Physiography and Glaciology

Owing to the restricted time that was available, no long-term glacial projects were attempted, but field observations were made whenever possible.

The Victoria Valley, formerly ice-filled is now free of ice for most of its 40-mile length. Remnants of the glacier system are now: The Lower Victoria Glacier, an invading tongue of the Wilson Piedmont, to the east; The Upper Victoria Glacier, flowing from a large ice-field to the north-west; and the Webb Glacier to the west. Bordering ranges reach an average height of 4500 feet and on these, hanging cirques and valleys show a general accordance of floor levels, These cirques often have remnants of ice on thier backwalls which commonly show small terminal moraines as evidence of recent wasting and retreat. No such evidence was seen at the snouts of major glaciers.

The valley floors are mantled by thick moraine which rarely shows any glacial structures, but is invariably patterned by frost polygons. Although the moraine varies greatly in size and rock composition, no glacial striations were seen. Large areas of sand occur and well developed sand dunes are found to the north and east of Lake Vida. The effect of wind erosion was shown by a differential polishing on the faces of larger rocks, and quite frequently by fields of well-developed faceted pebbles.

The form and setting of Lake Vashka suggests it originated as a kettle- a deep remnant of ice left in the moraine by irregular glacial retreat. Large boulders and fine sandy bands now exposed on the surface of the lake ice support this theory. It is possible that the majority of the lakes on the valley floors originated in this way, and many may never have been entirely melted. Certainly the small lake at the head of Balham Valley and the empty depression at the junction of Balham and Barwick Valleys are of this form.

Stream beds leading into these lakes differ greatly, depending on the type of moraine on which they develop. The streams flowing westward from the Packard and Lower Victoria Glaciers over flat sandy floors have a braided course up to 100 yds. Wide. In contrast the western stream flowing into Lake Vashka is often 20 feet wide out cut 10 feet deep in coarse moraine. A great quantity of water would be required to develop a bed like this, although this summer only a trickle was running here and there. Along these streams in Barwick, Balham and Upper Victoria Valleys, well developed strings of paternoster lakes were found.

Basement

Basement rocks occur over almost the entire length of Victoria and Barwick Valleys. They are best exposed at the eastern end of the valley because the Ferrar Dolerites and overlying Beacon sediments obscure them toward the west.

The oldest rocks are the metamorphics of the Ross System, early Palaeozoic or Pre-Cambrian in age. These include graphitic marbles, schists, granulites and gneissic rocks, all with a constant trend of 280°.

At Lake Vida a salmon-pink or grey-coloured granite of the Admiralty Intrusives crosses the valley in a north-south direction, cutting the metamorphic rocks discordantly. Occasional pebbles of this granite are found in the basal Beacon sediments and it might be the major source rock of the sandstone.

Further eastward, the schists and gneisses are cut by a porphyritic granite which is well developed in the Purgatory Peak and Miller Glacier areas. Its ago and relationship to the 'Vida' granite art not certain, but laboratory study of specimens will help to determine this.

The basement rocks, of both Rosa system and Admiralty Intrusives, have been intruded by a wide variety of acid and basic dikes ranging in composition from aplites to pyroxenites. It is hoped that further study of these will give a relative ago for the members of the Admiralty Intrusives.

Beacon Group Sediments

Beacon sediments are restricted to the western half of the valley with the most easterly exposures occurring on peaks to the north of Lake Vida. Sequences of Beacon sandstone show a marked thickening toward the west, for while the most easterly outcrop was only 50 feet of basal sediments, a virtually continuous sequence of 3500 feet was examined west of the Webb Glacier. In one eastern section, onlap of near horizontal sediments onto a planed basement surface dipping at 12° west shows the area of sedimentation at that page 8 time was gradually extending towards the east.

Small variations in a generally uniform quartz sandstone mark off broad divisions of the sedimentary column. The lowest bed is a conglomerate layer which passes upwards into a cross-bedded quatrz sandstone with numerous worm tracks and abundant pyrites as scattered crystals or concretions. Overlying this are 500 feet of pure quartz sandstones with occasional beds showing mud-cracks and ripple-marks. Several coarse conglomerate layers up to 6 feet thick follow, marking the base of a 2500 feet thick coal-measure sequence of cross-bedded sandstones, felspathic grits and green-coloured siltstones. Numerous thin carbonaceous layers occur at intervals throughout this sequence, and occasional impure coal seams reach a maximum thickness of 3 feet.

Samples of fossil leaf and stem impressions from this sequence have not yet been studied, but they might give an age to the sediments which are at present loosely dated as ranging from Devonian to Jurassic. Shale and carbonaceous siltstones were sampled for pollen-analysis also. No results are yet available.

Ferrar Dolerites

Intruding the basement and the Beacon group are near-horizontal sills of the Ferrar dolerites. A sill intruding the basement has a uniform thickness of about 800 feet, and dips westwards at 5°. The Beacon group is shattered and complexely intruded by a dolerite of different composition. This upper dolerite is at least 4-5000 feet thick, and the Beacon sediments can be considered as rafts floating within the dolerite. Bifurcation and complexity of intrusion of this upper sill increase towards the west.

Many specimens were collected for laboratory investigation.

Economic Geology

No significant mineral discoveries were made, but some minor occurrences were noted.

Pyrite and Chalcapyrites: Minor amounts of these two copper minerals occur in orthoclase dikes west of the Packard Glacier.

Haematite: A minor occurrence of haematite was found north of Lake Vida. It is only a few square yards in area and of no importance.

Amethyst: At the base of the lower dolerite an impure variety of amethyst occurs in small veins. It is not of gem quality.

Coal: Thin impure seams of coal with a maximum thickness of 3 feet were found south of the Webb Glacier. It is of no importance.

Soils

Restricted areas of soil which occurs within the region were sampled and profiles were examined. Generally they show a cemented topsoil, with a dry friable subsoil above the permafrost level. In Balham Valley red, green, and mottled soils were found. Specimens await further examination and some data will probably be handed over to the Soil Bureau, D.S.I.R.

Permafrost

Observations, and some excavations, were made on permafrost phenomena. Relationships to the deposition of salts and the formation of soils were noted.

Evaporites:

Evaporite salts forming in depressions were studied. Usually only a thin surface crust, one example near Lake Vashka had salts 30 inches thick and saline waters with a temperature of 20.5°F. The composition of salts awaits analysis, though the bulk is probably calcium sulphate.

Seals

All expeditions into the "dry-valleys" have found the carcases of sub-fossil seals from the coast to areas far inland, and this expedition was no exception. Seals were discovered over the whole length of the Victoria Dry Valley system, up to 45 miles inland near the head of Balham Valley and within a few miles of the inland ice. Twenty six seals were found, most of them on the floors of the valleys, although one was on a saddle at 2100 feet. They usually occur on moraines, on outwash or river-laid gravels or basement rock, under conditions which preclude their deposition by retreating glaciers. The available evidence supports the views held by R.E. Barwick (V.U.W.A.E., 1958-59): that the seals have travelled into the area over a long period of time, that they travelled over present-day terrain, and that they have remained undisturbed since page 10 death, the condition of the carcases varies greatly from single disarticulated bones to well-preserved whole animals with skin and hair attached. Only 8 of the 26 seals found were sufficiently well preserved to allow identification of species: four were Crabeater and four were Weddell seals. Several carcases at different degrees of preservation were brought back for C. 14 dating.

Birds

A total of 38 carcases of skua gulls were found within a few hundred yards of Lake Vashka. Most of them were lodged in the cracks of the frost polygons where they had presumably been blown by wind. The reason for this surprising concentration of dead gulls, forty miles from the sea, in an area which can offer nothing in the way of food except by a long chance a wandering seal, is unknown.

Live skuas were found in the vicinities of Lakes Vashka and Vida. Five were noted this year and one during the ten-day visit to Lake Vida in 1958.

Their numbers must be far in excess of those actually reported; four out of the six birds were first noticed when, flying overhead, they cast their shadows on the people below.

Lichens and Mosses

Lichens and mosses are uncommon in the area and occur only in a narrow range of habitats. Their distribution was found to fall into a well-defined pattern. They are found on bed rock or on stable boulders, generally above 3300 feet. They are not found on unstable rocky slopes, scree fans or metamorphic rocks. Twenty-one specimens of lichens comprising four or five species, and three specimens of mosses of two species were found.

Fresh-Water studies

Collections of algae, and water samples for culturing of plankton were made from the range of available habitats. The ecological programme, covering a comparison between the deep, ice-covered lakes, the shallow lakes which are usually ice-free during the two summer months and the connecting streams, was curtailed by the cold temperatures experienced this summer. Little free water appeared around the edge of Lake Vashka, no water flowed in the streams, and only some of the shallow lakes thawed.

Some chemical analysis of the water of Lake Vashka was made in the field. The hydrogen-ion concentration was determined, water was "fixed" for later oxygen determination, and samples were subjected to ion-exchange resins to calculate the salt content. Bulk supplies of water were brought back for laboratory analysis.

No insects were found.

Temperature

The average temperature for December was 32.2°F. and for January 27.8°F. The maximum temperature was 54.2°F and the minimum 9.6°F, both occurring in December.

Judging from ice-conditions on the lakes and streams, and from the experiences of the two previous expeditions into the area, the temperatures recorded this summer were considerably colder than in a normal year. This was also the case at Scott Base and other points in McMurdo Sound.

The temperature did not rise above freezing point for two days in December and eleven days in January. The longest cold spell was from January 18 to 23 when the temperature remained constantly below freezing point.

Slight thawing occurred at Lake Vashka on three occaions in December following three two-days periods when the temperatures rose above 40°F. Apart from these occasions the lake remained permanently frozen to the edges.

No running water (apart from accasional trickles from thaw-pods) was noted in any of the streams in the entire valley system. This was quite different from the summer of 1957-58, when in January large streams were running into the east and west ends of Lake Vida. The the west of Lake Vashka a stream has, in other years, made a deep cut through the moraines, which would require a considerable flow; but this year no water was running. Therefore the attempt to measure the inflow into Lake Vashka (from which no water flows out) was curtailed. Even some of the small shallow lakes in the valley system remained ice-covered.

Wind

Constant winds, relatively high temperatures and low precipitation are characteristic of the dry-valleys.

The wind at the main bases averaged 8.4 miles per hour. The highest wind-run over a 24 hour period was 24 miles per hour. The highest gust was not recorded, but it probably exceeded 60 Knots: The hand aremometer, capable of recording winds up to this velocity blew to pieces on January 24.

In the wright Valley, which is long and narrow and confined for the most part between 5000 feet walls, the winds at the western end blew either directly up or down valley. They tended to follow a rhythm with easterlies blowing during the afternoon and westerlies during the morning. Easterly winds prevailed in the eastern part of the valley.

Wind in the Victoria Valley system immediately to the north did not follow this pattern; it was invariably from the east throughout the length of the area.

That the easterly wind is predomenant in the Lake Vida area can he deduced from the conformation of the barchan sand dunes to the north of the lake.

The heaviest winds at Lake Vashka came from the south. It must he understood however that the general picture of wind flow in this mountainous region is governed largely by orographical features.

Precipitation

Snow fell at valley-floor level on twelve days. On most occasions it melted after a few hours, but twice it remained for several days.

Less precipitation occurred in the vicinity of Lake Vashka than in the areas immediately to the east and west - again the results of the orographical wind complex.