(d) The Labyrinth and the Lower Taylor Valley

Both the above localities are in the Dry Valley Region, some 150 kms NW of Scott Base. The surfaces at the western end of the Wright Valley are all structurally controlled by the inter-bedded Beacon sandstones and Ferrar Dolerites where a broad platform of dolerite is exposed called the Labyrinth. This particular 'bench' of dolerite has been eroded to form a system of steep walled canyons which anastomose within the dolerite lithology only. Conjecture as to the processes forming it have been many and varied. Our limited investigations there (due to support problems) suggest the Labyrinth was first exposed by glacial action by a previously expanded Upper Wright Glacier. During this cutting many of the accordant cirques to the north and south probably formed. Later development of the box canyons seems to be predominantly an 'in place' erosional process whereby the dolerites are broken down into their individual components. Small potholing within dolerite pebbles in the Labyrinth clearly display how the wind erodes the coarser crystals from the dolerite.

Whilst at the Labyrinth our ideas on the geological history of the region were formulated with respect to data from the Taylor page 20 Valley (about 85 kms from Scott Base). Recent American literature shows that volcanics were erupted 2.7 million years ago in an ancestral Taylor Valley (Armstrong, Hamilton & Denton 1968). This clearly indicates that pre-Pleistocene glaciations existed, and we therefore collected the highest basalt and kenyte erratics we could find in the Lower Taylor Valley. Dating of these volcanics could assist in interpreting whether events in the Lower Taylor match those in the Middle Taylor Valley. Such an assumption was made by early reconnaissance workers, but has yet to be validated. A potassium-argon (K/Ar) date of these samples would give a maximum date to these deposits. (See page 22).

Together with Vucetich and Topping, the Pleistocene sediments in the Lower Taylor Valley were sampled to see if there are any marine microfossils present within these sediments. Micro-faunal examination may support the hypothesis that these sediments were deposited in a fiord, and that they have since been uplifted above sea level. Alternatively, they may have formed in a huge lake. Microfaunal analyses are to be completed by Dr. P.N. Webb (N. Z. Geological Survey) on foraminifera, Mr. W. Briggs (Geology Department, V. U. W.) on ostracodes, and Neall on bryozoans.

The type locality of the Taylor Formation (Speden 1962) was also examined. The distribution of the deposit has been extended, our investigations showing that shells are in situ up to 9 metres above sea level. They are located at most points along the coastline of the mouth of the Taylor Valley. In all cases they are marine deposits on moraine, and they are not found in areas subjected to flooding or the build-up of deltas. A detailed map of these localities will be published later. Shells found in these deposits include Adamussium colbecki, two other genera of bivalves, an as yet unidentified gastropod, and two complete echinoderms. An age determination for these shells may assist in determining the rate of uplift of this section of the coastline.