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CALKIN, Parker Emerson, 1933- GEOMORPHOLOGY AND GLACIAL GEOLOGY OF THE VICTORIA VALLEY SYSTEM, SOUTHERN VICTORIA LAND, ANTARCTICA.
The Ohio State University, Ph.D., 1963 G eolo gy
University Microfilms, Inc., Ann Arbor, Michigan GE MORPHOLOGY AND GLACIAL GEOLOGY
OF THE
VICTORIA VALLEY SYSTEM,
SOUTHERN VICTORIA LAND, ANTARCTICA
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
By
Parker Emerson Calkin, B. S., M. Sc
The Ohio State University 1963
Approved hy
Adviset/Advisefc/ _ Department of Geology Atrial view from 15,000 ft looking southwest Into the Victoria Valley system. Symbols are: d, harchan dunes; dm, whaleback sand mantles. U.S. Navy photo, MA-353, no. 1 9 7 , F 31, 19 Dec *57
il ACKN0W1EDGMENTS
Support for the field and laboratory investigations in 1 9 6 0 -6 1 was provided by National Science Foundation grant No. G-I38U8 to Tufts
University, and In 1961-62-63, by National Science Foundation grant
No. G-I7 1 6O to The Ohio State University Research Foundation. The
logistic support of the U.S. Navy is gratefully acknowledged.
The writer is indebted to Dr. Robert L. Nichols of Tufts Univer
sity who suggested the problem and arranged and planned the first
season's expedition. Without his Initial encouragement and guidance, this study would not have been possible.
Thanks are due to Dr. Richard P. Goldthwait, Department of
Geology, The Ohio State University, who arranged for most of the finan cial support and who supervised my dissertation work.
Valuable information and data were obtained in discussions with
Peter Webb, Graham W. Gibson, Tony D. Allen, Dr. Alex Wilson, and Dr.
Harold Wellman, all of the Victoria University of Wellington, New
Zealand.
The writer gratefully acknowledges the help received from his field companion, Dr. Andre Callleux of the University of Paris, and fran Dr. Herbert Wright of the University of Minnesota, who visited the writer in the field. iii George H. Base It on and Thcmas C. Davis ably assisted the writer
In the field and undertook specialized projects to aid this study.
The manuscript was carefully reviewed by Dr. Colin B.6. Bull of the Department of Geology and Institute of Polar Studies, The Ohio State
University. The Innumerable discussions with Dr* Bull, who has also worked In the Victoria Valley system, were most appreciated.
Dr. Charles H. Simmerson and Dr. Sidney E. White, Department of
Geology, Dr. Nicholas Holowaychuck, Department of Agronomy, The Ohio
State University; and Dr. Arthur Mirsky and Dr. Richard L. Cameron of
The Ohio State University, Institute of Polar Studies, contributed helpful suggestions. CONTENTS
Page
ACKNOWLEDGMENTS...... iii
TABLES...... xi
PLATES...... xii
ILLUSTRATIONS...... xiii
ABSTRACT...... xix
INTRODUCTION...... 1
Location ...... 1 Nature of Investigations ...... 1 Previous Explorations...... ij-
DESCRIPTION Or’ A R E A ...... 7
Regional Physiography...... 7 General ...... 7 Inland Ice Plateau and High Rock Thresholds...... S Bedrock ■ Geology...... 10 Glacial Sculpture...... 14 Valleys...... 14 Glaclal Benches ...... 17 Cirques...... 22 Climate...... 27 Glaciers...... 33 General...... 33 Lover Victoria Glacier...... 33 Upper Victoria Glacier...... 37 V/ebb Glacier...... 33
v CONTENTS - Continued
Page
Packard Glacier...... 39 Accumulation and ablation ...... 43 Movement...... 45 Summary and Conclusions of Present Glacier Action ...... 45
SOME GE CI4ORPHOLOGICAL PHENCMEHA...... h'(
Meltwater • . • ...... 4-7 Running Water...... 46 Lakes ...... 51 Perennially frozen lakes...... 52 Stir face features . • ...... 53 Ice of Lake V i d a ...... 57 Strandlines and recent lake level fluctuations . . 60 Ephemeral and saline ponds...... 62 Mass-wasting...... 66 Talus . . . . • ...... 66 Mudflows...... 67 Solifluction ...... 69 Debris Tongues ...... 7^ Nonsaturated Creep ...... 60 Patterned Ground...... 86 General...... 66 Age Criteria...... 93 Wind...... 95 Blown Sand Accumulation of lower Victoria Valley .... 95 Dune b e l t ...... 96 General...... 96 Sand analysis...... 99 Movement...... 99 Sand sheets and whaleback-shaped mantles...... 105 Pebble Ridges...... 110 General...... 110 Formation...... 113 Wind velocity ...... 115
vi CONTENTS - Continued
Page
Vent If acts...... 116 General...... 116 Factors of formation and distribution...... 117 Pits, flutes, grooves, and faces ...... 119 Shapes of cobble and pebble ventifacts ...... 126 Wind abrasion by blowing ice ...... 126 Meterological significance - a summary ...... 130 Significance in estimating age of moraines ...... 131 Weathering...... 131 Cavernous Weathering...... 131 General...... 131 Processes of formation ...... 136 W i n d ...... 136 Crystal wedging ...... 139 Chemical weathering...... 1*4-1 Application of cavernous weathering to glacial chron ology...... 1*4-2 General ...... 1*4-2 Results and possible conclusions...... 1*44 Surficial Boulder Frequency...... 1*4-6 Lithology Counts of Pebbles and Boulders...... 1*4-8 Weathering and Texture of Deposits Within the Active Layer ...... 150 Field and laboratory examination...... 150 Discussion and significance...... 151 Desert Varnish...... 155
GLACIAL GEOLOGY...... l60
Introduction ...... 160 Previous W o r k ...... loO Succession...... 162 N omenclature...... 163 Glacial Deposits...... 165 Correlation...... 165
vii CONTENTS - Continued
Page
Early History of Glaciation...... 166 Preglacial Topography ...... 166 Local Initiation of Glaciation...... 167 Invasion of the Inland Ice...... 169 Insel Glaciation...... 172 Insel Drift and Associated Deposits ...... 172 Insel Range...... 173 McKelvey Valley...... 17^ Discussion...... 179 Glacial channels of southwestern Victoria Valley . . . 179 Extent and History of Retreat of Insel Glaciation .... 181 Correlation of the Insel Glaciation ...... 185 Victoria Valley system ...... 185 ./right Valley...... 185 Mt. Gran area: Alatna Valley...... 186 McMurdo Sound - Taylor Valley...... 187 Evidence on the inland ice plateau...... 188 Victoria Glaciation...... 188 Bull Drift and Associated Deposits...... 189 T i l l ...... 190 Distribution and morphology...... 190 Nature and preservation of till constituents . . . 193 Glacial marginal channels...... 200 Marginal channels in bedrock of southern Bull Pass . . 20^ Lacustrine deposits...... 20^ Debris fans of southern Bull Pass...... 206 Pecten (debris) fan of //right Valley...... 208 History of the Bull Drift Episode...... 211 Advance...... 213 Lower Victoria Glacier ...... 213 Upper Victoria Glacier ...... 2l4 Balham and McKelvey ice tongues...... 215 Cirque glaciers...... 216 Advance and retreat in the southern Bull Pass area . . 217 Recession in the Victoria Valley system...... 218 Sea level control...... 220
viii C ONTENTS - G ont inued
Pace
Correlation and Age of the Bull Drift Episode...... 222 Victoria Valley s y s t e m ...... 222 bright Valley . . . . • ...... 222 Mt. Gran area: Alatna Valley...... 224 McMurdo Sound - Taylor Valley ...... 224 A g e ...... 226 Vida Drift and Associated Deposits...... 226 Till...... 227 Distribution and morphology...... 227 Nature and preservation of till constituents. . . 230 Stratified drift...... 233 Debris lobes...... 236 History of the Vida Drift Episode...... 239 Balham and McKelvey ice tongues...... 23^ Cirque glaciers...... 240 Upper and Lower Victoria, and Nebb Glaciers...... 241 Outwash fans of Victoria Valley and a high stand of Lake V i d a ...... 244 Climatic factors...... 245 Age and Correlation of the Vida Drift Episode...... 246 Victoria Valley system...... 246 bright Valley...... 246 Invasion of ice from McMurdo Sound...... 248 Mt. Gran area: Alatna Valley. ••••..•••••• 249 McMurdo Sound - Taylor Valley...... 249 Packard Drift...... 249 General characteristics ...... 251 Barwick Valley: knob and kettle, and ice-cored mor aines ...... 253 Upper Victoria Valley: till and washed drift...... 257 Lower Victoria Valley: modified till...... 258 Ealham and McKelvey Valleys...... 259 Cirques...... 260
ix CONTENTS - Continued
Page
History of the Packard Drift Episode...... 260 General...... 260 Nebb Glacier...... 263 Upper Victoria Glacier ...... 264 Lower Victoria Glacier...... 264 Balham and McKelvey ice tongues and cirque glaciers. 265 Cause of recession and implications of ice-cored mo raine ...... 266 Age and Correlation of Packard Drift Episode...... 267 Vright Valley...... 267 Mt. Gran area...... 267 McMurdo Sound - Taylor Valley...... 268
SUMMARY OF INVESTIGATIONS...... 270
General...... 270 GeomorpholOGical Processes ...... 270 Glacial Geology...... 275
APPENDIX I ...... 278
REFERENCES CITED...... 2'i4
AUTOBIOGRAPHY...... 293
x TABIES
Table Page
1. Net ablation or accumulation on glaciers...... 35
2. Field comparison of ancient or old glacio-fluvial de posits with those of adjacent contemporary depo sition...... 49
3. Analyses of water samples from saline ponds...... 65
4. Data of dune movement...... 104
5 . Analysis of white salt from surface of cavernou3ly weathered boulder...... 139
6 . Percentages of boulders with hollows ...... 145
7» Characteristics concerning hollows ...... 146
8 . Summary of cavernous weathering data for granitic boul ders ...... 147
9. Frequency of upstanding boulders on moraines...... 149
10. Some average textural characteristics of till particles 156
11. Nomenclature and summary of glacial geology...... 276
12. Correlation...... 277
xi PLATES
Plate Page
1 , Gecmorphology and glacial geology of the Victoria Valley system...... pocket
2. Drift outline map of Victoria Valley system ..... pocket
xii ILLUSTRATIONS
Figure Page
1. Aerial view from 15,000 ft looking southwest into the Victoria Valley system ...... Frontispiece
2. Index map of southern Victoria Land ...... 2
3* Bedrock g e o l o ^ ...... 11
k. Aerial view looking southwest along McKelvey Valley and B&lham Valley...... 18
5* Aerial view looking northeast into Victoria Valley. . 20
6 . Aerial view looking northeast into the Victoria Valley s y s t e m ...... 21
7« Orientation of 58 cirques "bordering the Victoria Valley s y s t e m ...... 2U
8 . Elevations of north-facing and south-facing cirques and profiles of McKelvey, Barwick, and part of Victoria Valley...... 25
9. Mean monthly temperatures of McMurdo Sound...... 28
10. Maximum-minimum temperatures, precipitation, and cloudiness...... 30
11. A portion of the terminus of Lower Victoria Glacier . 3^
12. Barrier of Upper Victoria Glacier .... 37
13. -'/ebb Ice F a l l ...... 38
l k . Aerial view looking southwest into western Barwick Valley...... ^0
xiii ILLUSTRATIONS - Continued
Figure Page
15. Map of the Packard Glacier...... 4l
1 6. Barrier of the Packard Glacier...... 1*3
1 7. Meltwater and its d e p o s i t ...... 52
18. Ridge probably formed by thermal expansion of the Upper Victoria Lake i c e ...... 62
1 9. Deposit of 13a2SQi+ adjacent to ice-cored moraine. . . . 63
20. Saline pond in Balham Valley......
21. Active talus slope of dolerite ...... 68
22. Small mudflow levees ...... 68
2 3 . Alluvial fan and superimposed mudflow...... "(0
2k. Mudflow levee of fan shown in figure 2 3 ...... 70
2 5. Slope profiles formed by mass-wasting...... 71
2 6. Solifluction sheet of Balham Valley...... 75
2 7. View west to slope of Bull Pass...... 75
28. Debris tongue of upper Victoria Valley...... "(6
2 9. Debris tongue of upper Victoria Valley showing adjacent lower solifluction fronts ...... 76
30. Debris tongue of western Barwick Valley...... 78
31. Stone-fronted terrace riser of debris tongue of figure ...... 78
xiv ILLUSTRATIONS - Continued
Figure Page
32. Fan of Beacon sandstone extending into western McKelvey Valley...... 81
33* Disintegrating Beacon sandstone 'boulder and trail formed by creep...... 81
34. Patio-like surface of solifluction sheet cut by poly gons ...... 82
35* Polygonal furrow showing slight widening normal to 3 l o p e ...... 83
3 6. Stone-fronted terraces formed within polygons. . . . 84
3 7. Stone-fronted terraces of figure 3 6...... 84
3 8. Sketches showing development of polygonal contraction pattern on a slope and possible formation of stone- fronted terraces...... 85
39. Polygon and furrows in ice-cored moraine western Barwick Valley...... 67
40. Polygons in alluvial fan in front of debris lobes. . 87
41. Gand-wedge and polygon in eolian sand and interbedded n ^ v e ...... 87
42. Ground-ice laccolith ...... 89
4 3 . Dune belt...... 96
44. Gtratigraphic section of a barchan dune...... 98
4 5 . Barchan dune shown in figure 46...... 100
46. Map of barchan dune...... 101
xv ILLUSTRATIONS - Continued
Figure Page
47. Particle size analysis of barchan dune samples and a whaleback-shapod mantle...... 102
48. Dune belt stabilized by melting permafrost and inter bedded neve 105
49. Sand sheet at front of Lower Victoria Glacier ...... 107
50. Cut made by outlet of Lower Victoria Glacier...... 107
51. Portion of whaleback eolian mantle showing interstra tified s n o w ...... 108
52. Large ripples of vhaleback-shaped eolian mantles. . . . 109
53. Ripples of a barchan d u n e ...... 10 9
5 4 . Pebble ridge in gravel of Alatna Valley...... 112
55. Pebble ridge in till surface southeast of Lake Vashka . 112
5 6. Detail of pebble ridges in ground moraine...... 114
57. Range of inclinations of various imprints of wind abra sion typical of larger vent if acts...... 121
5 8. Ventifact of dolerite showing lower actively cut face . 123
5 9. Average inclinations of lower wind-cut face on stable boulders or large cobbles...... 124
60. Plan diagram showing rounding action on boulders or large c o b b l e s ...... 129
61. Ventifacts cut in fine-grained basaltic Ferrar Dolerites 127
xv i U L U S T L i A T IOULJ - Continued
Figure Page
62. Very small ventifacts cut in fine-grained dolerite and in siltstone-fine sandstone of Beacon rocks . . 127
6 3. Ventifacts cut in Beacon sandstone-quartzite and in Olympus Granite-Gneiss...... 128
6k, Ventifacts cut in fine-grained, basaltic Ferrar Doler- ites...... 128
6 5* Cavernously weathered erratic of Vida Granite...... 13^
66. Hollows of weathered and jointed bedrock of Vida Gran ite ...... 13*+
6 7. Cavemously weathered bedrock projections of dolerite. 135
6 8. Cavernously weathered boulder of Olympus Granite-Gneiss 135
6 9. Medium-grained dolerite boulder in second cycle of caver nous weathering...... 136
70. Orientation and depth of hollows of cavernously wea thered, erratic boulders...... 138
7 1. Sketch map of the lower part of Victoria Valley. . . . 1^3
72. Measurement of weathering depth...... 144
7 3. Textural relationships of particle of sand and silt- clay frcm active layer of till deposited by upper Victoria Glacier...... 152
7^. Frost rubble of weathered dolerite ...... 175
7 5. Till sheet of Insel Drift...... 175
7 6. Pattern of seme glacial raeltwater channels cut in bed rock of southwestern Victoria Valley...... iBl xv ii ILLUSTRATIONS - Continued
Figure Page
77. Typical weathered and abraded surface of Dull deposits, 19**
7 8. Aerial view looking north from Wright Valley into Bull P a s s ...... 198
7 9. Glacial meltwater channel series in Bull Drift south west of Lake Vida...... 201
80. Stream cut in debris fan below Bull Pass in Wright Val ley ...... 2 1 0
81. Map showing inferred extensions of glaciers in Wright Valley and the Victoria system during the Victoria Glaciation...... 212
82. Cavernously weathered boulders on Vida ground moraine of lower Victoria Valley ...... 231
8 3. Lag pavement of pebble ventifacts in ice-contact fan. . 23^
8U. Front of debris lobe...... 237
8 5. oketch showing a possible origin of terminal deposits of Vida Drift in the Lake Vashka area...... 2*+3
8 6. Lateral moraine terraces of the Packard Drift ...... 252
8 7. Kettles in Packard till...... 25**
8 8. Ice-cored ablation moraine of western Barwick Valley. . 25**
8 9. Blocky ice-cored moraine of the Packard D r i f t ...... 256
9 0. Ice-cored moraine at terminus of a cirque glacier . . . 26l
xviii ABSTRACT
In southern Victoria land, Antarctica, the inland ice plateau
is bounded by a mountain range. Outlet glaciers from the plateau have
carved valleys through the range. Most of these valleys are still ice
filled, but an amelioration of climate has caused the glaciers to
retreat from some, including the five valleys which constitute the
Victoria Valley system.
The walls of the Victoria Valley 3y3tem rise steeply to 2,000 m
elevation but are broken by cirques, many of them ice-free. Small
valley glaciers enter the area from ice fields in the east, north,
and west. Glacial and solifluction deposits mantle the valley floors.
The area is a cold desert. Drainage is largely internal; the meager stream flow is confined to the summer months when saline ponds
and larger perennially frozen lakes of the valleys are replenished by meltwater. Constant, strong winds produce sand dunes, sand mantles, pebble ridges, and well-formed ventifacts.
Two major glaciations are recorded in the Victoria Valley
system but these may have been preceded by other glaciations. The first distinguishable glaciation, the Insel Glaciation, was an eastward flow of ice from the inland plateau, through the valleys to the coast.
xix The Insel Drift includes: very silty till; erratic pebbles and cob
bles on mesas 300 to 600 m above the valley floors; and some lake
silts. The till lack3 morainal topography, and upstanding boulders
are rare. During the recessional phase of the Insel Glaciation,
deep meltwater channels were cut. Gince the end of the glaciation,
the shapes of the major valleys have not changed significantly.
The second, or Victoria Glaciation, was marked by strong
invasions from local ice fields and from the coast, and by weaker
invasion from the inland ice plateau. This glaciation, which began
more than 30*000 years B.P., is subdivided into three episodes.
The Bull Drift episode included the most extensive glaciers
of the Victoria Glaciation. At the maximum, the area was invaded by
at least six glacier tongues which extended up to 20 km beyond their
present positions, nearly filling the valley system. Till of the Bull
Drift occupies about half of the valley floor area. Two large end moraines are well preserved, but most of the morainal topography is
now subdued.
During the following Vida Drift episode, the regimen became more vigorous. The retreat of the glaciers from their maximum of the
Bull Drift episode stopped about 10 km from the present positions.
Locally the glaciers readvanced. Large outwash fans and karaes formed
xx at the borders of glacial lakes. . and end moraines were deposited. These moraines are moderately well preserved and hummocky, standing several meters above adjacent deposits of the Bull Drift episode. Upstanding boulders are much more plentiful than on the older drifts, but sire cavernously weathered. Vida till is very sandy. During the Packard Drift episode, which continues to the present, the glacier regimen has been less vigorous. Minor readvances occurred but most of the deposits represent a slow regular retreat of the gla ciers to their present positions. The Packard Drift occurs largely as ground moraine, with areas of kame and kettle topography, and very bouldery ablation moraine still ice-cored. In most areas, there is no sharp break in weathering between the Packard and Vida deposits. However, the Packard till is more bouldery and the Packard deposits are sandier and fresher than the Vida deposits. Cavernous weathering and wind erosion Is slight, v/ell-formed contraction polygons cover the Vida and Packard Drifts to within a few meters of the ice fronts. xxi INTRODUCTION Location Almost all of the Antarctic continent is ice-covered hut around the margins are small ice-free areas, exposed by recession of local glaciers and the main ice-sheets. The largest single ice-free area, about ^ ,0 0 0 lsm^f is in the rugged mountain and valley area of southern Victoria Land, on the vest side of McMurdo Sound. This report concerns part of this ice-free area, a region 45 tarn east-west by 26 lan north- south, comprising five interconnected valleys, referred to as the Victoria Valley system (fig. 2). Nature of Investigations The field work in the Victoria Valley system was begun in January and early February, 1961, and was concluded during the following season when 1 1 0 days were spent in this valley system. The field parties were transported to the area, periodically supplied, and occasionally moved within the Victoria Valley system by U.S. Navy helicopters from McMurdo Station. The main purpose of these studies has been to examine and map land forms and surficial deposits of an ice-free valley area in order to gain a better knowledge of the glacial history of Antarctica as displayed by fluctuations of the ice at the edge of the continent. 2 160 00 164 0 0 E GRANITE HARBOR — 77 00*5 GATEWAY NUNATAK GRANV G DETOUR NUNATAK • * C, L > • * MT. BASTION McMURDO SOUND MARBLE MISTAKE PK POINT WRIGHT TAYLOR )\ VALLEY VALLEY ICE-FREE BE D ROCK SURFACE 7- □ ICE-FREE WITH SURFICIAL DEPOSITS MILES 1 1 9 KILOMETERS 3.0 ✓ l ^ S ly- A MAP AREA & Figure 2 . Index map of southern Victoria Land showing the location of • the Victoria Valley system and area of plate 1 . 3 The Victoria Valley system was chosen for this study for the following reasons: (l) it is probably the largest system of Inter connected ice-free mountain valleys in Antarctica; (2 ) it is adjacent and connected to the Wright Valley where some glacial studies had been initiated and partially worked out; (3 ) the area is easily accessible by helicopter frcm McMurdo Station 100 km to the east; (k) the valleys of the Victoria system have been occupied in the past by local alpine glaciers, and by glaciers flowing from the coastal area as well as from the inland ice to the west; (5 ) the valley floors are mantled by drift. In the field, mapping was done by sketching, by ground photography, and on oblique air photographs taken by the U.S. Navy. These data were later transferred to U.S. Navy vertical air photographs and in turn to a U.S.G.S. topographic map enlarged to a scale of 1/50,000 (plate 1 - in pocket). The vertical photographs and the topographic map became avail able only after the 1 9 6 2 field season. Partly because of this map compi lation procedure, boundaries between deposits are subject to some posi tional error locally. Many boundaries which are shown as a line on the map for clarity of interpretation are more properly facies boundaries or gradual morphologic changes rather than sharp, textural boundaires. Some upland areas were studied critically in the field but have been excluded from the map. Deposits in these areas are thin, or often k have heen strongly disturbed by frost action or by solifluction. They are difficult to correlate with the more continuous deposits on the valley floors. Some of the unnamed geographic features of the valley system have been given temporary names to simplify this report and the maps. These names include: Bullseye Lake Haselton Ice Fall Balham Xeke Webb Ice Fall Webb Lake McKelvey Moraine Upper Victoria Lake Bullseye Moraine Orestes Valley Previous Explorations Scientific exploration of the McMurdo Sound-southern Victoria Land area has been carried out in two periods separated by 38 years. From 1 9 0 1 through 1917 the area was investigated by members of the National Antarctic (Discovery) Expedition, 1 9 0I-0 U , under Scott; the British Antarctic (Nimrod) Expedition, 1 9 0 7-0 9, under Shackelton; the British Antarctic (Terra Nova) Expedition, 1910-13, under Scott; and by the Ross Sea Party of the Imperial Trans-Antarctic Expedition, 1911*—17 j under Shackle ton. Some of the most detailed work done in the McMurdo Sound area by these scientists was of a gecmorphologlcal nature (Ferrar, 1 9 0 7; David and Priestly, 191^; Debenham, 1921a; Wright and Priestley, 1922; Taylor, 1922). A wide area was covered by these parties along the 5 coast from I.'ew Harbor to Granite Harbor and along the Taylor, Ferrar, Debenham, and Miller Glaciers. however, the ice-free area comprising the 'fright and Victoria Valley system was unknown until 19^7 when the U.S. havy Operation High- jump carried out aerial reconnaissance flights over the area. After this early work, field investigations in southern Victoria Land were begun in 1955 "by ":«w Zealand parties of the Trans-Antarctic Expedition. Much of the work wa3 topographic survey but it included detailed geological and geomorphological examination of areas previously unexplored (Gunn and Warren, 1 9 6 2). This Trans-Antarctic Expedition party traveled around the Victoria Valley system and delineated it, but the first ground party to enter the valley was a hew Zealand team in January, 1958* Their work included reconnaissance geological mapping of the central part of the valley system ('/ebb and UcKelvey, 1959)* In the summer of 1958-59# a party from the Victoria University of Wellington made more detailed geophysical and bedrock geology studies, mainly in the Wright Valley, but with some attention being given to the Victoria Valley system (McKelvey and '/ebb. 19^1, 19^2; Full, i9 6 0). The work included a reconnaissance of the glacial-geomorphological features (Bull, McKelvey, and l/ebb, 1962). In the summer of 1959-60, another party frcm the Victoria Univer sity of Wellington made geological and geomorphological studies in parts 6 of the Victoria Valley system (Allen, 1962; Gibson, 1962; Allen and Gibson, 1962). United States parties have made detailed gecmorphic studies in the ice-free areas. In 1957-58 Pewe^ investigated glacial deposits and land forms in the Taylor Valley and extended his observations on a re connaissance scale to the neighboring ice-free areas (P^we, 1959, I9 6 0, 1962). Parties from Tufts University made observations in the coastal area from the Hobbs Glacier to Granite Harbor in 1957-58, and 1958-59 (Ball and Nichols, i9 6 0; Nichols, 1961a, 1961b, 1963b); and in the -fright Valley in 1959-60 and I96O-6 1 (Nichols, 1961c, 1962, 1963a). Reference will also be made in this report to other geological and gecmorphic studies carried out in adjacent areas by U.G. and New Zealand workers. DESCRIPTION OF /REA Regional Physiography General The inland ice of East Antarctica is bounded along the vest side of the Ross Sea and Ross Ice Shelf "by a mountain range which extends, near long l6ow E, from lat 6 7° to 85 0 S , 1 Outlet glaciers from the inland Ice, have eroded east-west valleys through the mountain range. Host of these valleys are still occupied by large glaciers, but in the area of the Victoria Valley system and Wright Valley, these have dis appeared to leave an area of ^ ,0 0 0 kra- of valleys and separating ranges almost free of ice (fig. 2 ). The Victoria Valley system is bounded on the south by the Olympus Range, on the west by the inland Ice-sheet, and on the north by the Clare and It. John Ranges. Peaks of the bordering ranges reach from 1 ,0 0 0 m in the east up to 2,^00 m above sea level in the -west (plate 1 - in pocket). On the east, the ice-free Victoria Valley system is separated from VcMurdo Sound by the '■Illson Piedmont Glacier. This extends 60 kn from Cape lernacchi to Granite Harbor, Is up to 16 km wide, and is known to ^Thi 3 area Is known as Victoria Land. 8 be 300 m thick east of lower Wright Valley (Bull, i960, p. 5U9). The Wilson Piedmont Glacier which is fed by ice from the As gar d, Olympus, and St. Johns Ranges, maintains a steep barrier along parts of the coastal area and is known to advance seaward at about 7 m per year near Gneiss Point (Nichols, oral communication). However, its overall regimen is probably negative (Bull et al., 19^2 , p. 7 2 ). The Victoria Valley system itself consists of five main Inter connecting valleys totaling 90 km in length and lying at 400 to 1000 m above sea level. Of the 246 km^ of valley floor, over 75 percent is mantled by glacial and colluvial deposits. Three large glacier tongues, the Webb, Upper Victoria, and Lower Victoria Glaciers, flow into the valley system from neve fields in the neighboring ranges to the north. The Victoria system is connected southward to the Wright Valley, a long and narrow ice-free valley. The floor of this valley lies be tween 300 and 700 m below those of the Victoria system. The lowest point of Wright Valley is under Lake Vanda at the west end; the valley is bounded at opposite ends by the Upper and Lower Wright Glaciers. Inland Ice Plateau and High Rock Thresholds Immediately above the west end of the Victoria system, the nunataks of Mistake Peak, Shapeless Mt., and Mt. Bastion rise 100 to 300 m above the bordering inland ice plateau (fig.2 ). The plateau ice 9 surface riBes gradually westward frcm 2,500 m here at ah out 160° E, to 3/000 m at 150* E long; further vest the elevation decreases. Thus, probably the only Ice flowing eastward through the Victoria moun tain ranges is that which accumulates between 150® and l6 0 ° E (Bull et al.» 1962, p. 66). Further/ at present seme of the accumulation on Mistake Peak and Mt. Shapeless probably flows westward. The preferential starvation of the glaciers feeding Into these valleys Is related to the thickness and subglacial topography of the margin of the inland ice. At the west ends of the ice-free valleys are high bedrock thresholds which were overridden only at times when the surface of the inland ice was much higher than at present. There is evidence that the bedrock surface below the inland ice plateau decreases westward frcm the Victoria Valley system. This Is suggested by the lack of nunatak3 projecting above the Ice surface farther west (Bull, i960) and by geophysical studies (Wilson and Crary, 1961) along the Skelton Glacier (fig. 2 ). South-eastward down the Skelton Glacier from the inland ice plateau, between long 158* and l6 0 ° E, the subglacial surface suddenly rises frcm 3/000 m to 200 m as the glacier apparently thins over a high, subglacial, bedrock threshold. The large ice-falls which occur between 160* and 162° E long on the Ferrer and Mackay Glaciers are still able to reach the sea 10 and the Skelton reaches the Ross Ice Shelf, although little nourishment now canes from the Inland Ice (Wilson and Crary, 1961, p. 877). However, the lever Taylor Glacier Is nearly cut-off frcm the Inland ice plateau and now terminates 30 tan from the coast. Any further lowering of the plateau surface would probably cause this glacier to stagnate and re treat to the bedrock threshold (Bull et al.» 1$62, p. 7 2 ). In such an event the western end of Taylor Valley would resemble that of Wright Valley and the Victoria system. Bedrock Geology Much of the following discussion and nomenclature is taken from the work of McKelvey and Webb (1962) and Allen and Gibson (1962). The rock stratigraphic names given below in parentheses are the equivalent terms applied by Gunn and Warren (1962) in southern Victoria Land. The Victoria Valley system is underlain by igneous, metamorphic, and sedimentary rocks (fig. 3 ) of Cambrian or Late PreCambrian to Mesozoic age. The basement complex, cropping out over the eastern half of the Victoria Valley system, consists of the folded metasedlments of the Skelton Group associated with, or cut by younger rocks of the Granite Harbor Intrusive Complex (Gunn and Warren, 1962). The Asgard Formation (Koettlitz Marble) of the Skelton Group consists of white granular marbles, biotite, garnet-, diopside-, and scapolite-bearing paragnelsses EXPLANATION m 77*IS'S mmm + 1TIP*>iaiiiif ik: N U M U O U D I k or »iu. c W*},' ,//' -■■ 1 v%xv Momnco a f t c r '' ALLEN ANO OIIAON (iM I). v " ' AND MCKEIMV ANO WOO flMt). Figure 3* Bedrock geology P. CALKIN l— » IP* H H 12 and granulites; and quartzofeldspathlc schists* These rocks, subjected to strong folding during the Early Paelozoic (?) Ross Orogeny (Gunn and Warren, 1962), strike northwest and dip 1+5° to 90 * southwest* The oldest formation of the Granite Harbor Intrusive Complex Is the coarsely crystalline, blotlte-and hornblende-bearing Olympus Granlte-Gnelss. These pretectonic rocks form a transitional zone between the older met a sediments, which they parallel in strike, and the younger syntectonic Dias Granite (Larsen Granodiorite)• The Dias Granite Is a coarse-grained, sometimes gneissic, porphyritlc rock with large pink or white orthoclase phenocrysts. Small associated masses and dikes of fine-grained granodiorite, the Theseus Granodiorite, have also been distinguished. The widespread, post-tectonic Vida Granite (irlzar Granite) which cuts these rocks, is a homogeneous, coarse-grained Intru sive with orthocalse, oligoclase, quartz, and dominantly either biotite or hornblende* The orthoclase varies from salmon-pink to gray or white, giving the outcrops In Victoria Valley corresponding color variations. Dikes of the Vanda Lamprophyre and Porphyry cut the basement rocks and form prominent swarms In the eastern Insel Range, Sponsors Peak, and Vida - Clark Glacier Area* Most of these dikes are fine-grained and strike northeast* The basement complex Is truncated by an erosion surface known as the Kukri Peneplain (Debenham, 1921b, p. 105). West of Victoria Valley and Bull Pass this surface is overlain by Beacon rocks (See Mirsky et al., 1963) of Upper Paleozoic to Mesozoic age* In this area the Beacon rocks (Beacon Group, Allen and Gibson, 1962; Beacon Sandstone, Gunn and Warren, 1962) consist of a sequence up to 1,500 m thick in which white, cross-bedded quartzose sandstone predominates. Concretions are common in the basal part; silicious or cherty shales and siltstones occur in the middle; and carbonaceous sandstone and Interbedded coal seams occur in the upper section of these rocks (Allen, 1962). The Beacon rocks dip 3° to 5* west. Very large sills and associated dikes of the Ferrar Dolerites of Jurassic-Cretaceous age (McDougal, 1963; Everade and Richards, 1962) cut through the Beacon rocks as well as the underlying basement complex. Three main bodies are recognized. Sill "a" (basement sill) is a uniform sheet, kZJ m thick, which cuts acorss basement structures some 1*50 m below the peneplain surface and dips 3 ° southwest. It varies from resis tant basaltic rock at the borders to easily weathered gabbrolc rock In the middle. Sill "b" (peneplain sill), about 305 ni thick, has been Intruded along the contact of the Kukri Peneplain and Beacon rocks. In general this sill is somewhat finer grained than Sill "a" • A group of several sills, Sill wc" of Wright Valley, linked in places by dikes, cut the Beacon rocks* These sills, some as thick as 120 m, closely resemble rock types of Sill "b" in hand specimen although they are distinguished in thin-section by more abundant cryptocrystalline material* The basaltic, or finer diabaslc rocks of these sills as well as of Sill "b" display fine columnar Jointing* The present-day structure and much of the basic relief of this area is believed to have been formed by block-faulting during the Victoria Orogeny (Gunn and Warren, 1962, p. 56) of Tertiary and Quar- teraary times. Glacial Sculpture In cross-section, three important divisions of the valley area may be observed: (l) the deep valleys themselves; (2) glacial shoulders or benches, and structural terraces such as those that form the upper surface of the Insel Range; (3) the network of cirques and cirque- headed, alpine valleys cut in the neighboring ranges. Valleys The valleys, from 10 to 27 km long and averaging over 2 km wide at the valley bottoms, are arranged in a branching pattern. Two main trends are evident in this pattern; Balham, McKelvey, eastern Barwick, and the lower Victoria Valleys trend east-northeast, perpendicular to the coastline, while Bull Pass, upper Victoria Valley as well as the 15 valleys of the Webb and Clark Glaciers trend southeast. Such parallel trends are also clearly evident In the major glacial valleys between the Ferrar and Mavson Glaciers (Allen and Gibson, 1962, p. 2^1). These latter valleys parallel and sometimes follow faults mapped by Gunn and Warren (1962, p. 57-58) and Angino et al. (1962, p* 1555-1556). No faults have been recognized along the valleys of the Victoria system; however the upper Victoria Valley follows the contact of the Vida Granite with the Asgard Formation, while Bull Pass coincides with a presumed contact of Vida Granite with the undifferentiated basement complex (fig. 3 )• Such relations may indicate that the valleys were initiated by streams which selectively cut valleys parallel to struc tural or lithologic weaknesses. The valleys exhibit broad U-shapes which are probably related in part to the resistance of dolerite sills to vertical abrasion. Gunn and Warren (1962, p. 60) have noted that the valleys, "contrast with the much deeper and narrower glacial troughs of New Zealand." The valley floors, consistently 700 to 1,200 m below adjacent peaks, increase in width from about 1.5 km at their upper ends to about If- km where they Join. The steepness of the valley walls, like the width, is controlled in part by llthology. Granitic valleys form gentler slopes; the steepest walls are formed in the dolerite sills. The narrowest valley 16 and steepest vails are In western Balham Valley where the north vail Is formed of Beacon sandstone intruded by dolerite sills. Valley floors of the Victoria system have a maximum elevation of 1,000 m. Upper and lover Victoria, Barvick, eastern McKelvey and Balham Valleys slope Irregularly down to the shallow interior basin of Lake Vida at 390 m. However there are exceptions. Bull Pass slopes from a low divide at its Junction with McKelvey Valley toward the south east and ends abruptly 350 m above the floor of Wright Valley. To the east, a second and higher pass now occupied by the Clark Glacier, con nects the lower Victoria Valley to the lover Wright. Prom a divide at about 1,000 m on the Clark Glacier, this valley grades southeast to the lower Wright Valley. Another exception to this general flow toward lake Vida, is shown by the western ends of Balham and McKelvey Valleys which have been excavated into long, 100 to 150 m deep, enclosed basins. The lowest and best graded long profile is that of Victoria Valley which slopes from the Upper and Lower Victoria Glaciers, to lake Vida with a gradient of less than 5 m/km. One through-moving glacier played the dominant role in its formation. As noted, the west end of the valleys bordering the inland ice plateau rises to bedrock thresholds at 2,000 to 2,200 m. The Victoria Valley and the western end of Barvick Valley are terminated by glacier 17 tongues while McKelvey and Balham Valleys are separated from the edge of the Inland Ice plateau above by glacially sculptured steps (fig. 4 ) • In the McKelvey Valley one step, a 5 km-wide bench, stripped on the tap of dolerite Sill "bn, separates the plateau from the main valley. The origin of these steps is discussed on page Two small, vertically walled basins, slightly less than 1 km in diameter and over 20 m deep, have been partially excavated out of the basal dolerite sill in Barvick Valley. The western of these is now occupied by lake Vashka. Both appear to have been formed by local thickening of the trunk glacier, at the Junction with smaller, but steeply inclined tributary glaciers. Glacial Benches The uniform trough wall is interrupted on the north side of Bar vick and Victoria Valleys by three prominent sloping benches orglacial shoulders up to 2 km vide between 600 and 1,000 m elevation. These benches, now largely covered by till or rock-waste rise upward from the top of a dolerite sill, 100 to 200 m above the main valley floor, to near accor dant floors of cirques. These structurally controlled benches may be a result in part of the Joining together of adjacent trough or cirque floors of the bordering valleys by the abrasion of large trunk glaciers. 18 Figure I*. Aerial view from 20,000 ft, looking southwest along McKelvey Valley (left) and Falhaci Valley (right). Syntols are: ID, Insel Drift; BD, Bull Drift; s, solifluction deposits. U.S. Navy photo, no. 23*+, F 3 3 , 7 Nov '59* 19 More narrow benches occur in lower Victoria Valley at 800 to 1,000 m elevation. One of these, Roche Ridge, is a flattened spur between the Clark and lower Victoria Valleys. Two others at the same elevation straddle the terminus of the Packard Glacier on the north side of the valley (fig. 5)* The benches on Roche Ridge and east of the Packard Glacier are cut in basement rock. The most conspicuous, high flat surfaces are the two mesas of the Insel Range, formed by the eroded and weathered top of dolerite Sill "b" (fig. 6 ). The surface at 1,100 to 1,300 m elevation dips a few degrees westward, grading to the level of the large bench at the head of McKelvey and Balham Valleys. This whole surface is lower than the walls of Ealham and McKelvey Valleys; that it was glaciated is proved by the small erratic boulders and pebbles on its surface. Other small benches from 1,200 to 1,7°0 m elevation occur above the valley floors of the Victoria system. Some of these may be formed by such earlier invasions of the inland ice (Bull- et al., 19°2, p. 72). However, many can be related to local ice expansion; as examples, the beaches north of Lake Vashka were probably formed by an expansion of the ice field of the Upper Victoria Glacier while the bench to the south of the lake appears to be a product of cirque glacier convergence. 20 Figure 5 . Aerial view from 2 0 ,0 0 0 ft looking northeast into Victoria Valley. Symbols are: ED, Bull Drift; VD, Vida Drift; PD, Packard Drift, dl, debris lobe; — -, 20 m contour above present surface of Lake Vida (390 m) and possible shoreline of the lake during Vida Drift episode. Control points: -a, lU m east base of outwash fan, b, 22 m (2 m high ridge) on alluvial fan, c, 21 n base of hummocky area on alluvial fan, d, 22 m base of debris lobe and break to 5 ° slope, f, 20 m upper third of kamefan where algal peat sample taken. Ele vations locate some glacial benches. U.S. Navy photo, TMA- 5^0, no. 232, F 31, 7 Nov *59. Fijore 6. Aerial view frau 20,CC0 ft, lookinc northeast into the Victoria Valley system. Elevations indicate some glacial tenches. U.S. Uavy £koto, 1MA-542, no. 2kl F 31, " Uov *59* 22 Cirques The walls ahove the valley floors in the Victoria Valley system display a total of more than 60 cirques, sane of which are long enough to he called cirque-headed alpine valleys. Of these, less than 15 percent are occupied by large ice masses and most of these are at the far east end of the valley system (frontispiece). In most cases this reflects a strong change in climate and probably a reduction in accum ulation since the time of active formation of these cirques. The cirques show marked differences in elevation, shape, and degree of development which are largely related to lithology and exposure. Generally cirque erosion has been considerable and the region is mature so that the uplands adjacent to the valleys consist of horns, arretes, and col divides, sane of which have been overriden and eroded by local glaciers or by the inland ice. In profile, the troughs beyond the cirque headwalls grade down at 3 ° to 1 0 ° to the main valleys below. The deepest and widest cirque valleys occur in the Olympus Range, west of Bull Pass. Here, the high glaciers have eroded vertically through the Beacon sandstone, down to the resistant dolerite sills. The sandstone is much more resistant to lateral corrasion so that the intersection of the cirques has produced "beehive-shaped” horns (fig. 4) which rise 3ane 500 to 680 m above the cirque floors. 23 Although the dolerite sills are resistant to vertical corrasion, they are veil jointed so that once they have "been penetrated, horizontal, erosion can proceed rapidly* Hence, In the south and east of the valley system, relatively deep hut sharper troughs have heen cut in the under lying granitic basement rocks. One of the most marked characteristics of the cirques is their strongly preferred NNE - SSW orientation (fig. 7 )« More than 53 per cent of the cirques face northeast. The troughs beyond these cirques average over 1,500 m in length. Because the rocks dip to the vest, the preferred orientation and differences In length of the cirques Is not structurally controlled. These phenomena are associated with: (l) the Increased freeze-thaw action and greater erosion In the north- facing cirques; (2) the action of the strong winds from the southwest quadrant; (3) perhaps greater accumulation on the north-facing slopes from the dominant northeasterly precipitation-bearing summer storms. Northeast-facing slopes trap snow from both northeast and southwest winds while the stronger south or west winds cause the snow to accumu late In long drifts of this orientation. The elevations of the headvalls of the cirques show two definite features (fig. 8): (l) a decrease In elevation eastward especially in western Barwick and McKelvey Valleys: and (2 ) a difference in elevation 2k CIRQUE ORIENTATIONS (FREQUENCY in p e r c e n t ) Fi.~v.re 7* Orientation of 58 ciraues "bordering the Victoria Valley system shown in 1 0 ° segments. LOCATION OF m m mm W C H VALLEY Figure 8. Elevations of north-facing ( ° ) and south-facing (•) cirques (usually on south and north sides of valleys respectively), and profiles of McKelvey, Barvick, and part of Victoria Valleys plotted along an east-west line. 2 6 between the lower lying southwest-facing cirques on the north valley walls and the higher lying, generally northeast-facing cirques of the south walls. The significance of the eastward decrease in elevations is difficult to determine since both the valley floors and general summit levels show similar trends. The descending elevations may con trol the height to which cirques can be cut or, if the glacial erosion has gone on long enough, the summits may have been lowered to follow the highest level of cirque formation. Summertime meteorological observations by the writer in Victoria Valley and by C. Bull in the Wright Valley show that the western parts of these valleys are warmer and dryer than the eastern parts (p. 32 )• 3h addition, the more ccumon occurrence in the west of dark rocks with low albedo might explain an eastward descent of the orographic snowline. Further, the snow comes from the north-east. Of particular interest are the steep, short valleys frcm the inland ice plateau, opening onto the Webb Glacier and western Barwick Valley. Presently only two of these carry ice from the west. Because of their northeasterly orientation, steep headwalls, and cirque-like form, these sire interpreted as being cirques which subsequently carried ice from the inland plateau and were deepened as a consequence. Sane of these may have gone through more than one cycle of cirque development and modification by overriding inland ice. 27 In addition to the cirques, small nivation hollows are developed at all elevations above the valley floors. The most obvious and most uniformly developed of these occur between 1,000 and 1,200 m elevation, (300 to 500 m above the valley floors) and are cut back into the top of the valley walls. Most of these are in the dolerite 5111 "b", where the columnar Jointing pattern allows plentiful initial irregularities for snow collection. Like the cirques, these features are best devel oped in the lee of winds from the southwesterly quadrant. Many were full of snow during the 1960-62 field seasons, Indicating that they are active at present. Climate The Victoria Valley system lies within an arid zone in which low temperatures, low precipitation, and high winds are characteristic. The nearest permanent weather station is McMurdo Station on Ross Island, on the east side of McMurdo Sound. Here and in other nearby areas on Ross Island, during an 11 to 13 year period, all mean monthly tempera tures averaged below 0° C, the warmest months being December with temperatures of -4 .3 ° and -4 .2 ° C (fig. 9 )* ^he precipitation, mea sured with snow gauges, averages about 11 gm/cm2 per year (Nichols, 1963a, p. 21; USARP, 1960-63), but these measurements are unreliable and actual precipitation probably exceeds this amount (F. Loewe, oral communication). For comparison, the most arid region of the TEMPERATURE I t • 8 c, 13 I J M V j ' ; to • 'A l o 1: iK r - •s > *ij ‘l t- \ > \ i h' < V i f . \ ; \ ' V> S-J 'i ■ S -i O o Hh 2 I 29 United States receives approximately 12 cm of rainfall per year (Nichols, 1963a, p. 21). However, the difference "between such temperate, arid regions and the Victoria Valley system is that the former may often receive precipitation very erratically and in the form of destructive down-pours. Precipitation in McMurdo Sound and southern Victoria Land, is all as snow and may occur during all months, but appears to be slightly heavier during the summer (Gunn and Warren, 1962, p. lU). The climate of the valleys is orographically controlled and strongly influenced by both continental and marine air masses. Average simmer temperatures in the Victoria system may be as much as 4 * C higher than at McMurdo and the area is drier (Bull, oral communication; Pewe, i960). Figure 10 shows some climatic observations for December and January, 1959-60 and for the 1961-62 field season. The 1959-60 obser vations were made by R.H. Balham, Victoria University of Wellington, New Zealand. During late October and early November of 1961 clear and nearly calm days were more frequent than later in the field season. This weather change may well correlate with the rise in temperature, removal of the snow cover in Victoria Valley, and possibly with the clearing of ice from McMurdo Sound. Although snow fell during the field E.V. CAST CM) LAKE VBA 410 TEMPERATURES IP4I-A2 | TEMPERATURES ItSS-SS MSS 075 m , l a k e v a s h k a 507 S SNOW FALL ON VALLEY FLOORS S . SAL HAM CAKE 720 W.V. WEST END LAKE VGA 4 0 0 • CLOUDS SOTt OR LESS U.V. UPPER VICTORIA LAKE 4 5 0 P. PACKARD OL. TSO TTl| | •|l' ss I- <20 -JO 2 0 20 20 OCT NOV. DEC. Figure 1 0 * Maximum-minimum temperatures, precipitation, and cloudiness during the 1958-591 and 1961-62 field seasons. 31 season on various areas of the valley floor, it rarely exceeded 6 to 10 cm and, except In a few cases, remained on the ground less than a day. Winds of the Victoria system are predominantly either from the east or from the southwestern quadrant. The easterly winds which flow into the area from McMurdo Sound are hy far the most constant and are also the strongest and predominant winds In Victoria Valley east of lake Vida. During some 68 days after 9 November, 1961 In which obser vations were made In the Lake Vida area, the wind blew almost constantly from the east. Dally readings at 0000 and 2000 hours averaged over 8 knots and for prolonged periods, winds of 15 to 25 knots were experienced. During December and January of 1959-60, easterly winds were also preva lent throughout the whole valley system (R.H. Balham, written communi cation). However, in the 1961-62 season, west of Victoria Valley, the southwest, or westerly katabatic winds off the inland ice plateau were nearly as common as the easterlies. These katabatlcs were more sporadic but also w r y much stronger, and during February, southwesterly, gusty winds up to l»-5 knots and steady winds of 20 to 25 knots were recorded as far east as Lake Vida on a few days. The strong winds are somewhat variable in direction, following the deeper valleys. The easterly winds carry more moisture and are slightly colder than the westerly winds which are heated adiabatically in their rapid 32 descent from the plateau. Observations made since 1957 show that winter snow remains in the eastern end of the valley system while it may he absent on the valley floors to the west. In addition, as in the adja cent valleys, summer snowfall is heavier in the eastern end of the Victoria system. This has been well substantiated in western Wright Valley where Bull (unpublished manuscript) recorded higher temperatures and lower humidities with westerly winds than with easterly winds. An Important climatic factor in the ice-free nature of the Victoria system is the strong positive radiation balance. Bull has extended observations of the radiation balance made at Scott Base, adjacent to McMurdo Station, (Thompson and MacDonald, 1959) to Wright Valley. Under several simplifying assumptions, he calculated that the net gain in radiation per year is about 20,000 cal/cm^. This may be compared with a net loss of about 9,000 cal/cm^ per year for a fully snow-covered area with an albedo of 90 percent at the same latitude. Under such a positive radiation balance and low accumulation, the size of the Ice-free area tends to Increase continuously. The low albedo of the rock causes an increase in local summer air temperature, which in turn causes a reduction in relative humidity and increase in ablation. 33 Glaciers General Four major local glaciers enter the valleys of the Victoria system. These are the Upper and Lower Victoria Glaciers, at opposite ends of the Victoria Valley, the Wehh Glacier, at the inland end of Barwick Valley, and a smaller, alpine glacier, the Packard Glacier, on the north side of lower Victoria Valley. Five tongues of the inland ice enter at the western margin of the valley system. These are the tongue Joining the Webb Glacier, the Haselton Ice Fall, two tongues at the head of Balham Valley (north and west forks) and a glacier tongue at the inland end of McKelvey Valley. Probably the last four mentioned tongues are inactive; the tongues in the west fork of Balham Valley, and at the head of McKelvey Valley, are now almost disconnected from the inland ice. Lower Victoria Glacier The Lower Victoria Glacier is a lobe of the Wilson Piedmont Glacier. The highest part of the Wilson Piedmont Glacier occurs 5 km east of the snout of the lower Victoria Glacier. Probably the ice to the east of this divide now flows toward McMurdo Sound. The portion flowing west is steeply sloping and has an area of IB km^, very little of which is probably above the firn limit. However, tliis lobe is also fed by glaciers to tie north and south, of areas 8 and 3 respec- t ively• Host of the snout of the lower Victoria Glacier is a ramp (fi£. >) partially banked by snow and sand with only very thinly scat tered boulders or cobbles. The sand was originally wind-deposited on the glacier surface and occurs as horizontal layers within the ice and neve (fi*j. 11) • The western kilometer of the glacier has a very patchy snow cover at the end of the summer which is less tlian Uo cm thick. ^iyure 11. A portion of the terminus of Lower Victoria Glacier showing layers of wind-blown sand. View northwest in January, 1961 . 35 A row of seven poles placed across the terminus (See plate 2 - in pocket) at about 500 m elevation on 3 November 1961, shewed an aver age ablation of snow of 5 cm (l.3 gm/cm2 ) for the following 83 days 1 (table l). A movement survey was made on poles *fl,lf2 , and If3 at the south margin, center, and north margin of the glacier, Pole If3 moved approximately kj cm west (0.6 cm/day) while pole k-2 moved only 28 cm vest during this period. No movement was recorded for pole 4 l, The greater movement on the north is reflected in the shape of the terminus and is due to the larger tributary on that side. TABIE 1 Pole Approx, Net Ablation8, or Pole Approx, Net Ablation or Elev. Accumulation Elev. Accumulation (sn/cn2)^ (gm/cm2) Lower Victoria Glacier Webb Glacier (11/3/61-1/25/62) (11/8/61-1/12/62) Ul 500 m —0,26 85 775 m -5.2 I VI lf7 -0.26 89 -5.2 I H6 -1.82 88 -8.7 I lf2 -1.30 87 -5.2 I if5 -1.82 S&I 86 -4 -if I kk -2.08 S&I *f3 -1,56 36 TABES 1 - Continued Pole Approx. Net Ablation® or Pole Approx. Net Ablation or Elev. Accumulation Elev. Accumulation (gm/cm2 )b (gm/cm2) Packard Glacier (l0/30/6l-l/2lf/62) (l0/3l/6l-l/2lf/62) If 1,200-1,300 m +O.78 22 950-1,000 m -O.78 It It 5 +0.26 1 " 40.78 11 ft 6 +1.0*f 3 " " 0 7 1,100-1,200 m 40.52 2 " " -0.52 n it 8 4-l.Olf 16 " " 40.52 n ti 9 41.30 17 " " -0.26 10 1,000-1,100 m 40.78 19 " -0.52 n ii n 4 2 .3^ 18 " " -l.Olf 12 ii ti 40.26 20 " -1.82 it it 13 40.26 21 " -1.30 M 11 Ilf -0.52 11 fl 15 -0.26 (H/12/6I-I/21/62) (10/31/61-1/21/62) 25 950 m 1.26 29 750 m -1.56 S&I 11 32 0 30 -0.78 11 23 -l.Olf 31 -1.82 (11/12/61-1/21/62) 33 925 m -0.52 11 3*f -0.78 37 730 m -11.3 I II 35 -l.olf 38 H -1.30 S&I 36 -If ,U2 (10/31/61-1/21/62) (10/31/61-1/21/62) 26 805 m -1.30 tl 27 -0.78 11 28 —l.Qlf A 61f0 m -2.60 S&I B " -6.10 I (11/12/61-1/21/62) Uo 800 m -1.30 aAblation of snow unless indicated: 3&I - largely snow probably some ice; I * all loss of ice* ^Average density of snow down to 30 cm (beginning and end of summer) = 0.26; average density ice = 0.87 (assumed). 37 Upper Victoria Glacier The Upper Victoria Glacier has an area Greater than 80 lon^, more than two-thirds of which is occupied by neve fields above 1 ,0 0 0 m ele vation. The tongue entering upper Victoria Valley is cliffed on the margins (fig. 1 2 ) and is about 60 in high at the front. Figure 12. Barrier of Upper Victoria Glacier. View north. The upper 35 m the cliff is relatively free from debris, tut the lower portion is brown with fine englacial material. Most of the lower portion of the cliff is banked with an apron of ice, formed by dry calving. During the warmest part of the summer, meltwater often pours off the margins near the terminus, especially from widened crevasses, and 38 from two short but prominent medial moraines. The meltwater lias built small deltas into the large pro&Lacial lake. Very little debris is now melting out of the glacier and the proglacial moraine is less than a meter thick. A survey of boulders near the terminus of the Upper Victoria Glacier shoved a movement of up to 20 cm between > November and 15 January 1962 (0.27 cm/day). Webb Glacier The Webb Glacier, with its local neve fields and Webb Ice Fall, occupies an area of 31 kra^. Some ice enters over the 800 m high ice fall (fig* 1 3 )* and there is some flow from the compound cirques forming the neve, but stake survey showed that the 7 ton long tongue is stagnant. Figure 1 3 . Webb Ice Fall. Looking west. Note ice-cored moraine in foreground at left. 39 The end of the Webb Glacier is a ramp that grades almost imper ceptibly into the perennially frozen, proglacial, Webb Late (fig. 1*0 • The surface of the tongue has a very low gradient (150) mainly toward the terminus, hut toward the ice-fall the direction of slope is locally reversed and the surface shows irregularities of several meters. / / The Webb Glacier tongue is almost completely free of snow and neve. A line of five poles was placed at ahout 775 m elevation across the ter minus (see plate 2 - in pocket) on 8 November 1 9 6 1. After 65 days (table l) the ice surface showed an average lowering of 6 .6 cm (5 .8 gm/cm). The strong ablation here is due to the strong and dry katabatic winds which came down from the inland ice plateau (see p. 31 ). Packard Glacier The Packard Glacier has an area of 6 .5 km^, half of which consists / t of neve fields above 1,000 m elevation formed by compound cirques. The long tongue reaching down to 600 m elevation is largely barren of snow on the west side. Here, very numerous cryokonite holes and treacherous ice crusts are formed by the influence of strong radiation and a thin sprinkling of wind-blown sand and silt. The western border is cliffed and lined by a deep fosse while the eastern border has a profile concave upward, formed by a thick snow drift apron (fig. 15 )• 4o Figure I1*-. Aerial view from 20,000 ft looking southwest into western Barwick Valley. Symbols are: BD, Bull Drift; VD, Vida Drift; FD, Packard Drift; ic: ice-cored moraine; kk, knob and kettle topography. U.S. Navy photo, TMA-5^0, no. 228, F 33, 7 Nov *5 9. In EXPLANATION Figure 15. Map of the Packard Glacier h2 Although sand Is scattered over the glacier hy the wind, moralnal debris of other origin is apparently very localized and thin. Ice-cored, debris cones are formed by material which has slid onto the surface below the hanging cirque glacier above pole 28 (fig. 15 )• similar but more sandy cones occur in the middle of the glacier at about 950 m elevation. The latter are oriented uniformly toward the glacier margin and may be exhumed crevasse fillings. Fine englaclal material Is more common near the base of the Packard Glacier. However, because of the overall dearth of material carried, relatively little moraine Is being deposited at the glacier front. The Packard is an active glacier and possesses a vertical barrier terminus kl m high (fig. l6). Shear planes are outlined here and along the western border, by narrow bands of the englacial moraine. Early in October 1961 a thick fan of fresh angular ice blocks was found below the barrier. These Ice blocks had melted or sublimed away by the end of January 1962. The fan was produced by dry calving of the terminus during the winter. Movement is also displayed on the glacier surface by a well- developed pattern of tension cracks. Cracks line both borders of the glacier between TOO and 1100 n elevation and form an angle of ^0 * to 8 0° with the glacier’s axis. These are several meters long, often 15 to 20 cm wide at the surface, and were often open to 6 n depth. A temperature of -2b.5 °C was measured in one crack at 7 n depth. hi Figure 16 . Barrier of the Packard Glacier in January, 1962. Looking vest. Accumulation and ablation Forty poles were placed across the Packard Glacier (fig. 15) on 30 and 31 October, and 15 November l?6l. Measurements shcv that at the end of 86 to 'JO days of summer there vac an accumulation of 0.06 to 2.3 cm of crow In most areas above 1,000 n elevation. Belov 1,000 m there occurred vith fev exceptions a levering of the surface of from 1 to cm. Tills lowering vas largely due to sublimation; however, in the ice-ccvered surfaces local melting occurs vith the formation of superimposed ice and in some cases with the draining of meltvater into crevasses. Surface streams occur only vithin a fev tens of meters of the glacier terminus. kk /'Ji attempt was made tc measure annual snov accumulation on the Packard Glacier "by pit studies. Four pits were dug; on 11 and 13 Novem ber 1961, and companion pits on 22 and 2k January 1962. Two of these pits were at lOlO m elevation, one at 8d m, and a fourth at about 760 m elevation (fig. 1 5)* All pits reached dirty ice; the deepest was 106 cm (pit 3) and the most shallow h6 cm (pit U). A study of texture, hardness, and density suggests that there was a net accumulation of 20 to 27 cm of snow (5-7 £ja/cm2) over the winter of 1 9 6 1. The average density of this layer in the four pits was the same at the beginning as at the end of the summer, about 0 .2 6 gm/cm^. It is apparent from these studies that for the year of February 1961-January 19^2 , there was a net accumulation of from 13 to 26 cm of snow on the east side of the Packard Glacier tongue as well as in tlie neve fields above. However, the shallow depth to ice on the Packard tongue indicates that there liave been periods of negative balance within recent years. The surface of the lowest 3 laa of the glacier was snow-free in December 1957 • The low average density for the snow of 1961 and for setae previous years is due primarily to sublimation. It Is apparent that melting lias played little part in the change frcci snow to Ice. Movement Surveys of fourteen poles (fig- 15) were made on 1 November 1961 and 23 February 1962. Approximate calculations show that poles 26 to 31 (within 2 km of the Packard Glacier terminus) moved 12 to lUO cm, with the greater movement along the east side where the glacier is thicker. For the poles above 1,000 movements varied between 2 n and more than ^ m. Summary and Conclusions of Present Glacier Action Except for the Webb Ice Fall, the glacier tongues extending from the inland Ice into the Victoria Valley system are inactive and may be wasting away slowly. Of the four large glaciers in the Victoria system, the Webb is the least active and the Packard the most active. Although seme ice still comes over the Webb Ice Fall from the inland ice plateau, strong dry katabatic winds cause the tongue of the Webb Glacier (at about 775 m) to be lowered as much as 6 cm in two months of the summer; the tongue itself is now stagnant. Uet ablation is slightly less on the terminus of the Lower Victoria Glacier which is exposed to moisture-bear ing winds, but equal or greater ablation occurs below 80C m on the Packard Glacier; the surface ablation of the Upper Victoria Glacier was not measured. 3nov pit studies on the Packard Glacier suggest that daring 1961 there was a net accumulation of snow over most of the glacier. k6 Surveys show that near their termini the Lover and Upper Victoria Gla ciers are moving more than 1*5 m. per year. The Packard Glacier has a stronger regimen than the other glaciers and movement of up to 16 m per year may occur above 1 ,0 0 0 m elevation. The fronts of the Lover and Upper Victoria and Packard Glaciers, and of the tongues from the inland ice, have probably not recreated significantly in recent years. This is suggested by the occurrence of veil-developed contraction polygons a fev neters from the fronts (3ee p* 93 ), and by the occurence of some cavernously-veathered boulders a few tens of meters away. The possibility that these glaciers have advanced recently cannot be disproved at this time. Little moraine is being deposited at any of the glacier termini. 30ME GECMCRFH0L0GICA1 PHEIICHBIIA Meltwater Under the present climate, meltwater in the Victoria Valley system is very scarce and largely restricted to December and January. Very slight year to year climatic variations often control the complete appearance or disappearance of some smaller lakes and major streams. The low lying glaciers and large ice and snow fields are dominant in meltwater production year after year and the contribution from the winter snow cover is variable. At the end of the 1961 winter, up to 15 cm of snow covered valley floors in the eastern half of the Victoria system and in more extensive upland areas, but the snow cover was almost entirely sublimed before the temperature was high enough for noticeable melting to occur. Likewise, the amount of ground water formed by sur- ficial thawing of the permafrost was limited and only of local importance. Melting and minor stream flew began at the moraine mantled portions of glacier termini. A number of small puddles appeared on the thawing dunes and moraines of Victoria Valley on Ilovember lh, 1961 during clear weather and with maximum air temperatures of -6 ° C. Minor melting at ^7 even lower air temperatures was confined to hollows in the dark, dolerite "boulders and to moraines where heat absorbed was easily passed to the snow blanket. Running Water The stream channels and fluvial deposits formed recently usually can be distinguished easily from those of ancient times by: (l) the fresh appearance and sharply defined topography; (2 ) the lack of well- developed contraction cracks; and, (3 ) occasionally by the presence of encrusting algae. With a few exceptions, the contemporary deposits are much finer grained than earlier deposits. The largest x>articles of modem alluvial deposits of Victoria Valley vary between 2 and 3 ram while on adjacent but distinctly higher, old terraces, the largest sur face particles range between 15 and 55 ram (table 2). However, in both the present and older 3tream deposits, very fine deposits (silt and clay) are rare. These sizes are limited in abundance in the glacier deposits and much of the fine material is moved away by the wind before it can be picked up by the streams. Consequently, present streams are usually clear and free of rock flour. Table 2. Field comparison, by largest particle size, of ancient or old glacio-fluvial deposits with those of adjacent contemporary deposition by A. Cailleux. Ancient C ontemp orane ous Terrace, Floodplain, high low Packard Glacier stream Uo mm 2 mm Upper Victoria Lake stream 15-25 3 Tributary stream from cirque above west side Lake Vida 2^-55 3 Fan-terrace, west side Lake Vida So 2 Alluvial fan of western debris lobe, upper Victoria Valley t+2-^5 3 It appears that streams were formerly much more active than at present. Bull Pass is drained by an 8 m deep cut at its southern end into the Onyx River in Wright Valley, 305 m below. The stream bed contain a high percentage of pebbles and cobbles and yet the lower end of the cut is now completely blocked by a sand dune 2 .5 m high. Except for Bull Pass, the drainage of the Victoria system is internal with more tiian 50 percent of the area drained into Lake Vida. The remaining portions of the valley system drain to the basins of Lake Vashka, western McKelvey Valley and Balham Lake. The longest streams and those observed to run each year are the ones draining toward Lake Vida from the Lower Victoria and Packard 50 Glaciers (frontispiece); from the lakes below Upper Victoria Glacier; and from the lakes "below the Webb Glacier to Lake Vashka (fig. Ik). During the summer of 1961-6 2, none of these streams was full enough to reach its drainage basin. Meltwater from the Lower Victoria and Packard Glaciers reached its maximum distance (within 2 .5 km of lake Vida) on 20 January, 1962 when the maximum air temperature was 5-5* C. The maximum depth of this stream observed during the 1960-61 and 1961-62 summers was about 20 cm and most of the time it was probably less than 6 cm. In previous years the observed flow was greater. Aerial photographs taken on 5 December, 1956 show a strong though braided blow of both Upper and Lower Victoria streams. In 1957-58 the stream entering the east end of Lake Vida was more than 60 cm deep. The Lower Victoria Glacier stream east of its narrow cut in the moraine, when active, is a meandering stream. When more full, it runs in a braided pattern over a shallow, sandy, almost boulder-free flood- plain up to 2.5 km wide. The stream gradient is less than 3 m/km. The braided pattern provides optimum conditions for deflation by pre vailing easterlies. In some of the stream-cut sections, strata of ice or firn are revealed between eolian and fluvial sand layers. Such buried firn layers are especially common in the lower Victoria Valley. 51 The Upper Victoria stream is fed by the Upper Victoria Glacier, by a few small cirque glaciers, and occasionally by outflow from two small lakes in eastern Earwick Valley. It traverses and encircles older, thick, sandy valley train deposits in a narrow course. Little meltwater ccmes from the high-lying cirque glaciers and snow banks, and streams that do occasionally flow from them often evaporate and soak into broad fans before reaching the valley bottoms. Although weak and ephemeral, most of the present streams are cutting down rather than aggrading. This is especially noticeable with those streams traversing the younger, hummocky drifts of west Earwick Valley and below the Packard Glacier. Gullying and other small-scale drainage features are nearly absent west of Mt. Insel but are more obvious to the east where the winter snows are greater. For example, on the warmest days, water from melting snow patches may form small rills on the valley sides or in a few hours may build fans on the valley floors (fig. 17)* Lakes Large areas of the Victoria Valley system are occupied by peren nially frozen lakes, while highly' ephemeral and shallow ponds, 3one with highly saline waters, and recently dried lake teds occupy smaller areas. Most of the smaller ponds are in large funnel-like catchment "basins and are formed "by melting sn01/. Hence their size varies from year to year. The larger, perennially frozen lakes, such as Lakes Vida and Vashka, are supplied mainly by glacial meltwater. Figure IT* Meltwater and its deposit formed during a few hours above freezing in December. Bank in foreground is 30 on high. Looking southeast frau east end of Lake Vida. Perennially frozen lakes Most of the perennially frozen lakes are in two drainage systems — in western Barwick Valley, and in upper Victoria Valley. The 'Jebb and Upper Victoria Lakes are damned by the glacier termini. They are large but relatively shallow lakes. In some summers their out flows drain througl sliains of smaller lakes, occupying depressions in the ground moraine. 53 These lakes overflow throuch shallow, sinuous, ephemeral streams to the larger Lakes Vashka and Vida. Two other series of snail glacial meltwater lakes occur— one in southern Bull Pass, and one on the ice-cored moraines, adjacent to the 'Wot Glacier. Surface features The surfaces of the perennially frozen lakes show considerable nicro-relief. In winter much of the surface nay be snow-covered. In places this snow drifts into sastrugi and irregular transverse ridges, i/ind-blown sand and silt is scattered over the lake edges. Below the snow cover, the ice surface is sometimes flat and smooth, especially near the lake edges. In early summer, strong radiation sublimes the snow cover and a cusp or scalloped relief pattern is often etched into the winter ice surface. Such surfaces often reveal a lattice pattern of etched grain boundaries with perforating vertical air tubes (See Barnes, i960, p. 58- 6 5). Cracks formed by freezing and expansion of layers of water below the surface ice and cracks formed by contraction of upper layers of ice during winter cold cut across the surfaces. After the snow cover lias sublimed, the edges of the lake melt to form a moat of open water. The absorption of radiation is greater tiian in the middle of the lake because the ice lie re is dirtier and the lake 5^ shallower. Naturally the width of the moat depends on the summer tem peratures and cloudiness as well as on tlie lake profile the albedo of the ice and lake bottom, and on the inflow of meltwater heated by- contact with moraine. In the summer of 1961-62, open water began to form at east and west ends of Lake Vida (390 m elevation) on 9 December when the maximum air temperature was -1° C. This moat widened to a maximum of about 100 m and remained open, except in cold spells, until the first week in February. Aerial photographs show that this moat has been as wide as 200 m at the west end in recent times. During the summer of 1961-6 2, a moat only a few centimeters wide developed around Lake Vashka (5^7 m elevation) while no open water formed around Balliam Lake (720 m elevation). During the warmest part of the summer, when air temperatures remain above freezing point for several hours a day, narrow cracks and wide patches of the scalloped ice surface at the borders and sometimes nearer the middle of the lakes (particularly Lake Vida) may be healed or veneered by smooth new ice. During the exceptionally dry 1961-62 season, this process of new ice formation was not observed and its nature is not entirely clear. No meltwater was ever seen on the ice surfaces, except near the moat where open water occasionally spilled over the edges toward the lake centers. David and Priestley (l91^> P» 16*0 55 observed similar formation of new ice in early autumn in cracks of perennially frozen lakes of Ross Island, and ascribed its formation to condensation of the vapor from water and salt ice beneath, or to oozing-up of brine along the crack length. This phenomenon is certainly related to that of the Internal melt horizon, discussed later (p. 5 8)* The presence of wind-blown silt and sand on the lake ice surfaces has already been mentioned. Except at Lake Vaslika material larger than sand was not observed in or on the ice more than a meter from shore. At Lake Vashka, a few dolerite boulders have been moved by gravitational forces onto the surface, and out 100 m from the steep northeast bedrock wall of the basin. A pit more tiian a meter deep was cut in the ice of Lake Vashka at a point several meters from the west shore where the depth is at least 2 m. A section of the ice is described below: Depth (cm) G-21+ Coarse bubbly ice, with some finely disseminated algae O-^ Very bubbly, 2-3 mm rounded 5-10 Clear layer 10-11+ Clear blue ice with rounded bubbles up to 5 mm lh-15 Clear layer, no bubbles 15-21+ Clear blue ice with 5-7 ^ bubbles 21+-1+0 Coarse bubbly ice with vertically elongated bubbles up to 3 cm 56 2^-30 Some rounded "bubbles 5-7 mm 40-92 Fine bubbly ice, mostly clear bubbles 1-2 mm with nitration hollows up to 3 cm 52-120 Fine ice, scattered bubbles up to 5 urn, separated from above by a 1 mm horizontal layer of very closely spaced 0.5 itm bubbles The smaller lakes often reveal domed surfaces while the laryer Lakes Vida and Webb have ice surfaces which are essentially flat, but which are locally bulyed up into mounds. Ouch mounds, typical of many other lakes of Antarctica (See David and Priestley, lpl^, p. 166; Cailleux, 1962b; Van Autenboer, 1?6 2) are usually less than 10 m in diameter and 1 .5 m hi^h, and are radially cracked. The cracks are oper as much as 20 cm at the top and often reveal the lon^ columnar crystal structure typical of the lake ice surfaces. Lake Vashka shows an overall domed surface, superimposed on which are smaller mounds. Convex surfaces such as these are nest cannon on lakes known to be nearly frozen to the bottom cr containing little or no unfrozen water. Van ivnteuboer (1962, p. 35^) has ascribed the formation of ice mcunds in Sor-Podane, Antarctica tc the collecting of meltwater around the higher hillocks of moraine by the "hothouse" effect (9ee p. 5 9) beneath sliallow lake ice. In the Victoria Valley system, many mcunds were located in lake ice which was probably thicker than 10 n; therefore, 57 the effects of solar radiation on the ice at the ground surface below may be greatly reduced. Many of the ice mounds of the Victoria system are probably formed when local stresses are directed from expansion of freezing water trapped in small irregularities in the lake bottoms. A similar origin was suggested by David and Priestley (l^l^, p. 166). Since more tiian 75 percent of the larger, more permanent, peren nially frozen lakes are clearly domed or contain one or more local ice mounds, most of the perennially frozen lakes are frozen in part to their bottoms. Ice of Lake Vida Attempts by the writer to drill through the ice of Lake Vida to make temperature and salinity measurements were unsuccessful. However, one deep hole was made approximately 1 km from the east end of Lake Vida early in Ilovember, 1961. This hole passed through hard, blue ice with several intervals of scattered sandy and silty ice to reach an impene trable surface of frozen sand and gravel at 11.5 m. Some small pebbles of Vanda Porphyry were recovered by blasting and this surface was assumed to be the lake bottom. A second hole was started toward the western ;,alf of the lake, but after 6 hours of continuous drilling through very hard, clean ice, only 2 m depth was reached. The lack of water below the ice near the east end, and the 58 occurrence of a few large ice rounds in the north central portion of Lake Vida suggests that at least part of the lake is frozen to the bottom. The wind-'blown, sand discovered at 3, U , 10, and 11 m below the S'Arface implies that the lake may have been built up slowly, perhaps yearly, by superposition of water, and in between tines, it was littered with wind-carried sand and silt. This origin would also suggest that the lake now present has never completely melted and re frozen . The history and form of Lake Vida differe markedly fra.: that of Lake Vanda in Fright Valley, a perennially frozen lake, 8 'at long and 70 m deep. In the summer, Lake Varda is covered with m of ice. The bottom waters are usually saline (density 1 .1 gm/cn^) and warm (75° V). Investigations by Fils or. and Vellman (1768) suggest that these high semperatures are caused by the absorption of solar radiation in the water -which, because of the density gradient, is net able to lose heat by convection. Further drilling in the Lake Vida ice, a month later (in late December, 1761), revealed a melt (0° C) horizon at a depth of 20 to 30 cm below the surface. This melt horizon was less tl-an a meter in thickness and was underlain by cold ice. Only a few measurements of the melt horizon thickness were made before the coring auger became 59 trapped "by the freezing of water percolating down around the corer. The presence of this melt layer was also probably the cause of the loss of another auger in sinilar drilling attempts in Lake Vida in late January, 196c. The origin of the internal melt horizon on Lahe Vida is still unknown; however, some possible explanations are noted: (1) The ice surface down to several centimeters depth may be raised above 0* C by radiation and persistently high air temperatures. With a subsequent lowering of the air temperatures a surficial ice cover is formed, but refreezing is slow at depth. However, meltwater was never seen at the surface, and temperatures were never above 0° C for more than a few hours at a time. (2 ) Warn bottom waters ‘.under pressure are forced toward the surface via open cracks and invade a porous layer just below the ice surface. However, no widespread, very porous horizon was observed in the lake ice in November before the melt horizon formed. (3 ) The melt horizon was formed by absorption of the sun's energy by dirty ice Just below the lake surface. However, no widespread dirty ice was encountered above 3 ^ depth. (b ) Through the process often referred to as the "hothouse" effect, there is a net gain of heat below the unmelted thin surface 6o layer of Ice with consequent elevation of temperature and production of tie 0° C melt horizon. The short wave solar radiation is absorbed by the lake ice from the surface to fairly great depths, whereas lone wave length radiation is emitted only from the surface. The loss of heat from the surface ice may be large at tines in the evenings due to conduction. At these times, heat transfer is much increased by constant and strong summer winds. Such as explanation has been used by Van Autenboer (1962) to account for ice mounds at Sor Rondone, Antarctica and by Takahashi (i960) to explain the occurrence at Syowa (East Antarctica) of puddles formed below unmelted snow in freshwater ice. Takahashi (i960, p. 33^) notes: ’’the hothouse phenomena in water and ice is more conspicuous Ilian that in snow, especially where the wind is strong and eddy diffu- sivity is large." Such an explanation may be the easiest way to account for this widesj>read melt horizon in the summer; however, if the ice is very thick, as we may assume it to be, there mist be considerable heat gained at depth by conduction before enough heat remains near the sur face to cause melting. Gtrandlines and recent lake- level fluctuations Although a well-developed set of strandlines occurs up to 60 m above the present level of Lake Vanda, no strandlines or lacustrine 6l ■beaches with alpae deposits have "been found more than a few meters ah eve the lakes in the Victoria Valley system. The present lakes are nearly as full as they have heen for a lone period of tirae and may he in near-equilibrium with the present climate; however, it is apparent tliat relatively larpe yearly fluctuations can occur. The levels of many perennially frosen lakes dropped 20 to 50 cn toward the ends of the 1560-61 and 1561-62 summers hut in 1557-58 and 1 the levels increased. In the lakes that are undrained, she loss is by sublimation and evaporation. Recent lowering is recorded by numerous features. Ocaly algae and wafer-thin salt deposits occur around the borders of most lakes. Undisturbed and unoxidised benches and border strips up to 150 cm wide ..ere observed above lakes in Bull Pass and Tarvick Valley, and in out- vush sands at the east end of Lake Vida. Dry and snail inlets and ? n high marginal cMffs, cut in outwash on the northwest edge of lake Vida, were noted by Uelb and UcKelvey (155a7 p« 125)• Tn the south west corner of Upper Victoria Lake, a very fresh bnuldery ridge (fi^. IB), was observed 50 cm above the late summer ice surface. As outline that this lake is 753 r. wide, a change of temperature from winter 00 summer of 50° C would char-ge the width of the ice surface by almost 2 m, an amount suff-’cient to push up this ridge. 62 Figure IB. Ridge probably formed by thermal expansion cf the Upper Victoria Take ice. Tee axe in center is 90 cm high. Looking south toward Olympus Range. Ephemeral and saline ponds Many deep depressions in the younger drift and shallow kaslr.s in ledrock and in older drifts have recently teen water filled. Undisturbed and unoxidised laminated tot tar. silts, deltaic bedding, lacustrine ter races , or tie t channels, gray muds, and thin deposits of calcite occur in most small depressions. Occurring in the larger undruined basins and troughs are small play as and sulinas. Many lakes dried up completely during glacial re cession, while others, fed occasionally by glacial streams, continue to build up, salt deposits slowly. These are usually spongy with a silty 63 upper layer overlying the salt and varying amounts of interbedded silt and fine sand. Three of these evaporite deposits were examined by libson (1962, p. 365)- In a depression in Falnam Valley, nirabilite (’TapoO^.lOHnC) and associated decomposition products occur on the base of boulders in subsurface sheet-like aggregates; in VcKelvey Valley a depression contains unhedral, iron-stained gypsum deposits more than 30 cm thick; another isolated depression near Lake Vashka contains 70 cm of layered crystalline salts consisting mostly of euhedral, interpenetrant crystals of gypsum and some nitrate. A pond deposit cf maribilite in western Berwick Valley is shown in figure 1 9 . Figure 19* Deposit of ITaoSO^. (largely Mirabilite) adjacent to ice- cored moraine. Ice axe in front of deposit is 90 cm high. View southwest in western Berwick Valley. 6h During the summer of 1961-62, three small undrained depressions contained saline water. Hie largest (fig. 20) was in Ealham Valley. On 10 December, 1962 it had a diameter of 13.6 m and a depth of ^0 cm occupying the "bottom of a "basin with many tines its area. In late January all three saline ponds were almost completely ice-free. Table 3 gives a chemical analysis of two of these saline ponds. ^igure 20. Saline pond in 3alham Valley. View southwest. A dry salina occurs within a kilometer of the terminus of the ice- cored moraine adjacent to the Webb Glacier. It lias a white floor of sul fate salt 10 cm thick with no interbedded silt or sand. This is probably the result of very few cycles of filling and evaporation. 65 Table 3* Analyses of water samples from saline ponds (3ee plate 2 - in pocket - for locations). Analyses by U.S. Geological Survey, Quality of Water laboratory, Columbus, Ohio, WS 8B - Upper Victoria Valley 173 200 - Balhara Valley ( See fig. 2 0 ) Ca 96 ppn 2 ,1 2 0 ppn M g 1U0 13 ,7 0 0 Ha 1 ,0 7 0 1 6 ,3 0 0 K 17 194 HCOo_) 35 30^ 580 6 ,0 6 0 Cl 1 ,1+80 1+7,200 H03 k?b 3 0 ,6 0 0 Specific conductance 6 ,3 8 0 micromhos 118,000 D20 1.003 cm”3 1.095 Dissolved 00lid 3 3 ,9 0 0 ppn 1 2 6 ,0 0 0 As noted by Ilichols (1963a, p. 23), the occurrence of dried and saline lakes proves that evaporation is greater than precipitation in this area. The abundance of salts in many lake beds "indicates that it took a considerable period of time to accumulate them and that aridity, therefore, has had a considerable duration." The origin and significance of the salts in the ice-free areas has been discussed by Gibson (1962), by Ball and Ilichols (1960); Ilichols (1963a); Angino et al. (19^2); and by Hamilton et al. (1962). 66 Mass-Wasting Talus The highest and steepest Inclined deposits of the Victoria Valley system are accumulations of rock waste or sliderock. These vary consid erably in form and development hut all are less well developed than in more temperate and humid climates. Extensive deposits forming prominent talus slopes occur in the western half of the valley system at she foot of nearly vertical cliffs formed hy the dolerite sills. For example, on the steep northern wall of Ealham Valley, dolerite and lesser amounts of sandstone form a sys tem of large compound cones. The steep-sided dolerite caps of the Insel Range and the dolerite outcrops of western Rarwick Valley are fringed by talas aprons which frequently completely cover the bedrock. This localization of talus slopes around dolerite outcrops is undoultedly due to the steep-sided (columnar) nature of the dolerite sills. The granitic rocks are also readily split by frost vedgiipg but thick accumulations of granitic rock waste are common only in a few over-steepened cirque walls on the north c ’de of Victoria Valley. Most of the granitic slopes of Victoria Valley are rounded «nd bear little rock waste. Wr 11 -developed tal’is cones ^n'1 aprons cf granite or dolerite are usually formed of uniformly course, bouldery rock waste; their slopes vary from about 26* to 31°. 'There different rock types are rresent, sorting by sloe is often poor, and sand occurs vith very large boulders, as in the talus apron on the vest side of Pull Pass. In such areas, the slopes of talus nay approach. 37° or 3 8*. This May be due in part to the stabilizing effect of -inderlyir.g perrnafrost which holds the larger boulders in place and hence may tend to maintain segments of the slope at angles above the normal angle of repose (2 6° to 36% lharpe, 193B, p. 3C). Many of th.e talus slopes appear to be stable, frequently the bottom cf boulders in the talus are covered by salt efflorescences. However, active talus sheets of blocky dolerite line the southwestern vail of Harwich Valley where the Vebb Glacier lias recently’ over-steepened valley walls or removed earlier accumulations at the cliff base (fig. 21.), 'Tith wetter conditions than at present, the rate of talus formation may Jiave been greater. These conditions may have existed during active glacial retreat. Mudflows A few snail, recently active mudflows, and several small, freshly formed mudflow levees occur in Victoria and Barwick Valleys and in Pull Pass below snow-filled cirques (fig. 22). Figure 21. Active talus slope of dolerite on western "border Vebt Glacier. Looking southeast. Figure }2. Small mudflow levees on the south-facing jlone of -arvick Valley. 6 9 On the west side of Upper Victoria lake, near the glacier ter minus, a hummocky and irregular mudflow, sane 200 m wide, has "buried the upper part of an alluvial fan. This flow has apparently "been built up with the formation of successive natural levees (figa. 23 and 24), It consists of a mire charged with great numbers of angular pebbles, cobbles, and boulders up to 40 cm in diameter. The flow is supplied by meltwater and debris which has flowed t'nrough a deep notch leading from a large cirque 1300 m above. It has been formed very recently as indicated by the fresh stones and perfectly preserved sides of some of the levees. Solifluction Sheets of debris believed to be a product of solifluction may extend from the foot of steep talus or bedrock slopes of greater than 30°, down over inclines below as low as 3° (Tig. 2>). Through creep and mechanical weathering, rock waste is moved from talus slopes above to even lower inclines. Here, talus material is often mixed with varying amounts of glacial or wind-carried material, and moved directly dovn-slope, commonly forming a streaky pattern of long lines of debris called nonsorted stripes (Washburn, 1996, p. 837)* Boulders can often be traced to the outcrop above from which they were derived. However, some sheets of debris consist entirely of glacial and eolian material deposited on gentle slopes. TO Figure 23. Alluvial fan and superimposed mudflow near the Upper Victoria Glacier. Looking northwest. % Figure 2b . Mudflow levee of fan shown in figure 2 3 . Uote 90 cm high ice axe in trough at center of photograph. 71 BULL PASS (W SL O PE ) BALHAM VALLEY CSW SLO PE) / BALHAM VALLEY (N SLOPE) ✓ of 4 j ? / / r > BARWICK VALLEY Cn s l o p e ) 1 5 0 0 ^ ____ IOOO- SCALE UPPER VICTORIA VALLEY 5 0 0 - METERS (e SLOPE) ■ i ■ 5 0 0 IOOO 1 5 0 0 Figure 2$. Slope profiles formed by mass-wasting. 72 The surface fabric shows evidence of former flow (See Lundqyist, 19^9)* Boulders have lone axes parallel to the direction of movement except where flow is stopped "by an obstruction. Behind the laryer stones, secured in permafrost, finer material is often piled up, sar;- yestiny a more rapid surface flow of fines. hhere movement is not stopped, the front of the sheets may be outlined by a low scarp- a few meters hiyh and the forward edye of the material is sharply defined; above this "front" nay be shallower waves of debris, sometimes formimp distinct terraces. These characteristics ssyyest that movement occurred by solifluction in the original sense of the word, that is "the slow” flowing from hirher to Icrwer yreur.d of masses of -.ujte saturated with s'ater" (.sidersson, 2^)06 f p. 9>_9^J* The sheets of solifluction debris vary in Leusure deperdiny on the source; however all, regardless cf surficial weatheriny, show a nedi.n sandy ru trim luchiny silt or clay _ articles. Tit is texture is reflected in their ability tc ’’sold noisi’cse j.nd in the -..-ell -d eve lop ed, p-clyyonul pattern developed over them (p. 06). Bo weathering profile is found in these deposits. In areas such as Bull. Pass, the normal, silty textured, old, undisturbed deposits may rarely be found ’,Tithin the active layer below the sandy solifluction sheet. stmnrary of textural characteristics of rev.reser.tative solifluction deposits cf J -■ the Victoria system is given belov. Camples -rere taken from deposit: related to Full, Vida, and Packard Drift episodes. 1ampleza * lilt-Clay Phi i'ean Diam."^ Phi Deviation'" Avy. P.p. Avy. Py. Avy, Py, IK 7,P s'. 1 r *1 jm', »— 1 <■> tv 15,16 1 0 -> i -• • ( ™ .1 * ^ 1P,P 3.6, 17,15 alee ^late 2 - in p.ccket - for locations and apiendix for com plete analyses. 'hl.O-P.C Phi = coarse surd c0.J0-0.T5 Pcii - veil sorted, C.75-l»5- ~ moderately sorted. The sandy texture is ^robably due tc tie early removal of fines from the active layer "by wind ^.r.d ’.rater. This may occur d-riny initial periods of movement and ^erha^s after some vertical sorting arid segre gation of the coarse fraction "by frost action (Corte, Ipf2). After remove 1 of the fines, the formation of ice- or sand-’redye contraction polyyons vas strongly favored. A gotd example of the removal of the finer materials is on the north side of Lake ’"'Ida where iarye alluvial fans emanate from'boulder and pebble-rich debris lobes (fig. l) • The weathering of boulders in the older solifluction sheets is very nearly as great as tiut in the glacial deposits they cover. Prob ably most of the movement occurred soon after glaciers retreated, when valley vails were over-steepened and meltwater vus plentiful. The "best developed GOliflucLi.cn sheets of the Victoria Valley system occur "below the talus aprons in Bull Paso, ar.d in Balkan and McKelvey Valleys (3ee figs. 76 and 27)• In these ^reas, free from glaciers for many thousands of years, solifluction sheets mash glacial drift over more than half the area of the valley floor. Most of these deposits are old. In many areas, large granite "boulders have "been worn to the ground and their remnants lie undistrubed nearby. In recent years only siru.ll areas of saturated ground and small scale solifluction bus been observed in this and neighboring areas (lee McCraw, 1960, p. 3l) • Debris Tongues Down steep walls in upper Victoria and Parwick Valleys, large debris tongues extend from some cirques (ftps. 28 and 2 9 ). Older and less well-defined tongues occur in Balkan and McKelvey Valleys and in Bull Pass. The largest of the well-defined tongues occurs on the north wall of Burvick Valley. It extends ever 3->0 n vertically to the valley floor where it widens to 100 n. This tongue originates in thick accumulations of glacial drift or frost debris at the mouth cf a small cirque. Other tongues developed at the front and below cirques containing semipermanent snow or glaciers. The tongues are thin as they pass over the cirque lips but on valley walls inclined between 10° and 35°; they Figure 2 6 . Solifluction sheet of Balhajn Valley. Looking vest ever Balham Lake toward inland ice plateau. Figure 2 7. View west to slope of Bull Pass. Dark jagged line represented damp active layer and lower limit of sandy solifluction sheet. 76 Figure 20. Debris (solifluction) tongue of upper Victoria Valley. Looking east. L Figure 2 9. Debris tongue of upper Victoria valley shewing adjacent, lower solifluction fronts. Looking east over terminus of Lower Victoria Glacier. 77 thicken to as much as 15 m. Those of upper Victoria Valley terminate more than 1 0 0 m above the valley floor in relatively steep, blunt ends up to 5 m thick. In Barvick Valley the tongues reach nearly to the valley floor, where a few thin out and form more gently inclined ramp fronts, generally only a few meters in thickness. The surfaces of the tongues near the termini are covered with angular boulders up to 5 a in diameter, but where the surface incli nation is steeper and debris is thinner, 3and and pebbles may cover as much as one third of the surface area. Deep blasting in the largest tongue in Barvick Valley (figs. 30 and 31) shows that it consists of a thick subsurface layer of frozen debris in which scattered, unoriented boulders are mixed with a greater percentage of pebble and sand material. The fraction less than 2 mm is sandy (appendix I) like the solifluction deposits. Gullies, small mudflow levees, and alluvial fans occur on, and adjacent to the tongues. Polygonal wedge patterns are well developed everywhere on them. In Barwick Valley, on the best developed tongues, the true polygonal contraction pattern occurs over the upper-most part of the tongue but near the valley floor it grades into the stepped, or transverse stone-fronted terrace pattern illustrated in figure 3 1 * ^ell-formed stone-fronted terraces do not occur on the tongues in 7 8 Figure 30. Defer1* tongue of western Berwick Valley. Looking north. Figure 3 1 . Stone-fronted terrace riser of deferis tongue of figure 30 and subsurface exposure made fey felastlng. Riser is 3 m high and hole is 1.1 m deep. upper Victoria Valley but broad, gently inclined terraces and irregular transverse ridges are present (fig. 26). The ridges appear tc be due to successive flows, like shingles with edges successively less extended. The form, texture, and micro-relief of these tongues of debris fit early descriptions of rock glaciers. Sharpe(1938> P» *+3) defined rock glaciers as "glacierlike tongues of angular rock waste usually heading in cirques or other steep-walled amphitheaters and in many cases grading into true glaciers." Recently Vahrhaftig and Cox (1959) have shown that the movement of rock glaciers in the Alaska Range is due to flow of the interstitial ice. However, it is concluded that the debris tongues in the Victoria Valley system moved mainly by solifluction al though frost heaving lias probably played a minor role. The following arguments support this conclusion: (1) Roth types of transverse ridges on the debris tongues are also found on solifluction sheets. (2) The transverse ridges differ from those described by Wahrhaftig and Cox for the typical rock glaciers of the Alaska Range. (3 ) Some of the debris tongues resemble and grade into typical solifluction lobes (fig. 29). (k) All but one of the tongues are less than 15 n and most are less than 6 m thick. Ouch a thickness produces u stress of about 0.2 8 c 'cars, lauch lens t ^ u that required to preduce defornuticn of inter stitial ice Cut sufficient to cause sclifluctio.. (’Vuiriiufti^ ai:d Cox, 1 n t ; r - r - ]. oli > The delris (soli^lucsioii) to;.juca -re stable excert '’f'r ...cve::.e-.t d.:e to tae frost ooutrustia*. and i*.diced allcvi„l undermini^. However, the weatheriny of she surface hnvlders is less tl^ni tluit on adjacent .uoraines; they ;.uve forued after ike retreat cf the tru.il: alaciers. hensaturated Creep hlthouyh Iv.r^e scale solifluction is n^t a very active process ia the Victoria Valley system today, uonsaisraled roc’a a-.d soil creep does occur. Vue.! of it is u. result 0° frost action, which :..cves indi vidual stones down slope over finer aaserial (fiys. 38 and 33)- The rsost common evidence of recent frost action wi^h creep is tie occurrence of trails of overturned 1 oulders a~d collies. Rock and soil creep fro:- frost action was active in the past when it operated in cor.tiaatioa with solifluction. ^cr exanple, adjacent to steep valley walls, slopes of 3° to h* frequently exhit it a flat-sur faced mosaic or patio-like insetlay of surface stones in a weak, hut definite polygonal pattern (fiy. 3*0 • This is prchahly a result of slight flow with differential frost wedyiny and settling of surface cohhles and toulders. Figure 32• Fan of Feacon sandstone (light) extending into western TicKelvey Valley from exposure overlying dolerite 3ill "’o". Looking south to Olympus Range. Figure 33* Disintegrating Feacon sandstone "boulder to right of nan, and trail formed hy creep toward left. Looking southeast in Farwick Valley. 82 "i^ure 3^. Patio-like surface of solifluction sheet cut by polygons. View north from McXelvey Valley toward kullseye Lake pass. One of u*e most interesting effects of polygonal contraction on slopes is the formation of steps and terraces. On slopes which are mantled with stony and usually very, houldery delris, tetragonal sand or ice-wed^e polygonal cracks (fee following section) often develop with b order ii^ furrows nearly parallel and ^.cnral to the slope (flack, 1552* p. 130). On the steeper slopes (15° to 30°), the horizontal furrows tend to widen and become sand filled while those in the dip direction are narrower (fit;. 35)• Probably this is due to the more efficient trapping of debris and moisture by troughs alon^ the contour. The upturning of the contour furrow borders (3ee Pewe7, 1559, p. 5^5-552) is stronger on the dowu-slope side. In addition, coarse debris heaved 83 upward at the furrows will tend to accumulate on the down-alone side. Thus, narrow, sandy terraces (treads) with wide, intervening, ^ently inclined risers of pebble, cobales and boulders are formed. Figure 35 • Polygonal furrow allowing slight widening normal to slope. Under certain conditions, the process described above is accen tuated to the point where stone-fronted terraces and steps are formed (ftps. 31, 36 and 37)* The risers become as steep, as 37“ u-.d the treads are nearly flat. The process of formation is illustrated in '‘ijare 3 8. The terraces conform in part to Uashburn’s (l55^t I'* 833- 83,+ ) de fix', it ion of "sorted steps”, teinc a well-defined feature of "pattern -round with a step-1 ihe form and a sorted appearance.” However, they do act jrade down-slope into sorted polygons nor up-slope into sorted stripes, Figure 3 6 . Stone-fronted terraces for— a within polygons on slopes of Victoria Valley. Dotted line —rks polygonal furrow (See fig. 37). Figure 37. Stone-fronted terraces of figure 36. Dotted line — rks prcsdnent, widened, polygonal furrows joined along slope. Note — It encrusted boulders adjacent to lee axe. View west. 85 SAND AND/OR ICE WEDGE j / POLYGON 0 s ' INTER-POLYGONAL FURROW • a ■ o r \ *. METERS RAISED EDGE OF POLYGON AND PILE-UP OF BOULDERS •o 9 m a s s m o v e m e n t ? A? RISER 37* TREAD d'. Figure 38* Sketches shoving development of polygonal contraction pattern on a slope (A & B) and possible formation of stone- fronted terraces (C). 86 Patterned "round Cer.eral Tr. IIie Victoria /alley systen as elsevlere is seutlerr. Victoria Twid, areas nar.tled vita sandy or coarser delris are covered ly tleiv*.! contraction crad: pclyjons * Tlese are fro„ ?! so VO a across (e‘i0s. ZZ - ht*■-/ > • Taylor (11V2) referred to tie ;atterns as "tessellations?e\:e (lS‘33') lias studied ties: ir case detail and xroroced tie Lerra "sar.d-vedye" Tley are similar to ice-vedye polygons is tie f.rtic except lint tley are is jrovs.d devoid of vegetation and are outlined ;y textural claryes ia tie soil le- tveer. t^e inter-yciyyoral furrcv and tie enclosed Xolyyonal areas (Pev^, 1233, :• l^l)* Tsese r.clyyors» v..icl f « H under tie yei:eral ter.:, of son-sorted patterned yleno...enn, apparently fern, i.* rest or.se to a tler.,.nl te..sics set-up in tie icy perna'frost (as veil as p'ire ice) \y its contraction dvriuy tie colder via ter. Ir. tie /a: tic tie i olyjo..al tension crads: are sealed ty filliny vritl water vlicl freezes (Lef f ir.^vell, 1215)« In tie ilc’lurdo found area tie crac’ss (l to 3*2 deep) o^tes fill vitl smsd (Pev/, 1231, p. 3^8 ). ft.is meltvater or saad i.nles its way into tie cracl duriny tie spriny or surraer. Tie sard or ice vedyes are tlen zones of veaiaiesa vhicl open and fill repeatedly Ir. tie fallowixc0 seasons. 171 ijare 3?• Polygon and furrows In ice-cored noraine western Harwich Valley. Scale is Professor II.P. Vri0ht. Figure Uo. Polygons in all Figure Ul. Sand-wedge and poly uvial fan in front of delris gon in eolian sand and inter- lotes, Victoria Valley. tedded vAvA at front of Lower View soutlivest. Victoria flacier. 88 The sand-vedges (fig. hi) apparently form, because of the lac’: of melt- water. Ten excavations were cade in fresh moraine in the Victoria Valley system. In all of them lenses, pods, and veins c-f ground ice '..Ter e found up to 1 m below the centers of j. cly^ons. ^or this reason, it is suspected that in many cases the wedges :.uy also consist of Ice in iurt. Polygons of the Victoria system show all gradations ietveen hi.pl. and low-centered forms (Leffingwell, 1315/ p. 205-211). The distinctly high or low-centered types are most common in the very sandy ground moraine and eolian mantles where centers or polygon borders may be warped up 1 to 1.5 m. In front of the Packard 2lacier a fear polygons have centers 3 above the bordering farrows. There seems to be no very well-defined distinction; however, high-centered for_is appear to be particularly cctnmon at the foot of the valley walls of lower Victoria Valley and on the north side of the Lower Victoria flacier stream. The centers of two high-centered polygons were excavated; they were supported by lac eolith-shaped Ice masses (fie* ^2). host polygons in the Victoria system show a flat to very eligibly up or down curved surface with very slightly up-warped borders. These polygons are generally considered to be unsorted but there Is a definite preferential accumulation of coarse icuterial toward the edge of the inter-polygonal furrow. In many instances the concentration 8 ? is due to the up-turning of the polygon edge and a differential pushing up of cotLies and Loulders. The fine material remains at the furrow hot tom or drains into the oner, crach. This differential moving of Luried material shows up veil in areas of thin deposits. The crachs extend into well-fractured bedrock, and stones from the bedrock are moved to the surface. In high-centered polygons, there is gravitatio:a*l movement of the coarse material toward the polygon borders. I Figure b2* Ground-ice laccolith below high-centered polygon near Packard Glacier. Ice is 5 to 10 cm below permafrost table. In other parts of lower Victoria Valley, low-centered polygons often show an area in the center up to a few meters in diameter which is deficient in material larger than sand or pehtle sine. It is possible that these were once high-centered forms in which the center core of ice was removed after gradual thinning of the active layer fron the high center. The distribution of patterned pro and in the Victoria Valley sys tem suggests that the development of these features depends or* the amount of Ice in the surficial deposits. Via cl; (l^l) sugpested that the preater the ice content of the material, the preater Is its coef ficient of expansion. Three main factors appear to control the amount of ice present. These are the percent of silt arid clay in the deposit, the ape, and the location of the deposits. In addition to the ice con tent, the depree of development, cine, and the confipuruiiou of these inter-p olyponal f'urrows depends on she rate and amount of cooling, and *he direction of tensile stresses (fee Lichen':ruch, i;ff). The presence of cot'les and calders and/or heterogeneity of the component del ris may also he a factor Ir. the polypcu development. Thus-, the T. es t developed polypous with the deepest a. 1 widest furrows occur i„ the coarse, hlochy, ice-cored ...oraine cf western ~orvich Valley (fip. ZZ) • here, the furrows mce up to V ... deep and 6 to 1Z -* wide. Similarly well-defined bus trnch smaller wedpec occur i*. the young eoliuu sand mantles r.ear the Tower tTictoria Clacier (fip. 5;l). Tn this area layers 91 of flrn are interbedded vlth sand and coarser morainal debris* The fine and well-sorted character of material of the active layer allows only narrow furrows 10 cm or so wide to be maintained, although the sand- vedge below may be much wider. In general, icy permafrost, ground ice, and polygons are best developed in the more sandy deposits, although these are normally considered to be non-frost-heaving (Beskov, 1935/ P* 7 6 )* These de posits usually contain less than 11 percent silt-clay in the 2 mm and finer fraction. One exception is in the ground moraine Immediately west of lake Vashka where polygons are very well formed. The morainal debris here includes up to 36 percent silt-clay in the fine fraction, but in general the deposits are very bouldery, poorly sorted, and ground ice and permafrost is present below the thin active layer. Polygons may also be found in very silty deposits in areas of very recent meltwater drainage. Polygons are well developed on almost all the deposits of the Vida Drift and Packard^ Dr if t episodes (p. 229) / in the older sandy deposits in parts of Balham and McKelvey Valley, and in all of the solifluction deposits. Because the region is arid, the silty material is dry and lacks cohesive strength so that polygonal patterns are not developed. Large areas of the valley floors surrounding the eastern Insel Range are 92 covered by till in which the silt and clay averages 30 percent of the fine fraction* Ho permafrost occurs within 60 cm of the surface and no polygons are developed* The lack of moisture In silty material is due to the much greater capillarity and reduced permeability of the finer deposits. The capillarity at 0 * C for even coarse silt is 30 to 100 cm while It is 3 to 10 m for fine silt* On the other hand, permeability for coarse silt Is 36 to 3 cm per hour or 0*38 to 0*035 cm per hour for fine silt (Beskov, 1935# P* 86). Under this climate where evaporation greatly exceeds precipitation, moisture has been slowly removed from the silty deposits while their low permeability has prevented their regaining moisture during periods when snow Is melting* That moisture penetrates only 5 to 10 cm 13 shown by the occurrence of horizons of salt at this ► depth and also at the surface In the older silty material* Surficlal frost action Is also less than in sandy areas and is confined to the moistened upper layer* The occurrence of permafrost and patterned ground In coarse grained deposits and their absence in silt and clay has In the past been considered a striking anomaly. However, the same phenomenon occurs In the arid region of North Greenland (Davies, 1980)* 93 Age Criteria The use of polygons In determining tbs age of moraines In Vic toria land has "been discussed at seme length by Pewe (1962) • The main change with time Is the enlargvnent of the contraction crack by filling with ice, sand, or larger particles* Fere (l?62, p. 96-99) suggested that lacking good exposures of the wedge fillings, the best measure of growth may be obtained by measuring "the distance between the crests of the raised edges of the polygonal furrows," which usually varies directly with the wedge thickness. Pewe (p. 96-99) also noted that it may take "thousands of years to have the intersecting shallow furrows or trenches widen to 1 to 2 m (when measured at the crest edges)." It Is clear frcm observations in the Victoria Valley that these criteria of age must be used with considerable caution. Furrows do not always become wider with Increasing distance from the present glacier fronts* In addition, In fine-textured active layers, wind erosion and deposition often keeps ahead of the wedge grotrth so that the resulting furrow may be considerably smaller than its wedge. The relations of polygon and furrow size to age were not studied In detail In the field. However, It was noted that the polygons with inter-polygonal furrow crests at least 0*5 m apart occur at the edges of the Upper and Lower Victoria and Webb Glaciers, as well as at the fronts of the Ice tongue3 in Balham and McKelvey Valleys. Similar phenomena occur elsewhere In southern Victoria land. If these polygons do take hundreds or perhaps thousands of years to form, their presence at the Immediate glacier fronts Indicates that these glacier3 have maintained their present position for a long time or that they have advanced recently. Studies of photographs taken In the Hdfurdo Sound region and Church, 1962) indicate clearly that glacier fronts have remained essentially unchanged in position and shape for 50 years. A third possible explanation for these near-glacier polygons 13 that as the glacier retreats very slowly, It is exposing fossil polygons formed previously and later covered by advancing glaciers. This very plausible mechanism has been advanced to explain similar phenomena In the Shackelton Range (Stephenson, lp6 l) and in Baffin Island (Falconer, 1362) and is certainly worth Investigating In southern Victoria Land. Exhaustive field investigations of the patterned ground which have been undertaken in the ice-free areas of the IlcHurdo Sound region by Thomas Berg and Dr. Robert Black of the University of Wisconsin since i9 6 0 should shed light on the formation and occurrence of these features. 95 Wind Blown Sand Accumulation of Lower Victoria Valley A combination of the strong and steady (summer) easterly winds and an abundant source of sand permits a large part of lower Victoria Valley to be referred to as a desert erg. In other parts of the valley system, blown sand, presently unrestricted by a stabilizing desert pavement, occurs only in thin or localised deposits. One of the largest of these areas Is at the southern end of Bull Pass. With the last retreat of the Lower Victoria and Packard Glaciers, large areas of sandy ground moraine and fresh erratic boulders and bedrock of Vida Granite were exposed to weathering and wind erosion, i'uch of the present sand has been contributed subsequently by granular disintegration and break-up of the plentiful even-grained granitic and sandstone boulders. Figure 11 shows the sand, largely deposited by wind on the Lower Victoria Glacier, now covering the melting front. This sand, moved westward partly by streams but largely by wind, has mixed with glacial drift and gruss to take on various forms. These include, from glacier front to Lake Vida: hummocky deposits of sand lnterstratlfled with morainal debris, glacier ice, and compacted snow; a sand sheet and 9 6 desert pavement area; a belt of true dimes; and finally, a feld of whaleback-shaped sand mantles over moraine and interbedded with firn. Dune belt General An east-west trending belt of true dunes (Eagnold, 19**2 , p. Ifi6 ), 3.5 km long and less than 1 bn vide, occurs on the north side of lower Victoria Valley, south of the terminus of tire Packard Glacier (frontis piece and fig. U3). This belt consists of many partial barchan forms which together form northeast-trending, transverse and alternately arranged dune ridges between 1 and 15 m high and up to 800 m long. Figure ^3. Dune belt. View southeast. 9 T Three reasons for the extensive dune formation here are: (l) easterly vlnds are predcminant and are particularly strong and consistent in the summer; (2 ) there is an ample supply of sand to the east; (3) morainal hummocks deposited "by the Packard Glacier formed nuclei for seme of the larger ridges. The dunes exhibit well-developed slip faces oriented to the north west, transverse to the local predcminant wind direction. The closely packed arrangement of the dune forms and the external and Internal struc ture suggests that these are advancing west and northwestward, Obliquely up the northwest slope in the lower Victoria Valley. They are also locally and temporarily becoming larger. Sand avalanches on the northwest facing slip faces maintain angles of 30* and 31*, and to windward, slopes vary between 10* and 20*. In at least one dune this windward slope is underlain by 1.5 m of east-dipping compacted accretion deposits rather than encroachment deposits more typical of moving dunes stabilized in size. Figure W* illustrates how the buildup has occurred partly over layers of snow, a phenomenon shown more strongly in the surrounding sand sheets and mantles. 96 Figure Vt. Stratlgraphie Motion of a barchan duns. Section pictured above and tabulated below v u measured approximately 10 ft (3 m) below the dune ereet on the windward elope of a ridge south of Packard ftlacler. View west* (Photograph and section by- G. Gibson and A. Allan) Thickness (in.) 1 . Unstratified, loose sand (active layer) k 2 . Interstratified sand and soft snow; thickest sand - 1 in, snow 0.75 in. 12 3. laminated soft sand, even grained, no snow 6 U. 2 5. Soft sand It 6 . Hard, platy, frosen sand 2 7. laminated sand, moderately hard 1U 6 . Snow layer 0.5 9. Laminated sand, moderately hard It 10. Soft snow 3 11. (Below photograph) Soft, 'laminated sand 6 99 Sand Analysis A single 'barchan dune ridge Immediately east and north of the Lower Victoria and Packard Glacier stream was selected for sampling f and mapping (figs* ^5 and ^6) • This ridge was sampled at five evenly spaced locations from the trough at the east side of the windward 3lope, over the crest to the trough "below the lee slope (See fig. *+6). The results of the mechanical analyses, computed by lnnan*3 method (1252, p. 125-1^5) are shown In figure ^7 . A sample taken from a vhaleback-shaped eollan mantle to the west Is shown for comparison. The curves of figure *»7 suggest that the material at the crest is slightly finer and better sorted than that in the troughs but further sampling is needed to establish this point. The poorer sorting in the troughs may be due in part to the influence of the till beneath the thinner dime deposits. Itovenent On 27 December, 1561 part of this dune belt was mapped by plane- table and telescopic alidade (fig. ^6). At this time seven bamboo poles, 3ix with red flags, were Inserted as near as practicable at the foot of the dune slip faces. Flags 1 , 2 , and 2A (south to north) were placed on a small westerly projection of the mair. dune; flags 3 > ^ * end 5 Figure Barchan dune shewn In figure U6 . numbers show positions of movement poles; red flags appear as "black dots. 100 101 flfiN Nip of WrohMi duM, lowar Victoria Valley. PAHTICLC DIAMCTCA IN PHI UNITS AND (MILUMBTCRS) (4.00) (too) (I jOO) (.S00) CMO) ClSS) (.OSS) OS 7 0 £ SO g SO « s o 10 3 Phi Mean Phi Deviation* Specimen Diameter (sorting) SLV 26 foot of vlndeard slope 2.0 0.5 27 windward slope 1.9 0.5 2 6 " 2.1 o j crest area 2.g O.k 3 0 foot of lee slope 2.0 0.5 15 whaleback sand mantle l.k 1.2 *Tha smaller the deviation, the better the sorting. Figure . Particle slse analysis of barchan Aune samples and a vhaleback-shaped mantle. See figure k6 for location of sampli 103 were forward points (south to north) along the main continuous slip face; and flags 7 and 6 (south to north) were along the main slip faces Just east of flags ^ and 5 respectively# Beneasureaent of these poles on 1 and 25 January, 1262 showed an average advance of 1*H err. of the slip faces along a northwesterly direction. This is b,3 cn per day over the 29 day x^eriod (table H). The slow advance of the dune at flag 5 Is probably due to the proximity of the Packard Glacier stream which, during this period, removed the sand nearly as fast as it va3 brought down the slip face. Previously, the stream has been observed to "rapidly cut away the dune" (Webb and IlcKelvey, 1259, p. 127). It is Impossible to project the measurement rates of dune move ment even over the. remainder of the summer season. little movement occurs during much of the year when snow covers the dunes and the sand source to the east. Also, when snow nelt3 on the dune, the surface is moistened and may be subsequently frozen, temporarily retarding movement (fig. 1 During the 1961-62 season, meltwater appeared in the dune area about Ilovember l^th and movement probably began about then. The rate Increased through the period of maximum thawing and constant wind velocities into late summer. Meteorological data suggests that easterly winds are les3 constant and weaker during the winter and spring when the lower Victoria Valley has a snow cover* Table **. Data of dune movement* Flag Approximate Horizontal Advance of slip face Average height of distance from since 12/27/61 (cm) rate of 3llp face pole to bottom advance (m) of slip face* 8 days 29 days for 29 (cm) day period 12/27/61 l/**/62 1/25/62 (cm/day) 1 3 1*73 123 1**2 2 3 2«* 20 136 H.7 2A 3 115 163 5.6 3 7.5 76 (approx.) 101 (approx.) 3*5 l* 7.5 155 11*5 5.0 5 1.5 115 25 50 1*7 6 1*5 0 56 155 5.3 7 3 0 100 255 8.8 Average 1**1 ^.9 * Poles 3et at bottom of slip face of slightly up slip face. One Isolated barchan dune, comparable In size and orientation to those ridges below the Packard Glacier, occurs near the north edge of lake Vida* Here, the sand has been piled up by the steady summer easter lies against the edge of a debris lobe (p»236 ). A slip face, concave toward the west and northwest, has been preserved although surrounding vent ifac to clearly show dominant cutting on the west. Apparently, the 1 0 5 violent westerlies come largely at a time when the dune 13 •frozen or largely stabilized by snow cover. Figure U8. Dune belt stabilized by melting permafrost and interbedded neve* View southwest. Sand sheets and whaleback- shaped mantles Sand streams off the terminus of the Lower Victoria Glacier In late spring and summer. The sand not Immediately blown away may be interstratlfled with moralnal debris, glacial ice, or snow to form Irreg ular hummocks or more even mantles. In the late summer, tills sand may even take the form of active sand shadows or drifts, temporarily formed against parts of the glacier terminus. i o 6 Extending 2.5 tan. westward from the glacier is a flat, eolian sand sheet, in places unrippled and largely underlain "by compacted 3ncw (a niveo-eolian mantle®) (fig3 . ^9 and 50)* In most of this area, a tri angle formed by the glacier and two shallow outlet streams, only scat tered, partly 'buried "boulders are found. The sand sheet has only moderate sorting and over much of its area shows the clear outlines of 3 and-wedge polygons (fig. Ul) • West and on either side of this area, sand-mantled surfaces cover the valley ‘bottom hut are spotted with "boulders and partially stabilizing desert lag pavements. lie re, the presence of extensive underlying snow layers ha3 not been proved. Extending down the north side of lower Victoria Valley at the western end of the dime belt is a field of vhaletaeh-sh&ped eolian mantles, each about 0.5 to 1 km long (frontispiece). These deposits, covering broad mounds of morainal debris, merge into vague sand undulations and desert pavement north of lake Vida. These mantles exhibit the following characteristics and differ from the true dunes below Packard Glacier as: (l) they usually possess an elliptical plan and are elongated east-west, • 2 Cailleux (1962a) has discussed these mantles of all types found in the lower Victoria Valley in more detail and has referred to the features interstratifled with snow as "manteau niveo-eolien" or "niveo-eolian cover •11 Cailleux notes: "Le terne meme de niveo-eolien a et6 propose sur le terr&in par Van Strelen, lors d*une excursion du Congres (Sedimentation et quatemaire) en Campine, en 19^6 , «t a et6 aussitot adopte.” figure ^9 * gand sheet (eolian mantle) at front of Lower Victoria Glacier* View northwest* Figure 50. Cut made by outlet of Lower Victoria Glacier in sand sheet showing interstratifled snow* 1 0 8 parallel to the predominant wind direction; (2 ) they are thin and low (less than 10 m) and shew no slip faces; (3) they often reveal large, half-hurled boulders of nora Inal origin; (h) they are more often underlain by, and interstratified with thick beds of compacted 3now (fig. 51) than are the dunes, consequently, they are more subject to slumping and polygon formation; (5) surface 3ands are less well sorted than are dune sands (fig. U7), sane small pebbles are found; and (6 ) perhaps because of the coarser texture, the ripples are larger than cct the dimes (fig3 . 52 and 53) • Figure 51* Portion of vhaleback eolian mantle showing interstratified snow. View southwest across lake Vida. 1 0 9 Figure 52. large ripples of vhaltiback-shaped eolian mantles. Note smaller superimposed ripple. Figure 53. Ripples of a barchan dune. Note size compared to figure 32. 1 1 0 The westward limit of tins close-packed dune "belt in this collec tion of mantles may he controlled by a decrease In the intensity of sand flow (Bagnold, 19*1-2 , p. 221)* This in turn can he ascribed to a dissipation of carrying power of the wind as It moves west. Figure 52, showing bi-directional ripple narks, suggests also that these dunes and mantles are probably the resultant of a major and minor wind direc tion, east and southeast respectively. It has been indicated here that most of the thicker accumulations of wind blown sand are lnterstratlfied with snow in various stages of compaction. This suggests that same sand is deposited in the colder months when the ground remains 3now covered. It was also observed that sand deposition is at times rapid enough to bury and permanently pre serve early summer snow layers. t Pebble Ridges General Transverse wind ridges and ripples are common over sandy and pebbly parts of the valley mantle deposits of the Victoria Valley system. These features differ from the larger dunes in that the coarsest material collects at the crests or on the slip face, and they differ from ripples in that their "size and wave length increase indefinitely with time, HI rate of growth depending on quantity of coarse material available and on intensity of the oncoming saltation" (Bagnold, I9U2, p. 1^5 ). The pebble ridges In ice-free areas of southern Victoria Land^ are best developed in well-sorted outwash (fig. 5*0 # but are also found on the flat-lying, 3tony morainal material (fig. 55). The ridges are 2 to 50 cn high, up to 20 m long, and are slightly concave toward the direction of strongest wind (southwest in the Victoria Valley sys tem). They characteristically display steep lee slopes (20* to 35*) and more gentle windward slopes (10* to 25*). The wave length is vari able, but lengths of 3 to 5 n are most common here. The crests and lee slopes lack noticeable amounts of sand or silt to a depth of 5-15 cm# being composed of the largest wind-moved stones (pebbles or even small cobbles). This material is too large to be moved directly by the wind. On a till surface with a wide range of sizes, the trough surfaces are often partly bare of coarse sand cr pebbles but con tain scattered large cobbles and boulderc too large to be moved by direct wind or saltation Impact. Between troughs and crests, the area is often paved with pebbles, usually slightly smaller size tliar. those at the crest and slip face. Very fine pebble ridges are found on the outwash gravel terraces near the Hot!3 Clscier and ir. Alatna Valley (fig. 2 ). Debenhom (1521a, p. £5-65) has also described gravel-drifts formed in the lee of kills of Cape Evans, Ross Island. 1 1 2 ^igure Pe'btle ridge In gravel of Ala tea Valley, ’-rind "blare from right to left. Figure 55 • Pebble ridge in till surface southeast of Lake Vashka. Wind noved from ler.rer right to upper left. View east in Larvick Valley. 113 Figure 56 shews details of the well-foraed pebble ridges developed In ground moraine southeast of Lake Vashka. These ridges are the highest and contain the largest pebbles of any in the valley system. Bounded dolerite pebbles as large as 6 by h by 3 cm are common on the crests and slip faces. These pebbles are stable; their undersides often show a well-developed salt encrustation. Smaller pebble ridges developed in cutvash gravels nearby are not stable. VentIfacts are common among the pebbles of all ridges, but often their orientations suggest tiiat they were cut before their inclusion in the ridge. However, strongly wind- cut faces occur on the large boulders within t*ie trough areas and the orientation of these faces corresponds to the present wind direction. Formation It Is clear from the arrangement, orientation, and composition of these pebble ridges that the;'’ are wind formed. The origin of similar features is discussed 'ey “agnold, (l?^2 , p. 1J&-157)• lu addition to strong winds, the conditions of ridge growth according to bagnold include: adequate supply of large grains between 3 bo 7 times the mean diameter of the prevailing saltation; a constant supply of 3and to provide the necessary motive power in the form of saltation; the saltation must not be too intense; and the wind must not reach the threshold strength at which it can dislodge the crest grains. U k u H i o r t 5 6 . M a l i of pottblo r U | H in ground aomlnt 1 km aouthamot of L ate Vaahkm, Banrlok YaUagr. Skntoh aada fcy aaaartillng eroaa aootlooa w r uyid la flold. hrtleli also iialyili abeam kgr viltfd pvemt* Although the pebbles are too large to be moved directly by the wind, they creep along the surface under bombardment by sand grains. They move from the troughs on windward sides to the crest and lee sides where they are out of reach of the saltatJLng grains. Thus, both sand and pebbles are removed by wind action from the troughs, leaving only silt particles which are undistrubed because they remain below a pro tective surface layer of air (Bagnold, 19^2 , p. 90). Wind Velocity The minimum wind velocity required to set great numbers of sand particles in motion can be determined only approximately. The smallest stone which might move a pebble of 4 cm diameter (particle size on ridge crests) is assumed to be 0.57 cm in diameter, this being l/7th of the large pebble size (Bagnold, 19^2 , p. 155) • The initial wind velocity (fluid threshold velocity (vt) required to set dolerite pebbles of this size in motion is, according to Bagnold (19^2 , p. 100-101): vt ■ 5.75 gd log z/k where, A coefficient far air (.1 - an empirical constant) S' density of grain (2.85 gm cm-3) density of fluid (air - 1.22 x 10“3 ^ cjn-3 ) g value of gravity (983 cm sec*2) d grain diameter (0.57 cm) z height of velocity measurement (0.29 cm) k roughness factor (normally l/30th d or 0.019 cm here) 116 For the given conditions: vt x 12.45 m/sec, or 24 knots. Assum ing a logarithmic relation "between wind speed and height, this is equi valent to H I knots at 3 m above the ground. Many simplifying assump tions have been made Including: (1) That the surface consists largely of 0*57 cm diameter pebbles with only a few 4 cm pebbles to be moved. (2 ) That the surface under the 0.57 cm pebbles is flat. (3 ) That the small surface pebbles are spherical. Debenham (1921a, p. 65) noted that at Cape Evans, Ross Island: Whenever the wind force rose above 90 miles per hour, the roof of the hut was bombarded by large pebbles the size of the pebbles must have been considerable, for they produced a loud rattle on the roof, easily heard above the roar of the blizzard. To produce the pebble ridges of the Victoria system, strong winds must have blown over a long period of time. Because the coarsest pebble ridges are now stable, it appears that the southwest winds havebeen more prevalent or stronger in this area in the past. Ventif acts G eneral Wind-worn stones (ventifacts) are abundant, and are widely distri buted in the ice-free areas of southern Victoria Land. They are still being formed. Strang wind has combined with other agents of erosion and 117 weathering to form a variety of shapes, hut here ve discuss only the rocks shaped and polished mainly by the wind. These are abundant on the floors and are scattered through the upland areas of the Victoria Valley system. The following discussion is based on measurements of over 500 ventifacts. The ventifacts range In size from 1 cm to 4 m. The small ones are common on the older surfaces; the large ones are more common on the youngest surfaces. The western faces of boulders, especially those of sandstone or dolerite, generally exhibit one or two well-developed, smooth, broadly convex faces while opposing faces are weakly developed and may be oxi dized, pitted, or exfoliated. Small cobbles and pebbles often show irregular or various ridge-shaped, two-faced types described by Sohoewe (1932). Factors of formation and distribution Conditions controlling the local formation and distribution of ventifacts are: (1) Wind pattern and velocity. (2 ) Exposure and stability of the surface. (3) Presence of fine-grained rocks. 1 3 6 Moat of the well-developed ventifacts are In areaa exposed to the strong winda from the southwest. Usually they occur only oo stable surfaces not subject to sollfluctlon or other disturbances. Only the fine-grained rocks are very well polished. The most conaaon rock types forming ventifacts in the Victoria Valley system In order of decreasing tendency to preserve polish and wind-cut faces are: Black, basaltic dike rocks Ferrar Dolerltes Green and tan, quartz it ic or silicious siltstone Beacon rocks Fine-grained dolerite sill rocks Ferrar Dolerltes Quartzits and quartzitlc sandstone Beacon rocks Green, red, brown, porphyry dike rocks (rhyolltes?) Vanda Porphyry Medina-grained dolerltes Ferrar Dolerltes Fine and medium-grained sandstone Beacon rocks Granitic rock types basement rocks Finely carved, many faced ventifacts are most abundant in the eastern half of Berwick Valley, particularly where it meets Balham Valley, and on the sand-free slopes on the southern side of lake Vida. Above the valley floors, well-developed ventifacts occur in fine-grained dikes on the summit of the Mt. Insel mesa and at the western end of the valley of the Clark Glacier. Ventifact development is particularly poor in the westerly portion of upper Victoria Valley, in Berwick Valley west of Vashka, in western Balham Valley In the vicinity of Lake Balham, 1 1 9 and on the western portion of Bull Pass. Here, one or more of the required conditions is lacking. Pita, flutes , grooves, and faces Examination of these features was generally confined to cobbles and boulders which were stable, so that Inferred wind directions are reliable. Pits of varying dimensions, occurring singly or in groups, are found on fluted, grooved, or Irregular surfaces of cobbles and boulders. The daalnant features of the wind-cut pits are as follows: (1) They are preserved only on unexposed surfaces. (2 ) They are pin-head to several centimeters In diameter. (3 ) The largest and most symmetrical pits occur In the coarse-grained rocks. (k) They are usually completely wind polished. (5 ) They often represent differential etching of Individual crystals In coarse-grained rocks. Pits often thought to be wind formed but probably a result of cellular weathering are common in the Ferrar Dolerltes. These have the following characteristics: (1) They occur most often in clusters on unexposedsurfaces. (2) They are nearly always vertical. 1 2 0 (3 ) They average 5 nm in diameter and more than 5 mm deep. (U) They may frequently occur more them a meter above the ground. Flutes, or wind-formed furrows which open at one end, are ccnmton on the southwest and western sides of cobbles and boulders In the Vic toria system. These forms show the following features: (1) They occur in homogeneous fine-textured rocks as well as in the coarser and prophyritic rocks. (2 ) They assume a scalloped shape on nearly flat faces in the early stages of development. (3 ) They are developed commonly on faces inclined less than 4 5* on windward surfaces through the horizontal to less than 20" on the lee surfaces (fig. 57)* (If) They are short and deep when on windward surfaces inclined up to 53*• (5 ) The longest flutes measured were 16 cm and the deepest were 6 cm. (6) They normally open down wind. (7) They may originate or end in pits. Grooves are larger, often more shallow than flutes, and open at both ends. Grooves show the following features: (l) They are usually intimately associated with flutes. 1 2 1 WIND VARIOUS ANCLES OF UNDERCUTTING Figure 57 * Range of inclinations of various imprints of vind abrasion typical of larger ventifacts. Inclination with the horizontal shown by tangents to hemisphere. 122 (2 ) They are u s u a l l y inclined less than 30* and average 13 * on windward sides. They may occur on the lee sides of ventifacts and are common here at very low inclinations (fig* 57) • (3 ) The deepest forms occur in coarse granular rocks parallel with wind direction. (1)-) They are usually independent of mineral hardness and rock structure when parallel to the wind. Faces cut by wind or facets (generally considered to be flat faces) which are being actively abraded show the following general characteristics: (1) They lack distinct pitting, fluting, or grooving especially if they are inclined more than ^5° facing the wind. (2 ) They are poorly preserved on coarse-grained rocks. (3) On fine-grained sandstones and igneous rocks, windward faces are often dull or show a luster different from that normally displayed by the stone. Opposing leeward surfaces are covered by a more lustrous, smooth, limonitic stain or by desert varnish (fig. 58)• In the simplest and typical unidirectional case of wind cutting, an isolated boulder shows one strongly cut, broad, steeply-inclined face (usually facing southwest). This face is: (l) Broadly convex, transverse to the wind and very slightly concave, resuplnate, or overall convex parallel to the wind direction. 123 (2) Steeper at the base and more gently infeijped upwards (fig. 59), with an average inclination ng to 35 cm height of 5^*. Figure 5 8 . Ventifact of dolerite shoving lower actively cut face and greasy, varnished top face cut by flutes, pits, and a few grooves. Individual boulders usually show a convex profile with the distinct break in slope between 10 and 30 cm height (contrary to slightly concave profile of compos ite-figure 59). 12 k Ui 3 5 53 3 O (0 30 53' u. o WIND DIRECTION ut 2 0 47 o ID < 2 15 53' O AVERAGE SLOPE z = 54° + 56' I- X o in X 56 65 Figure 5 9 . Average Inclinations of lower wind-cut face on stable boulders or large cobbles. Connected points show one possible average profile of wind-cut face of boulders. 125 Faces which are in the plane parallel to the wind seem to he more common where the initial surface is more gentle. This lower, "broadly convex face is developed either from a flat hroad surface largely at right angles to the wind, or through the rounding of an original sharp leading edge dividing two faces oblique to the wind (fig. 60). This suggests that on large boulders projecting above the denser sand-laden wind, two good faces are not developed by w indsplitt ing. WIND TIME = Q Figure 60. Plan diagram showing rounding action on boulders or large cobbles with two different initial windward surfaces. A second more irregular and gently inclined "top face" or series of faces is sometimes found on smaller boulders and cobbles above the lowest face. These faces have the following characteristics: (1) They are often grooved, fluted, or pitted and weathered. (2 ) They have an average inclination in the windward side of lV (3) They are often formed from modified Joint surfaces. 126 Undercutting was observed on some cobbles and boulders resting on either bedrock or on surficlal deposits* This is most common, on the southwest side where the average depth of undercutting was 2 0 cm and extended to a height of about 10 cm. Shapes of cobble and pebble ventifacts Ventifacts, less than about 8 cm high show the most finely cut forms (figs. 6 l,6 2 ,6 3 >610 . Seme with a multiplicity of facets (poly gonal shaped) resemble a carefully cut gem (fig* 6 l upper right). Pyramid and truncated pyramid shapes are q.uite common as is the three- faced drelkanter variety. What determines the shape of ventifacts and the final end product in wind-cutting is not known. A faint tendency of the smallest venti facts, largely those that are less than 5 cm diameter, to assume the truncated pyramidal shape is recognized (fig. 62). The true pyramid shape (more rare) would often appear to be formed from both ridge-shaped ventifacts with near rectangular bases and truncated pyramidal-shaped ventifacts. However, this is stated without Important substantiating proof• Wind abrasion by blowing ice In some areas where surficlal sand is lacking or in very short supply, abrasion by blowing ice, particularly in the winter, may be Figure 6 l. Ventifacts cut in fine-grained basaltic Ferrar Dolerltes. Actively cut face at right. Figure 62. Very small ventifacts cut in fine-grained dolerite (brazil- nut at left and ridge or elnkanter right) and in siltstone-fine sandstone of Beacon rocks (pyramid and truncated pyramid or polygonal, center 4). 028 Figure 6 3 * Ventifacts cut In Beacon sandstone-quartzite (ridge & pyra mid at left and center); (laminated Beacon siliclous silt stone (lower left); and in Olympus Granite-Gneiss (polygonal upper right). Figure 61*. Ventifacts cut in fine-grained, Basaltic Ferrar Dolerites. Actively cut face at lower right. Shapes above are most ccumon for ventifacts of this size. 129 required to explain freshly cut face% and In sane cases, the partially polished Interiors of pits. Examples of such areas are on the summit of the Mt . Insel mesa and above the western end of the valley system at 2,000 m elevation* In the latter area, wind-polished and pitted dolerite bedrock and boulders project as islands above surrounding ice and snow fields of the inland ice plateau edge. Strong, but infrequent and sporadic southwesterly winds observed in the summer on the valley floors may not be capable of the extremely strong cutting on the southwesterly sides of ventifacts. In the winter these winds might carry quantities of abrading ice which would be hardened by the lower temperatures. Experiments and evidence collected by Teichert (1939), Black- welder (l9*tQ), and Sharp (19^9) (see summary by Fristrup, 1953, P. 57) suggest that the very minimum temperatures so far recorded on the floor of the Victoria Valley system (approximately -30* C) would produce an ice particle between and 6 in hardness. However, the average tempera tures would be much higher and therefore hardness would be less than It through most of the year. Although most of the minerals which must be cut by the snow are harder than k, it is probable that the velocity and duration of the wind drifting ice and snow are as important as particle hardness in abrasion; 130 at high speeds, fluid friction varies as the square of the velocity. In addition, occurrences of straws piercing telegraph poles or pine hoards being carried through palm trees (Tannerhill, I9I+4 , fig. 66) during hurricane winds are frequently recorded and indicate that there are factors other than hardness of the particle to be considered in wind erosion. Meteorological significance— a gumnf*--ry The occurrence of strongly abraded surfaces facing the southwest quadrant and the poorly abraded easterly surfaces suggest that: (l) at present, these southwesterly winds are by far the strongest; (2) repe titious, stranger, actively abrading winds have blown from the east through m&ch of the valley system in the past; (3 ) infrequent, very strong southwest winds observed in summer may have a greater abrasive capacity than the steady, simmer easterly winds or - southwest winds are stranger and more persistent in the colder months, and therefore a large part of the wind abrasion takes place in the winter. Although nothing is known of the winter wind direction at velo cities in this area, the latter possibility seems to explain the south westerly faces best. Nichols (1961b, p. Ill) has attributed cutting of south-facing surfaces on ventlfacts at Marble Point (fig. 2) to stronger winds during the cold months. 1 3 1 Significance in estimating age of moraines Probably ventifacts were formed during earlier glacial episodes but few buried, soled, or striated ventifacts have been found. Wind abrasion may be very rapid under ideal conditions. Glass bottles left In the Kamid Desert, southwest Africa were completely cut through in 24 years (G. Khetsch, oral communication). Evteev (1 9 6 1 ) noted that 5-7 cm pits have been cut into a melitlte basalt in the region of Gaussberg, East Antarctica since 1901, With such rates of abrasion ventifacts might be found even on the ice-cored moraines; however, these and other fresh and hummocky moraines are not stable, they have irregular surfaces, and sand is often deficient, so that the ventifacts have not formed. Old subdued morainal areas are favorable to ventifact formation. Therefore, ventifact development only secon darily reflects age of moraines. Weathering Cavernous Weathering General The most obvious processes of weathering affecting the erratic boulders, frost-riven blocks, and bedrock outcrops In the valley bottoms are those forms of differential, granular disintegration and exfoliation 132 which result in irregular, odd-shaped rocks. Hollows, pits, potholes, niches, or tafoni are common and therefore these rocks are discussed under the term "cavernous weathering" (Cotton, 19^2). in the Victoria Valley system this type of weathering has been used to determine relative ages of moraines (p. 1^2 ). Cavernous weathering occurs in several parts of the world. In Antarctica, cavernous weathering in "boulders has been reported frcm the Antarctic Peninsula (7 9 * W) (Nichols, 1953/ P* ^9-56) to "Bunger's Oasis" (102* E) (Arsyuk, et al., 1956, p. 36). In the McMurdo Sound area, this phenomena has been described by Ferrar (1 9 0 7 , p. 8 7 -8 9 ); David and Priestley (1907/ P* 305-307); Priestley (1923# P* 28-33); Wade (19^5, P* 72-75); and Webb and McKelvey (1958, p. 138)* In southern Victoria Land, cavernous weathering in medium to coarse-grained rocks produces a series of forms. Weathering begins with the granular disintegration and exfoliation of the rock corners and pro jections, and follows with the development of hollows and more open niches. The hollows broaden and deepen until they coalesce, producing much nailer residual or nubbin boulders which may be free of irregular ities. Such cases may be hard to recognize if the resulting debris has been removed from the rock base. With continued weathering, new hollows develop in a second or, rarely, a third cycle of cavernous weathering. 1 3 3 If the “boulders are small, veil-formed hollovs may not develop “before the “boulder disintegrates completely. Cavernously weathered “boulders are found on nearly all till sur faces and an “bedrock surfaces of the Victoria system, “but they are best developed on the intermediate to young tills of the valley floors. The hollows are varied In form (figs* 6 5 , 6 6 , 6 7 , 6 8 , 6 9 ) (See Blackwelder, 1929; Anderson, 1931). The "case-hardening" and glaze common In tem perate climates (Anderson, 1931) is poorly developed In the Victoria Valley system* Some of the most bizarre forms are in areas of the well-Jointed Ferrar Dolerite sills, for example at the southwestern corner of Lake Vida (fig* 6 7 ) and at the southwestern end of Bull Pass. The hollows developed In the dolerites are generally larger and more irregular than for those in granitic rocks. The sheltered surfaces of the weathering hollows often display crumbling scales and spalls. Piles of fresh debris are occasionally found within hollows and on the lee side3 of boulders indicating that after the exfoliation or granualr disintegration no further decomposition occurs. There is no preferred orientation to the hollows developed by cavernous weathering. However, hollows are slightly more numerous and 13** figure 6 5 . Cavernously weathered erratic of Vida Granite, in cirque south of Lake Vida. ligure 6 6 . Hollows of weathered and jointed bedrock of Vida Granite. View south fran the southeast end of Lake Vida. 135 Figure 6 7 . Cavernous 2y veathered 'bedrock projections of dolerite. Looking northeast from pass between McKelvey and Victoria Valleys. Figure 6 6 . Cavernous ly veathered boulder of Olympus Granlte-Gneiss In Bull Drift, Clark valley. 136 Figure 69* Medium-grained dolerite boulder In second cycle of caver nous weathering, Bull Drift of McKelvey Valley* numerous and larger nearer the ground. This is particularly true for the finer grained dolerite rocks where exfoliation is often noticeable in a band a few centimeters above and below the ground. Processes of formation Wind Many people have attributed the hollows to wind abrasion. To test the hypothesis, a study of cavernous weathering was made on the erratic boulders in lower Victoria Valley* Winds in this valley blow from either the northeast or the south west; very few of intermediate direction have been recorded. Winds 1 3 7 from the northeast are more common but less strong than those from the southwest. The orientation was measured for 100 hollows In a group of highly weathered boulders more than 70 cm high near the center of the valley one kilometer east of Lake Vida. Plotted orientations (fig. 70)are accurate to 3 °* The uniformity of the orientations was tested by the chi-square method (Pincus, 1953; P* ^92-^93)• Dividing the directions into 40 segments, the chi-square is 9*12* This corresponds to a probability value of less than 0 .0 5 ; meaning that there is less than a 5 percent chance that the observed distribution is significantly different from uniform. It is concluded that in this area there is no relationship be tween wind direction and hollow orientation. Other evidence against the direct effect of the wind in the for mation of the hollows is: (l) the noticeable lack of wind polishing on the feldspars of the granitic rocks; and (2 ) the development of hollows opening from narrowly separated joint surfaces. Deflation cuts in the coarse-grained boulders are clearly visible on the western basal portions of many boulders and are often several centimeters deep. They are readily distinguished from hollows discussed above by their relation to polished surfaces and ventifact orientation. 138 < Figure 7°* Orientation and depth of hollows of cavernous ly weathered, erratic "boulders. Boulders are of granite and granlte-gnelss and are on ground moraine at east end of Lake Vida. 139 Although it is not the primary cause of cavernous weathering, wind action plays a part by removing the weathering products soon after formation, preparing the way for further disintegration. Crystal wedging Kelly and Zumberge (1 9 6 1 ) have suggested that the formation of halite by evaporation of sea spray may play a significant role In dis integration of rocks near the coast at Marble Point. In the lower Vic toria Valley, a white powder, largely sodium chloride, occurs beneath thin weathering flakes in some of the hollows of the cavemously weathered boulders of Vida Granite (table 5 )• Table 5 . Analysis of white salt from surface of cavemously weathered boulder. Analysis by U.S. Geological Survey, Quality of Water Laboratory, Columbus, Ohio. 11a 0 . 2 0 grams 36.0 percent Ca 0.003 0.3 Cl 0.32 57.0 0.007 1.2 H2 O insoluble (by difference) 0.03 5-5 sample weight O .56 grams The sodium and chlorine content is rather high to have cane frcm the rock itself, but sodium chloride is readily available from the wind- carried sea spray or from local saline ponds. 11*0 Thin crusts of mixed salts are found on many boulders in the Vic toria system and in neighboring areas (Ferrar, 1907, p. 8 8 ; Bull, oral communication). On a large Vida Granite erratic east of Lake Vida, a calcium carbonate crust extends from 1.2 to 3 1 above ground. The salt may be wind-carried from the moraine surface to the east. The presence of the salts may suggest one type of crystal growth wedging, but other types may also be effective. Cailleux (1 9 5 3 , p. 1 3 2 ) suggested a process which may be effective in forming hollows in this region: . . . we Imagine a climate cold enough that the rock eventually freezes permanently to a great depth. Being exposed to the sun, the exterior reheats and thaws, while the bottom of the hollows still remains below 0° C or around that temperature. From thet time on, because of the cold face, water vapor toads to condense there, the water sinking into the smaller Interstices; night or winter comes, the boulders refreeze, breaking the rock into splinters, grains of sand, or dust. Thus the hollowing accentuates itself (translated). Many workers have noted that surface temperatures of rocks during the sumner months along the coast of Antarctica or well inland may exceed the air temperatures by as much as 5 0 ° C (Rudolf, oral communication; Siple, 1938). The difference between the temperatures at the boulder's surface and at the backs of the hollows in Victoria Valley exceed 3° C. More than 31* freeze-thaw cycles of air temperature were measured between I k l 5 December 1959 and 31 January, i9 6 0 at lake Vasbka (fig. 10). Probably the number of cycles at the rock surface exceeds this. Chemical weathering Blackvelder (1 9 2 9 ) and others have ascribed cavernous weathering to mechanical disintegration by expansive chemical changes such as hydration, carbonatlon, and oxidation * However, Kelly and Zumberge (1 9 6 1 ) in a study of the weathering of a quartz dlorlte at Marble Point noted that oxidation of ferrous iron in pyrrhotite and biotite to pro duce llmonite is the only appreciable change involving an original con stituent of the rock. They also note that volumetric changes caused by oxidation and hydration of original minerals is negligible. In spite of -the 3tudy described above, phenomena which may suggest chemical weathering are observed; for example, the very rapid disinte gration of the mafic rocks (coarse-grained dolerites) compared to the granitic rocks. Presence of saline ponds, and efflorescent segregations on the permafrost table (See p. 1 7 8 ) testify to the presence of chemical weathering. However, Gibson (1 9 6 2 , p. 373) notes: Evidence of the slow process of chemical weathering in a frigid climate becomes detectable In this region only because arid conditions permit the liberated salts to accumulate over a long period or time. 142 Application of cavernous weathering to glacial chronology General The cavernous weathering Of boulders has been used to determine the relative ages of moraines In the Victoria Valley system* The method was originally applied to the lower Victoria Valley (Calkin and Cailleux, 1 9 6 2 ), but later was applied to deposits elsewhere. In lower Victoria Valley, erratic boulders of coarse-grained Vida Granite and Olympus Granite-Gneiss occur on end and ground moraines A, B, C (fig* Tl)» These moraines were deposited by the Lower Victoria Glacier. The cavernously weathered boulders considered here lie In a desert pavement of ventifacts or among thin eollan sand mantles, or, in the case of moraine A, on a very thinly mantled bedrock surface. A tentative chronological arrangement of the morainal deposits had been made by various methods, but it was felt that the best estimate of rela tive age would be obtained by measuring quantitatively the weathering in the boulders. Two assumptions were made before undertaking the study; first, that the hollows were formed after the boulders were transported and, second, that the weathering of very small boulders might be Influ enced by local micro-climate and topography. Therefore, as an arbitrary standard, only boulders more than 3° cm high and 70 cm long were considered. 1^3 RfcCKARD GLACCR KILOMETERS Figure 71. Sketch map of the lower part of Victoria Valley shewing morainal deposits A, B, and C . An area on each moraine was selected which appeared to represent the average weathering. In each area, about 50 boulders of standard or larger size were measured, as encountered. The height and length of each boulder, and the number and depth of every hollow deeper than 9 cm were recorded. Where hollows had coalesced or where irregular recesses has been formed in the boulders, the greatest depth of weathering was measured from an Imaginary surface representing the pre-weathering shape (fig. 7 2 ). Errors in depth measurement due to irregularities in the original boulder shape are probably small. Ikh Figure 72. Measurement of weathering depth (B is side view of A). Results and possible conclusions Data shown in tables 6 and 7 show that cavernous weathering In the boulders Is greatest in moraine A, and least in moraine C. It is inferred that A is the oldest and C is the youngest deposit. This se quence agrees with the chronology Inferred from the relative position of the deposits. Figures in table 7 suggest that the hollows in the granite boulders are slightly deeper than those in the gneiss boulders, but the two rock types show no other important differences. This is due to the similari ties of mineral composition and grain size. This method has also been applied rigorously to tills in the upper Victoria, Berwick, and Wright Valleys and Bull Pass (table 8 ), and qualitatively to compare weathering in other areas, both in bedrock and on boulders. Table 6 . Percentages of boulders with hollows. Gn * Gneiss PG ■ Pink granite Tot ■ Gn + PG Number of Number of boulders with $ of boulders Boulders hollows with hollows Gn PG Tot Gn PG Tot MCRAINE A (OLDEST) Boulders: Total 37 13 50 30 13 43 8 6 Lower than 50 cm 20 2 22 13 2 15 68 Higher than 50 cm 17 1 1 26 17 11 26 100 Shorter than 120 cm 20 3 23 14 3 17 7^ Longer than 120 cm 17 10 27 16 10 2 6 96 MCRAINE B (OLD) Boulders; Total 1 1 35 46 6 20 2 6 57 Lower than 50 cm 5 16 2 1 1 10 11 52 Higher than 50 cm 6 19 25 5 10 15 60 Shorter than 1 2 0 cm 7 16 23 3 7 10 43 Longer than 120 cm 4 19 23 3 13 l£ 70 MORAINE 0 (YOUNGEST) Boulders: Total 4 46 50 1 5 6 12 Lower than 50 cm 1 20 21 0 l 1 5 Higher than 50 cm 3 2 6 29 1 4 5 17 Shorter than 120 cm 2 29 31 0 2 2 6 Longer than 120 cm 2 17 19 1 3 h 21 ll*6 Table 7 . Characteristics concerning hollows. Average number of Percentage of hollows hollows per boulders deeper than 20 cm with hollows on big boulders Gn PG Tot Gn PG Tot Moraine A (oldest) 2.2 3*° 2 *5 60 €h 62 B (old) 2.3 2.2 2.3 43 62 58 C (youngest) 1.0 1.0 1.0 0 0 0 Average 1.8 2.1 1.9 3^ ^2 1*0 # Big boulders - Higher than 50 cm and longer than 120 cm. This method can only be used with success on the granites or gra nitic gneisses with low percentages of platy minerals. With the Ferrar Dolerites, the development of cavernous weathering depends so much on texture and mineral composition that the assessment of relative age is not reliable. Other difficulties arise because the boulders on the older tills may be in a second or third cycle of cavernous development. Surficial Boulder Frequency The procedure for obtaining the frequency of surficial boulders and determining percentages of the major rock types was as follows: Three Table 8* Sunmary of cavernous weathering data for granitic boulders rH £ (Summary of data as lake Vashka to assembled similar S. side lower E. side upper Webb Glacier to tables and ) Victoria Valley Victoria Valley (Berwick Valley) Relative age (Packard, P V BP pa V Bb P V V B V? Vida, or Bull Drift) Boulders: Total 12 56 8 6 36 51 60 100 28 20 60 83 8 8 44 Lower than 50 cm 5 52 6 8 28 63 62 100 19 17 40 57 90 43 Hirtier than Higher than 50 cm 17 60 100 26 33 59 100 39 22 69 87 87 45 Shorter than 120 cm 6 43 74 36 50 60 100 32 22 42 8 2 75 50 Longer than 120 cm 2 70 96 33 53 60 100 21 17 66 88 95 36 Average number of hollows per boulders with hollows 1.0 2.3 2.5 1.3 1.4 2. 6 3.4 1.8 1.3 2.4 2.3 2.5 2.7 Percentage of hollows 20 cm depth on big boulders (> 50 cm high and ^ 120 cm long) 0 58 62 0 22 37 42 2.5 0 13 47 33 3.1 anearer glacier ^Boulders located on far eastern end of ground moraine and not typical of whole moraine where 2nd stage cavernous weathering more typical. 1A8 hundred meters were paced off, when possible, in a Btraight line of arbitrary direction. Over this course, every boulder over 2 0 cm hifch^ within arms' reach was counted and its lithology noted. The frequency depends on original number and lithology of the boulders. However, it is also an indication of the degree of weathering and erosion and the relative age of the deposit. Table 9 shows sane of the average frequencies on adjacent glacial deposits. The deposits have been tabulated vertically under the valley in which they occur or fran which depositing ice has moved. Averages of each of the four columns show a rough decrease fran left to right-recent to ancient. This is best shown by comparing deposits of one glacier fran its ter minus down valley, for example 1 5 6 -7 7 - 3 6 for the north side of lower Victoria Valley. Lithology Counts of Pebbles and Boulders Lithologlc counts of the very large pebbles were made throughout the valley area. The pebbles were taken from the surface; it was not possible to dig to the unweathered zone. Care was taken to avoid boulders which were disintegrating, but it is probable that the counts on the older deposits reflect weathering. ^On the Wentworth grade scale, this also includes sane large cobbles. Table 9* Frequency of upstanding boulders on moraines ...... TW\Ao4fe Af V4 A + A r ^ o i —, Deposits of Insel Glaciation PACKARD VIDA BULL IMSEL Location C Avg. Range Location C Avg. Range Location c Avg. Range Location C Avg. Range McKelvey V. Ml 83 249 M 3 e 36 36 M5-7 211 70 41-86 M1 5 -I8 179 24 16-31 - y'A Balham V. Bl,2 137 154 11*6-162 B3-6e 198 50 38-55 MU.12A, 185 6 1 54-75 14® Location - see plate 2 M9,10, 124 33 21-41 C - number boulders 1 12,13 counted Avg.-upstanding boulders Barwick V. per 300 m traverse Etfl,2 222 111 99-l23-*-BW4,5,8, 570 95 43-15^13-17 182 32 13-50 (arms width) i.e. per 10-12 approximately 6 0 0 m^ Upper Victoria V. e end moraine, predeter VU1,3,4, 791 195 71-3^9-^vu6 ,7 , 185 46 31-71-7 VUl6,20 46 23 15-31 mined traverse direction 5 ,8- 1 0 14,15 VU22-24 88 27 12-52 - higher frequency M19-29 453 33 18-51 VU36,38e 101 48 47-48 J - continuous deposits Lover Victoria V. VL1 156 156 VL2 77 77 Mlh 36 36 4l 20 iVL5,7 72 32 10-53 VL11 39 39 VL13 iVL9 e 41 4i £ increasing relative age & distance from glacier vo 150 Two size groups of surface 'boulders vere distinguished for the lithology counts; those between 2 0 and 7 0 cm in vertical and horizontal dimensions and those larger. The frequencies of boulders of selected rock types in each size group are shown on the sample location map (plate 2 - in pocket). For simplicity, the number of rock type cate gories was limited. The function of the surficial boulder and pebble counts is largely to contribute to the pattern of movement of the valley ice tongues. Weathering and Texture of Deposits Within the Active layer Field and laboratory methods In general, the active layer in the deposits is less than 6 0 cm, and frequently it is less than 3 0 cm thick. In addition, distinguish able horizons produced by weathering or soil processes are generally unccxmoon or poorly developed over the area. In consequence, it was practically impossible to obtain definitely unweathered drift samples or samples from a correlative soil horizon. One channel sample was taken at each locality shown in plate 2 (in pocket). The upper and lower limit of the channel sample varied between 1 0 and 6 0 cm depending on the thickness of the active layer. 1 5 1 At selected localities tiro samples were taken, one at depth and one 1 0 cm below the surface* The following were also observed: surface lithology; weathering properties of the active layer; occurrence of calcium carbonate and other salt accumulations; moisture content; and depths to the permafrost table. In the laboratory, samples of the material less than 2 mm were dispersed, sieved, and the results plotted and analyzed according to Inman's method (1952, p. 125-1^5)• Of 140 samples analyzed, 30 were examined for clay content by the pipette method. Results of the labor atory analysis are tabulated with some field data in appendix I. Discussion and significance Field work and laboratory analysis show that the oldest tills are usually much higher in the silt-clay fraction than are the fresher de posits. The percentage of clay itself appeared only very roughly corre lative with the percentage of silt-clay and the weathering of the sur face boulders. The sorting is also slightly poorer in the older de posits . These relationships of texture and sorting are unusually well displayed in the surface of the ground moraine of the Upper Victoria Glacier where a general decrease in mean grain size, increase in the silt-clay fraction, and decrease in sorting is shown with increasing distance from the present glacier terminus (fig. 7 3 ). 152 3 0 2 5 ' <20 ■ 10 1I 2 - Z < _ Z 0^ I i " ■ ■ i------1 I O K* [R^CKARD DRIFljj DRIFT j(0ULL DRIFT) > o * * A EFFECTIVE DISTANCE FROM PRESENT UPPER VICTORIA GLACIER TERMINUS IN KILOMETERS ' Figure 73* Textural relationships of particles of sand and silt-clay from active layer of till deposited hy upper Victoria Glacier. See plate 2 (in pocket) for sample locations. 153 These particle size relationships can he explained In two dis tinct ways, (l) Most of the old morainal deposits may he finer tex- tured because they were carried beneath or within the glacier end deposited by lodgnent; the younger tills were deposited by ablation where more washing or wind sorting segregated the fine and coarse particles, whereupon the former were carried off by wind or water* (2) The older deposits have been more weathered than the younger and as a result have acquired the finer texture and poorer sorting. Seme evidence for a lodgment origin for the oldest glacial deposits is suggested by the shape of McKelvey and Bulls eye end Moraines discussed later (p*1 9 l)* In addition, striated boulders, suggesting subglacial transport, are plentiful at at least one locality of very old (Bull) till. They are also present in young (Vida and Packard) tills west of Lake Vashka which have an exceptionally fine texture com pared to the other deposits of the same age. There may also have been less outwash produced and hence possibly less ablation during the earli est glacial times. Had the silty deposits ever been as sandy as those of the present, it is probable that polygons would have formed In them at one time. It is also possible that fossil polygons - i.e. concen trations of boulders, might be preserved in these areas now silty. Such fossil forms were not recognized over much of the older till. 15^ Much evidence nay also he gathered to support the second (weather ing) hypothesis. The rocks carried and deposited by the glaciers In the Victoria Valley system, with the exception of sane homfels and schists most cannon west of lake Vashka, are granular types which would probably not readily produce large quantities of rock flour during glacier transport. In addition, outlet streams at present do not carry rock flour and those very fine materials at the base of the gla ciers are largely wind deposited. Thus, even if deposited by lodgment, the percentage of fine material would be low. Mechanical analysis of boulders of more than 30 cm diameter, disintegrated or decomposed in situ in old, silty Bull till is as follows: Lithology 2mm Sand Silt-Clay Medium-grained granit gneiss 80 16 2 Green harnfels-schist 53 36 11 Coarse-grained dolerite A. 55 fcl ^ B. 33 6 2 5 It seems certain that a much greater percentage of this fine material may originate from in situ disintegration or decomposition of the same volume of glacial deposited pebble or sand material so common in the younger moraines. The poorer sorting in the older deposits may also be result of this in situ weathering. 155 Hare work is needed In this area to settle the origin of the t silty deposits. It Is likely that If truely unveathered samples could be taken from below the permafrost In the silty deposits, their simi larity or dissimilarity with samples from the active layer might shed considerable light on the problem. However, the weathering relations mentioned above together with field observations suggest that at least a large part of the textural differences from old to young tills may be a function of weathering, Influenced by time and climate; therefore, with some caution, textural differences are a reliable criterion In the overall determination of glacier activity and sequence of deposition in the Victoria system (table 10). The other criteria associated with in situ, sub-or near-surface weathering have been used with somewhat less regularity and success. Desert Varnish Most rocks able to maintain fine wind-cut surfaces display desert varnish (figs. 58, 6 l, 62, 63/ &*■)• The medium and fine-grained doler- ites and basaltic dike rocks usually show the most uniform and best developed varnish. This varies In color from black to light brown and is best developed near or below the ground line and in the rims of pits and shallow hollows. The ventifacts show good varnish even on the undersides although varnish is absent from those surfaces being actively Table 10. Sane average textural characteristics of till* particles, less than 2 mu size, from the active layer. (Grouped according to major depositing ice source - first listed nearest valley head and Ice source) Sample # Silt-Clay Phi Mean Phi Deviation (See plate 2) Diameter (sorting) (based on 3 sand fractions plus silt-clay fraction) Deposit Number Number of Samples Avg. Range Avg. Range Avg. Range McKelvey Valley SM 1 P 1 7.0 1.1 1.4 SM 2-6 B 5 19.0 9*29 2.3 1 .6 -2 .7 1.6 1.2-1.9 SM 12,13,l4B, I 4 26.8 7-43 2.5 1*7-2.9 1.5 1 .0 -1.8 15 Balham Valley SB 1-1* V-P 4 5-0 2-9 0.8 0 .7 -1.1 1.1 0 .9 -1.5 sbE 5 ,6 ,8-10 B 7 16.4 3-55 1.9 1.9-3-5 1.1 0 .8-1.4 SM 10,11 Barwlck Valley S'rf IB,2,4-6 V-P 6 17.0 5-36 2.1 1.4-2.6 1.5 1 .0 -2.2 14 sw 9,10 B 2 38.5 28-49 2.7 2.4-2.9 1.9 1.8-1.9 Sample $ Silt-Clay Phi Mean Phi Deviation (See plate 2) ^ o ^ Diameter (sorting) ■h ^ © (based on 5 sand fractions plus -| |* silt-clay fraction) q a w Avg. Range Avg. Range Avg. Range Upper Victoria Valley SVU 3 ,6 ,8 ,9 P 1+ 2.8 1-6 1.6 I.6 -1.7 0.8 O.6 -I.1 SVU 10,12B-l8 B 8 26 A 20-36 2.5 2.2-2.9 1.8 l A - 2 . 2 £M 19,21-28 B 9 28.3 11-60 2 A 1.2-3.2 1.8 1.5-2.0 SVU 11,20,21, B 5 23.8 5-1*8 2.3 1.6-2.7 1.3 0.7-1.9 23,2lf Lower Victoria Valley SVL 3-10 P 8 l* A 1-10 2.0 1.7-2.2 1.0 0 .6 -I.3 SVL 16-20 V 5 l*.8 1-8 1.6 1.5-1.7 l A 1.1-1.6 Upper-Lower Victoria and Packard Glaciers SVU 1, SVL 1,2,32 Pres. 1* 3*5 1-10 1.9 1.1-2.8 1.0 o.S-1.3 (superglacial moraine) I - Insel Drift, B - Bull Drift, V - Vida Drift, P - Packard Drift (oldest) (youngest) Phi Units Wentworth Equivalent Phi Deviation (Sorting) Scale 0 - 1 very coarse sand 0*50 - 0.75 - well sorted 1 - 2 coarse sand O.75 - I.50 - moderately sorted 2 - 3 medium sand 1.50 - 2.00 - poorly sorted 3 - b fine sand If - 5 very fine sand * As far as possible definitely recognized lake or solifluction deposits have been eliminated from averages* Deposits largely ground moraine except where noted as single end moraine samples (®). 159 wind abraded and hence is often uncomnon on the southwest faces of ventifacts. The following factors may favor varnish format Ion in the Victoria Valley system (Hunt, 195^i Engel and Sharp, 195o): (1) Arid climate with rise and evaporation of subsurface water or snow meltwater and associated lack of chemical weathering; (2) Abundant medium to fine-grained dolerlte rock of high iron and manganese content, not particularly susceptible to physical weathering; (3 ) Strong winds, forming desert pavements and moderate wind polish. Engel and Sharp (1958, P* 492) note that high temperatures and perhaps strong solar radiation appear important in ventifact formation. The low temperatures of Antarctica may limit the rate of varnish for mation although solar radiation may sometimes raise temperatures of dark rock surfaces 50° C above air temperatures (p. 1^0 ). Although the most distinct varnish generally occurs with the bet ter ventifacts and older deposits, there are many exceptions. In many areas close to retreating glaciers, varnish has apparently developed quite rapidly. The same relations are true for oxidation, a process associated with varnish formation. Therefore, degree of varnishing and accompanying oxidation cannot be used reliably as age criteria on the glacial deposits. GLACIAL GEOLOGY Introduction Previous Work Mercer (1 9 6 2 , p« 7 ) has given a sumnary of the literature on glacier variations in Antarctica, including the southern Victoria Land area* He sunmarizes: "Observations in the Antarctic since 187^ have given this broad picture of glacier variations: (a) Everywhere the ice cover has been greater; (b) In the Sub -Antarctic Islands and much of Palmer Peninsula (Graham land), shelf ice and many glaciers have been receding during recent decades, probably because of rising temperatures; (c) In Antarctica, except for Palmer Peninsula, the ice margins are either stationary or receding very slowly; (d) The Antarctic Ice Sheet as a whole may have a positive regimen. Evidence of the formerly more extensive ice cover in the McMurdo Sound - southern Victoria land area, and the hypothesis of an earlier "flood glaciation epoch" was advanced by geologists of the early British 160 l6l expeditions (Scott, 1905* P* 330; David and Prlastly, 1914* p* 267-269; 5 Wright and Priestlay, 1922, p. 436) . In their disaussIon these workers did not mention more than one advance nor did they attempt to correlate this "glacial flood epoch" in Victoria land with that recorded at other localities in Antarctica (Pewe, i9 6 0 , p. 496). In 1946-47, Hough (1 9 5 0 ) secured deep-sea cores from the mount of the Roes Sea which were believed to span a period of about one million years* After examining the sequences of alternating fine and coarse sediment, he concluded: "glacial stages occurred in the Antarctic which are correlative with the Nebraskan, Kansan, Illlnolan, Iowan and Iete Wisconsin stages of North America*" However, the first terrestrial study and mention of multiple glaciation in this region was by T. Pewe in 1997-98 (Pewe, 1958, i9 6 0 ). At this time, Pewe's examination of the glacial deposits of the ice-free areas of McMurdo Sound and particularly in Taylor Valley revealed (i9 6 0 , p. 4 9 6 ): "at least four major fluc tuations of the ice cap, each successively less extensive than the former." These he called, the McMurdo, Taylor, Fryxell, and Eoettlitz Glaciations• During the Victoria University expeditions into the Wright Valley and Victoria system, reconnaissance studies of the glacial deposits and C See Nichols (1953* P* 22) and Mercer (1 9 6 2 ) for more complete listB and summary* 1 6 2 land forma war* made by Bull, McKelvey, and Webb (1962). They recog nized evidence of four glaciations (First through Fourth) in the area* During the simmers of 1959-60 and 1960-61, more detailed studies were made by R.L. Nichols and associates of the Tufts College Antarctic Expeditions In the eastern tmo-thirds of Wright Valley. Nichols (1961, 1962) also recognized four glaciations which he referred to as: "oldest," Pecten, Loop, and Trilogy Glaciations. Nichols in i960 drew the attention of the writer to the need for detailed study in the adjoining Victoria Valley system. Preceding the work in the Victoria system in 1960-61, the writer made a brief study of the deposits in the Ht. Gran area and the adja cent ice-free Alatna Valley. Two major glaciations (as defined In tills section) are distinguished in this area (Mirsky, Treves, and Calkin, 1 9 6 3 )* These are the "A" Glaciation and the "B" Glaciation. The latter is subdivided into the first and second episodes. Succession A minimum of two major glaciations, defined on the basis of deposits and land forms, are recorded in the Victoria Valley system. The first, the Insel Glaciation, represents the strongest invasion of ice from the ice plateau and may have been preceded by one or more still earlier glaciations in this area. The second glaciation, 163 f the Victoria Glaciation, was marked by many reversals In direction of ice flow, with a strong Invasion of ice fran local ice fields and from the coastal area in combination vlth weaker invasion from the inland ice plateau. The Victoria Glaciation is subdivided into three glacial "episodes", the last of which extends to the present* Nomenclature The precedent for using the term "glaciation" was set for this region of Antarctic by Pewe (i960) and subsequently by Nichols (1961c) and Bull et al. (1962) who used the tern as their fundamental unit of description and correlation* In this report, an attempt has been mads to stay as close as possible to the term "glaciation? as used as a geologic - climate unit for use in the Quaternary and as defined by the American Commission on Stratlgraphic Nomenclature who state (4-961, Articles 39 and ^0 , p* 660): A glaciation was a climatic episode during which extensive glaciers developed, attained a maximum extent, and receded* / ✓ Fundamentally, this is the definition followed by Fewe, Nichols, and Bull et al. An interglaciation has been defined as "an episode during which the climate was incompatible with the wide extent of glaciers that characterize a glaciation" (A.C.S.N., 1961, p. 660)* No intergla- ciations have been distinguished by previous authors In the McMurdo Sound area and none is distinguished at this time* Studies of the 1 6 k thermalumlnescence of rocks from Marble Point by Zeller and. Pern (i9 6 0 ) suggest that Antarctic temperatures were reduced below 2 3 * C at least more than 17 0 , 0 0 0 year’s ago and have not been above this temperature for more than 125 hours since. The lack of true Interglaciations In Antarctica such as have occurred In the Northern Hemisphere has also been noted by Rozycki (1961, p. 278). It is probable that glaciers have never left the southern Victoria land area since the Quaternary and there is no deposltional evidence In the Victoria Valley system for an interglaciation as defined above. A glaciation is subdivided (American Conmission on Stratigraphlc Nomenclature 1 9 6 1 , p. 6 6 0 ) into a stade and Interstate: A stade was a climatic episode within a glaciation during which a secondary advance of the glaciers took place. • • An interstate was a climatic episode within a glaciation during which a secondary re cession or a stillstand of glaciers took place. The writer has found it impractical to apply this terminology extensively in the glacial chronology of Victoria Valley system. For example, during the same roughly outlined period distinguished by deposits correlated within the Valley system, there has apparently been a still stand, an advance, and a retreat in different parts of the Victoria Valley system. For this reason the Victoria Glaciation has been sub divided into three "episodes", represented by deposits and land forms that can be distinguished from other deposits and land forms. These 165 "episodes" involve glacial advances, st111stands, and retreats which are clearly subsidiary to, and within the major advance and retreat comprising the Victoria Glaciation. Glacial Deposits The deposits that define and give their names to the glaciation and glacial episodes, i.e. Insel, Bull, Vida, and Packard Drifts, are often differentiated of necessity in part on inferred geologic history and on primary or secondary surface form (erosional morphology). Because of the relatively thin active layer in most areas and the lack of fresh river cuts, no stratigraphlc sections showing one drift over another could be examined and also the lithologic descrip tions of the drifts are based almost entirely on their characteristics within the zone of weathering and frost action. Correlation Many factors must be taken into consideration before even tenta tive correlations can be made of glaciations or parts of glaciations in areas of southern Victoria land not contiguous. Without distinguished interglaciations It is difficult to delimit the scale of a glaciation or to know how extensive an advance was if it is not known how far ice receded following the last advance, or if ice receded completely or stagnated (See Bull et al., 1 9 6 2 , p. 7 2 ). In addition, many factors 166 other than regional climatic character or latitude in the ice-free areas of Antarctica control the contemporaneity of advances, retreats, or Btillstands, including: exposure; the presence of absence of bedrock thresholds at valley heads; and the position or action of sea level* It is a familiar sight to see glacierized valleys adjacent to others which are partially or completely ice free. Because of the difficulties in sampling the unweathered deposits, their correlation Is difficult. It is not always clear how much of the surflcial characteristics are due to weathering and erosion versus primary factors of accumulation and deposition (See previous page). Early History of Glaciation This section considers the period from the initiation of local glaciation up to but not including the retreat of the last major glacia tion of the valley system from the inland ice plateau (Insel Glaciation). The following interpretation, based largely on the glacial sculp ture, is complicated by the lack of evident preglacial topography and by the fact that ice from three main sourse areas has played a part in the development of the valleys. Preglacial Topography Because no direct evidence is available, it is not certain whether the directions of the valleys in the Victoria system follow a preglacial 167 drainage pattern, are controlled by a fault pattern, or perhaps have some other control. Upper Victoria Valley and Bull Pass follow geo logic contacts which suggests that the glaciers may have enlarged preglacial, structurally oriented stream valleys (David and Priestley, 191^, p. 201; Taylor, 1922, p. 130). Nichols Implies a stream ances try for the Wright Valley In saying that the oldest glaciers produced a reversal of drainage. On the other hand, Gunn and Warren (1 9 6 2 , p. 6 0 ) noted: It seems unlikely that large rivers have existed In Victoria Land even In interglaclal periods, and it is probable that the present topography has been produced entirely by glacial dissection of block- faulted mountain ranges. Local Initiation of Glaciation In southern Victoria Leuad, the main source of moisture has pro bably always been from the northeast. With a deterioration of climate, glaciation probably started in the mountainous coastal areas, rather than in the drier and lower inland areas west of the mountains. The time of this onset is not determined. Wright and Priestley (1922, p. 1 8 3 , ^31-^35), Priestley (1923), Taylor (1930), and Gould (1939, p. 739) have all maintained that it occurred before the Pleistocene, Wright and Priestley (1922, p. 1 8 3 ) believing that all the major erosional effects were produced in late Tertiary times. This thesis, based on relations 168 of volcanic debris with Intercalated Ice and on the occurrence of mor aine-like deposits, was questioned by Nichols (1953/ P» 15-18) who noted: "there is no good evidence for Tertiary Antarctic Glaciation," However, recent work on deep ocean bottom cores by Eric son et al* (1 9 6 3 ) Indicates that glaciation of Antarctica may have preceded the faunal break to the Pleistocene (800,000 yr B.P.) by some 250,000 years. Ideas on the evolution of the inland ice have been given by Taylor (1922, p. iBo) and Bull et al. (1 9 6 2 , p. 7 2 ). A coalescence of the glaciers draining towards the low Interior, perhaps accompanied by increased snowfall, caused a thin but growing Ice sheet to farm. Eventually by direct accumulation In the Interior, this ice sheet attained a thickness sufficient to cause reversal of ice flow in the east-west valleys. Taylor (1922, p. 174-186) has also considered that the form of the outlet valleys, such as the Taylor and Ferrar Valleys, is due initially to headward erosion of cirque glaciers, subsequently modified and enlarged by the overflow of Ice from the Inland plateau. However, Gunn and Warren (1 9 6 2 , p. 6 0 -6 3 ) challenged this, noting that high level moraines are continuous down valley from the present glaciers at the heads of ice-free valleys so that these are remnants of former outlet glaciers. The cirque form is merely due to selective erosion of parts of the boundary scarp by overflow of the plateau glacier. 1 6 9 The three valleys opening onto Berwick Valley and the Webb Gla cier shov the reshaping effect of Ice frcm the Inland plateau on the cirques (p. 2 6 ). The Webb and Upper Victoria Glaciers are now small, relatively Inactive, and are fed from their own neve^ fields; hut both were better developed at seme stage In the past and may have been veil developed at least In the western parts of their present valleys before the valley was Inundated with Ice from the Inland. The orientation of the deep, western 1 0 km of both valleys show strong flow from their respec tive ice fields. Invasion of the Inland Ice After the initial glaciation of the coastal mountainous area / / with the development of cirques, small neve fields, and valley glaciers like the Webb and Upper Victoria Glaciers, the area was Inundated by ice flowing fran the Inland plateau. The quantity of ice flowing and the modification of the existing valley form varies from pass to pass. In the Balham and McKelvey Valleys, no cirque-like form had been pro duced in the Initial stages, and their courses, normal to the coastline, are more typical of outlet glaciers of this region than the courses of either the Webb Glacier or the upper Victoria Valleys. The deep basins at the heads of Balham and McKelvey Valleys (fig. *0 are not found in 170 any of the ice-free cirque valleys of the Victoria Valley system, but are typical of the heads of outlet valleys such as Wright and Alatna. In addition, valley floors which rise steeply westward to the plateau through narrow, stepped troughs as In Balham, or more abruptly over vide dolerite steps leading to the high plateau as in McKelvey Valley are common for the larger, ice-free, outlet valleys of Victoria land. The similarities to such resistant bedrock scarps or benches beneath some active outlet glaciers which reach into or through the Victoria land ranges have been cited previously (p. 9 ). All of these, including Balham and McKelvey Valleys, appear to be the end product of inland ice overflowing bedrock thresholds with consequent erosion through sandstone and/or basement rocks Intruded by thick dolerite sills. The processes and resulting forms have been clearly described by Gunn and Warren (1 9 6 2 , p* 6 0 -6 3 ) and by Bull et al. (1962). They considered that back-cutting occurred which Gunn described as being a process acting similar to plungepool erosion with resultant formation of "pseudo-cirques" and benches on the dolerite sills. These forms are a consequence of the columnar jointed dolerite which more strongly resists veritcal erosion than the Intruded rocks, but which once penetrated is worn back more easily by lateral corrasion. During the full-bodied stage of Inundation, some true cirque-cut 1 7 1 topography vas mod if lad and perhaps erased. With continued Invasion of ice, cutting back of the plateau border scarp continued with the formation and/or enlargement of Balham and McKelvey Valleys and the consequent formation or accentuation of the Insel Range mesas. The shallow, cirque -shaped scarp, concave eastward on the southwestern part of the Insel Range, may be the isolated remnant of the back- cutting process. When the retreating scarp line intersected the unusually resis tant series of dolerite sills (Sill "c") within the Beacon rocks, the headward enlargement of these valleys was Impeded* The consequent pro longed overflow of ice at this location facilitated excavation of the deep bedrock hollows at the heads of Balham and McKelvey Valleys. While McKelvey and Balham Valleys were being cut, the Webb Gla cier, substantially enlarged by glacier tongues from the inland ice, expanded southeastvards, merging with the undivided ice stream in the early Balham and McKelvey Valleys and with the Upper Victoria Glacier. It is also probable that some of the McKelvey ice stream broke through a col ridge at the head of Bull Pass to form a tributary of the outlet glacier occupying the Wright Valley. Before Inundation of the area by the inland ice, the expanded Upper Victoria Glacier may have flowed southeastward through the Clark 172 Valley Into the lower Wright Valley* However, when it was augmented by the overflow fran the inland plateau, more of the eastward flowing ice was turned to fora a deeper valley northeast to McMurdo Sound* High level valley walls and benches are continuous from upper Victoria through lower Victoria and Clark valleys (fig. 6 ). This is consistent with the theory that a continuous stream of ice from local ice fields and inland ice plateau flowed through the valley system* Truncated spurs between alpine valleys on the southwestern margin of the Clark valley preserve an indication of the earliest southeastward- moving outlet glacier. Insel Glaciation Insel Drift and Associated Deposits The sequence of cirque and alpine valley cutting and inundation by inland ice may have been repeated many times, but the depositional and eroslonal evidence of early cycles has been obliterated by later ones* Hence, the only cycle which can be recognized definitely is the last one, here called the Insel Glaciation* This glaciation is represented by two contrasting glacial deposits, one on the Insel Range and the other 200 to 300 m below at the eastern end of the McKelvey Valley; and by a succession of glacial channels cut in the bedrock southwest of lake Vida. 1 7 3 Insel Range The oldest of the glacial deposits recognized In the Victoria Valley system consist of a small number of individual boulders, cobbles, and pebbles which rest on the weathered dolerite sill cap of the Insel Range mesas, 200 to 6 0 0 m above the adjacent valley floors. The most profuse accumulation occurs within the low, shallow saddle at an ele vation of about 1 2 0 0 m (400 m above the valley floor) on the western most mesa (fig. h). At this location the deposits consist of a few 20 by 50 cm boulders of Beacon rocks (quartzite), a few cobbles of granitic rock, one of which Is Dias Granite, and scattered small pebbles of quartz and quartzite with a few dike rocks of Vanda Porphyry. Most of these erratics have probably been derived from within the valley system. Fragments of basement rocks and abundant cobbles of quartzite occur within the Mawson Tillite (Gunn and tfarren, 1962, p. 119), a formation which crops out on the nunataks of Shapeless Mountain and Mistake Peak about 12 km west of the Victoria system. However, rock types other than the Beacon rocks and Ferrar Dolerltes are absent from the younger moraines in the valley system which lead from the plateau. Dias Granite crops out 200 m below the Insel Range at the head of Balham and McKelvey Valleys, (fig. 3) and dike rocks, although not exposed as bedrock, are abundant in the moraine here. 17^ The position, paucity, lithology, and form of these deposits suggests great antiquity. They occur high above the valley floor on a surface untouched by later glaciations, and are spread over an area of 20 km^. They occur largely as individual pebbles and cobbles, and only the most resistant rock types still exist as boulders. The present form of most erratics is due entirely to wind abrasion. The quartz, quartzite, and porphyry pebbles are veil faceted. The only other deposits observed on the Insel Range are products of weathering and erosion. Sheets and Irregular accumulations of frost rubble of dolerite (Richmond, 1 9 6 2 , p. 19) are localized in nivation hollows and small cirques at the margins of the mesas (fig. 7*0* The boulders and cobbles forming the surface of these deposits are usually well rounded by exfoliation and are oxidized. A basalt dike which transects the Mt. Insel mesa stands up to one meter above the only slightly less resistant dolerite cap rock. Fragments of this fine rock have been shaped into some of the finest ventifacts found in the area. McKelvey Valley In contrast to the scattered deposits of the Insel Range, the Insel Drift on the eastern floor of McKelvey Valley consists of a till sheet (fig. 7 5 ), probably many meters thick, upon which in many parts a poor, but distinguishable weathering profile has been developed. Figure Frost rubble of weathered dolerite on the Insel Range. View southeast. Note white map case 25 cm square. Figure 75. Till sheet of Insel Drift. View southeast from near Bulls eye Moraine in McKelvey Valley. 1 7 6 This deposit grades rapidly into the McKelvey and Bulls eye end Mor aines (fig* 4) and associated'deposits of the Bull Drift episode on the east and vest respectively* Much of the Insel Drift has been covered hy solifluction sheets from the valley vails, so that the unaltered exposures are narrov and limited to the flatter parts of the valley floor* This material vas apparently deposited largely as ground moraine but the surface is nov the most subdued and flattened in the valley system. No moralnal form remains and frost polygons occur only near the borders of the solifluo- tion sheets. Most of the boulders on the surface have been reduced to ground level; the frequency of the surficial boulders is much lover than for the younger moralnal surfaces (table 9)* The upstanding boulders are nearly all of the more resistant rock types, including: 93# medium to fine-grained dolerite 6# sandstone 1# granite-gneiss A fev of the granite-gneiss boulders are porphyritic Dias Granites, similar to the rock exposed at the vest ends of Balham and McKelvey Valleys* The percentage of the sandstone is markedly lover than that in surrounding deposits, and as many as half of these boulders are higher than 7 0 cm, most of the smaller boulders having disintegrated 1 7 7 completely. These houldsrs of the sandstone, coarser dolerite, and granitic stones usually occur as thin, llmonltic stained, wind-abraded shells, the remnants of cavernous weathering and wind abradion (fig. 7 5 ). Below the boulders, pebbles farm a lag pavement consisting of: 90$ very resistant, medium or fine-grained dolerite 3$ banded sillclous siltstanes or quartzites 3$ sandstone 6$ Vanda Porphyry Thus In both the boulders and the pebbles of this deposit, the frequency of sandstone and porphyry are much lower than in the neighboring young deposits. In part, this is because of more rapid weathering of the sandstone, but the low percentage of the resistant dike rocks also indi cates that the Insel deposits were not carried from the east. In con trast, the deposits left by the Victoria Glacier In the area between the McKelvey and Victoria Valley are rich in these porphyry a (See plate 2 in pocket). Within the tap 60 cm of the till, most of the boulders have dis integrated to cobble or smaller size. The sorting of the fine material Id moderate to poor, but the material is uniformly silty and soft. Analyses show that there is from 27 to 43$ silt-clay of which 4 to 11$ is clay (table 1 0 and appendix I). A shallow and poorly developed weathering profile, defined by oxidation and salt accumulation, occurs in these deposits* Below the 1 7 8 2 to 8 cm pebble and coarse sand lag deposit, a typical profile consists of an upper horizon of oocldlzed and often brown or yellowish-brown silt loam* This weathered till is very dry and structureless, being loose or soft in consistence and from 15 to 25 cm thick* Frequently, this horizon displays no white salts but may show a moderate carbonate re action* Remnants of disintegrated boulders are often present. Often occurring with a sharp break below the oxidized upper horizon is a hyer of similar texture and consistence but including white salts^ and producing strong carbonate reaction* These visible salts may occur as narrow bands 5 to 10 cm thick, or may decrease gradually downward* The lower limit of the oxidation profile is not well defined* This weathered till color and the occurrence of the white salt horizon are variable; either may be absent but carbonate reaction is always strong In the silty material* The depth and coloring of the oxidized layer is closely related to the proportion of fine dolerite particles on or within the profile. Because of the high content of ferro-magnesian minerals, the dolerites, more than other rocks present, are readily oxidized. Color changes in the vertical due to local sub surface weathering of varying llthologic rock types is not uncommon. ^ Nichols (1 9 6 3 , p. 26-30) has discussed the composition and origin of a similarly occurring, subsurface efflorescence of salt In a deposit of Loop Glaciation age in Wright Valley* The salt in Wright Valley is predominantly halite, but Includes Ca, Mg, CO3 and 30^. 1 7 9 This profile in the older deposits is not significantly different from that in the younger deposits, but it is somewhat more consistently developed* Discussion The more subdued topography, the consistently greater weathering, and the distinctive lithological composition Indicate that this Insel Drift was deposited before the neighboring Bulls eye and McKelvey Mor aines. Further, this till was deposited by glaciers mowing from the west. It has thus been related to the earliest recognized glacial deposits and the Insel Glaciation. The difference between the degree of weathering of the two deposits (Insel Range and McKelvey Valley) appears to be great. However, the greater weathering of the higher deposits may be due to their more exposed position, the rapid removal or initial absence of fine material, and the longer period of exposure. The top of the Insel Range may have become ice-free several thousand years before the eastern part of McKelvey Valley. Glacial channels of southwestern Victoria Valley In the southwestern corner of Victoria Valley, a system of vide channels has been cut in dolerite Sill ' V and basement rock (fig. 5)« 3B0 Leading from the pass at the far eastern end of McKelvey Valley and having gradients of 2* to 5° toward lake Vida and the Upper Victoria stream, these channels show many relations anomalous to the present drainage. The pattern was produced along the edge of a glacier re treating westward Into McKelvey (fig. 76 ). Consequently, the channels are probably related to the Insel Glaciation. In the upper half of the slope, many of the channels are short, curved, and truncated successively upslope against one another and toward the axis of the pass. In many cases the channels have dead ends upslope. Several channels may emanate from a depression in the bedrock, halfway up the slope. In the lower part of the slope, the channels are resolved into several cross-contour cuts which are obscured beneath a blanket of moraine near the valley bottom. The channels are quite uniform, often being 5 to 10 m deep and 30 to 90 m wide. They are slightly wider and more V-shaped when cut in the Vida Granite and more steep-sided in the dolerite. Their greatest depth is attained in the slope near the pass and they become shallower toward the Victoria Valley bottom. Here, they can be traced beneath the morainal cover to within a few hundred meters of the valley axis. The area occupied by these channels was overridden by glaciers flowing westwards during the succeeding Bull Drift episode of the DJBl Victoria Glaciation. These glaciers left the till which now obscures the upper and lower ends of these channels. V — McKCLVEY VALLEY BEDROCK CHANNELS VICTORIA VALLEY LAKE VIDA Figure 7 6 . Pattern of some glacial meltwater channels cut in bedrock of southwestern Victoria Valley. Extent and History of Retreat of Insel Glaciation The Insel Glaciation is that during which the oldest glacial deposits recognized in the Victoria Valley system (insel Drift) were laid down. During this glaciation the inland ice plateau west of the 282 Victoria Valley system vas higher than at any time since; Ice flowed eastwards over the 'bedrock thresholds Into the valleys and probably right through to McMurdo Sound. The Insel Glaciation was brought to a close by the lowering of the plateau ice level, the emergence of the high rock thresholds, and hence the cutting-off of ice to the valleys (Bull et al*. 1 9 6 2 ). During the lowering, the glaciers gradually lost their cutting power and after the severance of the plateau supply, the glacier ablated and even tually disappeared. The glaciers in the Balham and McKelvey Valleys, without local ice fields and with higher bedrock thresholds, retreated more rapidly than those in Barwick Valley. This sequence of events is reflected in the present-day conditions in valleys north and south of the Victoria system. In the area of the Maws on Glacier, the lowering of the plateau has caused thinning of the glacier over a rock threshold, but an underfit glacier still extends to the coast. In the Taylor Valley, the ice supply has been so reduced that the Taylor Glacier now ends 30 km frctn the coast (See p. 10). Seme details of the vertical extent of the glaciers and of the recession can be determined frcm the distribution and lithological com position of the remaining drift. At some early stage, the ice covered all of the Insel Bangs, but with gradual lowering of the ice plateau, the east end of the Range 18 3 (Mt. Insel mesa) emerged, and the ice level in the McKelvey and Balham Valleys dropped to about 1,200 m at the vest end of the range. It may have remained at this position for a long time where Its base reached several hundred meters below the dolerite mesa top Into the basement complex. At this stage, the slope of the glacier surface In the McKelvey and Balham Valleys was less than 1 in 6 0 ; eastward flow was small and the cutting power was negligible. The Webb and Upper Victoria Glaciers are fed In part by local Ice fields and have lower bedrock thresholds at the plateau edge. During the lowering of the Inland ice, these glaciers continued to flow and deepen their valleys for some time after those in the McKelvey and Balham Valleys had almost stagnated. Of the boulders and cobbles of well-cemented Beacon sandstone. These may have been carried east wards originally by the expanded Upper Victoria Glacier. later, temperatures may have risen and local accumulation reduced, so that the local glaciers and the near-stagnant and almost severed tongues of the inland ice began to retreat more rapidly. At the eastern end of the tongue in McKelvey Valley, streams Initiated the system of channels now leading fran McKelvey to the bottom of Victoria Valley. The formation of the large McKelvey Moraine may have been Initiated 15b at this time, although the present form is ascribed to the later Bull Drift episode. Judging from the depth of the channel system, the glacier may have remained in this state for a long time. With a continued drop In the level of the plateau ice, all ice supply to the valleys was severed; the tongues retreated at least to the heads of McKelvey and Balham Valleys and into the upper ends of Barwick and Victoria Valleys. The nov greatly subdued, highly weathered ground moraine east of McKelvey Moraine was first exposed at this time. At the end of the Insel Glaciation the valleys probably had much the same dimensions and appearance as now, especially in the eastern areas of McKelvey and adjacent Victoria Valley. U-valleys up to 1 , 1 0 0 m deep, triangular facets and glacial benches to 1 , 7 0 0 m elevation, all structural evidences of the Insel and possible earlier glaciations, have been discussed under previous sections. It seems probable that the benches, most of which are structurally controlled by the resistant dolerite sills, do not Represent more than interim periods of valley widening before breaching of the sills and profile deepening. This is at variance with the ideas of Bull et al. (1 9 6 2 ) and Bull (1 9 6 2 ). Subsequent invasion of ice probably recovered the benches in the east, but elevations above 1,2CXD m were not reached in the west of the Victoria system, and the east end of the Insel Range was a nunatak during later invasions. 185 Correlation of the Insel Glaciation Victoria Valley system The oldest deposits of the Insel Glaciation (occurring on the Insel Range) were used, by Bull et al. (1 9 6 2 ) to partly substantiate their First Glaciation In the Wright Valley and Victoria system. The essential differences In the sequence of the First Glaciation and the Insel Glaciation outlined here Is largely In presentation! terminology! and extent of glacial sculpture implied. This writer has mentioned the possible importance of structure! stream action! and local glaciation In tho Initial establishment of the present valley courses and is further heaitemt to ascribe all of this valley formation to a single glaciation as Bull et al* have done. In addition! It has been suggested In this report that at the close of the Insel Glaciation the valley glaciers reached below the flat surfaces of the Insel Range and below higher benches which Bull et al. (1982, p. 7 2 ) believed to be "remnants of the valley profiles cut during this glaciation." Wright Valley The earliest glaciations In Victoria Valley! including the Insel Glaciation, are clearly those which in the adjacent Wright Valley Bull et al. (1 9 6 2 ) referred to as First and Second Glaciations and which 186 Nichols (1 9 6 1 c) recognized as the "oldest glaciation" and later (1962a, p. 49) as the "oldest glaciations". Nichols (19 6 2 a, p. 49) noted: The carving out of the bedrock basin of Lake Vanda, the truncation of spurs, the development of the reversal of drainage, and the deposition of high- level glacial deposits by outlet glaciers that moved from the Antarctic Ice Plateau eastward down the Wright Valley represent the oldest glaciations recognized in the Wright Valley. Mt. Gran area: Alatna Valley Mt. Gran lies to the northwest of the Victoria Valley system (fig. 2) at the western margin of the mountains; Alatna Valley is a northeast-southwest-trending ice-free valley adjacent to the north, lying at approximately 6 5 0 m elevation. At least two major glaciations have been distinguished. During the first of these, ice from the inland ice plateau flowed directly eastward over the bedrock scarp and through the valley, while during the following glaciation, ice moved westward into the west end of the valley, possibly from the coast of McMurdo Sound. During the last re treat of the inland ice from Alatna Valley, large depressions up to 30 m in diameter were cut by meltwater in the sandstone bedrock at the west end of the valley. No till of this first glaciation, referred to as "A", is recognized in Alatna Valley; however, the depressions con tain a few very resistant dolerlte erratic boulders left by the re treating ice. The "A" Glaciation is here veiy tentatively correlated 167 with tbs Insel Glaciation on the basis of similarity of pattern of flow, and position and scarcity of deposits. McMurdo Sound - Taylor Valley The earliest and most extensive of four major Quartemary gla ciations recognized by Pewe (i9 6 0 ) was the McMurdo Glaciation. This glaciation has been tentatively correlated by Bull et al. (1 9 6 2 , p. 7 7 ) / ✓ .. with their First Glaciation. Pewe identified deposits of the McMurdo Glaciation at heights up to 2,500 ft (760 m) above the valley bottoms in Taylor Valley and adjacent ice-free valleys, and he noted that ice must have filled McMurdo Sound to an elevation of at least 2,000 ft (610 m). Deposits of this glaciation lack morainal form; most of the boulders and cobbles are planed level with the ground surface; in Taylor Valley, exposed diorlte and andeslte dikes have been etched out 3 to 8 ft (l to 2.5 m) in relief* In all these respects, the deposits resemble those of the Insel Glaciation of the Victoria Valley system. Pewe (i9 6 0 , p. 513) believed that the McMurdo Glaciation was at least pre-Sangamon in age "even if the rate of wind erosion and morainal modification in general were twice as rapid as the rest of the world;" and he has tentatively correlated the McMurdo Glaciation with the pre-illinoian glaciation of Worth America. This writer also believes that the Insel Glaciation must have occurred in pre-Sangamon time; how ever correlation beyond this point is not attempted. 188 Evidence on the Inland ice plateau The Increase In elevation of the surface of the inland ice plateau to the west of the Victoria Valley system need "be relatively small to produce the "flood" glaciations which are recorded in the Victoria Valley system and in other valleys. Such a rise is indicated by minimum ice limits shewn by nunataks at the western edge of the mountains of southern Victoria Land (fig. 2). At the head of the Skelton Glacier to the south of the Valley system, the Ias'nly Moun tains, now some 1 , 0 0 0 ft (305 m) above the level of the inland ice, and the Portal Mountain, have been overriden by ice. Detour, Gateway, and Carapace Hunataks at the head of the Mackay Glacier to the north have also been overridden although they now extend 1 , 0 0 0 to 1 , 6 0 0 ft (305 to 1*88 m) above the ice surface (Gunn and ./arren, 1 9 6 2 , p. 53-5^)* Victoria Glaciation All of the glacial deposits of the Victoria Valley system not assigned to the Insel Glaciation are here collectively referred to the second and last glaciation recognized in the valley system. This is here named the Victoria Glaciation after the valley where the most complete sequence of the deposits occur. The deposits are divided into the Bull, Vida, and Packard Drifts. These show distinguishable characteristics and were exposed and largely 189 deposited during three consecutive episodes of the Victoria Glaciation, each of which marked a change In glacial regimen believed to be corre lative between the individual valleys. Bull Drift and Associated Deposits Slightly more than half of the valley floor area of the Victoria system is blanketed by highly weathered and topographically very sub dued Bull Drift and associated deposits which represent the initial and most extensive advance and recession of the Victoria Glaciation. The deposits are named from Bull Pass where there are thick and varied occurrences. Slight variations in age exist between different areas, particularly at opposite ends of Bull Pass, but these differences are largely gradational so that the drift is not readily subject to sub division. The type deposits consist largely of till, with small areas of lacustrine silts. Associated deposits include large debris fans emplaced by mass-wasting in Bull Pass and on the adjacent floor of ./right Valley, undifferentiated talus, and extensively developed solifluction sheets which mantle and substantially reduce the areas of exposed drift. Important alluvial deposits are lacking or are undlstingulshable from much younger material. 190 Till Distribution and morphology Till of the Bull Drift (Bull till) is found on the floor of each of the valleys, and is particularly extensive In areas bordering the Insel Range mesas. Deposits in Bull Pass may be almost entirely of this material, but in the other valleys the deposits are separated from their distal ends by the distinctly younger Vida and Packard Drifts. Deposits on the 500 to 1 , 0 0 0 m benches on the north side of eastern Barvick and above the floor of Victoria Valley are of equi valent age. Nearly all the cirques of the Olympus Range and a few elsewhere bordering the valleys contain remnants of glacial deposits attributed to this episode. The deposits, consisting largely of subdued, low, hummocky to flat ground moraine, vary considerably in thickness. Accumulations, possibly tens of meters thick, occur in the depression in the west of McKelvey and Barvick Valleys, and surprisingly extensive areas of thin and spotty accumulation of this till or free stones on highly weathered bedrock are found in the valley bottoms. These latter areas include: the area south and southwest of Lake Vida; the lip of western Clark valley; and the area at the southern end of Bull Pass. Southwest of Lake Vida and at the south end of Bull Pass, extremely cavernously weathered projections of the dolerite sill stand up as much as ^ to 5 m 1 9 1 above the surrounding sill rock (fig. 6 7 ). In other areas, ice-covered during the Bull Drift episode, basaltic and felsitic porphyry dikes have often been weathered out up to 1.5 m above granitic and gneissic bedrock. The two most distinct and well-defined end moraines In the Victoria Valley system are products of this advance. The largest, the McKelvey Moraine, stretches across the eastern end of McKelvey Valley and it concave eastward. It has a broadened, inverted V-shaped cross section with slopes 3 ° east and 5 ° west, and has an average relief of about 50 m. In profile, it slopes 2* to 3° north to a wide, V-shaped stream cut (fig. 6 ). A resistant dolerite knob above its southern end suggests that the moraine may have a bedrock core. Older deposits on its southwestern flank suggest that its formation was initiated during the previous glaciation; however, the major surficial deposits and its eastward concavity identify it with the second glaciation. A second, smaller, probably contemporaneous end moraine forms a loop around the southern side of Bulls eye Lake (fig. **■)• This is more narrow and steep, sloping 5 ° to 1 0 * north and 15* south, and its well-defined crest is uniformly about 25 m high. Niether the Bulls eye or McKelvey Moraines have been dissected by post-glacial stream action. These well-defined end moraines do not appear to represent the maximum extent of the glaciers; Bull Drift in the valley system is 192 attenuated, and terminal positions are represented only "by a slight increase in boulder concentration in the till. These end moraines having steeper sides away from the ice tongues are typical of the end moraines of the Bull Drift; most of those of the Vida Drift are more irregular or even symmetrical in cross section. The regular asymetrlcal shape of the former is exhibited by the end moraines of Ohio vhich consist of lodgment till topped by ablation moraine and banked on the distal side by push type end moraine deposits (R.P. Goldthvait, oral c onmun i cat ion). Other glacial margin features, including glacial meltvater channels, occur over the drift, but these features are now disconti nuous and barely distinguishable as distinct topographic forms except in Victoria and eastern Barvick Valleys. Seme remnants of end moraines cure more than 2 to 5 m high. Many indistinct and poorly defined con centric linear elements seen in air photographs proved to be either marginal channels in the till or slightly raised ridges of till. Such llneatlons are concave eastward in northern Bull Pass and McKelvey Valley, probably indicating glacier movement from Victoria Valley. In Barvick Valley, weakly discemable, marginal channels and low lateral moraines sloping westward appear to be products of glacial retreat Into upper Victoria Valley. Northward sloping marginal channels and hunnocks (remnant end moraines?) at the southwestern end of Bull Pass suggest 193 that this area was invaded by a lobe of the Wright Valley Glacier. The fact that these channels in southern Bull Pass are preserved as well as those at the other end of the Pass may indicate that they are a product of the sane glacial episode. The major dissection of these deposits has been due to weathering and wind action, but mare recent alluvial action has altered and burled both ground and end moraines In eastern Barvick Valley and on the north edge of Lake Vida. Solifluction sheets probably cover as much as half of the original total area of deposits. Polygons are absent or only weakly active on the Bull Drift. Nature and preservation of till constituents Surficial boulders have been extremely weathered; most of them are reduced to ground level and many have disintegrated completely below as well as above the surface (fig. 77)* The average frequency of upstanding boulders averages about 3 6 boulders per 3 0 0 m traverse (table 9)* Within these traverses as many as 100 to lUO boulders, many more than a meter in diameter, have been observed to be reduced to ground level, and an unknown number have been worn below the surface and are thus uncounted. Boulders are more frequent than average in Balham Valley and in the western McKelvey Valley depression, where the original concentration was greater due to the steep and narrowly spread valley walls. 1 9 ^ Figure 77* Typical weathered and abraded surface of Bull deposits showing boulders completely and partially worn to ground level. A late first cycle or early second cycle of cavernous weathering and associated granular disintegration of rock is displayed by the upstanding boulders. In most cases, well-formed hollows of cavernous weathering are displayed only in the larger boulders (table 8 ). Striated and faceted, medium-grained dolerite boulders, absent elsewhere, are unusually numerous on the parts of the till surface above the southwestern end of Lake Vida. The extensive weathering of other adjacent boulders in the Lake Vida area suggests that the striated boulders have been exposed recently by down-wearing of the surface or frost movement. 195 Quantitatlve study of surficial stones at over 100 localities on the till of the Bull Drift reveal some narked differences from valley to valley which when related to known Bedrock outcrops may suggest a pattern of glacier movements* In the deep depression in western McKelvey Valley, 20$ of the surficial stones are granitic gneiss, probably derived from the immed iate valley walls. These granitic rocks are much more rare on the till to the east and their concentration in the depression appears to delimit the farthest easterly extension of ice tongues from the plateau. Tough, well-cemented Beacon sandstone fragnents are more preva lent east of the depression in McKelvey Valley where they may he traced through Bulls eye pass and then west over the till in Balham Valley. Dias Granite stones, typical of exposures at the west end of Balham Valley also occur on the surface in Balham Valley as far east as Bullseye lake. At the junction of Balham and Barvick Valleys, the stones are more heterogeneous in composition and include: a few yellow granite cohhles and boulders found in abundance in the younger deposits of Barvick Valley vest of Lake Vashka; Beacon sandstones; Vanda Porphyry ( as pebbles); and cobbles and pebbles derived from the Asgard For mation. These latter include rusty-weathering, quartzo-feldspathic 196 gneiss, a diopside gneiss, and rarely marble fragments. A H except the yellow granites are indicators of the non-doleritic ccnpoBents of the Bull till of eastern Barvick Valley, southwestern Victoria Valley, and the McKelvey Valley east of the McKelvey Moraine. These rock types resemble those rocks exposed on the north and western walls of upper Victoria and Barvick Valleys (fig* 3) and appear to he related to a former divergent extension of the Upper Victoria Glacier* In particular, strikingly large (2 by 3 m) boulders of the veil-cemented sandstone can be traced from the west side of the front of Upper Victoria Glacier into Barvick Valley and around the eastern flank of Mt. Insel into the eastern McKelvey Valley-Bull Pass area* In contrast to the above distribution, surficial lithology of tills along the north and east vail of Victoria Valley, including remnant patches 200 m above Lake Vida, contain as much as 12 percent white or pale pink Vida Granite in the boulder fraction. This weakly colored granite, which is carried east by the Upper Victoria Glacier, contrasts with the deep salmon pink stones derived frcm exposures near Packard and Lower Victoria Glaciers and distinguished in till as far west as the south side of Lake Vida. Very highly weathered drift at the southern end of Bull Pass has been disturbed and also Isolated from the rest of the deposits of 197 the Victoria system by more recent solifluction (fig. 7 8 ), and it is not as clearly placed in the relative glacial chronology. However, this drift has been related to the Victoria Glaciation rather than to the Insel Glaciation for the following reasons: (l) marginal channels are preserved to the same degree as elsewhere in the Bull Drift; (2 ) the lack of complete destruction or mantling of the deposits by solifluction as has occurred in the adjacent area of Bull Pass since the Insel Glaciation; (3 ) The adjacent dolerite sills show almost identical weathering as the drift-free patches in the area below the McKelvey to Victoria pass which was also ice-covered during the Bull Drift episode (fig. 6 7 ). Northerly sloping marginal channels and a parallel hummock alignment (plate 1 - in pocket) suggest that this moraine was deposited by ice advancing from v/right Valley. Gome alternative hypotheses for the origin of the drift on lower Bull Pass are: (l) that deposition resulted from a tongue of the east ward flowing Upper v/right Glacier during the "oldest" glaciation of Nrlght Valley; and (2) that the drift was deposited by a glacier from the Victoria system during the Insel Glaciation or Bull Drift episode. In the latter case, the anomolous relations of the lake deposits, channels, and hummocks to the present topography may be a result of formation around stagnant ice. 198 Figure 7 8 . Aerial view from 6,000 ft {approximate) looking north from bright Valley into Bull Pass. Symbols are: BD, Bull Drift; hr, bedrock (Ferrar Dolerites); df, debris fan; c, marginal channels; s, solifluction. U.S. Ilavy photo, TKA-350, no. 15^, F 31, 1 Jan *58. 199 The texture and weathering of the Bull till within the active layer Is similar to that developed on the Insel till, hut the morpho logy is more variable. In general, this till is distinguished from younger deposits by the frequent occurrences of dry, loose, silty (sandy loam) deposits. These silty deposits invariably show a strong carbonate reaction and often contain salt accumulations. Porting of the fraction finner than 2 mm is moderate to poor, and in general is poorer than in adjacent younger deposits of similar derivation. The sllt-clay fraction averages between l£ and 38 percent (table 10). The clay content is erratic, varying in most samples from 1 to about 11 percent* Boulders are frequently highly disintegrated below the surface to a depth of lj-0 cm, particularly where the tills are silty and polygons are absent or very poorly developed. Beacon quartzose sandstone is often completely disintegrated to its component grains. Thus, in areas such as Balham Valley where boulders of the less well-cemented sandstone are plentiful in the till, small, isolated patches of nearly pure quartz sand exist. Significant differences in the upper layers of the Bull till occur from place to place in the texture, color, salt content, degree of oxidation and weathering, and vertical sorting. Most of these 200 variations may be related directly to the local lithologic composition of the till. Such differences distinguish the Bull Drift from the younger and much more uniform deposits. Glacial marginal channels A series of glacial marginal channels occur in the far eastern McKelvey and Barvick Valleys, southwestern Bull Pass, and on the south- western side of Lake Vida. In the first three areas, the channels are Indistinct and may exhibit little more than 1 or 2 m relief. They can be Identified by the patio-like arrangement of the boulders on their floors, concentrations of boulders, or anomolous relation to slopes. A regular spacing is exhibited, particularly by the series in Barvick Valley below Sponsors Peak. This series may suggest a regularly inter mittent glacier retreat. The morphology of the belt of ground moraine bordering the south west end of Lake Vida is dominated by a cross-hatched pattern of glacial channels (fig. 19) • Two sets are distinguished; the deepest and most distinct are those channels extending directly downs lope, while the second set consists of shallower and more irregular marginal channels, closely following the contours of the slope. The former are the buried equivalent of the bedrock channels exposed upslope and related to the westerly retreating McKelvey Valley glacier of the Insel Glaciation (p. 1 7 9 ). Figure 79* Glacial meltvater charnel series In Bull Drift southwest of Lake Vida* Till blankets downslope channels cut in bedrock and in turn is cut by marginal channels trending obliquely to the older bedrock channels* Numbers 1 through 5 show probable sequence of channel cutting and indicate possible submarginal origin* Note channel to left of dovnslope arrow which makes sharp bend toward lake* This may be a subglacial chute* U*S. Navy photo, 27 Jan *6 2 . 201 203 Probably acme deepening has occurred in unblocked segments of these channels by short meltvater streams operating after the glacier re treated. Sane channels have also carried meltvater from McKelvey Valley In recent times. The marginal channels which slope gently frcm vest to east are much more Irregular and more difficult to distinguish in the field. However, they are marked by concentrations of boulders which are more numerous in the higher channels than near the Lake. They vary in width from 5 to 2 0 0 m, are generally less than a few meters deep, and some can be traced for 16 0 0 m without appreciable discordances. These dis cordances are vertical breaks up to 8 m which are formed In either the downslope channels, marginal channels, or in both sets where the two types intersect. The lateral spacing of the marginal channels is irregular. Some anomalous relationships are revealed by these marginal channels (fig. 79) • Some lower channels appear to be truncated by higher lying channels, while a few have branches which suddenly turn directly downslope far short distances. The marginal channels described above probably delineate the retreating, easterly sloping Upper Victoria Glacier terminus. The erratic spacing may indicate erratic retreat. These anomalous rela tionships may be explained by local and small readvances or by poet t glacial, downs lope runoff of meltvater from sncv accumulating in the channels. Such patterns are often also Indicative of sublateral and subglacial drainage (Maxmerfelt, 1959; Sissons, 1 9 6 0 ). Marginal channels In bedrock of southern A series of distinct glacial meltvater channels have been cut Into bedrock on the southeast wall cf Bull Pass between 6 0 0 and 1,200 m above sea level (fig* 78)* These appear to be glacial margin* 1 channels while their lover extensions may be subglacial chutes. Configuration and occurrence suggest their formation by meltvater from a large ice tongue which Invaded the pass from Wright Valley. These channels may be related to the low, half-buried, north- trending hummocks on the opposite side of the valley which In turn may be part of the Bull Drift. However, the channels and drift below may be a product of an earlier glaciation. Lacustrine deposits Contemporaneous lacustrine deposits are an integral part of the Bull Drift, and probably many more areas exist within this drift cover than have been mapped so far. The largest areas include the depressions east of Lake Vashka, the basin area of Balham Valley between Balham and Bulls eye Lake, the hollow at the vest end of McKelvey Valley, and the 205 area to the vest of the i lake In the drainage of southern Bull Pass* Most of the deposits are small and surround more recent lake deposits* Areas of lacustrine deposits that cure more than about 25 m across usually have a much thinner lag concentrate of sand and pebbles, and are rarely covered by large boulders* Below the surface is moder ately vell-stratlfled silt and sand, often with widely scattered large pebbles or cobbles and small boulders* The silt and clay content Is usually much higher than In the surrounding till (See plate 2 and appendix I). Some of the lakes were by moraines or glaciers* For example, In Bull Pass bedded silt and sand occurs In a nearly continuous section as high as 4o m above the present shallow lake. The lake de posits are contiguous and probably of the same age as the surrounding till. The lake was probably damned at the southern end by the ice invading from Wright Glacier as no basin exists now which could have contained such a deep lake* A stratigraphic section In the upper 1*5 m of this deposit is shown below. The material is dry and loose at the top and slightly more moist with depth. It is moderately to well bedded, and the beds are nearly horizontal* 206 Thickness (on) Desert pavement, sand and fine gravel 6 Silt loam, white to cream, with few 1 cm pebbles 7 Mechanical analysis VC C M F VF S&C1 tr tr 1 7 12 8 0 Silt loam, cocoa; slightly larger than above 11 U 6 8 11 8 811- Gravel with 2 cm dolerlte pebbles, gray 7 Sand, brown k Snad, coarser than above, gray 5 Pebbles in silty matrix 10 Sandy loam 9 Sand and granules; contorted bedding 5 Loamy sand, brown 5 Sand, coarse, in lens 1 Loamy sand with 3-^ cm granitic pebbles 7 Silt loam 1 Sand, gray 2 Sand, interlaminated fine and coarse 13 Loamy sand, with folded and contorted bedding k Silt loam grading downward to fine sand, white k Sand, brown'to gray, interbedded with white silt loam 11 Sand and loamy sand, grayish-brown, with nut structure, moist 36 The silt may be the parent material of an Important debris fan below the lip of Bull Pass in Wright Valley described on the following pages. Debris fans of southern Bull Pass A large fan of debris emanates from a deep bedrock notch leaning from a hanging cirque valley above the southeast end of Bull Pass (fig. 7 6 ). The fan has a maximum width of more than 2.5 km and a slope of 3* to 8 °. Superimposed on this and covering the upper third of its area 207 Is a second and steep-fronted fan which, In turn, 1s covered In part by a third more hunmocky and very much smaller fan. The active layer of the lowest and largest fan consists of boul ders up to several meters in diameter in a matrix which consists of either debris rich in powdery, yellow, sometimes stratified sand and silt (sandy loam) or less commonly of sandy material (See plate 2 and appendix I). Most of the boulders come from the back of the cirque above the fan, but some Vida Granite boulders on the lower fan may have originally been supplied by a glacier moving down Bull Pass from the north. Most of the original surface irregularities which might have Indicated the nature of movement have been subdues and most of the boulders at the surface have been worn to ground level. An average of 6 l upstanding boulders per 300 m traverse occur at the surface; however, within this area some 100 to 1 ^ 0 leveled remnants were observed, many over a meter in diameter. The smaller upper fan, some 10 to 13 m thick at its steep margins, has a surface slope up to 12*. It consists of large boulders of dolerite, granlte-gneiss, and porphyry dike rocks, derived entirely from the cirque above. These boulders are held in a very sandy matrix. This fan surface has also been subdued, and many boulders have been weathered to the ground, but it is distinctly less weathered than the larger underlying 206 fan. The upstanding 'boulders are as frequent as on the fan below, but the cavernous weathering is not as intense and only half as many boul ders have been reduced to the ground. A number of meltvater gullies radiate across both large fans, but these are new partly mantled, by wind-carried or frost-heaved debris. These fans have been deposited at three distinct times by flow of debris with some alluvial action. This debris was probably moved from the cirque and valley wall by the release of large amounts of meltvater, temporarily Impounded between the small glacier and its terminal moraine In the cirque above. The largest and earliest distin guished flow must have been thin, perhaps associated with considerable alluvial action, and it included and redistributed much of the debris left by earlier, through-valley glaciers. The second and third flows were successively more viscous and possibly emplaced more slowly than the first. Pecten (debris) fan of Wright Valley Although deposits in the Wright Valley have not been the main subject of this report, the follwing debris fan is described as it plays an Important part in the relationship of the Wright Valley glacia tion to that of the Victoria system. In ./right Valley, the scattered erosional remnants of a debris 209 fan now stand as much as 10 m In relief* This has been very deeply stream-dissected and is new largely covered by alluvium (fig. 7 8 ). The debris fan emanated from a deep notch leading from Bull Pass and its original surface sloped 5 * to the bottom of bright Valley. The remnants are composed largely of sparse, subrounded to angular pebbles, cobbles, and boulders, set irregularly in a powdery matrix of fine yellow sand and silt (the less than 2 mm fraction has 39 percent silt- clay of which 2.5 percent is clay). However, cuts near the bases of a few of these remnants reveal slumped, poorly bedded sands and gravels, underlain by powdery yellow debris similar to that which overlies them. In one of these gravel beds, 2.7 m above the present stream level, Nichols (1961c) found a bed of pecten shells^ (fig. 8 0 ). These have been dated by carbon-lU analysis as greater than 35/000 years old. This fan was apparently formed by the flow of meltvater charged with debris from Bull Pass. The debris consists of lithologic types derived from surficial deposits and bedrock of Eull Pass. The great quantities of silt have been derived from the thick lake deposits des cribed above. The unsorted texture, alluvial gravels, and apparent irregular margins of the fan suggest that it may have been formed by a series of mudflows with associated alluvial action. ?Bull (1 9 6 2 ) ha3 discussed the conditions under which these pecten shells were carried into the Wright Valley by invasion of ice from McMurdo Sound. Figure 80. Stream cut In debris fan below Bull Pass in Wright Valley shewing sand and gravel with layer of pecten shells. This fan appears to be slightly older than the large debris fan in Bull Pass. Almost all boulders are reduced to ground level, and in a 300 m traverse across two fan tops, only 3 upstanding boulder shells were encountered. This may in part be due to the much stronger and more constant winds which sweep Wright Valley, compared with those of Bull Pass, which is nearly transverse to the predominant wind directions. The pecten debris fan formed after the ice had retreated eastward in Wright Valley. The morainal deposits of southern Bull Pass are due to this glacier and are probably contemporaneous with the Bull Drift elsewhere in the Victoria Valley system (as discussed above); hence, 211 the pecten fan Is also related to the Bull Drift episode of the Vic toria Glaciation. Perhaps the strongest argument for linking the pecten debris fan and the drift and debris fans in southern Bull Pass to the Bull Drift is the similarity in the pattern of glacial flow. Nichols (1961a) notes that of the three younger glaciations marked by deposits from glaciers which moved westward up the Wright Valley, the oldest is the Pecten Glaciation, the type deposits of which are the Stratified sands and gravels containing pecten shells within the pecten fan. This, he notes, followed the earlier episode when an outlet glacier moved eastward down Wright Valley. History of the Bull Drift Episode During the Victoria Glaciation the maximum, volume of Ice came from local ice fields and from glaciers moving west from the area of McMurdo Sound. The earliest and major advance of the Victoria Glacia- t ion took place during the Bull Drift episode. Glaciers which moved into the valley system from all six distal valley ends, together with local ice fields and cirque or piedmont ice, occupied nearly the whole valley bottom and much of the upland, cirque-dissected area (fig. 8l). Approximately 2k6 km2 more valley floor was covered by ice than at present. Ice in the valleys attained a thickness of as much as 500 212 Figure 8l. Nap showing inferred extensions of glaciers In Wright Valley and the Victoria system during the Victoria Glaciation. 223 to 600 m in the area of Lake Vida but failed to cover the Insel Range mesas by only a few tens of meters. Advance Lover Victoria Glacier The Lover Victoria Glacier flowed westward, being joined by the Packard Glacier and adjacent cirque glaciers from the north and the Clark Glacier from the south. The northwestward expansion of the Clark Glacier was initiated partly through the impetus of the flow of ice moving westward through lower Wright Valley. The Lower Victoria Glacier probably reached at least 9 km farther vest than its present position, but the western border of its drift is attenuated and deposits are covered on the north and are scattered or very thin on the southeast. Large, salmon pink granite boulders, pro bably derived east of the terminus of the Lover Victoria Glacier, are scattered on bedrock near the southeast end of Lake Vida. Five hundred meters vest of the large group of boulders is a very large isolated granite boulder 169 m above Lake Vida, lhis may possibly have been derived from a cirque above, or from the east. Two kilometers west of this large boulder sore the eastern remnants of the drift left by the Upper Victoria Glacier. Physical relations of the drift in the Victoria 2 1 k system suggest that the Lover Victoria Glacier may have been as thick as 600 m in this area, and that the Lover Victoria met the Upper Vic toria Glacier here* However, scattered pebble-sized ventifacts of banded chert and silicifled silt-sandstone of the Beacon rocks, perhaps carried here originally from the vest, are the only glacial deposits remaining in this 2 km vide area south of lake Vida* / / The source of this westward flowing ice was probably from neve fields around the 1,^ 0 0 to 1,500 m peaks flanking the east end of the valley and was augmented by the accumulation and buildup of glacial ice in McMurdo Sound at this time (See p. 220). Upper Victoria Glacier The Upper Victoria Glacier with its tributaries expanded at least 15 km beyond its present position before merging with glaciers from the lover Victoria, Balham, and Berwick Valleys. This extension was due mainly to an increase in accumulation on the neve fields north of Sponsors Peak, but some nourishment probably came from the area of Mackay Glacier to the north. South of Sponsors Peak, the upper Victoria tongue split Into two branches, one flowing vest into Barwick Valley whereas the southern branch flowed around the east flanks of the Insel Range into the eastern end of McKelvey Valley and northern Bull Pass (fig. 8 l). This latter 215 tongue probably merged with the westward flowing Lower Victoria Glacier, but convincing evidence In the font of Interlobate moraine or Indicator erratics Is lacking* Glacier flow Into HcKelvey Valley brought very large sandstone boulders from the upper Victoria Valley and formed the high Mckelvey Moraine across eastern McKelvey Valley. End moraines as large as this are unusual In ftoathera Victoria land (Debenham, 1921a, p. 9 3 -9*0 and suggest rapid glacial movement, perhaps influenced by stronger accumulation and ablation. At .the Intersection with Balham Valley, the Berwick Valley branch of the Upper Victoria Glacier met the eastward flow from the expanded Webb Glacier, and a short, southflowlng tongue from the ice fields to the north (fig* 8 l). The composite glacier flowed southwestvard to the area of Bulla eye lake* This interpretation 1b based in part on the presence of glacial marginal features concave northeastward and formed by glacial recession from the Bulls eye lake area (plate 1 - in pocket). Balham and McKelvey ice tongues The Inland ice plateau did not thicken as much as did the Ice in the McMurdo Sound area (Hollin, 1962; Bull, 1 9 6 2 ) so that the overflow Into Balahm and McKelvey Valleys was only small* Most of it came Into Balham Valley fran two ice lobes on the sides of Shapeless Mt. (fig. *0* ,-v This ice reached the Bulls eye Lake pass area where it merged with the westward moving tongue from Berwick and upper Victoria Valleys. 216 Into Berwick Valley, with Its lover 'bedrock threshold, -me overflew from the plateau was greater. From this junction, a glacier tongue flowed south through the pass to the eastern edge of the depression in western McKelvey Valley (fig. 8 l). The glacier terminus apparently did not remain at this position long hut retreated to Bulls eye Lake where it stood to form the Bulls eye Moraine. At the same time the Blaham Ice tongue overflowed Into McKelvey Valley at the western end of the valley (fig* 8 l) and joined with the less extensive tongue there. The resulting ice apparently terminated In the deep hollow at the head of McKelvey Valley where it was joined hy tongues from the adjacent Olympus Range cirques. In this, as in all other cases where glaciers may have net "head on", there Is a conspicuous absence of clear marainal evidence. Cirque glaciers Most if not all of the cirques were occupied hy ice at this time, and many cirque glaciers, such as those of the Olympus Range, extended "beyond the confines of their valleys. Three cirque-fed glaciers north of the west end of Lake Vida coalesced to form a piedmont which pushed the Upper Victoria Glacier to the south side of the valley. A similar piedmont exists now on the northeast side of the St. Johns Range (fig. 5)* Mass-wasting has modified many of the deposits formed hy these extended cirque glaciers. 217 * Advance and retreat lo the southern Bull Pass area Reasons have already been given (p. 197 ) for relating the de posits at the southern end of Bull Pass with the Bull Drift in the Victoria Valley system* The glacial history of this area can he inferred to he as follows. With strong ice flor from the coastal area, both the Lower Vic toria and Lower Wright Glaciers grew to maximum lengths. The Wright Glacier probably reached lake Vanda and a lobe penetrated the southern end of Bull Pass, extending northwards to meet the small Orestes Valley glacier. The surface elevation of this Bull Pass tongue was at least 6 ^ 0 m and, if the high bedrock channels were formed at this time, it was 1 , 0 0 0 or 1 , 1 0 0 m. After forming a low terminal moraine in southern Bull Pass, the glacier began to retreat southward with the formation of the marginal channels. Meltvater streams from the Bull Pass lobe of the extended Victoria Valley glacier and from the Orestes Valley glacier carried seldments to the dammed by the retreating lobe of the Lower Wright Glacier. When the ice front had retreated eastward from Bull pass, a fan of alluvium and mudflow debris formed in Wright Valley below the lip of Bull Pass. This included a mass of pecten shells which had been carried westward from McMurdo Sound by the Lower Wright Glacier (p. 209)* 218 Soon after this Wright Valley fan vas formed, the over-lapping series of debris fans formed In southeast Bull Pass as described above (p. 206). Between the formation of the first and second fans, the glacier from Orestes Valley receded, leaving a coarse ground moraine* This Inferred history fits the field evidence in Bull Pass, but produces some difficulties. For example, if the Lower Wright Glacier surface were at 1,100 m in the Bull Pass area, the glacier would also have extended to lake Vanda, where it probably met the Upper Wright Glacier, extended by overflow of ice frcm the plateau. However, there is no drift at the lip of Bull Pass or in the area east of lake Vanda. The same difficulty, the absence of till at the inferred junction of opposing glaciers in the Victoria Valley system, has already been men tioned (p. 214). Alternate hypotheses for the origin of the drift in Bull Pass have been discussed previously (p. 197). Recession In the Victoria Valley system Deglaclation in much of the Victoria system probably began after the Lower Wright Galcier had retreated frcm its position in and below Bull Pass. As the inland ice plateau was lowered below the bedrock threshold, the supply to the McKelvey, Balham, and Barwlck ice tongues was cut off and these glaciers began to stagnate. 3mall recessional moraines in the Balham depression indicate that recession involved some 2 1 9 pauses. At the same time, there was a steadier and slower retreat of the Lower Victoria Glacier where nourishment diminished more gradually. The greatly extended Upper Victoria Glacier disconnected from the inland ice, but still fed from its own neve basin, retreated relatively slowly from its positions in McKelvey and Bulls eye Lake areas. Very low reces sional end moraines, some 125 to 375 m apart, were formed only in eastern Berwick Valley. Here and southwest of lake Vida, suites of lateral drainage channels were formed. Many small lakes, formed against the retreating termini or in natural depresions nearby, now comprise the only significant strati fied deposits. The dearth of recognizable outwash accumulation suggests that temperatures were not high enough to produce great amounts of meltwater. During and after the retreat of the ice tongues from McKelvey, Balham, and Barwick Valleys and Bull Pass, the presence of over-steepened valley walls, higher temperatures, and perhaps wetter conditions allowed the formation of solifluction sheets. Much of the valley floor that was ice free at the end of the Bull Drift episode has not been ice covered since. This includes most of Bull Pass, and McKelvey and Balham Valleys. The //ebb and Lower Victoria Glaciers retreated behind Lakes Vashka and Vida respectively, but now 220 far Is not known. The Upper Victoria Glacier shows no evidence of having retreated completely from the valley, but probably paused in its retreat seme 2 km west of Lake Vida. Sea level control In contrast with the conditions in the Insel Glaciation, the Bull Drift episode of the Victoria Glaciation involved only a small overflow of ice from the inland plateau. However, in this Bull Drift episode, a large quantity of ice invaded the Victoria Valley system from the east, which cannot be explained in terms of the present physiography of the coastal area. Considerations of the problem have been given by Hollin (1 9 6 2 ) and Bull (1 9 6 2 ). Hollin demonstrated that the lateral extent of the grounded ice sheets of Antarctica is determined by sea level. The lowering of the sea level produced by the Pleistocene glaciations in the northern hemisphere was followed, tfith a slight time lag, by a seaward extension and an increase in volume of the Antarctic ice sheet. Because the profile of a grounded ice sheet is approximately parabolic, lateral expansion causes a large increase in thickness at points near the edge while inland the increase is very much less. During the Illinoian and early Wisconsin Glaciations, the lower ing of sea level was probably about 150 m (Donn et al*» 1 9 6 2 ). This 2 2 1 caused an extension northwards of the eastern Antarctic Ice Sheet of about 9 0 tan, but the increase in thickness in the inland parts west of the ice-free valley area was only of the order of 100 m (Bull, 1 9 6 2 ). Hence, the increased flow from the plateau into the valley system was small. A second effect in the Ross Sea area of this decrease in sea level is that the Ross Ice Shelf became grounded, probably as far north as 7 6 * 30* S. Ice, mainly from western Antarctica, accumulated in the area to produce the equilibrium parabolic profile of a grounded ice sheet. East of the ice-free area, this ice sheet attained a thickness of at least 1,200 m (Bull, 1 9 6 2 ). The ramifications of such a situation are clear. Hollin (1 9 6 2 , p. 1 9 1 ) stated: . • . the "dry valleys" of Victoria Land would be filled not as much by the frequently postulated "ice floods" from the interior to the west (though such may have occurred) as by the intrusion of ice lobes from the grounded shelf to the east. The ice thicknesses during the maximum extensions of ice from McMurdo Sound into the Victoria Valley system and bright Valley are broadly in accord with the thicknesses calculated for this grounded ice sheet. The great extension of the Upper Victoria Glacier may have been a result of the "backing-up" of the Mackay Glacier and diversion of a branch of this outlet glacier toward the south. 222 The minor fluctuations in the vest-flowing glaciers and the eventual deglaciation of the Victoria system may he related to fluc tuations and the general Increase in sea level (Hollin, 1 9 6 2 , p. 190). However, after the disappearance of the grounded ice sheet in the Ross 5ea area, the controlling factors in the fluctuations are purely local ones. Seme of these have teen discussed hy Bull (1 9 6 2 ). Correlation and Age of the Bull Drift Episode Victoria Valley system The Bull Drift of this report includes most of those deposits attributed hy Bull et al. (1 9 6 2 ) to the Second and Third Glaciations. ;/right Valley The Bull Drift is here correlated with the Pecten and Loop depo sits described hy Nichols (1961 c) and with most of the deposits of the Second and Third Glaciations of Bull et al. (1 9 6 2 ) at hoth the east and west ends of the valley. The correlation of the Pecten gravels and Glaciation with that of the Victoria Valley system has been discussed previously (p. 210). Bull (1 9 6 2 ) has discussed the differences in inter pretation between Bull et al. (1 9 6 2 ) and Nichols (1961c) and concludes that: . . . the only significant difference in interpretation occurs with the stratified gravels(of the pecten debris fan) near Bull Pass. • • with the age attributed to the moraines which overlie them. 2 2 3 As noted previously, the gravels are the type deposits of Nichol's Pecten Glaciation while Bull et al. regarded then as outwash from Loop or Third Glaciation. This writer has found that these gravels are underlain and overlain hy deposits of similar texture and composition which he believes were deposited with the gravels. Nichol's Loop Glaciation, following the Pecten Glaciation, is identified by Nichols only in the eastern end of the Wright Valley. It is represented by a steep-sided end moraine 50 to 75 m high, about 12 km west of the Lower Wright Glacier (See fig. 8 l). This moraine and the other Loop Glaciation deposits to the east and west display weathering and erosion comparable to that of the Bull Drift. However, Loop Glaciation deposits have a slighly lower surficial boulder fre quency that may be a result of the stronger and more regular winds of the Wright Valley. The form of the Loop moraine, the degree of preservation of its components, and its relation to older and younger deposits is very similar to those of the McKelvey and Bullseye Moraines. It is quite possible that all three end moraines were deposited during the same period by glaciers in equilibrium. The glacial stillstand represented by the Loop moraine In the eastern Wright Valley may have a counterpart at the west end of Lake 22k Vanda in a thick 75 m) > hummocky moraine showing similar weathering and erosion. This is west of a more subdued ground and lateral moraine which shows erosion comparable to that of the Pecten deposits. Mt. Gran area: Alatna Valley After the retreat of the inland ice tongues from Alatna Valley the area was invaded by glaciers from the coastal area. Deposits of the first episode of the second glaciation ("B" Glaciation) Include very cavernously weathered erratic boulders of pink granite and subdued ground and lateral moraine at the far west end of the valley. Since this episode, basaltic dikes have been etched out seme 1 to 2 m above the including sandstone. The weathering and erosion is less than that of the Bull Drift in the Victoria system, but this first recognizable westward advance may be correlated tentatively with the major advance (in Bull Drift episode) of the Victoria Glaciation. McMurdo Sound - Taylor Valley Bull et al. (1 9 6 2 ) attempted a correlation of their Second and Third Glaciations with Pew^'s (i9 6 0 ) "Taylor1 and PryxeH" Glaciations respectively. Taylor moraines are greatly subdued; boulders are wind abraded vent ifacts and desert pavement are well developed. Moraines of the succeeding Fryxell Glaciation are better preserved, and also contain well-developed desert pavement and ventifacts. During the 22$ Taylor Glaciation, ice reached 1,000 ft (305 m) above sea level in the eastward trending valleys on the northwest side of the Koettlitz Glacier, and about 400 m above sea level at the east end of lake Bonney in Tayjcor Valley (Angino et al. 1 9 6 2 ). Ice in southwestern McMurdo Sound near Marble Point reached at least 1,200 ft (36 6 m) above sea level. During the Fryxell Glaciation, ice in McMurdo Sound was probably less extensive and may not have reached above several hundred feet on the flanks of Ross Island (Pewe, i9 6 0 , P* 506). With the present lack of quantitative data and description avail able for the Taylor and Fryxell deposits, it is difficult to maka any correlation. However, granitic bedrock exposed near possible deposits of the Taylor Glaciation on slopes 120 to 300 m above Lake Bonney in Taylor Valley shows deflation on the order of 0.6 to 3 m (Angino et al. > 1 9 6 2 ). This is comparable to erosion shewn by bedrock exposed since the Bull Drift episode in the Victoria system. The thickness of ice in McMurdo Sound during these glaciations may be of Importance in correlation. Nichols (1961a) suggested that at the time the Pecten shells were being transported into Wright Valley (Pecten Glaciation) the ice was 3,500 ft (IO67 m) thick, while Bull (1 9 6 2 ) suggested that it may have been 1,200 m. However, these thickness are IfOO or $00 m greater than those suggested by Pewe for the McMurdo Glaciation and 800 to 900 m greater than thickness postulated for the Taylor Glaciation. Additional detailed study of glacial limits along 226 Age It Is not possible to determine the absolute age of the Bull Drift episode. The carbon-1^ age of the pecten shells (35,000 years) is subject to small errors (Broecker, 1963), but does reliably indicate that the minimum age of the deposits is 30,000 years. Considerations of age of the maximum glaciation based on lowering of sea level are ambiguous. The lowering required is of the order of 150 m but this could be related to the early Wisconsin Glaciation (>30,000 years) when the drop was 115 to 13^ m, or to the Illinoian when the lowering was 137 to 159 m (Donn et al., 1 9 6 2 ). Pewe has corre lated the Taylor Glaciation with the Illinoian Glaciation of North Amer ica. Vida Drift and Associated Deposits The Vida Drift is named from Lake Vida where till and outwash are well exposed. The drift comprises two major units: till, often somewhat sorted and sometimes with bedded areas; and silt, sand, and gravel out wash as fans or cut-flll deposits. Associated with the drift are debris lobes with large alluvial fans emanating from their fronts. Seme soli- fluctian deposits are adjacent to the older portions of this Vida Drift, but they are usually confined to the steeper valley walls and benches above the valley floors. 2 2 7 The type deposit is the till; the alluvial deposits and products of mass-wasting are correlated to these deposits on the has is of their preservation and interfingering or intergradational relations. Till Distribution and morphology The till of the Vida Drift is everywhere sharply differentiated front that of the Bull Drift in the following ways: (1) It is thicker. (2) It shows less surface weathering and erosion. (3 ) It has greater general relief. (1+) It displays widespread development of active polygons. (^) It is much less mantled by sollfluction. (6) Its fine fraction is coarser. (7 ) It is marked by an abrupt change in -type of deposition. (8) It is close association with alluvial deposits. However, the transition to the younger deposits of the succeed ing (Packard) episode is less sharp, and weathering grades toward the depositing glaciers. The dividing line is based largely on a change of type of deposition. The three main localities of the Vida till are: (l) the east side of Lake Vida between 10 and 6 km frcm the Glacier; (2) the upper Victoria Vallay, 10 to 8 km from that glacier; and (3 ) Berwick Valley, 9*5 to h km from the Webb Glacier. Vida till la also distinguished on the basis of weathering at the high, far western ends of McKelvey and Balham Valleys where the drift is recognized up to 2 km frcm the stagnant tongues of the inland ice. A well-defined terminal moraine with several meters relief, also of this episode, occurs 2.5 km from the northern terminus of the Clark Glacier. Till showing a similar degree of weather ing occurs in the four cirques north of Lake Vida (fig. 5) end in the cirques opening northwestward toward the Clark valley (frontispiece). Above Lake Vida, these deposits extend at least a few hundred meters beyond the cirque boundaries and approximately 2 km beyond the present cirque glaciers. However, their boundaries are gradational with younger or older deposits, and in some cases have become diffuse through frost action and sollfluction. The till of the lower Victoria and Barvick Valleys occurs entirely as ground moraine, usually some 2 0 to 30 m thick with surfaces often standing several meters in relief above the much more weathered and thinner Bull. Drift. The moraines terminate against or are associated at their termanl with outwash deposits bordering Lakes Vida and Vashka respectively. Here, ice-contact and channel scarps are still relatively well preserved. An ice-contact moralnal front, 23 m high, with a 3?° slope, forme a semicircle around the western side of Lake Vashka; 229 however^ the Vida moraine itself terminates in lower and thinner de posits on the east side of the lake (fig. ]Jt)* Hie Vida till of upper Victoria Valley occurs as a series of high, relatively closely spaced end moraines (15 distinguishable crests), some with as much as 35 m relief; the largest of them is 2 3 0 m vide. To the northeast of these deposits, the moraines have been breached and partially covered by outwash sand and gravel. The boundary drawn between this and the Bull Drift is based primarily on a fairly abrupt change from ground to end moraine deposits. To the vest in eastern Barvick Valley, these Vida end moraines, some reaching to 550 m above sea level cm the east end of the Insel Range, stand up in sharp contrast to the subdued ground moraine and boulder accumulations of the Bull Drift. Unlike the Bulls eye and McKelvey end Moraines, the Vida end moraines of upper Victoria Valley are more irregular In outline and very hummocky. In upper Victoria and Barvick Valleys, the contact of the Bull Drift aith the Vida Drift is also expressed by hummocky ground, broken by widespread, active, and veil-developed polygons. A sharp micro-relief of up to 2 m is developed by the polygons above lake Vahhka. At the east end of lake Vida, the original hwmocky topography of the deposits has been masked by secant eollan sand, but polygons are active and veil developed everywhere except on the dunes. Axial stream channels 230 cut as deeply as 12 m Into the Vida Drift of Victoria and Berwick Valley. Solifluction has been slight since the retreat from the maxi mum of the Vida Drift episode and only very slight mantling of the Vida till has occurred. Nature and preservation of till constituents Boulder frequencies of Vida deposits average between 58 and 7^ per 3 0 0 m traverse (table 9 ), compared with less than 35 on the older Bull and Insel deposits and more than 100 on most of the younger (Packard Drift) deposits. Considerably less than 50 percent of the boulders have been worn to the ground and of these, more than 8 0 per cent are medium to coarse-grained dolerltes which weather rapidly. Vida till of McKelvey and Balham Valleys is distinguished from older deposits by the lack of rocks other than Beacon rocks and Ferrar Dolerite. In Berwick Valley, the sandstones are less cannon. In this valley, 15 to 35 percent of the boulders consist of a yellowish granite and Intruded gneiss, schist, and horafels. These are probably derived from outcrops on the valley walls and are rarely preserved on the surface of the older till to the east. The surface litbology of the Victoria Valley deposits is not distinct from that of the earlier episode. The number of cavernously weathered boulders is much greater on the Vida deposits than on either the younger or older deposits (fig. 8 2 ). 231 The effects of wind abrasion are really restricted probably because of the hummocky topography. Well-faceted ventifacts In well-developed lag pavement8 are present in open areas, and wind-cut hollows, 5 to 15 cm deep at the bases of boulders, are more common than on most of the younger deposits. Figure 82. Cavernously weathered boulders on Vida ground moraine of lower Victoria Valley. Looking west toward lake Vida. The Vida till within the active layer is coarser than the older till (table 10). Excluding deposits in Barwick Valley, the mean size of the material of less than 2 mm consists of coarse sand, and the silt- clay fraction makes up only from 1 to 9 percent. The till (a sandy loam) comprising the deposits of Barwick Valley consists of 5 to 3 6 percent 3 ilt-clay fraction of which 8 to 13 percent is clay. This is only 232 slightly coarser than the till of the Bull Drift In Barvick Valley to the east of Lake Vashka, but the Vida till Is much more pebbly than the older tills. Samples from below the active layer In Barvick and Victoria Valleys shew nearly the same particle size as those fran the active layer. Thus surface texture is not due to weathering, but probably Is the original texture of the deposits. In the Barvick Valley deposits, the finer texture is due to the presence of easily weathered gneiss and schist. In the Vida till, the sorting is much better, the deposits are more moist, and the active layer more shallow than in the Bull till. Efflorescent salt accumulations are generally lacking. Oxidation of the near-surface material is noticeable In areas high in dolerlte particles. However, in general no clear weathering profile is distin guished in most of the Vida till. Scattered areas of stratified sand associated with the Vida till are most conmon in the lower Victoria deposits. Examination of stream cuts and a pit formed by blasting reveal that Vida till In this area is better sorted, sandier, and less bouldery than elsewhere. It closely resembles the ablatlon-eolian deposits forming at present at the glacier front. The subsurface text lire and weathering characteristics of the Vida till are not sharply different from those of the younger (Packard Drift) till (table 10). 2 3 3 Stratified Drift Deposits of stratified silt, sand, and gravel of glacial origin occupy areas of from 0.25 to 0.75 km2 adjacent to the termini of mor aines of the Vida Drift in upper and lover Victoria and Barvick Valleys. Ice-contact deposits occur near the termini of morainal deposits in Barvick and lover Victoria Valleys. At the southeast end of lake Vida, a fan of stratified sand and gravel, 30 m thick at its origin, slopes 2 ° to 1 2 * westward from the southern terminus of the Vida ground mo raine to the surfacd of lake Vida (fig. 5). A few large granite boulders (0.5 to 2 m diameter) are scattered over the surface, which is mantled by a lag pavement of vell-formed pebble vent if acts (fig. 8 3 ). That it is of ice-contact origin is suggested by the presence of contorted bedding, a large kettle, and a channel hanging at its upper end. Buried patches of green, dlatcmaceous (algal) peat, including botryoldal, calcium carbonate-cemented concretions of sand and diatoms, (D. Koob, oral ccnmunication; also see ./ebb and McKelvey, 1959* P* 130) occur on the slopes up to at least 20 m above lake level. These patches are 2 to ^ m in diameter, usually 10 to 2 0 cm thick, and are often burled 2 0 cm in the gravel of the fan surface. The algae accumulations can be either pond deposits or perhaps deposits formed during a high stand of Lake Vida. If these are pond 23k deposits, the topography of the fan must have teen greatly changed because water could not accumulate in these areas at present. In this connection, it is remotely possible that the algae date from a time when the fan had overlain stagnant glacial ice, and that when this ice melted, the ponds were drained and beds distorted. Figure 8 3 . Lag pavement of pebble ventifacts in ice-contact fan, east end of Lake Vida. 235 An algae sample frcm 20 m above lake level at this location has been found by the carbon-14 method to be 9*7°0 - 350 years old (1*1, Traut- man, Isotopes, Inc.), On the southwest side of Lake Vashka Is an area of kame and kettle topography formed of bedded and well-sorted gravel, moist sand, or silt (appendix I), Included with these deposits are patches of till and single cobbles and boulders, A a (pinre-shaped alluvial fan-terrace of 1 km^ In extent and at least 2 to 3 ® thick occurs 2 km west and approximately l£ m to 25 m above Lake Vida, diverting the main stream drainage from the Upper Victoria Glacier (fig. 5)* The surface of this fan 3lope3 1° to 3° radially from a narrow stream terrace on the west. This stream terrace, 1 to 2 m above the present Upper Victoria stream bed, narrows from 2 5 0 m in width at the fan to less than 2 0 m at the border of the younger (Packard) drift. The eastern, lower end of the large terrace stands one meter above a somewhat younger outwash terrace leading to Lake Vida in which a few pockets of burled diatomaceous peat occur. At the surface of these terraces, the original bedding has been greatly changed by wind so that the surface displays well-formed pebble ridges. The position, shape, and texture of the terrace fan suggest that it may have been deposited in shallow water at an extended stage of 236 Lake Vida (fig. 5)* Lt has strong similarities with the terraces farmed by damming of meltwater of the Hobbs and Salmon Glaciers (fig. 2) (See Debenham, 1921a, p. 75-76). However, the terrace fan is much coarser than the outwash fan deltas forming at the present time in the shallow margins of Upper Victoria Lake where the largest material being de posited is only about 8 cm in diameter. Alluvial fans below Orestes Valley and gravel terraces above the present stream bottom in southern Bull Pass may have formed during the Vida Drift episode. Debris lobes Two large lobes of bouldery, moraine-like debrlB project from the 25° to 30° slope forming the riser of the bench northwest of Lake Vida (fig. 5). Alluvial fans, several meters thick and covering 5 km2 , radiate from the lobe margins and reach to Lake Vida, covering some of the Bull and older Vida Drift. The eastern one of these lobes is approximately 875 m wide and slightly greater in length, and is covered by a large barcan sand dune. It is k3 m thick at its terminus (fig. 84) but may be more than 70 m thick elsewhere. Two kilometers to the west is a second lobe which is actually compound, consisting of a short, 600 m wide tongue, trending southwest, superimposed over a second, longer but narrower tongue, 2 3 7 treading southeast. This caepound lobe la last 15 m thick at its terminus hut la probably 50 * thick In places. Both lcfbea bare steep sided, scalloped margins which wary fraa 26* to 39* inclination and are unstable. Their surfaces, which are hvanocky, slope at 6* to 8* hut steepen to 20* where they grade upward Into the debr la -covered bench. Snail, sore recently foread solifluetlon fronts occur on the steeper surfaces of the lobes. Figure 8 4 . Front of debris lobe at the north aargln of lake Vida (also see fig. 5 )« Looking northwest. The debris lobes consist of angular, granitic, and gnelsslc boulders and cobbles In a satrlx of send 10jt allt-clay) and pebbles all derived t r m the slopes above. At the top, sany large boulders 238 have been weathered to the ground and no suggestion of alignment of the stones has been preserved* Some deep stream channels occur on the lobes which contain water-worn boulders* The scalloped margins, the irregular diverging shape of the western lobe, the superimposed small solifluction fronts, and the position of the lobes below the dolerite bench suggest that they were emp laced by mass-wasting. Movement must have been slow as no scar was formed, and the flow must have started on the very gently inclined bench• The following sequence is suggested. Moraine was deposited on the bench by a piedmont glacier during the Vida Drift episode as well as earlier by a coalescence of cirque glaciers. Later, it was soaked by meltwater from the retreating glacier and began to flow a3 a solifluction sheet. As the front reached the steeper slopes (5° to 8 ° near the edge of the dolerite bench), movement was concen trated in the areas of meltwater channels. Then streams of wetter debris separated, flowing more rapidly and thickening as the front descended more than 190 m down the 30° bedrock slope. Movement ceased near the slope bottom as the thickness became too great (tfahrhaftig and Cox, 1959# P* and water loss increased the viscosity. The two debris lobes show about the same degree of weathering, but the eastern one may be slightly older. Near the lobe termini, 2 3 9 half of the boulders are worn to ground level. The boulder frequency In these areas varies between kO and 13 per 300 m traverse, but many of the upstanding boulders look fresh, especially near recent super imposed lobes. The degree of weathering on the main lobes Is between that of the Bull Drift and of the Vida Drift, but they are correlated with the latter since the alluvial fans at their fronts truncate and cover Bull Drift adjacent to Lake Vida. These fans have also probably been formed in part during the succeeding Packard Drift episode and have been even more recently cut by meltwater streams. History of the Vida Drift Episode The Vida Drift episode followed the major recession of the Bull Drift episode, of the Victoria Glaciation. This episode is dis tinguished not so much by distinct or important glacial readvance, which cannot be proved, as upon a change in the regimen of the Upper and Lower Victoria and Webb Glaciers. This involved a glacial still- stand, or very slow retreat, increased deposition of till, and possibly the formation of terminal glacial lakes at the borders of which distinctive outwash deposits were formed. Balham and McKelvey ice tongues In the western half of Barwick Valley, a thick Webb Glacier was fed by overflowing inland ice as well as by local accumulation, sko \ whereas at the heads of Balham and McKelvey Valleys, the inland ice tongues extended no lower than 1,000 m ahove sea level, about 2 loo beyond their present ice fronts* Weathering relations of the moraines of the Vida and Bull Drift episodes suggest that only a minor pause within the general retreat may have occurred at this time* Cirque glaciers Most of the cirques were occupied by glaciers which were only slightly smaller than in the earlier episode, but in the cirques opening onto McKelvey Valley from the Olympus Range, former glaciers had so destroyed the peaks and scarp that Insufficient area sheltered from the wind remained for accumulation of snow. The Clark Glacier, fed by cirque glaciers, built a broad terminal moraine 2.5 Ion northwest of the present front. However, end moraines were not formed in many of the cirque-valleys at this time, and the deposits show weathering which is gradational with the lower and older deposits. This is par ticularly evident north of lake Vida, where glaciers remained extended beyond their valley confines or 3 to 5 kn beyond cirque headwalls since the earlier episode. 2 b i Upper and Lovrcr Victoria, and Webb Glaciers During the Vida Drift episode, the Upper and Lover Victoria and Webb Glaciers all extended 9 to 10 km from their present fronts (fig. 8 1 ). The Vida Drift episode marks a pause within the general recession from the maximum of the Victoria Glaciation. In Barvick and lover Victoria Valleys, strong differences in weathering between Vida and Bull Drifts suggest a moderately strong glacial readvance to Lakes Vashka and Vida, but stratigraphic or other good evidence for this readvance is lacking. In upper Victoria Valley there was no Important readvance. The relatively abrupt changes in degrees of weathering from Bull Drift is a consequence of interrupted glacial retreat, a pause, and slow, general retreat with deposition of large amounts of debris In the form of closely spaced recessional moraines. Such glacial action suggests conditions of increased local accumulation and an almost equal increase in ablation. These changes were less accentuated in Barwick Valley. Here, elevation, lover accu mulation, and interdependence on a slower reacting inland ice sheet were Important. Mass-wasting continued on most of the steep valley walls from the preceding recession through at least the early part of the Vida 2 k 2 Drift episode. The debris lobes north of Lake Vida formed during the retreat of the Upper Victoria Glacier from its Bull Drift episode maximum and early in the Vida Drift episode, Water from the retreat ing glaciers above and from the ice within the debris flowed frcm the debris lobe termini, forming large, gravelly, alluvial fans. These fans continued to be enlarged through this episode and perhaps into the Packard Drift episode. The large amounts of debris contributed by mass-wasting in the Victoria and Barvick Valleys before and during the early part of this Vida Drift episode, along with the vigorous regimen, enabled the three main valley glaciers to deposit thick blankets of till. In upper and lower Victoria Valleys and to a lesser extent in Barvick Valley, much of the glacial debris was redeposited by outwash streams or soiled by wind action. Lake Vashka area Figure 8 5 shows a possible origin far the terminal deposits of the Vida Drift near Lake Vashka. In the Vida Drift episode, the Webb Glacier readvanced as far as the east end of Lake Vashka (fig. 8l). The bedrock basin, excavated previously (p. 1 7 ), Impeded the eastward flow of the glacier and caused a buildup of ice to the vest. The presence of the basin and the postulated stagnant ice may account for the lack of a terminal moraine. w. SHEAR MORAINE EAO ICE I RELICT SHEAR MORAINE JTHN TERMINAL DEPOSIT O P VIDA DRIFT EPISO D E 77T7777tx 117 IORABME OF n r m EARLER EPISODE MAIN 1 SUBSCHARY SLUMP SLUMP FACE REMNANT * ^ 1 ICE MASS 777777 T ’i K AME 'KETTLE 777777 AREA EASTERN LIMIT OF VJOA DRIFT 777777 77777 LAKE VASHKA (FROZEN) BEDROCK BASIN MAY HAVE FORMED OURING EARLIER ADVANCE P.CALKAI 1903 Figure 8 5 . Sketch shoving a possible origin of terminal deposits of Vida Drift in the Ieke Vashka area, Barvick Valley. 2kk Outvaah fang of Victoria Valley and a high stand of Lake Vida The Lower Victoria Glacier, with its northern tributaries including the Packard Glacier, was about 2 km longer on the north side of the valley than on the south side, much as it is today (fig. 5 ). Some of the moraine at the terminus was washed into a lake (Lake Vida) formed in the bedrock basin between this glacier and the front of the Upper Victoria Glacier. However, much of the material formed a thick outvaah fan, built partly over stagnant ice into Lake Vida. At nearly the same time, as the Upper Victoria Glacier was retreating in a slow, pulsating fashion, a broad outvash fan began to form of the terminus and probably continued to grow through the Vida Drift episode. The coarse texture of the outwash deposits at both the east and vest ends of lake Vida, compared with similar fans forming today, suggest that they were formed in wetter and perhaps warmer conditions than exist at present. There is some evidence to suggest that during part of the Vida Drift episode, Lake Vida was I** m or even 20 m higher than its present level of 390 m above sea level (U.S.G.S., Topographic Map, Ice-Free Valleys - Victoria land). It extended 2 to 3 km farther west between the opposing ice fronts. No shoreline features higher than 2*4-5 a few meters cure clearly distinguished. However, the position and shape of the outvash fans at loth ends of the lake suggest that they were deposited at the lake edge. This was about 20 m above the present lake level (fig. 5 )• If there were a yet higher level, it did not persist long enough to allow the accumulation of thick depo sits or to form Important shorelines. Wind, alluvial, and frost action may have also largely destroyed any lacustrine features on the gently inclined lake endge. Climatic factors It has been suggested that temperatures and moisture were Increased during the Vida Drift episode. However, it is possible that under present temperatures, such melting and resultant outvash phenomena might exist if the Victoria Glaciers advanced back into the lower areas toward Lake Vida. The 9*700 years old. buried algal peat from a fan at the east end of lake Vida may date a warm period when burled glacial ice was in the process of melting. From an examination of ocean bottom cores from the mount of the Robs Sea, Hough (1950, p. 259) has suggested that the climatic optimum of the northern hemisphere also occurred in the Antarctic between 6,000 and 15,000 years ago. 2k6 Age and Correlation of the Vida Drift Episode The carbon-I1* analysis of the peat (p. 235 ) demonstrates that the Vida Drift at lake Vida Is more than 9*700 ± 350 years old. Victoria Valley system Bull et al. (1962) mapped the drift vest of lake Vashka as a deposits of their Fourth Glaciation and noted (p. 75)i Ground moraine close to the sides and fronts of the Upper and Lower Victoria Glaciers, Lover Wright Glacier and the alpine glaciers may be contemporaneous with, or younger than the fourth glaciation. The m^ifiniinn of the Fourth Glaciation is equivalent to that of the Vida Drift episode* Wright Valley The Vida Drift is equivalent in preservation to those deposits of Nichols' (1 9 6 1 c) Trilogy Glaciation west of the meltwater stream frcm Clark Glacier in lower Wright Valley (fig. 81) and to the Fourth Glaciation deposits mapped by Bull et al. (1 9 6 2 ) in the South Fork of western Wright Valley. The oldest and most extensive stage of Nichols' Trilogy Gla ciation is represented by discontinuous end moraines, approximately 8 km west of the Lower Wright Glacier, whereas the youngest deposits 247 are represented by Ice-cored moraines near the glacier* Nichols (1 9 6 1 c) noted: All deposits of Trilogy age except those contaminated' with weathered Loop material show: (l) A m a n amount of wind cutting; (2 ) an absence of odd-shaped weathered rocks and of boulders weathered to ground level; (3 ) many upstanding boulders; (4) only minor staining. No sharp break in degree of preservation was noted by the writer between the terminal deposits of the Trilogy and the Loop deposits; however, there are more end moraines eastward from the Trilogy terminus, perhaps suggesting a change In glacial regimen. Cavernously weathered boulders, which may not be a result of Loop "contamination/ 1 are sprinkled over a bedrock bluff of the same lithology, ice-covered during the Trilogy maximum. The morainal debris In flat areas west of the meltwater stream from the Clark Glacier 3hows numbers of cavernously weathered boulders and boulders weathered to ground level, very similar to the Vida Drift of the Victoria system. Raised marine and lacustrine beaches and outwash deposits were correlated with the Trilogy Glaciation. During the retreat of the Trilogy glaciers, the raised beaches which reach 67 feet above sea level around McMurdo Sound were built, and the level of Lake Vanda dropped approximately 185 feet. Carbon-lU analysis of the elephant seal burled In a raised beach at Marble Point Indicates that the full-bodied stage of the Trilogy Glaciation probably occurred more than 7,OCX) years ago (Nichols, 196lc). 2k8 Also, with the Trilogy retreat, extensive valley train de posits were formed in lover Wright Valley. Much of this sequence is similar to that of the Vida Drift episode. Invasion of ice from McMurdo Sound If the Trilogy maximum and the maximum of the Vida Drift episode are contemporaneous, the Lover Victoria Glacier extended vest of its present position for 1 or 2 km more than the Lover Wright Glacier did at this time. Since the bedrock divide below the east end of the Lover 'Wright Glacier is about 300 m above sea level (Bull, i9 6 0 ), whereas that of the Lover Victoria Glacier must be 30me 800 to 900 m above sea level, any direct flew of ice from McMurdo Sound should have penetrated much farther vest into 'Wright than into Victoria Valley. Since the reverse is true, the greater extension of the Lover Victoria Glacier must be due to factors other than direct flow of ice from McMurdo Sound. These factors may be that temperatures were lower, or that accumulation was greater in Victoria Valley than in Wright Valley. It is also quite possible that there was no ice in McMurdo Sound at this time. This is in agreement with Thomas (i9 6 0 ) who after examination of an ocean bottom core from McMurdo Sound (77° 25* 3) suggested that the Ross Ice Shelf has not advanced materially beyond its present limits during the past 3 3 * 0 0 0 years. 2k9 Mt. Gran area: Alatna Valley No widespread or distinctive deposits occur here which are comparable in preservations with those of the Vida Drift. The drift of the first episode of the "B" Glaciation (See p.l62 ) is slightly more weathered than Vida Drift hut that of the second episode is much less weathered and erroded than the Vida Drift. There may he no advance or stillstand here contemporaneous with the Vida Drift episode• McMurdo Sound - Taylor Valley Bull et al. (1 9 6 2 ) attempted a correlation of their Fourth Glaciation with the Koettlitz Glaciation of Pewe (i9 6 0 ). However, the preservation of the older drift of the Fourth Glaciation (equi valent to Vide Drift) is much poorer than the deposits of the Koett litz, which are ice-cored. This writer briefly examined Fryxell deposits (See p.l6l ) at the mouth of Taylor Valley which appear similar to those of the Vida Drift in degree of weathering, presence of ventifacts, and preservation of morainal form. Packard Drift The most recent widespread glacial deposits in the Victoria Valley system extend ^ to 6 km from the fronts of Upper and Lower Victoria and Webb Glaciers. These glacial deposits are distinguished 250 from those referred to the Vida Drift by narked differences in topo graphic form and preservation, or, in at least one area, by an abrupt change In degree of weathering. Although the distinguishing criteria used varies from valley to valley, the changes from the Vida deposits suggest a correlatable and significant change in glacial regimen. This drift is named after the Packard Glacier in lower Victoria Valley, south of which are thick ablation deposits. Similar deposits are identifiable at the Upper Victoria, Lower Victoria, and tfebb Glacier fronts and also near the tongues of the inland ice in Balham and McKelvey Valleys. However, near the plateau edge and the bordering cirques, the Packard Drift is not always as easily distinguished from the Vida Drift. All the other deposits which were laid down or exposed during the Packard Drift episode (post Vida Drift episode - to present) are tied to the till of the three main valleys. These deposits include: outvash sand and gravel; alluvial fans; accumulations of wind-blown sand; and deposits of mass-wasting, Including solifluction sheets, debris tongues, and mudflows. These deposits associated with the Packard till have been discussed previously under "Gecmorphological Phenomena". 251 General characteristics The till left during the Packard Drift episode on the valley floors falls Into tvo main types* These are the poorly sorted till; and the better sorted and more sandy or gravelly material deposited with the aid of wind or more rarely running water* Smaller areas of ablation moraine believed to be cozed by stagnant glacial ice occur in Barvick and lower Victoria Valleys. All these types display more youthful characteristics than those of the Vida Drift and in fact they grade to and include deposits now being formed* In Victoria Valley, where deposits are thick at the valley margins, the ground moraine is more hunznocky, and marginal channels are very well defined; solifluction mantling has been slight, and in many areas lateral moraines remain unaltered, some preserving slopes greater than 30* (fig. 8 6 ). However, in lower Victoria Valley, the deposits have been mantled by wind-blown sand. Polygons are well displayed in the deposits usually to within a few meters of the gla cier fronts* Weathering of till is less at the surface than in the older deposits and is only a few centimeters deep* The till, excluding that of the Lower Victoria Glacier, is very bouldery, with average fre quencies in excess of 100 upstanding boulders per 300 m traverse (table 9 ); cavernous weathering and granular exfoliation has been 252 slight in most deposits (table 8 ). Wind cutting is limited, only a few moderately faceted ventifacts being found, and even the less resistant surface boulders are preserved. Figure 8 6 . lateral moraine terraces of the Packard Drift (Webb Glacier). Glacier moved from left to right. View north across Webb lake, Barvick Valley. The Packard till is more sandy and often better sorted than the Vida till (table 10). The weathering profiles such as those of the Vida and Bull tills are absent or are developed only locally as oxidation profiles for a few centimeters below accumulations of dol erite stones or where conditions have favored the format ion of a sub surface salt layer. 253 Barvick Valley: knob and kettle, and ice-cored moraines In the center of the valley, 5 ku east of the Webb Glacier, Is a relatively abrupt change from hummocky (Vida Drift) ground moraine of a few meters relief to ridges, and knob and kettle topo graphy in (Packard) till (fig. lA). Belief is considerable in this material and is greatest (30 m) in a north-south belt, halfway between Hourglass Lake and Webb Lake. Ho break in surflclal weathering is distinguished at the contact here with the lower ground moraine of the Vida Drift; however, vest of Webb Lake, within the Packard Drift, there is vlthln a few hundred meters, a complete disappearance of cavernous weathering in the boulders, but the knob and kettle topo graphy is continuous (fig. 8 7 ). To the south of the lake, the knob and kettle moraine is bordered sharply by a high-standing ablation moraine which appears to overlie stagnant glacial ice (fig. lA and 86). The knob and kettle moraine east of Webb Lake contains deep, channel-like troughs between ridges and is pock-marked by elongate kettles* Hie channels slope irregularly east and have hanging upper ends while those adjacent to the ice-cored ablation moraine below Haselton Ice Fall have more regular slopes but trend west toward the glacier or sharply north into Webb Lake. The irregular configuration of these channels and slopes opposing that of the glacier suggest that Figure 8 7 • Kettles in Packard till* View northwest across Webb Lake to the Webb Glacier, Barvick Valley* Figure 88* Ice-cored ablation moraine of western Barvick Valley Note milky patches of ice In center and lower right. 255 they were formed around stagnant ice masses. No glacial ice was found within the upper meter of these deposits and probably they are not ice-cored. Hex/ever, the larger kettles east of Webb Lake are occu pied by lakes which are part of the drainage system from Webb Lake. Many striated boulders of medium-grained dolerlte and a few of sandstone occur on both ridge tops and channel bottoms on the knob and kettle moraine which is not ice-cored, but are absent on the ice- cored moraine nearby. The striations on the boulders are very often parallel and aligned with the long axis of the boulder. Many of these boulders are oriented parallel to the morainal ridges and intervening channels, i.e. northwest-southeast, slightly askew the valley axis here. Striated and aligned boulders are rare elsewhere in the valley system and are not cotononly associated with thick, hunmocky deposits. Their origin here is not understood. The ice-cored ablation moraine adjacent to the lake and along the west margin of the Webb Glacier preserves stagnant ice, probably of glacial origin by virtue of its great thickness of dolerlte boulders (fig. 8 9 ). These have been carried from the plateau and from Immediate valley walls by glacier undermining and talus creep (fig. 2 1 ). Material smaller than cobble size occupies considerably less than 50 percent of the surface area of these ice-cored moraines, and boulders larger than 1 m occur at the surface every 1 to 3 m. In other 256 respects, these ice-cored moraines more than a few ten3 of meters frcm active glaciers cure typical of those commonly found along the coast of McMurdo Sound. The "boulders are very angular and all exhibit little or no wind-cutting; hummocky relief is augmented by particu larly veil-developed polygons, often vith marginal furrows more than a meter deep (fig. 3 9 ); many closed depressions contain frozen ponds; and accumulations of mlrabillte and associated salts occur in some areas where ice has recently been exposed and ponds have drained (fig. 19). Figure 8 9 . Blocky ice-cored moraine of the Packard Drift on the vest edge of the Webb Glacier. 257 The presence of very numerous ponds vlthin moraines of doler- ite may in mos'b cases he ascribed ho a melting ice core; as the snow often sublimes frcm the dark rocks long before the temperature Is high enough for melting and for water to flow. Therefore, the ponds also Indicate that the ice core is melting. The isolated position of the fresh, ice-cored moraine adja cent but higher than the material carrying more weathered boulders requires sane explanation. The glacier which stagnated and is still preserved in the ice-cored moraine must also have occupied the whole valley area and covered or deposited the older appearing, lower lying knob and kettle moraine at the southeast end of //ebb lake. One hypo thesis is that during a short readvance, the part of the glacier in the valley center was unencumbered by thick talus accumulations so that it picked up, and perhaps overrode weathered material without depositing fresh till on retreat. Upper Victoria Valley: till and washed drift The boundary between the Vida and Packard Drifts is not marked. The weathering is apparently gradational frcm the Vida end moraines to the present ice front. The dividing line has been placed at a broad end moraine showing some 2 0 m relief, which crosses the valley 8 km south of the Upper Victoria Glacier. The closely spaced, hummocky sequence of recessional moraines of the Vida Drift south of this 258 moraine contrasts strongly with the ground moraine of the Packard Drift "bordering Upper Victoria Lake to the north (fig. 5)* On the valley walls, sane lateral moraine terraces, distinguished up to 350 331 above the valley bottom, slope 2° to 5° south. At the valley margins where the till is thickest, these lateral depositional fea tures often become indistinguishable with ridges formed by glacier marginal streams. Farther toward the valley center on the west 3 lde, these ridges divide deposits of sorted, gravelly and sandy drift, washed and redeposited by the short glacier marginal streams. Only a few end moraines reach far toward the valley center; one of them, with sane 30 a relief, almost breaches the Upper Victoria Lake chain at the south end. Lower Victoria Valley; modified till On the south side of the valley, 6 km west of the Lower Vic toria Glacier, an end moraine of 17 m relief is distinguished sharply in degree of weathering from the Vida Drift farther west. This mor aine marks the western limit of the Packard till here, neither the plentiful Vida Granite boulders nor the less resistant boulders on the valley bottom show significant cavernous weathering (table 8 ), and no boulders have been worn to the ground. On the other hand, on the north side of the valley, opposite the end moraine, there is 259 no sudden change In degree of preservation of deposits, and the end moraine is represented only "by a slight concentration of "boulders and a wide alluvial fan. The deposits of the Packard Drift on both sides of the valley bottom here are uniformly fresher appearing than the deposits in the other valleys. No recessional moraines occur In this till sheet, but weak lateral moraine terraces and a regular succession of marginal channels and cut ridges occur on both sides of the valley to the gla cier front. Above the valley floor, the till is contaminated by older, cavernously weathered boulders and on the valley floor, large areas of wind-deposited sand mantle the deposit. Extending 100 to 3 0 0 m from the front of the Lower Victoria Glacier is stagnant glacier ice, overlain by eolian sand and drift from the active glacier terminus (figs. 49 and 50). The material here is gradational in weathering with that farther vest. It is typical in its sandy texture, better-than-average sorting, and occa sional bedding of the deposits extending westward to Lake Vida. Balham and McKelvey Valleys In the northwest fork at the head of Balham Valley (fig. 4), fresh angular dolerlte boulders extend 1 , 2 0 0 m south of the Ice front i and may contain a glacial ice-core over this distance. At the head of 260 McKelvey Valley, a morainal lobe of dolerlte boulders terminates In a depression 1,000 beyond the McKelvey Ice tongue. It Is not Ice- cored. Cirques From the cirques, ground moraines of the Packard Drift often extend only a few hundred meters beyond the present glaciers. However, most deposits, even where end moraines occur, are gradational in de gree of preservation with the Vida deposits. An exception occurs In the larger Orestes Valley where a fresh, sandy ground moraine with plentiful upstanding, relatively fresh granitic boulders extends 1.5 tan fran the cirque headwall. Here it meets a till bearing many cavernous ly weathered boulders, probably deposited during the Vida Drift episode. The termini of most of the cirque glaciers consist of a sec tion of melting stagnant ice overlain by fresh morainal debris (fig 9 0 ). History of the Packard Drift Episode General The last major glacial episode in the Victoria Valley system for which there is widespread depositional evidence is referred to here as the Packard Drift episode. The episode began with a minor glacial 261 stillstand and perhaps a minor readvance In some parts of the Victoria system, but the bulk of the deposits describe a general recession of Upper and Lover Victoria, and Webb Glaciers to their present positions from those occupied at the end of the Vida Drift episode. The thicker lateral accumulations but very thin deposits in the valley centers, particularly in the area of the present proglacial lakes, contrast with the uniformly thicker deposits left during the Vida Drift episode. This In part suggests that retreat was more sluggish and glaciers less active than during the Vida Drift episode. Figure 90. Ice-cored moraine at terminus of a cirque glacier north of Lake Vida* Looking northeast. 262 Most of the cirque and alpine glaciers have also retreated during this very ‘broadly defined period, hut the episode Is defined on occurrences of Packard Drift In the main valley areas. At the close of the Vida Drift episode, the Upper and Lover Victoria, and Webb Glaciers stretched 5*5* 8.9, and 5*5 km respec tively from their present positions (fig* 8 l). These glaciers vere probably between 3 0 0 and 6 0 0 m thick at the positions of the present fronts during the full-bodied stage of the Packard Drift episode. During the major portion of the Packard Drift episode, over steepened valley walls, frost action, and available moisture have allowed the formation of frost rubble and talus, especially below dolerlte and sandstone cliffs of western Barvick Valley. This was accompanied by the minor amounts of solifluction, confined largely to the steeper slopes of Victoria system. Along the main valleys seme tongues of solifluction, alluvial fans, and a few small mudflows vere fanned below hanging valleys containing patches of ice or snow. However, slope movement was not as active during the Packard as during the earlier glacial episodes. Probably this was a strong factor In the paucity of material deposited by the trunk glaciers, particularly during the latter half of the recession of the Packard Drift episode. 2 6 3 There la no evidence that the volume of meltvater during the main part of the Packard Drift episode greatly exceeded that at present. Apparently, early In the episode, there vas a change in stream regimen from deposition to erosion, perhaps induced in part "by decrease in glacier load and deposition following the Vida Drift episode. Evaporation was also strong during the major portion of the episode. In western Barvick Valley, salt accumulations up to 50 cm thick vere formed near the ice-cored moraine. Wehh Glacier The retreat of the Wehh Cflacier from its maximum during the Vida Drift episode vas interrupted hy a short readvance vhich, near the axis of Barvick Valley, locally redistributed older till rich in weathered, locally derived boulders. At the same time, at the southern and western margins of the glacier, frost action and undermining of steep dolerlte and sandstone cliffs caused large amounts of fresh, blocky talus to spread over the glacier margin, adding to that carried from the plateau over the Webb and Haselton Ice Falls. The glacier front did not retreat gradually but stagnated, forming knob and kettle topography near the valley center. Bouldery lateral and ablation moraine at the south and vest margins vas thick enough to preserve some of the buried glacial ice to the present time. The ridges, lateral moraine on the western and southern margins of the Webb Glacier seme 900 m vide below the Webb Ice Fall, rests on dead ice (fig* 1 3 )* The presence of this vide moraine suggests that the severance of the inland ice tongues vas the cause of the stagna tion; probably the Webb ice fields vere also reduced at this time and vere unable to maintain an active glacier front. Upper Victoria Glacier The Packard Drift episode began In upper Victoria Valley with the building of the high recessional moraine. Frcm here, the glacier front retreated slowly and regularly. Marginal channels formed and a few recessional moraines were deposited. Melting was stronger on the vest side of the glacier where short marginal streams washed and helped redeposlt gravelly moraine. Sorted deposits of ground and end moraine vere formed less commonly on the eastern side of the valley. Lower Victoria Valley The Packard Drift episode began in lower Victoria Valley by a short glacial stillstand or possibly by a minor readvance within the general recession from the Vida maximum. At this time, an end moraine was built across the southern half of the valley, and gravelly 265 outwash fans formed, along the entire front. Slow and regular retreat of the glacier front followed with the formation of marginal melt- water channels as in the upper Victoria Valley. Here, glacial debris vas washed or blown off the retreating glacier terminus more than elsewhere, and frequently was deposited as beds of sorted sand. Often these have been redeposited by the wind or meltvater streams. and McKelvey ice tongues, and cirque glaciers At the heads of Balham and McKelvey Valleys, there vere very short stills tan da or readvances of the retreating tongues of the Inland Ice. These deposited till about 1.2 km beyond the present ice fronts. Subsequently, this ice was almost completely Isolated by the emergence of dolerlte thresholds at the plateau edge, and seme of it remains today as stagnant ice masses covered by thick boulder accumulations • Cirque and alpine glaciers paused in their retreat and In seme cases probably readvanced from positions nearer the headvalls, built terminal moraines, and then retreated. The retreat was probably mare due to a decrease in accumulation than to stronger ablation. During this final episode, some of the larger alpine glaciers in the St. Johns and eastern part of the Olympus Ranges have retreated as much as 1 km. 266 % Cause of recession and implications of ice-cored moraine The cause of the general recession of the episode seems to have been the reduction in local anew accumulation, and in some cases, a reduction in ice flew fed to the valley glacier tongues from the inland ice plateau. There vas apparently no abrupt or strong Increase in ablation due to higher temperatures for the reasons given above (p.2 6 2 and p .2 6 3 ). The ice is ablating each summer (p. 257 ) and there has pro bably been no extended period of temperatures much higher than the present average since its deposition. The glacial ice-core beneath the Barvick deposits and the apparent lack of this ice-core beneath deposits older than the Packard Drift suggests that there has been insufficient time since their deposition for any buried ice to be removed under the present temperature conditions. Although the higher level of Lake Vida and the formation of outvash fans and kames during the Vida Drift episode can probably be accounted for under present temperature conditions {See p.2^5 ), the possibility of higher temper atures during the Vida Drift episode may not be ruled out. The still- stand or minor readvance initiating the Packard Drift episode in Victoria and Barvick valleys may have resulted from a temporary cooling. Further reduction in accumulation could have followed continued cooling, 267 so that glacial retreat (Packard Drift episode) continued without the formation of end moraines and with general diminishing glacial activity and deposition. Age and Correlation of the Packard Drift-Episode Wright Valley Deposits similar in degree of preservation to the Packard Drift occur within 8 and 2 km of the fronts of the Upper and Lower Wright Glaciers, respectively. They have been included, with parts of the younger stages, within the Trilogy Glaciation of Nichols (l96lc) and the Fourth Glaciation of Bull et al. (1 9 6 2 ). These deposits have not been examined in detail by the writer. Mt. Gran area Most of the ice-free area near Mt. Gran and that within Alatna Valley is mantled by moraine similar and perhaps correlative with the Packard Drift. These deposits have been ascribed to the second episode of the "B" Glaciation. At the maximum of episode 2, glaciers extended eastward into the west end of Alatna Valley. Here, a series of three prominent, intersecting end moraines represent a stillstand or a minor readvance. Deposits on the end moraines are extensively wind abraded and many resistant dolerite boulders have been 268 weathered, to ground level, "but boulders of pink granite, similar to those of the Victoria Valley, show only the earliest stages of cavernous weathering with few hollows more than 10 cm in depth. Much of the youngest till of episode 2 , 50 to 250 m fran the present glacier fronts, is believed to be cored by glacial ice. McMurdo Sound - Taylor Valley . The Packard Drift episode in the Victoria Valley system is probably contemporaneous with Pewe*s Koettlitz Glaciation, the latest major glaciation in this region and the least extensive of the major advances. The Koettlitz Glaciation in McMurdo Sound and the Taylor Valley area is represented by fresh and well-preserved moraines, cut by polygons, lacking ventifacts, and containing stagnant glacial ice (Pewe, I9 6 0 , p. 510). Number and position of deltas in drained glacier- ice-blocked lakes suggest possibly three stlllstands or minor advances during this glaciation. Radiocarbon dating of algae in drained ponds indicates a minimum age of 6,000 years for this glaciation (Pewe, i9 6 0 , p * U9 6 )• During the Koettlitz Glaciation, the alpine glaciers were extended only a few hundred yards beyond their present position but outlet glaciers such as the .Koettlitz were much more extensive. By 2 6 9 / / projecting profiles, Pewe has concluded that ice reached at least to 500 feet (152 m) on the west side of Ross Island hut that the ice probably did not extend far into the Ross Sea. This is prc’:ably in disagreement with Thcmas (i9 6 0 ) (See p. 2k8). SUMMARY OF INVESTIGATIONS General The valleys of the Victoria system were probably carved largely by outlet glaciers flowing from the inland ice plateau to McMurdo Sound. The stagnation and subsequent disappearance of these outlet glaciers from their valleys is due to the lowering of the inland ice surface below the level of bedrock thresholds at the northern and western borders of the valley system. Seme adjacent valleys without high rock thresholds continue to bear ice from the plateau. The glacier tongues In the Victoria Valley system, cut off from their source of supply, slowly wasted away. Geomorphological Processes With the exception of the Webb Ice Fall, the tongues of the inland ice are now inactive. Of the four large glaciers in the Victoria system, the Webb Glacier is the least active and the Packard Glacier the most active. Parts of the surfaces of the Webb, Packard, and Lower Victoria Glaciers are lowered more than 6 cm by sublimation and melting during the summer months. The loss from the latter two 270 271 glaciers may be partly made up by snowfall from easterly winds. Although accumulation and ablation apparently vary greatly from year to year, the fronts of the active glaciers have probably not re treated significantly in recent years. Whether they have advanced cannot be proved. Little till Is now being deposited at the glaciers' termini. Under the cold desert climate, meltwater is meager. The streams from the Upper and Lower Victoria, Webb, and Packard Glaciers vary from year to year with glacier melting, sometimes not forming at all. The coarsest material carried and deposited by the present streams ranges in size from 2 to 3 mm, and contrasts sharply with the older, much coarser deposits. Several large, perennially frozen lakes exist in the valley system. Most of these, including the 5 to long Lake Vida, are pro bably frozen to their bottoms. During the summer, after the surface snow cover is removed, strong solar radiation causes scalloped subli mation or evaporation patterns in the ice of the lakes and the formation of subsurface melt horizons. In addition to the perennially frozen lakes, there cure numerous small saline or brackish ponds which are more ephemeral and indicate the long continuance of arid conditions. Processes of mass wasting involving saturated surface materials 2 7 2 have been active in the past; solifluction sheets, debris (solifluc tion) tongues, debris lobes, and debris fans (mudflows?), a n now inactive, cover more than one quarter of the valley system. Most of these deposits formed immediately after retreat of the glaciers when valley vails were over-steepened and moisture vas locally more abundant. There 1s very little solifluction at present; however, mud flows and alluvial fans have formed recently below hanging cirques containing melting ice or snow. Non-saturated creep may be one of the more effective processes of mass wasting today. Talus and rock fall deposits are more limited than in temperate desert regions, but thick aprons are forming below well-Jo in ted dolerlte cliffs in Ber wick Valley. Thermal contraction polygons have formed over nearly all of the sandier deposits. They are similar to the typical artic lce- wedge polygons but, because of the arid conditions, the wedges fre quently consist of varying amounts of sandy or stony debris. Sane concentration of coarser material occurs at the furrow borders, due to gravitational movement from high-centered forms. Polygons are absent from most of the older deposits because of the silty texture and low moisture content. The best developed polygons, with the 273 deepest and videst furrows, occur in the ice-cared moraine of Barvick Valley, Their extraordinary development here is due to the higher coefficient of thermal expansion of the ice and the very coarse nature of the material. Well-developed polygons are coomonly found at the fronts of the large glaciers of the Victoria system. Wind is the most active agent of deposition and erosion in the valley system today. The strangest winds are katabatic and blow from the southwest quadrant. They have formed many finely carved ventifacts and groups of pebble ridges. Pebbles of It- cm diameter are common on these ridges and may have been moved by saltatlng particles under the influence of winds of over 90 knots. The predominance of northeasterly-trending cirques is probably also related to these southwest winds and suggests that these winds have blown for thousands of years. The southwesterly winds probably predominate in the valley system during the winter. During the summer, easterly winds from McMurdo Sound are predominant in the eastern part of the valley system where they have formed extensive sand deposits, interstratifled with snow. These deposits include barchan dunes, vhaleback-shaped sand mantles, and sand sheets. The slip faces of the barchan dunes, up to 15 m high, move westward as much as ^ cm per day during the warmer parts of the summer. z j k Differential weathering is an outstanding geomorphic process in the valley system and produces various rock forms, here collec tively referred to under the tens cavernous weathering* A cycle of weathering is recorded which begins with granular disintegration, is followed by progressive development of hollow’s, and ends with the reduction of the boulder or bedrock projection to a remnant too sm^n for further development of hollows. This cycle has been used to differentiate moraines containing granitic boulders and to determine relative ages of cavernously weathered bedrock surfaces* The hollows of the boulders are not a direct result of wind, but are possibly explained by the wedging action of ice crystals or the growth and expansion of wind deposited salts* 3ome minor chemical weathering, particularly hydration and oxidation, may be active in this rock weathering* Such action is suggested by the concentration of salt deposits in ponds, the oxidation and staining on rock and soil material, and the occurrence of fine desert varnish on dolerlte stones* tflthin the active layer of the surficial deposits, physical disintegration and seme decomposition has been active In the production of fines in the older deposits* 275 Glacial Geology The glacial geology of the Victoria Valley system Is summar ized In table 11. A summary of the correlations presented In this paper Is shewn in table 1 2 . It should be emphasized here that corre lations are presented as a basis of discussion and at the very least, are speculative in nature. Before this work in the Victoria Valley system, most studies of the glacial geology in southern Victoria Land and the McMurdo Sound region had been very localized or of a reconnais sance type. Published works of more detailed studies have been pre liminary in nature. It is suggested that valid correlations must be based on more qualitative and quantitative data than are now available. Variations in the local physiographic setting may influence glacial Inflow frcm the plateau or from McMurdo Sound, and also may effect local climate. Therefore, it is also reasonable to suppose that there may be no close correlation of glacial sequences and deposits outside of the Victoria system, particularly with individual subdivisions of the Victoria Glaciation. Table ll. Nomenclature and summary of glacial geology. Subdivision Glacier Action Deposits Character of Deposits Packard Possible minor readvances; Packard Till and morainal debris, sandy and often Drift general slow retreat or stagna Drift very bouldery, same washed and sorted drift; episode tion to present positions. and asso knob and kettle areas: ice-cored moraines; ciated little mantling by solifluction. Associated deposits deposits Include all those forming in the valley system today i.e. extensive alluvial and eolian deposits. (> 9 ;TOO years) — Change in Glacial Regimen- § ^rl Vida Drift Probable minor readvances Vida Drift Till, and morainal debris, sandy; $ episode to, and stillstand at 9 to 11 and asso moderately preserved moraines; thick or broad o km beyond present positions ciated outwash - kame deposits; associated debris A followed by retreat. deposits lobes; minor mantling by solifluction. o -Change in Glacial Regimen. -Marked Difference in Preservation Bull Drift Strong westward advance of Bull Drift Till, usually very silty; subdued topo A episode of Upper and Lower Victoria and asso graphy but two large, well-preserved end mor o Glaciers extending from 12 to ciated aines; extreme cavernous weathering of boul ■p 2 0 km beyond present positions; deposits ders and bedrock; isolated areas or erratic ■rlo > reduced Invasion frcm inland boulders; local lake deposits; associated ice plateau; followed by still debris fans; extensive mantling by solifluc stand and retreat. (Major ad tion. ( > 30,OCX) years) vance to and retreat from ter minal positions of Victoria Glaciation.) -Many Glacier Reversals -Marked Difference in Preservation— Strong advance of inland Insel Till, very silty; no morainal topogra Insel Glaciation ice into and probably eastward Drift phy, few upstanding resistant boulders; exten through valley system followed and asso- sive mantling by solifluction. Very resistant, by partial or complete retreat deposlts erratic ventifacts and associated frost of glaciers. rubble preserved on high benches. o\ Tab le 12. CorrelatIon. Victoria Valley Wright Valley and Wright Valley Mt. Gran Area McMurdo Sound - System Victoria Valley (Nichols, 1 9 6 1 ) (Calkin) Taylor Valley System (Peve, i9 6 0 ) (Bull, McKelvey, and Webb, 1 9 6 2 ) g Packard Drift Fourth Glaciation Trilogy Glaciation episode 2 Koettlitz Glaciation !p episode (youngest part) (youngest part) 3 $ Vida Drift Fourth Glaciation Trilogy Glaciation § episode 1 ? Fryxell Glaciation ° episode (oldest part) (oldest part) ■p CO A •H 0 | Bull Drift Second and Third Pecten and Loop ^ episode 1 Taylor Glaciation o episode Glaciations Glaciations 0 > £Q Insel Glaciation First and Second "oldest glaciation" "A" Glaciation McMurdo Glaciation Glaciations .... -j3 APPENDIX I - MECHANICAL ANALYSIS OF SAMPLES FROM SURFICIAL DEPOSITS* Total Sample Fraction of Sample-2 mm & finer $ Sieve Retents $ of $ Sieve Retents Significant Parameters In Fraction •H Phi Units £ c 1 % rlx § O ri CM rO 3 *H o P< 03 1 u WA wI o 0 ir\ CO 8 ir\ 3* « & a lf\ CM SI « o ft A e • • • 1 « % o S o s 08 03 m 0 CM H O O O 0 ft-. -Pi % t.H M «i w "W w a O ■I 08 A o cl<3 jd £ Sn i3 ■d S 3 3 4* 3 9 £ 3 s s £ S d oo g 3*« a 4> e u rl £ 3 o O c u P i C 3 35 CO CO1 Cm CO CO J* < O e 0 a > SVL 1 AM N 51 6 85 9 3 20 1*0 27 5 2 8 2 AM N 182 t 90 10 1 1* li* 35 36 10 8 2 S 3 GM (fin 60 cm)° N 235 2 96 2 1 1* 29 56 9 1* GM (fin 80 cm) L 220 3 9k 3 6 13 33 36 10 3 S 5 GM 20 M 202 5 93 2 2 5 32 1*8 12 2 a 6 GM to 2?1* 9 87 1* 11 10 23 38 15 a 8 a 7 GM 1*0 N 131 3 89 8 6 19 1*1 21 6 1 0 10 a 8 m 50 N 21*8 6 85 9 1.5 l* 10 36 36 a m N 196 1* 93 3 7 3k 33 35 9 3 9 31 s 10 GM 22 N 175 t 97 3 1 11 3k 38 13 3 lk 1*1 1 8 11 W 13 N 1*01 1 98 1 l* 36 5 2 t 8 12 W 26 N 21*6 t 100 t 1 3 1*1* 50 4 2 a W N 31*1* 7 91 2 7 20 1*2 2k 13 23 22 1* 2 8 lk w 38 N 328 29 70 1 16 20 36 11 32 5 t s 15 tf N t 23 29 S5- £JKPS*oa> g g ssssss aasss>£ g«s«SK&s >>>essss - - . n - t< 9 £ 1 3 tfgWggiiS 8 3* qp* 03 co cogscnco t-* f £ co £ a tr* a ss a ss a a a a a a a a a a tr> > naHsssstiinm&s * as CO to -J JrSvt (\jHHHHHH H U ) U) H l\> H UI\0 O- J O 05U1H - P O P ftvoui-pwui Co H H C o -P*ct to to ONOwn o\vo— j NJ1 VI £ ? © £ 8 8 8 $ g^Stt? 8$ § § §$ 8 8 & 3 W S g$5?8 8 WlUlfMHHPHHH H P V I -p-'!o to ■*■ 10 ON-J H -4 CO ftm c• o •09 W H 09 vi vi u» CDooNONCNMHto—jif'tovivi —jt-»rt-c+c+t-»NoCDe*-to-f^oooPfo&Np P O On Vi VO S^ljO &N&ONC0 8SS 8 S2^ (8 £$>53 gltt 8W3 P P H K> CD ■P'VJI f \ 0 W H H On tO Ovt*> IO CO -4 —J O vS 09 10 VO ■^3 co O R § n ON CO f B H H H H H N H tBiDa|ag|na « « |ai«a|«>me|nai ua«*itiai>atiagiti«Bnn fOWWWHHfOHHHMHHHHPH MMWMPMPPMMPrOWPPPH • ••••••••*••••••■ •••••••••••••••** co On CO 00 09v i O on 09 09 O ON Co to On On ro O O Co O 09 o VO On-J CD On O O 09—J co —] towM wiopwpppwpppppp proiotoptoioptoroHPPPppp • ••••••••••••••a* •••••••••■••••••• VI —J VO H -F" ON ON ON—J VO H ON CO t-> On ONH 09OU) p v o O P ON® 00—J 09 VI —4 ON ON-J HHHHHHHOHOOOOHOOH OOOOOOMP'OHOHHHHHH -J• -J•••••••••••••••a -F* P'VO Co 09 VO H ON ON-J 09 o ON VO CO oo• vi P"vi••*•••••••••«*•• cncnONH—JCOVOtoK ■F'CO ON -F* 61Z 260 ON CO CVJ O t— ON ON H t— C—NO VO l - r t O CNO O V O O N O ON O CVJ O CVIO H O CO 0\t-UN0 • ••••• ••••••••• HrlOlrlHrlOrtHOrlHOHW rtW W H H H H CM CM H HOI Ol wvo i-c -o c—co o t-vo ri^^^vovom (O UN VO 4 N ^ t ^ O l O H ON Jt PO UN UN • ••••••«••••••••••• **•••• •*••••••» CVJCVJCVJtOCVJCJCVJHCVJtOCVJCVJCVJCVICVJCVJHHH H CVJ OJ Oi CVJ H CJCVJ CVJ CVJ OJ CVJ CVJ H CVJ { J\O V O ^H jtC N t- on NO (OH H -4 VO O CVJ -4 CO CO ON J - ONUNt— t o t —- 4 NO O CVJ CVJ NO o • ••••■••••••••••a** • •••It ••«•••••• HCViH-4C\JOJHHCVJtOCVJCVJCVJCVJCVJCVJOOO H H C U H H H CVJ H H H .4 CVJ CVJ H OJ H a rl rl rl rl H H B U H b H b b a b b b e> b a H nHnDaoioDnuHrlaan (0 H a H H a HH HH ttHH a H S J8 « P S ? a “' “'K 3 S3 81w °'ASlt~'Da> a a s - a s ^ a NO ON J - VO ONCO VO UN UNCO ON O ON NO t o ON UN ITVNO t o NO CO CO UNCO UNCO NO NO NO t“ _4 CO C— H H H H H assess $&a 9“ "'a asssaa asaaasissss ssiss aaaafcaassaa a srsa&sis 9a^^sjaaa®as“'“'aasr«« aasa8»CT'S8iao'ssa3 o t—t^-cvjNO c— t o t o _ 4 cvj u-n-pvo cvj oncvj Ct h on irvco Q 4 Q .4 cm 1-7.4 . un c— on un_4 .4 t o t o a ONC— c— O N O t o . 4 -4 CO H trv • • ON tO CO-4- CO CO H co r— sj“ CO t—. . ,H...... 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AM, ice-cored moraine; GM, ground moraine; EM, end moraine; '*T, wind deposit; A, Alluvial deposit (including ice-contact); L, lake deposit; S, solifluction debris; M, other mass-wasting deposits; E, individual weathered rock. 6 0 cm), sample from permafrost "by blasting. ^N, no reaction to 10$ sol HC1; L, low reaction; M, moderate reaction; S, strong reaction. es, sand; Is, loamy sand; si, sandy loam; 1 , loam; scl, sandy clay loam; sil, silt loam. f A, sample taken in upper 10 cm; B, taken below 10 cm. t, trace. REFERENCES CITED Allen, A. D., 1962, Formations of the Beacon Group in the Victoria Valley region, pt. 7 of Geological investigations in southern Victoria Land, Antarctica: New Zealand Jour. Geology and Geophysics, v. 5> P* 278-294. Allen, A. D., and Gibson, G. J., 1 9 6 2 , Outline of the geology of the Victoria Valley region, pt. 6 of Geological investigations in southern Victoria Land, Antarctica: ibid., p. 234-242. 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AUTOBIOGRAPHY I, Parker Qnerson Calkin, was bora in Syracuse, New York, April 27, 1933* I received my secondary-school education in the public schools of Ridgewood, New Jersey, and my undergraduate training at Tufts University, which granted me the Bachelor of Science degree in 1955 m From the University of British Columbia, I received the Master of Science degree in 1959• In September, 1959, 1 enrolled in the graduate school of The Ohio State University where I specialized in the Department of Geology. Through part of the period of residence at each of the above mentioned universities, I was an assistant in the respective departments of geology. From September i960 to August 1 9 6 1 , while still in residence at The Ohio State University, I was employed as a research geologist by Tufts University under a National Science Foundation grant. During the following two years, until completion of the requirements for the Doctor of Philosophy degree, I was a research assistant with The Ohio State University, Institute of Polar Studies. 293 *>* F*— gn? > r » ^ r VW $ W ¥* P ? t ‘ f e r & ^ E ^ e ISO. .LAKE v " J Y//& "n&ifr°t.' 8 'a *.“ V*'* ■' \o\ 2230 # > ! W ^ V W - £ * 5 fej>&;S^nP§83 ICC MOO 1200 1000 2020 woo isrooE MOO 1 1 1 !-- GEOMORPHOLOGY and GLACIAL GEOLOGY wroov o r TIC VICTORIA VALLEY SYSTEM SOUTTCNN VICTORIA LAND * ANTARCTICA ’SCALE CM,000 1 0 • 1 J J 4 * "«**«"» •TMUTl MUS C0NT0U«i NltMM. tOOMfrtm m » *rrw us. m o l o o c a l surar ICE-mR *L1A»S**CI»I» LAND iii i if i m |I .1 I * 1 • * sii iik m I ;i ;i I III !i Si! I If iS I* I* H itl itl llSI !;! !!! !!! !ii! E H H H I BEl | ^ i i* g ft Si! f. if! l!:! rii *B| m 1 i ! 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