Visit to Lower Taylor Valley

A base camp was established on the north corner of a delta opposite the peninsula on the eastern shore of Lake Fryxell. The first four days were spent in general reconnaissance of the middle part of the valley, observation of local phenomena, e.g. polygons, salt deposits, sand entrained on down valley sides of boulders, ridges; removal of varnish, solifluction and other flow phenomena, stream channels, screes, etc. No progress was made towards recognition of till strata until the type section of Wellman and page 23 and Vucetich In New Harbour Stream had been examined, and their Taylor and New Harbour formations understood.

The impression of a universal homogeneous mantle of till is reinforced by the thinning of the patina on the surface of all exposed boulders on the up-valley side, apparently due to the sand-blasting effect of the down valley gale (this effect is not so obvious in the Taylor Valley as in the Wright, but one such gale was experienced in each valley, that at Vanda gusting up to 59 knots). Sand entrained behind boulders during such winds tends to be partly dispersed after a week or so by the persistent north-easterly. McCraw divided his surfaces on the basis of “light” and “dark” moraine. This is a dubious distinction as (a) it may belong to the Kenyte Till where this is thin, and in the process of deposition the underlying volcanic till member has been cut and involved in the upper till; or (b) it may belong to another deposit, typified in this case by apparently undisturbed olivine basalt scoria patches often ten metres across and 25 cm thick, which apparently thinly overlies the Kenyte Till to the southeast of Fryxell and extends beyond it around the 500 metre bench on Nussbaum, and probably into the upper valley.

Each till member has a typical suite of rocks which can be recognised. This suite receives additions from local sources (as (a) above) but retains its essential characteristic. The Upper Till Member of the Taylor Formation carries boulders of kenyte and a medium grained dolerite, the underlying Volcanic Till Member has a high percentage of scoriacious sand and gravel, while the more recent advances from the east wall consist almost entirely of material derived from the Kukri Hills basement of granite, quartzite and marble.

Visit to Wright Valley

Bedrock is exposed in the valley floor in the vicinity of Vanda Station but thin drift mantling the southern valley wall has been described as moraine. Quaternary deposits were examined superficially from above Don Juan Pond to Wright Lower Glacier. At the confluence of the valleys near the west end of Lake Vanda a sequence of moraines was examined in some detail, and these are the limit of recent down valley glaciation. This does not necessarily imply an page 24 extension of the Wright Upper Glacier to this limit; in fact this seems most unlikely.

The presence of a 5 cm pecten layer in the deposits at the foot of Bull Pass which can only be satisfactorily interpreted as in place, implies that the Wright valley was once an arm of the sea. Local glaciers have extended into the valley floow at the Meserve Glacier, and these show a number of advances and retreats. These carry abundant olivine basalt scoria which has been dated greater than three million years (Denton & Armstrong, 1968). This is restricted to the flood plain of the Onyx River on the Vanda side and is not present in the loopMoraine, which without a doubt advanced inland. However, scoria is again present in the younger moraine at the Wright Lower Glacier, but there was insufficient time to determine whether the source was the Clark Glacier, the Newall Glacier, or the Wilson Piedmont proper. No kenyte was seen in this valley.