700, and 1000, and 300 14C yr BP. This discussion points to a reoccurance interval of 700 years on average throughout the latter part of the

Holocene. Several authors have proposed patterns in Holocene climate before, however with the accumulation of decades of research on western North American glaciers, these estimates stand to be revised. Denton and Karlen (1973) proposed a 2500 year cycle based on glacial evidence, but as glaciers release additional evidence, the complex history of glacier movements is being revealed. 89

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Laxton, S. 2005. Dendroglaciological reconstruction of late Holocene glacier activity at Todd Glacier, Boundary Range, northwestern British Columbia Coast Mountains. M.Sc. thesis, University of Victoria, Victoria, British Columbia.

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Chapter Five: Summary

The dendroglaciologic and lichenometric research methodologies employed in this study provide a long-term perspective of environmental conditions from ca. 4200 14C yr BP to present in the southern Coast Mountains of British Columbia. Insight into mid-

Holocene glacial activity is limited by the coarser resolution of the earlier dendroglaciologic records, but subfossil wood from the study area nonetheless suggests that ice advanced to present-day elevations by 4270±60 14C yr BP, and again at 3500±60

14C yr BP. More definitive dates are offered from in-situ forests found in the study area that indicate: a) culmination of an “early Tiedemann” event at Manatee Glacier ca. 3430

14C yr BP; b) a distinct “late Tiedemann” event beginning by ca. 2350 14C yr BP for at least two glaciers in the study area; and, c) a maximum ice standstill during the early-18th

Century. A relatively continuous record of ice-level fluctuations extends from the 1700's

AD to present for Manatee and Oluk valleys.

The rapid adjustment of relatively small valley glaciers to variations in climatically driven mass balance conditions (Bahr et al., 1998) make glaciated valleys in the southern Coast Ranges particularly attractive for dendroglaciologic studies. In fact, the ice-cover of valley glaciers in southern B.C. has decreased the most among western

Canadian glaciers (Bolch et al., 2008), which has probably resulted in the greatest exposure of long dendroglaciologic records from the early- Holocene (Garibaldi Range:

Koch et al., 2007b; Mt. Baker, Davis, 2007).

Since the longest instrumental records of glacier mass balance exist for only a 96 limited number of representative glaciers in the southern Coast Ranges of PNA (ie. Place,

Sentinel, Helm, South Cascade, and Hoh glacier), there is considerable value in sampling dendrochronologic material from glaciated valleys with similar ice distributions. In this study the qualitative comparison of subalpine fir tree ring-widths with lichenometric moraine stabilization dates (Figure 3.8) shows a general coherence, however, correlation analysis does not show a significant relationship with any glaciers monitored for mass balance changes on an interannual scale.

Limitations and Suggestions for Future Work

Investigations in Manatee Valley provided additional detail about Holocene glacial activity and helped to improve lichenometric dating techniques in the region, but several questions are further worth exploring.

In Manatee Valley dendroglaciologic and lichenometric approaches to lateral moraine dating were applied in concert. The disparity between moraine dates based on the total number of annual rings from first-colonizing trees, and the diameter of R. geographicum thallus, prescribes caution when interpreting surface stabilization dates from different methods. With the exception of one definitive date from dendroglaciology, lichenometry overall proved to be a more applicable to morainic surfaces in the study area and offered further support for the regional applicability of the R. geographicum curve developed for central B.C. Coast Mountains by Larocque and Smith (2004).

Further improvement could be made to lichenometric investigations in the region by obtaining additional control points from historic surfaces, paricularly those exceeding

100 years in age. 97

The considerable variability noted in the colonization rate of subalpine fir trees within the study area prohibits the equation of conditions on valley floors with lateral moraine crests. Allen and Smith (2007) also experienced limited success with this dendrochronologic approach to geobotanical dating in Bridge Valley. In practice, the application of geobotanical techniques is extremely site-dependent. Although proxy records of Holocene glacial activity are often interpreted to be in support of regionally synchronous adjustments to climatically induced changes, the comparison of glacial histories from independent study sites remains troubled by the heterogeneous character of mountainous environments. In addition to the methodological concerns mentioned above, the local topography of glaciated basins also determines the distribution of datable evidence (ie. dendrochronologic, licenometric, morainic, or tephrochronologic) as well as the degree to it is preserved, and subsequently exposed by the paraglacial erosion. One way in which the application of dendroglacilogy could be further improved is by investigating the development of cells in the cambium in response to root disruption, for example, from approaching ice fronts. If a cellular signature could be recognized, it would be possible to further detail the relative position of the ice front prior to forest destruction.

Continued sampling of dendroglaciologic material that is being release by ice fronts in southern B.C. would also improve the understanding of Holocene glacier activity by i) extending the dendroglaciologic record back in time to include the early-

Holocene; ii) bridging gaps in the tree-ring record by correlating floating chronologies from different sites, which would potentially allow glacier mass balance and/or climate reconstructions during interglacial intervals; and iii) improving the spatial coverage of 98 dendroglaciologic histories to incorporate data from different glacier sizes, geometries, and topographies. Since it is likely that there are several factors influencing the regional glacial regime that are acting on various time scales, continued sampling should be beneficial in the identification of the potential drivers of climate change.

Lastly, as more information about Holocene glacial environments becomes available, it is important to revise the nomenclature appropriately and develop a language that reflects a deeper understanding. One complication is that language is often been used interchangeably to describe both glacial events and climatic intervals, such as the LIA

(Mathews and Briffa, 2005) and the Neoglacial. In addition to this ambiguity, it is also difficult to know what part of the glacier advance is being compared, for example the onset, culmination, or end date for a glacier advance.

99

Works Cited

Allen, S.M., and Smith, D.J. 2007. Late Holocene glacial activity of Bridge Glacier, British Columbia Coast Mountains. Canadian Journal of Earth Sciences, 44: 1753-1773.

Bahr, D.B., Pfeffer, T.W., Sassolas, C., and Meier, M.F. 1998. Response time of glaciers as a function of size and mass balance: 1. Theory. Journal of Geophysical Research, 103: 9777-9782 .

Bolch, T., Menounos, B., and Wheate, R. 2008. Remotely-sensed Western Canadian Glacier Inventory 1985-2005 and regional glacier recession rates. Geophysical Research Abstracts, 10: EGU2008-A-10403.

Koch, J., Clague, J.J., and Osborn, G.D. 2007a. Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia. Canadian Journal of Earth Sciences, 44: 1215–1233.

Koch, J., Osborn, G.D., and Clague, J.J. 2007b. Pre-'Little Ice Age' glacier fluctuations in Garibaldi Provincial Park, Coast Mountains, British Columbia, Canada. Holocene, 17: 1069-1078.

Larocque, S.J., and Smith, D.J. 2003. Little Ice Age glacial activity in the Mt. Waddington area, British Columbia Coast Mountains, Canada. Canadian Journal of Earth Sciences, 40: 1413–1436.

Larocque, S.J. and Smith, D.J. 2004. Calibrated Rhizocarpon spp. growth curve for the Mount Waddington area, British Columbia Coast Mountains Canada. Arctic, Antarctic, and Alpine Research, 36: 407-418.

Larocque, S.J., Smith, D.J. 2005. Little Ice Age proxy glacier mass balance records reconstructed from tree rings in the Mt Waddington area, British Columbia Coast Mountains, Canada. The Holocene, 15: 748–757.

Lewis, D., Smith, D.J., 2004. Dendrochronological mass balance reconstruction, Strathcona Provincial Park, Vancouver Island, British Columbia, Canada. Arctic. Antarctic and Alpine Research, 36: 598–606.

Watson, E., Luckman, B.H. 2004. Tree-ring estimates of mass balance at Peyto Glacier for the last three centuries. Quaternary Research 62: 9–18.

Wood, L. and Smith, D.J. 2008. Using Fibre Properties in Dendroclimatology. Ameridendro Conference, Vancouver, B.C. 100

Appendix A: Manatee Valley Master Tree-Ring Chronology

One master chronology was constructed from subalpine fir trees (Abies lasiocarpa) for the purpose of dating Little Ice Age events in Manatee Valley. This chronology is unique in that we were able to greatly extend the dating potential by incorporating both living and dead trees. The collection site is located in the subalpine parkland in between Beluga and Manatee glaciers at elevations around 1628 m asl (50°

36. 822' N; 123° 41. 628' W).

The subalpine fir trees sampled in the study area reached exceptionally old ages.

The mean segment length of this master tree-ring chronology equaled 252 years, but one core from a snag cross-dated into the chronology with a total of 557 annual rings

(MC07-37a). The previously reported age for the oldest Abies lasiocarpa tree was 507 years from a tree living in the Yukon Territory (Luckman, 2003). The oldest subalpine fir discovered in Manatee Valley also nearly double the figure typically quoted for old- growth subalpine fir, which can increase with elevation up to ca. 250 years (Alexander et al., 1990). Although trees may actually attain ages much greater than this figure, the wood is characteristically susceptible to heart-rot (Alexander et al., 1990). The ground at the selected sampling location was exceptionally well-drained, and boulder-covered, which may have discouraged wood deterioration. Bark, however, was not generally preserved on the cored snags, so the total ages of these individuals may in fact be much older than reported here.

The expansive temporal range covered by the ring-width data of the Manatee

Valley chronology was successful in estimating a calendar year date for the deposition of 101 till along the lateral margins on the confluent Orca/Beluga glacier. The dendroglaciologic samples that were incorporated into the master chronology further expanded the dating potential of this record. Attempts were made to cross-date subalpine fir floating chronologies that were previously collected on the valley walls of the Bridge River valley by Allen and Smith (2007). Despite repeated efforts, the two floating chronologies with radiometrically assigned perimeter wood dates of 680±50 14C yr BP (Bridge 5) and

540±50 14C yr BP (Bridge 6: Allen and Smith, 2007) could not be correlated with the

Manatee Valley chronology. 102

Figure A.1. Subalpine fir master tree-ring chronology (raw and standardized versions). 103

Figure A.1. (continued) Subalpine fir master tree-ring chronology (residual and ARSTAN version. 104

Works Cited

Alexander, R.R., R.C. Shearer, and W.D. Shepperd. 1990. Abies lasiocarpa. in R.M. Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol. 1. Agri. Handbook 654, USDA For. Service, Washington, D.C. pp. 60-70.

Allen, S.M., and Smith, D.J. 2007. Late Holocene glacial activity of Bridge Glacier, British Columbia Coast Mountains. Canadian Journal of Earth Sciences, 44: 1753-1773.

Luckman, 2003. Old Canadian Trees. http://www.mta.ca/candendro/old.htm. Accessed on February 21, 2009. 105

Appendix B: Subalpine Fir Subfossil Tree-Ring Chronology

Figure B.1. Subalpine fir floating chronology (raw and standardized versions). 106

Figure B.1. Subalpine fir floating chronology (residual and ARSTAN versions).