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Victoria University Antarctic Research Expedition Science and Logistics Reports 1968-69: VUWAE 13
Visit to Wright Valley
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
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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.
| (a) | The ice flowing off the Antarctic continent caused erosion of the margin, concentrating the ice flow into a number of channels which progressively erode headwards. Stream capture would occur in the same manner as normal drainage, concentrating the flow into fewer and larger streams. |
| (b) | The last down-valley ice in any beheaded valley would bear no relationship to any climatic fluctuation, or to that of any other valley. |
| (c). | The replacement of rock with ice during erosion should cause isostatic upwarping of the continental margin (observed) and partial deglaciation should accentuate this. Conversely the upwarping may help reduce the flow of ice in the less vigorous streams. |
| (d). | The local glaciers in particular will be sensitive to climatic fluctuations, and these may on occasions coalesce to form down valley glaciers in such situations as the Upper Taylor Valley, and the record of fluctuations of a fair number of this type of glacier from several dry valleys should be compared. |