(a) Wright Valley

The Wright Valley continues to attract summer field parties after 14 years of exploration. A glacial origin has been proposed for the valley and deposits representing four glaciations have been recognised at varying heights. The basin occupied by Lake Vanda is assumed to be of glacial origin and it is this area which has received most attention for it now occupies the lowest and perhaps driest part of the valley. Supplied mainly by melt water from the Lower Wright Glacier, the Onyx Stream water flows 18 miles into Lake Vanda.

The glacial and allied deposits together with their acquired characteristics have not attracted serious attention. They are scanty and generally lack the status of "moraines". In a period of 30 days in the Wright Valley, the unconsolidated deposits were examined from the Lower Wright Glacier to the Labyrinth. Provisional results indicate:-

1.	'Ancestral' Lake Vanda dates from the stranding of a shallow arm of the sea in excess of one million years ago. Two layers of well preserved fossil pectens (Turner 1967) within boulder sands occur 1.0 and 1.5 metres below two poorly defined benches near Bull Pass. Additional benches formed within corresponding tills to those at Bull Pass are well preserved westwards towards page 25 Lake Vanda.
2.	The higher Lake Vanda bench levels record: (a) a maximum level marked by incomplete erosion of glacial tills at approximately 72 m above the Vanda datum level; (b) a 3 m lower level, on bedrock, also marked by thin weakly iron-stained sands; (c) a level 6 m lower, on bedrock or marked by almost fresh sands. None of the lower benches can be differentiated as significant static periods.
3.	The last down valley ice preceded the marine benching and the till sheet then deposited survived on the south side of the valley. A subsequent very limited advance into the North and South Forks predates bench level (b).
4.	The Lower Wright Glacier has advanced westwards for 15 miles from the present day glacier front and the ice at the maximum advance was 200 ft thick at a point 6 miles along the valley from the eastern end. The advances post-date the marine episode and a lack of lacustrine and fine tills in the valley is taken to indicate the presence of limited barrier ice in the past.
5.	No significant sources of Lake Vanda water, other than the Lower Wright Glacier, have been demonstrated. The bench level (a) is related to a short-lived maximal flow of meltwater following retreat of the glacial advance. Bench levels (b) and (c) may mark the retreat stages of later advances. A generalised water balance will be calculated on the assumption that there have been relatively small changes in the Lake Vanda environment. The available evidence on the ground indicates that this environment has been continually arid during this period.
6.	The above interpretations provide negative evidence of the four glaciations initially defined in the Wright Valley. It does provide a time scale which permits the dominant weathering processes to be rationalised - notably the complete disintegration and wind dispersal of glacial deposits, weathering of the exposed basement rocks around Lake Vanda, and deepening of the valley floor around Lake Vanda.

(b) Note on Vanda Station

Vanda Station established near Lake Vanda in 1969 is particularly well sited for hydrologic and environmental studies in a polar desert region. Our appreciation of this environment is so limited and biased by experience in other latitudes that the present day processes acting on and within the basement rocks and the "soils" remain largely unknown. The Vanda 3-year programme is costly to operate, is beset with many logistic problems and requires a hand picked staff. The staff must have the full backing and continued support of the people who have proposed or initiated projects which they want continued. What is not sufficiently appreciated, particularly at a distance of 2,000 odd miles, is that the local Vanda experimental conditions change and equipment may need to be modified. At the Vanda end any such thing as "splendid isolation" is completely fictitious.

(c) Lower Taylor Valley

VUWAE's 12 and 13 have designated glacial tills in this region, and they have attempted to identify a depositional sequence. Following a brief VUWAE 14 visit some anomalies have been explained.

(i)	Tills of the New Harbour Formation, 200+ metres thick, pass upwards to drop-pebble beds evidently deposited from floating ice. The tills are considered to have been deposited within a fiord when glacier ice occupied the Taylor Valley to a height of 300-400 metres above the valley floor.
(ii)	Subsequently, the ancestral Lake Fryxell formed behind the barrier of New Harbour Formation and a sequence of sheet tills was deposited, firstly lacustrine sediments, followed by coarse tills.
(iii)	The volcanic erratics assist in a limited evaluation of time control. The 2.7 million year old olivine basalts erupted in the middle Taylor Valley (Denton and Armstrong 1968) almost certainly comprise some of the erratics up to 600 m elevation above the valley floor down to the New Harbour and Fryxell Formations. Kenyte, not known to outcrop in the valley, is widely distributed in the Lower Valley and the erratics were deposited after 2.7 million years and after the last advance of Taylor Glacier. Volcanic erratics have been sampled both in the Wright and Taylor Valleys for petrologic study.page 27
(iv)	In view of the as yet little evaluated eustatic - isostatic marine control at New Harbour, events cannot be related to sea level control. However, the New Harbour Formation is clearly not a moraine and the sediments deposited from floating ice have subsequently been uplifted and tilted (approximately 5° SW). New Harbour sediments are involved in the isostatic rebound well recorded in the McMurdo Sound region, and they are apparently very old (from evidence of subsequent till weathering and the deposition of the younger Fryxell Formation).

(d) Collection of Samples

Samples of volcanic erratics, tills, "soil layers" and basement rocks were collected mainly from the Wright Valley. The tills are as yet poorly defined and are not known to be marine. Their mineralogy and chemistry will be the major laboratory study.

A sequence of algae samples has been collected from 10 surveyed bench levels above the north shore of Lake Vanda. A case for C¹⁴ dating will be made.

(e) Conclusions

A substantial break-through in correlating glacial events awaits further geochronology. For the volcanics, kenytes remain undated and selected basalt erratics could be dated. Carbonates within old lacustrine sediments and Lake Vanda water samples (plus Onyx Stream water) could be examined using established methods.