(c) Cape Crozier

Little geological field work has been attempted at Cape Crozier, and since 1957 the area seems to have assumed a 'biological playground' function with the large number of penguins nearby. The cape is located on the most easterly extremity of Ross Island and is about 70 kms northeast of Scott Base.

Only one fossil - a gastropod, has previously been found at Cape Crozier, but a search in the area did not reveal any further fossils. An outcrop of tuffaceous sandstone was discovered adjacent to Post Office Hill, samples of which will be submitted to the recognised experts for microfaunal and microfloral analysis. Three page 18 raised beaches were also measured at the Northern Penguin Rookery to the north and south of Williamson's Rock.

The rest of our time was spent on the volcanic geology of the coastal section at Crozier. The area mapped was a 9 km strip of land, about 6 km wide, which extended up to an altitude of about 600 m a. s. l., but not including the 150 metre high cliffs which fringe the sea. This mapping was possible because a base-sheet existed of this area, prepared by Lands and Survey Department, Wellington.

The two principal cones in this region are The Knoll and Post Office Hill, both composed of trachyte. In both cases a small crater is preserved at their summits, and The Knoll crater contains a frozen lake. Basalt has been erupted from The Knoll as a late phase of activity, forming thin black flows over the steep-sided, light yellow trachyte. On a nearby basalt cone spirally twisted volcanic bombs were located. Further to the north another basalt cone is exposed to show a trachyte dyke. From this type of evidence the age sequence was established. Detailed examination of these interesting and important rock sequences will proceed shortly when the specimens arrive back in New Zealand.

Many more basalt and trachyte cones extend eastwards along the flanks of Mt. Terror, almost to the summit. These cones remain unmapped, but a request has been made to U.S. Geological Survey, Washington, to obtain aerial photographs of this region.

A great variety of lichens were found at Cape Crozier, including red, yellow and green crustose types and a black and green fruiticose lichen.

At this point it should be noted that the detailed examination of the volcanics was limited to Ross Island. Here the Tertiary and Quaternary volcanic rocks constitute the McMurdo Volcanic Group, page 19 a suite of rocks quite different from those occurring in the North Island of New Zealand. Whereas the North Island andesites and rhyolites belong to the calc-alkaline suite of volcanics more typical of orogenic areas, the alkaline suite of the McMurdo Volcanics is more typical of continental volcanic areas.

Ross Island consists of the central basalt - kenyte cone of Mt. Erebus (3,794 m) which is symmetrically surrounded by three volcanic lineations characterised by a basalt - trachyte - basalt sequence of eruptions. These three lineations consist of the Mt. Bird (1,766 m) eruptive centre to the NNE; the easterly lineation of Mts. Terra Nova (2,130 m) and Terror (3,230 m) to Cape Crozier; and to the SSE, the Hut Point Peninsula lineation. Samples collected by Scott's expeditions (Smith 1954) showed the basalts of the Erebus vent to be different from the surrounding linear vents. The dissimilarity of Mt. Erebus from the eruptive centres of Cape Bird, Cape Crozier, and the Hut Point areas offers an interesting problem requiring detailed geochemical and petrological investigation of samples collected. This study is planned for this year's laboratory research work.