GLACIOLOGY REPORT

In the Darwin Glacier area indications of three distinct phases of glaciation were found. The initial phase was a complete covering of the area by ice except for several peaks which protruded as nunataks. (This phase after retreating left a ground moraine of boulders which have been stained brown by the formation of iron oxides and exhibit cavernous weathering. Other features noticed were the disintegration in situ of coarse grained boulders, exfoliation shells, salt encrustations, well developed polygonal ground, and some ventifacts in the Diamond Hill area.)

A later phase less extensive than the first was confined to valleys, cirques and glacier margins. (In the Darwin Mountains several cirques (5500 - 6000 ft a.s.l) showed lateral and terminal moraines formed during this period. The hanging glaciers in the Darwin Mountain area did not extend down to the Darwin or its present day tributaries. In the Brown Hills area the North and South glaciers flowed into the Darwin and the ice level was approximately 100 ft. higher than at present. The formation of frost polygons and iron oxides is not as well developed as in phase one. The cavernous weathering and salt formation are similar. Several-crevasse fillings were noted in the moraines at Brown Bills.)

A more recent advance of the ice is indicated by limited areas of lateral moraine along the Darwin and Hatherton Glaciers and by terminal moraine in Smith Valley and a small area in a cirque on Colosseum Ridge. (The rough outlines of the moraine heaps are being modified by solifluction which is causing slumping. No brown weathering, cavernous weathering, salt formations or lichens were noticed. In Smith Valley coal fragments are lying on the surface showing no signs of decomposition.)

Three glaciers were staked in this area. The Darwin Glacier was staked at its narrowest part between Diamond Hill and Cranfield Icefalls using six bamboo poles placed half a mile apart. North Glacier was staked just below the icefall with five poles one hundred yards apart. South Glacier was staked up the centre with six poles half a mile apart, two poles approximately on the firn line and a row of six poles across the glacier three miles from the glacier snout. The position of the poles relative to reference points on bedrock was found using a theodolite but no resurveying to check the ice movement was carried out.

Evidence for four phases of glaciation was found in the Taylor Valley. The accordance of summits of the Asgard and Kukri hills is not due to structural control and indicates an ancient ice planed surface. The Taylor Valley was carved out down to the high benches best preserved on the North side of the valley where they are 3800 ft. a.s.l. This was followed by an interglacial period during which the valley was probably deepened by fluvial action. The second glaciation formed benches 2100 ft a.s.l. on the slopes of the Kukri Hills. An early eruption of basalt now occurred and the basalt fragments on the 2100 ft benches were later covered by moraine from the third glacial advance, when ice refilled the valley to 2500 ft. (Heights in the vicinity of Lake Bonney.) After the ice retreated extrusion of basalt from numerous small vents took place. These are found on both valley walls west of Hussbaum Reigel between 2500 and 5000 ft. and overlie the moraine deposited during the first three glaciations.

After more downcutting, possibly by fluvial action, the Taylor Glacier readvanced and rose to the highest lateral moraine level visible near Lake Bonney (1050 ft.) The present-day hanging glaciers also advanced and coalesced with the Taylor Glacier.

The Ross Ice Shelf was much higher at this time (J. Holling: Journ. Glaciology) and flowed into the Taylor Valley up to the base of the bedrock exposed on Nussbaum Reigel. (Evidence for this is given by the presence of kenyaite pebbles in the moraine and by the lateral moraines 1500 ft a.s.l. near the coast which dip gently inland (Kenyaite outcrops in the Mt. Discovery and Koelitz Glacier areas to the south of the Taylor Valley.)

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During the most recent retreat of the Taylor Glacier a cool phase or increase in precipitation caused the side glaciers to increase slightly in size. These have now also retreated leaving lateral moraines which overlie the lateral moraines of the Taylor Glacier. The glaciers in the Taylor Valley seem to have reached a state of equilibrium at present except for the Taylor Glacier itself which may be still slowly retreating.

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